University of California

Livestock Production

Melvin R George, John Harper, Josh Davy  and Theresa Becchetti

Introduction

Ranches or range livestock production systems are complex. Range livestock production is an adaptive process that is continually balancing seasonal forage availability and quality with the changing physiological needs of the animal.  While each ranch is unique to the family that runs it and the land that supports it, there are some regional production processes that are similar within a climatic region. Calendars of operations, stock flows and feed flows are useful for visualizing production processes for a ranch.

Calendars of operations describe the annual production process for the livestock enterprise.  The timing of breeding, calving/lambing, nutrition and health practices are included in the calendar.  The annual sequence of activities illustrated in a calendar of operations is controlled by balancing the timing of forage resources with animal reproduction.  Stock flow calendars are a monthly inventory of each kind and class of animals on the ranch with births, deaths, sales and purchases included to explain changes in animal numbers throughout the year.    They are useful to understand how livestock numbers are gained and lost in an operation, estimate monthly and yearly feed and forage demands, and plan for marketing.   Monthly or seasonal forage resources used by the ranch to support the herd or flock can be described in a feed flow calendar.  In the following sections we will use calendars of operations and stock flow calendars to describe the production processes for fall and spring calving cow herds, beef stocker operations, and sheep operations.  Seasonal forage sources commonly used by California ranches will be illustrated in feed flow calendars.

Production Systems

Cow-Calf

Fall Calving vs. Spring Calving

Fall calving is common on annual rangelands where winters are generally mild (Figure 1).  Like much of the western U.S., the colder intermountain counties commonly calve in the spring (Figure 2) to take advantage of high elevation range and pasture.  However there is a great deal of variation in breeding calendars.  Some annual range operations calve in the spring.  The calving periods and other activities in the calendars in Figures 1 and 2 are only approximate.  Calving can start earlier or end later than illustrated in these figures. 

Fig1

Figure 1.  Calendar of operations, stock flow and feed flow for a fall calving beef cow herd.

 

Fig2

Figure 2.  Calendar of operations, stock flow and feed flow for a spring calving beef cow herd.

 

Cow-Calf (Fall Calving)

Fall calving cows (Figure 1) usually calve during the fall and calves are branded, vaccinated, and castrated in the fall.  The calves are not weaned from the cows until close to the end of the annual range production season, often in May.  At this time replacement heifers are selected and the rest of the calves are marketed.  In very poor annual range production seasons, weaning fall calving cows early in the spring helps maintain body condition through the dry forage period prior to calving and then rebreeding in the late fall.  Rebreeding success decreases when body condition scores (see Body Condition Section below) are low (Selk 2010). Vaccinations may occur throughout the year but are usually given in conjunction with other management activities (e.g.  branding, castrating and pregnancy checking) that require handling of cattle in corrals or chutes, to save labor and decrease disturbance of cattle. Besides shipping between winter and summer pasture, cattle are commonly worked two times per year.  These two working times may include the following activities:

Time 1: Brand, vaccinate, deworm, and castrate calves.  Vaccinate and/or deworm cows.  Sell any open (non-pregnant) cows.

Time 2: Wean calves, select replacement heifers, vaccinate cows/replacement heifers and possibly calves, sell steers and non-replacement heifers, pregnancy test and sell open cows and heifers.

In a cow-calf operation animal numbers change during the year due to selling, buying, births and deaths.  Females in the breeding herd also change classes as they mature.  Heifer calves selected from the annual calf crop to become part of the breeding herd (re-placement heifers) are managed separately from the cows until their second breeding season because the bulls used on heifers are usually different, heifers require more management attention, heifers usually get the better quality forage pastures, all the calves from heifers are considered terminal (will not enter the breeding herd), and young heifers are not competitive with bigger older cows.  The heifers are commonly bred earlier than the rest of the cow herd with the intention of giving them more time to cycle before the next breeding season when they join the regular cow herd.  In addition, the heifer breeding season is commonly limited to two months, compared to the cow herd season which is three months long.  Figure 1 illustrates the shifting of animal numbers for a 50 cow herd through the course of a year.  The logistics would be very similar in larger operations.  Notice that at any given time a 50 cow operation will have more than 50 animals because of the replacement heifers, bulls and calves that are also part of the cow-calf production system.

Table 1 describes the production classes used in the stock flows.  The fall calving stock flow calendar shows the addition of calves born in the fall, animals that are culled from the herd and females transferred from one group to the other as they mature and enter the breeding herd at the beginning of the breeding season, January in this example.  There are also death losses during the year, especially among the calves.

Table1

Table 1. Heifer development and subsequent stages of production.

Feed flow calendars illustrate seasonal forage sources, seasons of use, periods of hay feeding, and mineral and protein supplementation.  In Figure 1 (fall calving cows) the operation has access to annual rangeland all year but cows are transported to a high elevation U.S. Forest Service lease in May 15 through October 15.  On October 15 they return to dry forage on annual range left from the previous year.  Hay and protein are fed during part of the fall and winter.  Once the annual range growing season gets started hay feeding and protein supplementation ends.  Salt and minerals are provided all year. 

Cow-Calf (Spring Calving)

Spring calving is commonly practiced in regions of the state with cold winters, mainly the Intermountain regions east of the Cascade and Sierra Nevada Mountains. This is done so that cows are on high quality summer forage sources during lactation and rebreeding.  Figure 2 is an example of a calendar of operations for a spring calving beef cow/calf operation. Calving may start in February or March.  The breeding season is in the late spring and summer.  In the fall calves are weaned from the cows and sold just prior to the winter season.  Heifer calves that will enter the breeding herd to replace culled cows are selected at this time.  Cows are also pregnancy checked in the fall and non-pregnant cows are culled from the herd.   Bulls may also be culled from the herd in the fall or late summer.   Similar to the fall calving herd, animal handling is minimized to reduce labor costs and animal disturbance.  Cow herds that reside on Intermountain ranches during winter are usually fed hay in an accessible pasture or hay field.  Many of these ranches transport the cow herd to lower elevation owned or leased annual rangelands for the winter and early spring.

Using the production classes described in Table 1, the spring calving stock flow calendar shows the addition of calves born in the spring, animals that are culled from the herd before breeding and those culled in the spring because they are not pregnant or have health problems.  The calendar also shows the transfer of females from one group to another as they mature and enter the breeding herd at the beginning of the breeding season, June in this example.  There are also death losses during the year and purchases.

In Figure 2 the spring calving herd grazes on a BLM Lease during the summer until October 15.  During the late fall to late spring the herd is fed meadow hay harvested from privately owned meadows the summer before.  They may graze on the meadows in the spring just prior to entering the BLM Lease and in the fall (mid-October to November).  Protein is provided part of the year and minerals all year.  Some Intermountain ranches take the herd to annual rangelands for the winter and spring.

Stocker

Stocker cattle, commonly referred to as yearlings, are purchased in the fall and turned onto annual rangeland (Figure 3).   These calves weigh around 500 lbs when purchased and can gain 200 lbs or more before they are sold in the spring.   In our stock flow example 100 stockers are purchased in late fall or early winter and placed on annual rangeland.  Death losses can occur anytime but we have recorded only two in January.  All yearling cattle are sold in spring if the operation does not have irrigated mountain meadows available for the summer.  In some cases operators are able to use privately owned irrigated pasture/meadows in summer in addition to annual rangeland. 

Fig3

Figure 3.  Calendar of operations, stock flow and feed flow for a stocker operation.

 

Sheep

Like cattle, the commercial sheep production calendar is controlled by the reproductive calendar with the goal to market spring lambs and capture the usually high spring lamb prices. Most lambs are born in the fall and winter (Figure 4). Rams are often purchased in April and May.  Ewes with condition scores of less than 3 on a 1 to 5 scale are flushed in June. The breeding period for mature ewes starts in late summer with most ewes being bred in the fall.  Three weeks prior to ram turn-in mature ewes are vaccinated for Campylobacter (Vibrio) and Chlamydia and boosted 60 to 90 days later. Ewe lambs are vaccinated at 6 weeks and again at 3 weeks prior to turning in the rams. Because extra management is needed for replacement yearling ewes, they are exposed to the rams in July and August at least two weeks ahead of the mature ewes. Tagging and paint branding occur in October and bagging starts then or 3 weeks prior to lambing when ewes are vaccinated for Clostridia perfringens and tetanus.  Weaning occurs as early as January and continues through April and is dependent on feed and management practices. Docking, castrating, weighing and ear tagging occur during lambing.  Wool is sheared and sold in May.  External parasites are controlled in May and worming occurs in September and May.  Replacement ewes are selected to go into the breeding herd in April and May and the rest of the lambs are sold.  Culling occurs in October, March and May. 

Fig4

Figure 4.  Calendar of operations, stock flow and feed flow for a sheep flock.

 

In this stock flow table for a sheep operation we see that at the beginning of September, we have 400 ewes (80 are yearling ewes) and 20 rams (Figure 4). The stock flow is also keeping track of gains and losses. For gains, the most obvious are the births staring in November.

We also lost animals to death and culling along the way. After the breeding season we decided to sell 3 rams and in July we bought three replacements. Probably the most complicated part of the stock flow occurs when animals get older and change classes such as when yearling ewes are transferred to the ewe category.   The sheep feed flow calendar (Figure 4) shows that sheep graze annual range all year.  Hay is fed in the fall and winter and minerals are provided all year. 

Seasonal Forage Sources

Each ranch has a different mix of forages sources to support production.  Forage sources are seasonal in their availability, productivity and quality.  Season of grazing is controlled by seasonal availability and lease agreements.  Following are some common forage sources that support California ranches including annual rangelands, mountain meadows,  Great Basin rangelands, and irrigated pasture.  California range livestock operations vary in their operational characteristics and some ranch operations are spread across several vegetation communities.

Annual Rangeland

The annual grasslands and oak-woodlands (Figure 5) are the largest source of grazed forage in the state.  Being dominated by annuals these rangelands begin to grow with fall rains.  They grow slowly during the winter and then have a burst of production when temperatures warm up starting in late February and early March.  Production reaches its peak in April or May, followed by soil moisture depletion and onset of the dry season.  So they provide green feed in late fall, winter and spring.  On annual rangeland grazing can occur all year round but forage quality is poor during the dry season.

Fig5

Figure 5.  Map of the annual grasslands, chaparral and oak woodlands.

 

Mountain Meadows and Great Basin Rangelands

Mountain meadows and Great Basin rangelands begin growth in the spring as winter dormancy ends with rising temperatures.  Growth is rapid for several weeks and then slows during summer and fall.  The plants enter dormancy in late fall.  Dry feed may be used during fall and winter depending on snow conditions.  Public land leases are often at high elevations where forage is dormant and covered in show part of the year.  Public land permits control the start date and end date for the grazing season.  Public land grazing seasons are often from May through October. 

Irrigated pastures

Growth is very slow and pastures are often wet and muddy in December and January so pastures are not grazed or grazed very little. Valley and foothill irrigated pastures grow rapidly in the spring when temperatures are optimum for cool season grasses and legumes.  Hot weather slows growth in the summer and this is sometimes called summer slump.  Production may increase with cooler fall temperatures.  Growth is slow in winter and trampling damage during wet weather my preclude grazing during part of the winter.

Seasonal Transport

Annual rangeland ranches usually calve in the fall and use annual rangelands for forage during all or part of the year. Around the time that the fall calving season ends annual rangelands begin to green up but it is usually cold and forage growth is slow. Annual rangeland operations may rely on annual rangelands all year or they may transport cattle to summer forage. Typically ranches along the Sierra Nevada foothills have moved cattle to higher elevation public lands for summer grazing.  USDA Forest Service permits in National Forests provide forage on meadows and associated shrub and forest land.  USDI Bureau of Land Management permits are common in the Great Basin where livestock graze on sagebrush and sagebrush-grass ecosystems. Ranchers in northern California have also transported livestock to public and private high elevation pasture in eastern California and southern Oregon. Some annual rangeland operations own or lease irrigate pasture in the central valley that is also a source of green forage during most of the year.

Some ranches, especially those on the central coast, are too far from public lands and have developed supplemental feeding programs to maintain herd nutrition through the annual rangeland dry season and winter slow growth period.  In recent years some Sierra foothill ranches have decreased use of public land leases and increasingly relied on dry annual range forage and supplemental feeding.

Ranches in the Great Basin usually own high elevation pasture that is used to produce hay and some grazing.  The hay is fed during the winter months.  In the summer the livestock usually graze on public land leases on BLM and Forest Service grazing allotments. Some ranches transport livestock to the annual rangelands for winter and spring grazing and reduce the use of hay. Some of these California ranches move cattle into Oregon and Nevada for part of the year.

The north coast of California has another set of forage sources.  They have annual rangelands, often with an important perennial grass component and they have a longer green season due to the longer rainy season.  Many of these ranches have high quality irrigated pasture in the lowlands along the coast.  Many of these ranchers are also timber producers and have opportunities to graze private forestland following timber harvest.  Ranchers in eastern California are similar to northeastern California but they are less likely to use annual rangeland.  Many of these ranches use grazing land in California and Nevada.  Some use annual rangelands in the southern Sierra Nevada foothills.

Most sheep operations in California are small.  The largest operations are in the northern Sacramento Valley, southern San Joaquin Valley and the desert.  Sheep operations in California commonly use annual rangelands throughout the year.  Some graze alfalfa hay fields in the fall and winter and others use irrigated pastures in the valley or desert all or part of the year.

Nutrition and Forage Quality

Introduction

Animal nutrient requirements can be determined from several published sources. The National Research Council publishes nutrient requirements for most common domestic livestock. Management guides for various livestock species commonly include nutrient requirements for different physiological states that occur during the reproductive cycle.  

Nutrient requirement for grazing animals change as the physiological needs of the animal change.  Table 2 presents an example of the nutrient requirements of a 1000 lb beef cow for 5 different physiological stages.   Period 1 is the 45 days around calving and Period 2 is 45 days around breeding when the cow is nursing the calf born during Period 1.  This is the period of highest nutrient requirements.  Periods 3-5 show changing nutrient requirements as pregnancy progresses and the calf born in Period 1 is weaned.  While weaning the calf reduces cow nutrient requirements the growing fetus places increasing nutrient requirements on the cow. 

Table2

Table 2.  Nutritional requirements for a 1000 lb. beef cow.

 

Nutrient requirements for growing calves can also be found in nutritional references.  As a calf grows its daily dry matter requirement increases.  High protein and highly digestible forage is required for high rates of growth.  A 500 lb steer requires 12 lbs of dry matter that contains 8.5 percent protein to gain 0.5 lbs/day.  To gain 2 lbs/day that same steer requires about 13.8 lbs of dry matter per day containing 11.4 percent crude protein. Similar requirements for ewes and growing lambs can be determined from nutritional references.

Seasonal Forage Quality

Matching the nutrient demands of livestock with the nutrients supplied by range forage is a balancing act for a considerable portion of each year. The quality of range forage varies with plant species, season, location, and range improvement practices. Range forage is optimal for livestock growth and production for only a short period of the year. Early in the growing season, forage may be of high nutrient content, but high water content in the forage may result in rapid passage through the rumen and incomplete nutrient extraction. Indicators of high forage quality such as protein, energy, vitamins, and minerals decline as the growing season progresses (Figure 6). Conversely, indicators of low quality such as fiber and lignin increase as forage plants mature. Typically, four nutrients are of primary concern to managers of animals on California’s annual-dominated foothill and coastal rangelands: protein, energy, carotene (the precursor of vitamin A), and phosphorus. Additionally, certain minerals may be deficient or toxic at certain times or locations.

Fig6

Figure 6.  Stages of growth and forage quality.

 

Forage quality decreases as plants progress toward maturity (Figure 6).  At any stage of maturity forbs are usually higher in protein than grasses.  Legumes are usually higher in protein than other forbs and grasses. Additionally forbs are often more digestible than grasses at the same stage of maturity.  The leaves of shrubs are usually higher in protein than grasses.

Cell wall content of leaves and new stems of shrubs and trees increase with maturity.  Stems eventually become woody and much lower in quality and digestibility.  Standard stages of maturity have been established by the National Research Council (1982) to facilitate feed composition comparisons. Estimates of crude protein, crude fiber, and energy for seven stages of maturity are reported in Tables 3, 4, and 5. These seven stages of maturity include:

Early vegetative: Early growth stage, before stem elongation and flowering. For annual plants, this stage follows germination. For perennial plants, this is the new plant growth following dormancy or regrowth following harvest. New growth usually is high in nutrients and low in fiber. In annual rangeland this stage occurs during the inadequate-green season (Figure 7). 

Fig7

Figure 7. Landscape (A) and close-up photographs (B) of annual range forage during the inadequate-green season.

 

Late vegetative: Stage at which stems are beginning to elongate, continuing to just before blooming. Nutrients usually are lower than at early vegetative stages. This stage occurs during the adequate-green season’s spring flush of growth (Figure 8) 

 

Fig8

Figure 8. Close-up photos of annual range forage with (A) and without (B) legumes during the adequate-green season’s spring growth flush.

 

Early flowering: Stage between the initiation of bloom and the stage at which half of the plants are in bloom. Nutrients are beginning to accumulate in flowers. This stage occurs late in the adequate green season.

Late flowering: Stage from last half of bloom to seed set. The dough stage in grass seed occurs during late flowering. Nutrients accumulate in flowers and seeds, resulting in a loss of nutrients in leaves and stems. This stage occurs late in the adequate-green season.

Mature: Stage at which seed is ready to harvest or to be dispersed from the plant; plants are dry or drying. This is about the time when half of the forage is green and half of it is dry (Figure 9). Forage quality has declined to such an extent that it does not meet the nutritional requirements of some kinds and classes of livestock.

Fig9

Figure 9. Close-up photos of annual range forage during transition from the adequate green season to the inadequate-dry season, when about half of the forage is green and half is dry.

 

Dry: Stage where plants are cured, seed has been dispersed, and weathering is in progress (Figure 10). Plant nutrients are low and fiber is high.

Fig10

Figure 10. Landscape (A) and close-up photos (B) of annual range forage during the inadequate-dry season (midsummer), when seeds have shattered and residual dry forage is brown.

Dry, leached: Dry plants have weathered. Weathering has been accelerated by rainfall that leaches nutrients from the dry residual forage (Figure 11).

 

Fig11

Figure 11. Landscape (A) and close-up photos (B) of annual range forage near the end of the inadequate-dry season, when residual-dry forage is gray and quality is at its lowest.

 

Protein

Protein is often used as an indicator of forage quality. Protein is composed of amino acids linked together by peptide bonds.  Proteins are long chains made from up twenty different types of amino acids. During the digestive process, these chains are broken down into individual amino acids, transported, and synthesized back into proteins that the animal needs. Essential amino acids cannot be synthesized by the animal and must be transported intact from the plant material. If any of these essential amino acids are limiting, it can affect metabolic processes such as tissue growth.  Herbivores need protein for two main functions.  The first is to supply amino acids that make up proteins, to the microbial population in the rumen.  The second function is to supply amino acids for all the necessary functions that take place in cell metabolism throughout the animal.  

Actively growing plant parts have much higher protein levels than more mature or dormant plant parts.  Protein is most likely to be deficient when forage is dry and green forage is not adequate. Use of liquid supplements and blocks has increased drastically in recent years. Supplemental protein is usually the largest annual cost of maintaining a beef cow.  Supplements such as cottonseed or safflower oil meal, and alfalfa hay are primary sources of protein.  Urea is a non-protein compound which ruminants may convert to protein with varying degrees of efficiency. Presently, urea has a low to moderate value for cattle on dry range when it replaces protein in a natural protein supplement.  Proper management procedures are important when urea is fed to prevent ammonia toxicity and to enhance urea utilization.  Urea is toxic to horses.

Forbs and shrub leaves are higher in protein than grass leaves. Legumes are nitrogen fixing forbs and have higher protein than other plants. Protein in a feed is most often expressed as crude protein (CP).  Since most feed proteins contain about 16% N, Crude protein % is estimated by multiplying the N concentration in the feed by 6.25. However, some portion of the N in most feeds is found as non-protein nitrogen (NPN) and, therefore, the value calculated by multiplying N x 6.25 is referred to as crude rather than true protein. 

The crude protein (CP) concentration in feeds is determined using the Kjeldahl procedure. A dried sample is first digested in concentrated sulphuric acid, which converts most of the nitrogen (N) to ammonium sulphate (N present as nitrate is only partially converted). This mixture is cooled, diluted with water and neutralized using sodium hydroxide, resulting in the dissociation of ammonium sulfate. Distillation drives off ammonia and the distillate is titrated with acid to determine its ammonium concentration, from which the N level in the original sample is calculated 

Hart, Guilbert, and Goss (1932) conducted a regional forage analysis of annual species on 17 ranches along a north-south transect of the Central Valley of California. Figure 12 shows seasonal and regional changes in crude protein (CP). Seasonal CP content of composite forage samples ranged from greater than 20 percent CP in late winter to less than 7 percent CP at the end of the dry season. Early in the growing season, annual plants contain the highest protein content: over 15 percent in grasses, over 25 percent in filaree, and nearly 30 percent in bur clover (Table 3). This declines when plants flower, to about 10 percent protein in grasses and 15 to 20 percent in filaree and bur clover. Other annual legumes such as subterranean clover and rose clover follow the same seasonal trend as bur clover. The minimum dietary CP requirement for a 500 lb steer gaining 2.5 lb per day is about 12.5 percent CP, showing that growing animals require substantial supplementation during the dry season (NRC 1984). Fall-calving cows require only 7.5 percent CP in their diet during the last third of pregnancy in summer, while a spring-calving cow (3 to 4 months postpartum) would require more than 9 percent CP. Depending on the legume and forb content of the forage, supplementation may be required.

Fig12

Figure 12. Seasonal crude protein content of composite samples taken from 17 ranches along a north south line from Red Bluff to Coalinga, California (Hart, Guilbert, and Goss 1932).

 

Table3

Table 3. Crude protein and crude fiber content of annual grasses, filaree, and bur clover at seven stages of maturity.

 

Crude Fiber

Crude fiber is inversely related to digestibility, indicating declining forage quality from the adequate-green period (spring) to the dry-leached forage period (summer-fall) described by Bentley and Talbot in 1951. As shown in Table 3, crude fiber is less than 25 percent in annual grasses early in the growing season, increases to 25 to 30 percent during flowering and reaches 30 to 35 percent at maturity. Vegetative filaree contains less than 15 percent crude fiber, which increases to about 20 percent during flowering and reaches 25 to 30 percent at maturity. Crude fiber content of bur clover increases from about 15 percent early in the season to about 20 percent at flowering and 25 percent or more crude fiber at maturity.

Energy

Most of a grazing herbivore’s energy comes from forage consumed.  Forage is made up of soluble carbohydrates such as sugar and starch, protein, cellulose, hemicellulose and lignin.  Sugars, starch and proteins are easily digested but decrease as forage matures.  Half of the world’s organic carbon is tied up in cellulose.  To use cellulose as an energy source requires the ability to break cellulose down which most animals cannot do.  But many large herbivores can because of their complex stomachs and the cellulolytic microorganisms that reside there. What makes cellulose plant walls so hard to digest? The answer lies in the glucose bonds that compose cellulose.   Readily digestible proteins and soluble carbohydrates such as sugars and starches differ from cellulose in the isometric bonds of their glucose monomers. Intestinal enzymes called “hydrolytic enzymes” can split the alpha configuration found in starch and sugar, but not the beta configuration found in cellulose.  The glucose beta bonds in cellulose can only be cleaved by special “cellulolytic” organisms found in ruminant digestion. As the forage passes through the animal, metabolizable energy is extracted by breaking down the cellular bonds in the forage.

The energy in forage before metabolism is known as gross energy. Only some of the gross energy is digestible, the rest is lost as feces. The digestible energy, or DE, is further processed by the animal. Some energy escapes in methane gas during rumination and some is lost as urine leaving metabolizable energy (ME). Metabolizable energy is dedicated to the day to day activities of the animal.  Some of ME is used for maintenance (NEm-Net Energy Maintenance), some is used for weight gain (NEg-Net Energy of Gain) and some may go to lactation (NEl-Net Energy of Lactation). Both metabolic processes are inefficient, so there is loss as increment heat.

Metabolizable energy (ME) is digestible energy (DE) minus the energy losses in urine and combustible gases (see Energy sidebar). The ME content of annual grass as calculated from crude fiber analyses (Mertens 1989) is about 2.8 megacalories per kilogram or roughly 77 percent TDN during the early vegetative growth stage (Table 4). By the time grasses dry in early summer, ME is down to 2.2 Mcal/Kg and TDN is about 60 percent. The energy levels of filaree and bur clover are higher than for grasses at all stages of growth, declining to less than 70 percent TDN in the summer. Rangelands with high amounts of clover require less supplementation than grass-dominated rangelands as a result of higher energy and protein concentrations. While very high energy and protein contents may occur early in the growing season, this forage is often short enough to limit forage intake by grazing cattle. Consequently, grazing cattle may fail to consume adequate nutrient.

Table4

Table 4. Estimates of metabolizable energy (Mcal/kg) and total digestible nutrient (%) content of annual grasses, filaree, and bur clover at seven stages of maturity.

 

Minerals

Minerals are inorganic components of the animal’s diet and cannot be decomposed or synthesized by chemical reactions.  Minerals are divided into two groups; macro nutrients and micro-nutrients. Macro-nutrients are required in large amounts and include sodium, chlorine, calcium, phosphorus, magnesium, and sulfur.  Phosphorus may be borderline to deficient in diets during dry seasons.  Protein supplements usually supply adequate phosphorus to supplement native forage.  Mineral blocks should always be accessible for livestock to use as needed in loose pack or block form.  Placing salt away from water is a common practice for improving livestock distribution. 

Micro-minerals are only needed in small amounts but are crucial. They include cobalt, copper, iodine, iron, manganese, molybdenum, potassium, and selenium.  They function as co-factors, which are the inorganic components of enzymes, and if limiting will be just as problematic as macro-minerals.  Other elements have been suggested as essential but little scientific data is currently available for cattle.  Annual range forage may be deficient in copper. A high amount of molybdenum aggravates copper deficiency. Potassium, iodine and zinc may also be deficient in some locations. Other minerals such as selenium may be found in deficient or toxic levels in certain areas of the state. It may be desirable to provide a trace mineralized salt mix as a precautionary measure if there is any reason to suspect deficiency. 

Calcium content decreases with increasing plant maturity. The calcium level is usually high enough for all classes of livestock during the vegetative and bloom stages of plant growth (see Stage of Maturity sidebar). When the dry summer period begins, Ca is down to about 0.23 percent (Table 5). This would be enough for a 1,000 lb dry pregnant cow (requiring about 0.18 percent), but lactating and growing animals usually require a higher Ca content in their diet depending on body weight and rate of gain. Phosphorus content in forage changes from 0.45 percent in winter to a little less than 0.2 percent in the dry season (Table 5), which is below the requirements for all classes of cattle. The phosphorus content of Hart, Guilbert, and Goss’s forage samples from 17 ranches along a north south transect of the Central Valley were highest in late winter or early spring and declined to their lowest levels in late summer or fall (Figure 13). The content of phosphorus and other minerals followed a similar seasonal trend at the UC Sierra Foothill Research and Extension Center (Figure 14) between Marysville and Grass Valley (Morris and Delmas 1980).

Table5

Table 5. Calcium and phosphorus content of annual grasses at seven stages of maturity.

 

Fig13

Figure 13. Seasonal trends in phosphorus content of composite forage samples taken from 17 ranches along a north-south transect from Red Bluff to Coalinga, California (Hart, Guilbert, and Goss 1932).

 

Fig14

Figure 14. Seasonal mineral content of range forage dry matter from UC Sierra Foothill Research and Extension Center (Morris and Delmas 1980).

 

Vitamins

As with energy and protein, vitamins are generally highest in actively growing plants. Vitamins are “cofactors” or catalysts in metabolic reactions. This means that they do not appear in the products of the reactions, but they must be present in order for the reaction to take place. Animals cannot produce vitamins so they must be obtained from the consumed forage or produced by the bacteria in the ruminant gut. Vitamin A is usually the only limiting vitamin. It is produced from carotene that is present in green plant material.

Vitamins must be present within cells to act as catalysts. In ruminants they are synthesized by the ruminal bacteria and absorbed by the intestine. If not absorbed in adequate amounts they can limit metabolic activity.  Vitamins B and K are produced in the rumen soon after solid feed is introduced in the diet. Vitamin D is synthesized when the animals are exposed to sunlight and is also found in sun-cured forages. High quality forages also contain large amounts of vitamin A precursors and vitamin E.  Vitamin A is the only vitamin likely to become limiting since it is not available in plant tissue. Instead, it must be synthesized from beta carotene found within green plant tissue. Thus, it is most likely to be limiting when green plants are unavailable to the animal.

Vitamin A deficiencies occur in California beef cow herds. The carotene content of grasses declines rapidly as plants begin to dry and turn brown, and carotene is the precursor to Vitamin A. A beef cow can store several months’ supply of Vitamin A in her liver during the adequate-green season, but that supply can be depleted rapidly in a lactating cow. Green foliage from woody plants is a good year-round source of carotene. Many ranchers use injectable vitamin A on the cow herd at weaning if cows are going to be placed on weathered forage for several months.

Water Requirements

Sufficient water must be available for the number and type of animals given the current and expected climatic conditions (Table 6). Ambient temperature, activity, and lactation status can all affect water requirements.  For example, beef cattle requirements increase with increasing temperature (Table 7).  Availability of water can limit the season of use of pastures in arid regions.  For example, water from snowmelt may provide sufficient water for spring grazing, while in the summer there may be inadequate water after intermittent water sources dry out.  The presence of snow during the fall and winter may reduce the amount of water livestock must drink. In Montana, a cow tracked with a GPS collar did not visit any water sources for 6 consecutive days in January when snow was available.   In California’s annual rangelands water content of forages may be sufficiently high in early spring that cattle make little use of stockwater sources.  In rough terrain in northeastern California, cows tracked with GPS collars occasionally traveled nearly 2 mi (3.2 km) from preferred summer feeding sites to stockwater, drinking only once in two days.

Table6

Table 6.  Range animal water requirements (USDA NRCS)

 

Table7

Table 7. Temperature influence on beef cattle water intake (gal).

Seasonal Animal Performance

Bentley and Talbot (1951) described three seasons (Figure 15) based on the adequacy of annual range forage for weight gains. The inadequate-green season (Figure 7) begins with the fall germination of stored seed. Cattle grazing this forage may lose weight, hence the term inadequate-green forage. The onset and length of this period depend on prevailing weather conditions. If the fall and winter are dry or cold, green forage production will be poor and range supplementation may be necessary to maintain cattle performance. If warm weather coincides with adequate precipitation, forage production will be greater and animal performance will improve. Dry residual forage from the previous growing season is commonly available for grazing and provides energy but is low in protein and other vital nutrients. The leaching of nutrients by precipitation further decreases the nutritional quality of this dry residual forage. For short periods during the green season, livestock may occasionally be unable to consume enough forage to meet their daily requirements for some nutrients because the high water content of the forage limits their dry matter intake. Rapid spring growth begins with warming conditions in late winter or early spring. This also is the period when animal performance improves. The period is commonly called rapid spring growth or the adequate-green forage season (Figure 8). This forage usually is nutritionally adequate for maintenance, growth, and gestation. Rapid spring growth continues for a short time until soil moisture is exhausted. Peak standing crop occurs at the point when soil moisture limits growth or when plants are mature (Figure 9). This period is followed by the summer dry season (Figures 10 and 11) when the forage is a fair energy source but is low in protein, phosphorus, carotene, and other nutrients. Some classes of livestock can be maintained on dry feed while other classes may perform poorly if they receive no supplementation during the inadequate-dry season. During this summer period ranchers commonly provide supplements, transport their stock to green feed at higher elevations, or move their stock to irrigated pasture.

Fig15

Figure 15. Variations in length of time of the inadequate-green season, adequate-green season, and inadequate-dry season at the San Joaquin Experimental Range (Bentley and Talbot 1951

 

Body Condition

Body Condition Scoring (BCS) of beef cows (Table 8) and other livestock is used to monitor animal condition (Selk 2010).  It can be used throughout the year to assess nutritional needs and avoid nutritional stress.  Overgrazing promotes under nutrition and even animal stress during seasonal low forage periods and during drought. BCS can be used to identify animals that need extra nutrition.  BCS is also an important indicator of future calf vigor, re-breeding, milk yield and calf weaning weight.  BCS is easy to use and publications describing how to score body condition are available on the internet. There are also BCS systems available for horses, sheep and goats. 

Table8

Table 8.  Description of body condition scores (BCS).

 

Body condition refers to the degree of fatness of a cow and is ranked on scoring system of 1 to 9.  One is extremely thin and 9 is extremely fat.  5 is moderate and often the goal of herd nutrition programs.  On average 80 to 100 lbs of body weight equals one condition score. Body condition scoring is done by visual assessment of appearance.  During the procedure you are observing areas of fat deposition and muscle deterioration along the back and spine, ribs, brisket, hooks and pins and tail head.  The observer will also take fill, pregnancy and age into account.  BCS is easy to use.  There is also a system available for horses.  There are several publications on the internet that discuss and demonstrate BCS.

Beef cattle in body condition 1 and 2 are starving (Figure 16).  In the fall and winter it is not unusual to find starving cattle and horses on rangeland.  Too many animals on too few acres is common on small properties in the foothills. Sometimes starvation occurs because animals are not observed frequently and declining body condition goes undetected.  Infrequent observation can be the result of negligence but sometimes it is the result of the livestock producer being overwhelmed by financial issues or health issues. Most stockman monitor animal condition closely and provide additional feed or move cattle to new pastures to reverse any observed downward trend in body condition. 

Fig16

Figure 16.  Beef cattle in body condition 1 and 2 are starving.

Animal Health

Introduction

Animal health can be affected by contagious diseases, internal and external parasites, nutrition and toxic substances ingested during grazing.  Vaccination, parasite control, proper nutrition and animal management are standard practices for preventing disease and avoiding health issues.  The University of California School of Veterinary Medicine has published reports for California livestock producers that address many of these health problems. This section focuses on animal health problems that are related to rangelands or pastures and the forage produced on these lands.  These include nutritional problems such as grass tetany and white muscle disease, and parasites such as liver flukes, anaplamosis, pinkeye and foothill abortion.  Health issues related to grazing such as bloat and poisonous plant are also discussed.

Parasites

Liver flukes

Liver flukes (Fasciola hepatica) are found in the livers of almost all cattle slaughtered in California.  The life cycle of liver flukes begins when cattle graze on grass harboring the fluke in its encysted stage.  The encysted stage protects the fluke in a resistant coating that allows it to stick to blades of grass and protect it from the environment.  After cattle eat grass contaminated with the encysted fluke, the juvenile flukes “burrow” through the lining of the intestine, escape into the peritoneal cavity (the inside of the abdomen) and migrate to the liver. The flukes bore their way into the liver and over the next 6 weeks or more make their way to the interior of the liver and finally arrive in the bile ducts where they begin to lay eggs. The fluke eggs are shed into the manure and are deposited back in the pasture. These eggs then hatch and make their way to fresh water snails, which they infect and undergo additional development. They eventually emerge from the snail as young flukes and encyst (form a resistant coating) on blades of grass. When cattle ingest them, the life cycle begins again.

Mild California winters do not reduce the snail population, so liver flukes are quite common.  In addition, warm, wet spring weather can favor liver flukes.  Low rates normally do not affect cattle, but high infestations can cause serious damage to the liver causing diarrhea, weight loss, and jaundice.  In replacement heifers, studies have shown an increase in age to puberty as well as a decrease in pregnancy rates can be attributed to liver flukes. 

Indirectly, liver flukes can play a part in Bacillary Hemoglobinuria better known as redwater. Redwater can affect cattle at any time of the year; however, it is most common in the late spring, summer, and autumn. Redwater is caused by a bacterium called Clostridium hemolyticum, which colonizes in the liver of susceptible cattle and produces protein toxins that destroy the body's red blood cells, damages other organ systems and rapidly causes death.  Migrating liver flukes damage local areas in the liver creating conditions that the redwater bacteria prefer.  The bacteria then begin to grow rapidly in these damaged areas. The disease has a short incubation period and the vast majority of affected cattle are usually found dead and bloated 

The best practice for controlling the spread of liver flukes is to treat cattle before moving to a new pasture to kill adult flukes and prevent eggs from being deposited in the pasture.  Timing will depend on location of the ranch.  Maximum transmission of flukes occurs in spring and summer in warmer regions and late summer to fall in cooler regions.  At a minimum, cattle should be treated in fall or late winter/early spring.

Anaplasmosis

Anaplasmosis is a disease that attacks the red blood cells of infected cattle,  causing anemia and often death.  The disease is caused by a rickettsia parasite of ruminants that causes the disease called Anaplasma marginale.  All cattle are susceptible to infection by A. marginale as are wild ruminants such as deer and elk. The transfer of the agent from a carrier animal to a susceptible animal can occur by a number of routes, typically through ticks. Cattle under 1 year of age do not become ill, but do act as a reservoir for future infections.   Cattle infected between 1 and 2 years of age become ill after the incubation period, with severity increasing with age. Cattle over 2 years of age become very ill and approximately 50% die unless treated. The older the animal and the better shape they are in--the sicker they get! Usually, if they survive the infection, they stay infected for life. They are "immune carriers" that do not get sick, but act as a reservoir for other susceptible animals.  Therefore, being an infected carrier protects the animal from becoming sick if re-infected by ticks or other means.

The location of the herd is important in determining whether or not problems will occur. The cattle and deer that might be reservoirs and the ticks that naturally transmit the disease are the primary factors in disease transmission. Thus, the disease is important in California’s foothill oak woodlands.

Conversely, herds raised in the central valley of California on permanent pasture, with no ticks, no deer, and no carrier cattle have little risk of anaplasmosis. These cattle are free of the disease, have no immunity (unless vaccinated), and are totally susceptible to infection and disease. If these cattle are introduced to oak woodland pastures, especially during a bad tick year, they will become infected, get sick, and 50% will die if not treated.

When cattle are raised in the coastal foothills, Sierra foothills, and many mountain areas of California, they become infected early in life, have no clinical disease when infected (because they are young), and are “immune carriers”. If new, susceptible cattle come into these areas, they are at risk. If these carrier cattle go to the valley pastures, they may act as sources of infection especially via blood transfer (dehorning instruments, ear taggers, horse fly transmission, etc.). Many cattle herds are between these two extremes and it is common for a percentage of the adult animals to become infected and sick every year. These are herds that need to vaccinate routinely to prevent losses.

It is common for bulls that come from anaplasmosis-free areas to be very susceptible when introduced into areas where anaplasmosis is common. When bulls become infected and are successfully treated (do not die) they are often sterile for many months.  Therefore it is important to make sure that purchased animals such as bulls or replacement heifers are protected. Either they are raised in anaplasmosis areas or they have been vaccinated. A veterinarian can help ranchers institute best practices for preventing this disease.

Pinkeye

Pinkeye is an eye infection caused by the bacteria, Moraxella bovis.  Pinkeye results in oozing, discolored and bulging eyes in cattle.  Factors that contribute to the spread of pinkeye include flies, tall vegetation, dust, pollen, foxtail awns, and humans.  Reducing flies, cutting tall pastures before cattle are turned out, and wearing disposable gloves are practices that can reduce the spread of pinkeye in a herd.  When infected animals are brought into the chute to be treated, disposable gloves should be worn, disposable needles and syringes should be used and disposed before the next animal comes into the chute.  If large numbers of animals are being treated a change of clothing may also reduce the spread of pinkeye.  Any other equipment that is used such as a halter should be sanitized as well. 

Not all weepy, discolored eyes will be caused by pinkeye.  Foxtail can cause similar effects, with one notable difference.  Foxtail effects areas off to the side of the eye while pinkeye effects the center of the eye.  However good sanitary practices should also be used with foxtail to prevent infection with pinkeye. 

Vaccination against pinkeye with commercially available M. bovis vaccines can be effective if the vaccine contains the M. bovis strain found on your ranch.  Failures are often the result of the wrong strain in the vaccine and changing vaccines may result in success. Reading the vaccine label to make sure the new vaccine contains different strains than the failed vaccine and working with your veterinarian can be helpful in treating this disease.   It is possible to develop an autogenous vaccine based on the strains of M. bovis found on your ranch by working with your veterinarian.

Vaccination should begin 6-8 weeks before you typically see the first pinkeye case.  By starting to vaccinate early, you give the calf’s body time to develop the necessary antibody responses against Moraxella.   If you need to treat any animals, be sure to discuss the current best practices for treatment with your veterinarian. 

Foothill abortion

Foothill abortion, a bacterial disease also known as epizootic bovine abortion (EBA), is transmitted by bites from the pajaroello tick (Ornithodoros coriaceus). This tick lives in the soil around trees, in dry brush areas and around rock outcroppings of foothill rangelands, both on the east and west side of California’s Central Valley. Although infected pregnant cows show no obvious clinical symptoms, they will abort their calves six to nine months into pregnancy. Some infected cows will carry the pregnancy to term, but their calves are born weak and fail to thrive.  A necropsy can be completed to positively determine the cause of the abortion.  After cows or sexually mature heifers are exposed to the ticks and the EBA agent they carry, the cattle tend to develop immunity and are not susceptible to abortion for a considerable period of time. This occurs in the natural setting when a cow or heifer aborts or when they are exposed before becoming pregnant.  Pregnant cows and heifers without pre-exposure to EBA are most susceptible with abortion of 50%, or more, of the expected calf crop. It is important when replacement cattle are purchased that you ensure they are from tick infested areas or keep them out of tick infested pastures until after 6 months of gestation to prevent an abortion due to EBA. 

The UC Davis School of Veterinary Medicine has made progress on producing a vaccine that can take the place of exposing cows and heifers to the pajaroello tick and a vaccine may be commercially available in the near future.  Until a commercial vaccine is available, it is important to ensure heifers are exposed to tick infested areas either before breeding, or after 6 months of age.  Bulls or stockers can be placed in pastures infested with ticks since they are not affected by the bacteria. 

Bloat

Under normal conditions, the gas produced in the rumen separates from the solid and liquid contents and then rises to the top of the rumen, where it collects as a free bubble. Eructation, or belching, is initiated by increasing gas pressure in the rumen. Bloat occurs when the eructation mechanism is impaired or inhibited and the rate of gas production exceeds the animal's ability to expel the gas. Forages are classified as either bloat-causing or bloat-safe.  Legumes, especially grazed clover and alfalfa, are the plants that are most likely to cause bloat.

There are two types of bloat, frothy and dry gas.  Causes of bloat include 1) certain proteins in forage, 2) the amount and rate of roughage intake, 3) the coarseness of the roughage, 4) the rumen microbial population, and 5) enlargement of the lymph nodes between the lungs.  Animals can also inherit a tendency for bloat.  Diagnosis can only be confirmed on necropsy.  Frothy bloat can affect multiple animals while dry gas bloat affects single animals in the herd.

Frothy bloat is the more common form and occurs on pastures containing clover or alfalfa.   Sainfoin (Onobrychis viciifolia), birdsfoot trefoil (Lotus corniculatis), and cicer milkvetch (Astragalus cicer)are the only legumes known to not cause frothy bloat.  There are many different reasons why cattle can bloat on legumes including, stage of maturity, plant height, moisture, soil fertility, and temperature.   Frothy bloat is a stable foam created when the quick digestion of legumes produces gas that mixes with rumen contents.  Key management practices that can help reduce the chance of frothy bloat in cattle include: feeding dry roughage before moving cattle to high legume pasture, move to high legume pastures in the afternoon, leave cattle in the pasture and try to reduce disturbance,  and begin feeding an anti-foaming agent 48 hours prior to turnout. 

Poisonous Plants

Forero et al. (2011) recently revised “Livestock-Poisoning Plants of California.  This publication reports that oleander is the most commonly diagnosed plant poisoning for cattle, sheep and horses.  Ingestion of nitrate/nitrite accumulating plants is also a commonly diagnosed plant poisoning.  Nitrate/nitrite is often present in johnsongrass (Sorghum halapense), sudangrass (Sorghum bicolor), goosefoot (Chenopodium spp.) and pigweed (Amaranthus spp.).  Johnsongrass and sudangrass have often been the source of prussic acid (hydrocyanic acid) poisoning. Pyrrolizidine alkaloids in fiddleneck (Amsinckia spp.), tansy ragwort (Senecio jacobaea) and groundsel (Senecio spp.) are also causes of livestock poisonings in California.  Oxalates present in sorrel (Oxalis spp.), dock (Rumex spp.), pigweed (Amaranthus spp.) and lambsquarter and goosefoot (Chenopodium spp.) have also been implicated in livestock poisonings.

Prevention of loss from poisonous plants in general is a range and livestock management problem. Under normal conditions, some poisonous plants form an important part of livestock diets without negative effects on the animals. However when animals are hungry or otherwise stressed they may eat too much too fast resulting in plant poisonings.  Examination of a pasture or range each year before use is crucial to preventing plant poisonings.  Oak toxicity and acorn calves are plant toxicities that are specific to California’s foothill oak woodlands.

Oak Toxicity

Several years ago, in a few northern California counties, about 2,700 cattle died due to oak toxicity.  Disease problems due to ingestion of acorns or oak leaves are infrequent but when they occur the result can be catastrophic.   This problem is so infrequent that each generation of ranchers needs to be alerted by the older generation. 

Tannins and phenols are the toxins and they occur naturally in all of California’s more than 50 species of oak trees and can be toxic to cattle. The buds, young leaves, and fresh acorns have the highest level of these toxins. There is considerable variation in the concentration of toxins in the plant tissues and is dependent on (1) the species of oak trees, (2) the season of the year, and (3) the climate of the year in question.

These oak toxins (tannins and phenols) attack the proteins they contact. Thus, the gastrointestinal tract (mouth, esophagus, rumen, and intestines) is damaged by direct contact with the toxins. This results in ulcers, bleeding, and perforation in some cases. So if the cattle live long enough, bloody diarrhea or dark diarrhea is seen. Also, in the rumen, some of the tannins are converted to other chemicals (gallic acid and pyrogallols) that are absorbed into the blood stream, travel to the kidneys where they cause severe damage. This kidney damage results in renal failure, which can cause more deaths. Younger cattle (less than 400 pounds) are usually more severely affected than older cattle.

Symptoms usually appear shortly after cattle consume a diet exceeding 50% oak leaves, buds, and/or acorns. Some animals may simply be found dead. A day or two after eating oak leaves or buds, bloody or dark diarrhea may be noticed. As kidney failure progresses, fluid may accumulate around the anus or vulva. Throughout the course of clinical disease, the cattle appear weak, listless, and have no appetite.

The presence of large numbers of acorns when forage is scarce is one of the main risks. Wind, hail, or snowstorms can cause large numbers of acorns or limbs with leaves and buds to drop so that cattle can gain easy access to these potentially toxic materials. California outbreaks have been worse in the late winter and early spring when oak buds and small leaves are present in large numbers and a wet snowstorm occurs. This potential problem is exacerbated when snow covers the available forage, leaving cattle very hungry.  This leads to consumption of the only green feed available, oak leaves and buds.

Successful treatment of affected animals usually requires fluid therapy, antibiotics, and supportive care. Your veterinarian should be consulted and a treatment protocol set up to increase the odds of success and to provide the most relief for the cattle. The antibiotics help prevent secondary pneumonia and abscessation of the bowel. Fluid therapy will be necessary for many cattle to survive and must be planned with your veterinarian. Ready access to water and good quality grass hay will be very important parts of providing adequate nursing care.

Oak toxicity can be prevented by supplementing the cattle with hay or other supplemental feed when forage conditions are poor and acorns are abundant. Likewise, when late snowstorms cover the grass and knock down oak limbs with large amounts of buds and young leaves, be sure to start hay supplementation immediately. Do not wait until cattle get sick or die. A delay of only a day or two can easily result in many more deaths and ill cattle. If cattle are in conditions where toxicity is a longer term possibility the use of calcium hydroxide in a supplement can prevent sickness. The addition of 10% calcium hydroxide (hydrated lime) to a supplement will still be palatable to cattle. Then if the cattle will consume about two (2) pounds of this supplement per day it will prevent many cases of oak toxicity. This supplemental calcium hydroxide has to be consumed before exposure to be effective.

Acorn Calves

The acorn calf syndrome is completely different from the problems seen due to oak toxicity from ingestion of acorns, leaves, and/or buds. Acorn calves are congenitally malformed calves. The syndrome is associated with poor feed conditions during the second trimester of pregnancy (3rd -7th month of pregnancy). The exact cause is not known but seems to occur more often following autumns with large numbers of acorns. These calves have very short legs, abnormal hooves, and misshapen heads (either short noses or long narrow heads). The acorn calves look like dwarfs in most instances. Occasionally, more than 10% of the calves in a herd can be acorn calves.

Nutrient Deficiencies & Toxicities

Grass Tetany

Grass tetany is a problem usually confined to lactating cows. It is always associated with low levels of magnesium in the blood serum.

It is more severe when cattle are grazing young forage. Grass tetany occurs most frequently in the spring, often following a cool period (temperatures between 45 and 60°F) when grass is growing rapidly, but also is seen in the fall with new growth of cool season grass or wheat pastures. Typical signs of grass tetany begin with an uncoordinated gait and terminate with convulsions, coma, and death. The prevention of grass tetany depends largely on avoiding conditions that cause it. Early supplementation with mineral blocks containing magnesium can lower the chances of getting grass tetany.

Grass tetany is commonly associated with grazing on lush pastures in the spring. Grass tetany is a problem usually confined to lactating cows. It is always associated with low levels of magnesium in the blood serum.  Potassium and ammonium interferes with the absorption of magnesium.  Rapidly growing grasses often are low in magnesium and high in potassium which interferes with the absorption of magnesium.  Grasses that are high in crude protein can also be a concern because protein digestion releases ammonium.  Lactation not only increases requirements for calcium, but also magnesium.  Thus, heavier milking cows are at a higher risk of magnesium deficiency. 

Grass tetany can be prevented by offering magnesium supplements.   Salt-mineral mixes or molasses supplements are the most common methods.  Beet molasses is high in magnesium, and is normally a large percentage of molasses made in the west.  Read the labels closely and if the supplement contains urea, it may not help prevention of grass tetany since urea breaks down easily in the rumen to ammonia. 

Selenium (White muscle disease)

Selenium deficiency, sometimes called “white muscle disease” is a degenerative muscle disease found in large animals.  Selenium (Se) was identified as an essential nutrient for beef cattle in the late 1950's. Selenium deficiency is frequently observed on soils of volcanic origin. Selenium deficiency should always be suspected on volcanic soils.  Selenium deficiencies are concentrated in northern, especially northeastern, California (Figure 17).  In these selenium deficient areas it can be administered as an injector or as a pellet placed into the reticulum.  Selenium provided in supplement blocks has generally not proved effective.

Fig17

Figure 17.  Selenium status of California Counties.

 

A sign of Se deficiency in beef cattle is nutritional myodegeneration particularly affecting the heart muscle and producing a disease commonly called white muscle disease. In this disease, white sections are observed in heart muscle. Lameness and/or death can also occur with Se deficiency. Other symptoms of inadequate Se may be reduced weight gain, poor feed conversion, diarrhea, reduced reproduction (particularly retained placenta) and lowered immune response. Rough hair coats and general "ill-thrift" may also be observed. Due to effective diagnostic and supplementation methods, Se deficiency can be identified and economically corrected.

Selenium deficiencies occur in the western US and elsewhere, but selenium toxicity can also be a serious threat to livestock in the western United States. There are two general types of toxicity, acute and chronic. Acute poisoning is caused by the consumption, usually in a single feeding, of a sufficient quantity of highly seleniferous plants, which produce severe symptoms. There are two different types of chronic poisoning dependent on the chemical form of the ingested selenium. "Blind staggers" occurs when animals ingest water-soluble selenium compounds naturally found in accumulator plants. Toxicity from eating plants or grain with protein-bound, insoluble selenium is called "alkali disease." Symptoms usually start with wandering, stumbling over objects, anorexia, visual impairment. It ends with blindness and paralysis. The most effective way of preventing selenosis is to remove the animals from the seleniferous area. 

Energy Analysis (Sidebar)

Forage contains fixed energy in many forms that can be roughly divided into those that are easy to digest in the cell interiors and those that are hard to digest in the cell walls. The cell walls are composed of hemicelluloses, cellulose, and lignin. The cell interiors are filled with a cytoplasmic soup composed of lipids, amino acids, proteins.  There are three well known laboratory analyses used to determine the easily digested cell interiors and the hard to digest cell walls.  They are 1) Detergent fiber analysis, 2) In vitro digestion of dry matter, and 3) near infrared spectroscopy.

Figure 18 describes the cell components that can be digested using the detergent fiber system of analysis. In the lab, scientists can artificially digest, or dissolve, forage to describe forage quality. When forage is digested with neutral detergent the soluble components (proteins, sugars, etc.) are removed.  These soluble components are reported as neutral detergent soluble (NDS).  The components that are not dissolved (hemicellulose, etc.) are reported as neutral detergent fiber (NDF).  The NDF is further dissolved using an acid detergent.  The part that is soluble in acid detergent (hemicellulose and insoluble ash) is reported as acid insoluble ash (AIA).  The part that remains is cellulose and lignin is reported as acid detergent fiber (ADF).  Further digestion of ADF with 72 % sulfuric acid is sometimes used to separate cellulose and lignin.  NDF measures most of the structural components in plant cells (i.e., lignin, hemicellulose, and cellulose), but not pectin.  Most of the structural components are in the cell wall. A high NDF content indicates low quality forage.  It can be used to estimate the ratio of cell wall to cell content. NDF can be used to estimate total digestible nutrients (TDN).  Acid Detergent Fiber (ADF) is a measure of the less digestible portion of the plant cell wall material (cellulose and lignin).   The ADF content of a feed can be used as a predictor of digestibility and thus energy. If a feed has a high ADF value, and all other nutrients are similar, it will likely be less digestible than a feed with a lower ADF value.  TDN can be estimated using the following equation: TDN (%) = 88.9 – (.779 × % ADF).

Fig18

Figure 18.  Detergent fiber system of analysis.

 

In vitro digestion is the second method used to estimate digestibility of forages. This procedure is known by two acronyms in the literature, IVDDM and IVDMD, but both mean virtually the same thing and have the same procedures. In-Vitro dry matter digestibility (IVDMD) is the quantity of dry matter digested when a known amount of forage is anaerobically incubated with buffered rumen fluid typically in a test tube for a defined length of time (typically 24 to 72 hours). This procedure measures the amount of dry matter lost when forage is digested in test tubes using rumen fluid.  The rumen fluid contains the tiny micro-organisms that live inside the guts of ruminant animals like cows that allow them to digest fibrous material. In vitro digestion is usually expressed as a percentage: the weight of a dry matter sample less the weight of the residue after the procedure divided by the weight of the original dry matter sample.

Near Infrared Reflectance Spectroscopy is the third method used to determine energy content.

Near infrared reflectance spectroscopy is a rapid and low-cost computerized method to analyze forage and grain crops for their nutritive value. Instead of using chemicals, as in conventional methods, to determine protein, fiber, energy and mineral content, NIRS uses near-infrared light. The procedure is similar to the human ability to visually distinguish color when light strikes a material that absorbs some wavelengths and reflects others.

This method of analysis involves the drying and grinding of samples which are then exposed to infrared light in a spectrophotometer. The reflected infrared radiation is converted to electrical energy and fed to a computer for interpretation. Each major organic component of forages (and grain) will absorb and reflect near-infrared light differently. By measuring these different reflectance characteristics, the NIRS unit and a computer determine the quantity of these components in the feed.

The detection of specific nutrients is possible because reflectance spectra from forage samples of established nutrient values (by wet chemistry procedures) are programmed into the computer. When a similar feed sample is evaluated by NIRS, the computer compares the wavelength reflections caused by the sample, and matches them to previously tested samples. 

The NIRS method of determining forage nutritional content is very rapid, about 25 times faster than conventional laboratory procedures, and less expensive than wet chemistry methods. Accuracy depends on good sample collection, storage and consistent drying, grinding and mixing of samples prior to analysis. The calibration set that is used must be developed from an adequate number of wet chemistry samples, similar to those being analyzed. Without proper calibration, the NIRS analysis can have serious error.

List of Tables

Table 1. Heifer development and subsequent stages of production.

Table 2.  Nutritional requirements for a 1000 lb. beef cow.

Table 3. Crude protein and crude fiber content of annual grasses, filaree, and bur clover at seven stages of maturity.

Table 4. Estimates of metabolizable energy (Mcal/kg) and total digestible nutrient (%) content of annual grasses, filaree, and bur clover at seven stages of maturity.

Table 5. Calcium and phosphorus content of annual grasses at seven stages of maturity.

Table 6.  Range animal water requirements (USDA NRCS).

Table 7.  Temperature influence on BeefCattleWaterIntake (gal).

Table 8.  Description of body condition scores (BCS).

List of Figures

Figure 1.  Calendar of operations, stock flow and feed flow for a fall calving beef cow herd.

Figure 2.  Calendar of operations, stock flow and feed flow for a spring calving beef cow herd.

Figure 3.  Calendar of operations, stock flow and feed flow for a stocker operation.

Figure 4.  Calendar of operations, stock flow and feed flow for a sheep flock.

Figure 5.  Map of the annual grasslands and oak woodlands.

Figure 6.  Stages of Growth and Forage Quality.

Figure 7. Landscape (A) and close-up photographs (B) of annual range forage during the inadequate-green season.        

Figure 8. Close-up photos of annual range forage with (A) and without (B) legumes during the adequate-green season’s spring growth flush.

Figure 9. Close-up photos of annual range forage during transition from the adequate green season to the inadequate- dry season, when about half of the forage is green and half is dry 

Figure 10. Landscape (A) and close-up photos (B) of annual range forage during the inadequate-dry season (midsummer), when seeds have shattered and residual dry forage is brown.

Figure 11. Landscape (A) and close-up photos (B) of annual range forage near the end of the inadequate-dry season, when residual-dry forage is gray and quality is at its lowest. 

Figure 12. Seasonal crude protein content of composite samples taken from 17 ranches along a north south line from Red Bluff to Coalinga, California (Hart, Guilbert, and Goss 1932).

Figure 13. Seasonal trends in phosphorus content of composite forage samples taken from 17 ranches along a north-south transect from Red Bluff to Coalinga, California (Hart, Guilbert, and Goss 1932).

Figure 14. Seasonal mineral content of range forage dry matter from UC Sierra Foothill Research and Extension Center (Morris and Delmas 1980).

Figure 15. Variations in length of time of the inadequate-green season, adequate-green season, and inadequate-dry season at the San Joaquin Experimental Range (Bentley and Talbot 1951).

Figure 16.  Beef cattle in body condition 1 and 2 are starving.

Figure 17.  Selenium status of California Counties.

Figure 18.  Detergent fiber system of analysis.

Literature Cited

Bentley, J. R., and M. W. Talbot. 1951. Efficient use of annual plants on cattle ranges in the California foothills. Circular 870. Washington DC: USDA.

Forero, L., G. Nader, A. Cragmill, J.M. DiTomaso, B. Puschner, and J. Maas.  2011.  Livestock-Poisoning Plants of California.  Berkeley, CA:  University of California, Division of Agriculture and Natural Resources Publication No. 8398.  44 pgs. (http://anrcatalog.ucdavis.edu/pdf/8398.pdf, accessed November 17, 2013).

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Hart, G. H., H. R. Guilbert, and H. Goss. 1932. Seasonal changes in the chemical composition of range forage and their relation to the nutrition of animals. Bulletin 543. Berkeley: University of California, Agricultural Experiment Station.

Maas, J.  2008.  Killer Oak Trees.  Davis, CA:  UCD Vet Views.  http://www.vetmed.ucdavis.edu/vetext/local-assets/pdfs/pdfs_beef/cca0801-oak-toxicity.pdf

Mertens, D. 1989. Conversion equations for ADF to ME (personal communication).

Morris, J. G., and R. E. Delmas 1980. Seasonal variation in the nutritive nature of Californian range forage for cattle. In Beef cattle day. Browns Valley: University of California Sierra Foothill Range Field Station. pp. 16–20.

National Research Council. 1982. United States-Canadian tables of feed composition. Washington DC: National Academy Press. p. 144.

National Research Council. 1984. Nutrient requirements of beef cattle. Washington DC: National Academy of Sciences.

Selk, G.  2010.  Body Condition Scoring of Beef Cows.  Sweetwater, OK: Oklahoma Cooperative Extension Service ANSI-3283.  4 pgs. (http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-1965/ANSI-3283web.pdf, accessed November 18, 2013).

Additional Reading

Adams, J. R., and M. W. Stellmon. 1999. Cow-calf management guide, second edition. Moscow, ID: University of Idaho, College of Agriculture. http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex6769 - bloat

Bruce, B., R. Torell, and B. Kvasnicka. 1999. Nutritional management of beef cows in the Great Basin. Reno: University of Nevada.

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