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RANGELAND MANAGEMENT SERIES Publication 8021
Balancing Beef Cow
Nutrient Requirements
and Seasonal Forage Quality
on Annual Rangeland
Melvin George, Extension Range Specialist, Agronomy and Range Science, University of
California, Davis; Glenn Nader, UC Cooperative Extension Farm Advisor, Yuba-Sutter-
Butte Counties; and John Dunbar, Emeritus Extension Animal Nutrition Specialist,
Animal Science Department, UC Davis.
Range beef cow nutrition programs are greatly influenced by the changing nutritional
needs of a cow as it progresses through the reproductive calendar and seasonal
changes in the quality of rangeland forage. Matching the nutrient demands of range
beef cows and the nutrients supplied by rangeland forage is a balancing act for a con-
siderable portion of each year for producers of beef cattle who depend on annual
rangelands for all or part of their yearly forage supply. This publication is intended
to supplement basic beef cow management information in the Cow-Calf Management
Guide (see Additional Reading) and will be useful to range management profession-
als, beef cattle producers, and students. Additional cow nutrition and annual range-
land forage quality information is available in Annual Rangeland Forage Quality (UC
ANR Publication 8022). In this publication we discuss the cow reproduction calen-
dar, several macro- and micronutrients and related deficiency symptoms that may
affect beef cows grazing on annual rangelands, and the potential for specific season-
al protein gaps associated with common forage sources.
THE REPRODUCTIVE CALENDAR
Time of calving. There are various ways of looking at the cow reproductive calendar,
but one of the best is to divide the 365-day beef-cow year into five stages of produc-
tion, beginning with calving (Figure 1). The herd manager determines the calendar
of operations by selecting the time of calving and thus the time of breeding. Fall calv-
ing is a common practice on California’s annual rangelands because of mild winters
with available green forage. Spring calving is common in regions with more severe
winter weather. The major factors that influence the selection of calving time include
• weather conditions
• quality and availability of range forage
• supplemental feed
• labor
• capital inputs
• calf crop production goals (i.e., calving percentage, weaning weights, calving
interval)
• relative weights of calves produced in the different calving seasons
• diseases (i.e., foothill abortion, calf scours, etc.)
UNIVERSITY OF
CALIFORNIA
Agriculture
and Natural Resources
http://anrcatalog.ucdavis.edu
California Rangelands
Research and
Information Center
http://agronomy.ucdavis.edu/
calrng/range1.htm
Balancing Beef Cow Nutrient Requirements and Seasonal Forage Quality on Annual Rangeland 2
ANR Publication 8021
RE-BREEDING
Cows must re-breed within 80 to 85 days after calving if a 365-day calving interval
is to be maintained. The reproductive year of the beef cow (Figure 1) is a very tight
schedule if management’s objective is to produce a calf each year from each cow.
Adequate nutrition is crucial to meeting this objective. The period from conception
to birth is about 283 days (Hereford 286, Angus 281). Most cows will not come into
estrus until 30 to 45 days after calving; longer if nutrition is poor. Cows come into
estrus at 21-day intervals, so it takes 42 days for a cow to become pregnant in two
services. From 365 days in a year, subtract 283 days for gestation and another 40
days before first estrus cycle after calving, and you have a window of only 42 days
(two breedings) if you are going to stay on schedule for the next year.
Period 1
45
days
Period 2
45 days
Period 3
90 days
Period 4
90 days
Period 5
90 days
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Figure 1.
Beef cow reproduction calendar.
Table 1 shows why it is so difficult to achieve a high percentage calf crop. Under
good management, cows bred after their second calf are expected to wean an 80 to
90 percent calf crop. Bred heifers that will remain in the herd must also wean a high
percentage of their calves. To successfully breed heifers at one year of age, you need
to maintain a high plane of nutrition throughout their first 2 years. While annual
range forage provides adequate nutrients during the late winter and spring (adequate
green season), forage quality in the summer and early fall (inadequate dry season) and
late fall and winter (inadequate green season) is insufficient to maintain this high
plane of nutrition. Irrigated pasture, high elevation summer range and meadows, or
supplementary feeding is usually necessary to maintain replacement heifer nutrition
at an adequate level.
Table 1. Cow herd reproductive success, death loss, and weaning rate.
Pregnancy rate Death loss Weaning rate
First Second Third Embryo Cow Calf Calves
Population service service service Open loss loss loss weaned
Cows (2nd year +) 64 20 7 9 2 2 2 85
Heifers (1st year) 55 17 8 20 4 2 4 70
Pregnancy-tested cows 68 22 10 0 2 2 2 94
Notes: 17 to 20% of cow herd is replaced annually; for every 4 bulls there are 100 cows; 25% of bulls are replaced annually
(death loss 9%, culled 16%); calves weigh 75 pounds at birth and gain 1.4 pounds (heifers) and 1.6 pounds (steers) per day
until weaning (about 45 pounds per month).
Balancing Beef Cow Nutrient Requirements and Seasonal Forage Quality on Annual Rangeland 3
ANR Publication 8021
Even if cows are checked for pregnancy after the breeding season and open cows
are sold, one is lucky to have a calf crop of more than a 94 percent. A typical cattle
operation will replace 10 to 20 percent of the cow herd each year. Bulls are general-
ly replaced at a 25 percent rate. Four bulls per 100 cows is typical. Fewer are need-
ed in intensive operations, more on rough terrain. Calves weigh about 75 pounds at
birth and typically gain 1.4 lb (heifers) and 1.6 lb (steers) per day to weaning age of
7 to 10 months, or about 45 lb per month.
Calves after weaning vary greatly in gain on the range. Most operators expect at
least 200 lb gain on a weaned calf (commonly called a stocker calf) during the green
season. Most of the gain is during the spring. Yearlings gain better on range than
freshly weaned calves.
COW CONDITION
Cow condition at the time of calving is an important factor determining how quick-
ly after calving a cow returns to estrus. By monitoring their cows’ body condition,
producers can adjust feeding levels to ensure an adequate re-breeding rate. Body
condition scoring assigns a numerical value of 1 (very thin) to 9 (very fat) depend-
ing on the degree of body fat reserves visually observed. Experience and research
have shown that mature cows should be at a condition score of 5 or 6 at calving,
while first-calf heifers and second-calf cows should be between 6 and 7. Body con-
dition scoring is discussed by Momont and Pruitt (1999) and in numerous text-
books.
COW NUTRIENT REQUIREMENTS AND FORAGE QUALITY
Nutrient requirements for a 1,000 lb cow over five stages of production are present-
ed in Table 2. The nutrients that you should consider as potentially deficient in
foothill rangelands of California are energy, protein, phosphorus, calcium, magne-
sium, sodium chloride (salt), potassium, certain trace minerals, and vitamin A
(Table 3). You can identify potential nutrient gaps in seasonal forage resources by
comparing seasonal cow nutrient requirements with seasonal forage quality. Figures
2 through 5 describe protein requirements and forage protein content to help you
identify potential protein nutrient gaps. Protein requirements for fall and spring
calving cow herds are superimposed on the forage protein content in these four fig-
ures (NRC 1984). The protein percentages in these figures are adequate only if there
is sufficient forage to meet the animals’ daily forage dry matter intake requirements.
Table 2. Nutrient requirements for a 1,000 lb beef cow.
Stage of production
Period 3: Period 4: Period 5:
Period 1: Period 2: early mid late
calving breeding gestation gestation gestation
Nutrient (45 days) (45 days) (90 days) (90 days) (90 days)
Dry matter (lb) 20.60 21.00 19.50 18.10 19.60
Protein (lb/day) 2.50 2.60 2.00 1.30 1.60
TDN (lb) 13.80 14.00 11.50 8.80 10.50
Calcium (g/day) 36.00 38.00 25.00 15.00 23.00
Phosphorus (g/day) 25.00 27.00 20.00 15.00 18.00
Vitamin A (x 1,000 IU) 37.00 38.00 36.00 25.00 31.00
Source: National Research Council 1984.
Balancing Beef Cow Nutrient Requirements and Seasonal Forage Quality on Annual Rangeland 4
ANR Publication 8021
Table 3. Nutrients that have the potential for deficiency in forage on California foothill rangelands.
Nutrient, and potential for deficiency Deficiency symptoms*
Energy
Energy, often measured as total digestible nutrients (TDN), Retarded
Net Energy for maintenance (NEm), Net Energy for gain (NEg), Delayed sexual maturity
Digestible Energy (DE), or Metabolizable Energy (ME), is the Poor conception rate
most important nutritional factor to consider for beef cows Shortened lactation period
for several reasons. It is the nutritional factor most commonly Decline in milk yield
lacking due to the shortage of forage.Were it not for energy, May be complicated by protein, mineral, and/or
the nutrient requirements of the beef cow could be met by vitamin deficiency
2–4 lb of total feed per day. Insufficient energy intake may Loss of body weight
occur when cattle are forced to graze deficient dry forage in Failure to conceive
the fall (inadequate green season).
During this period low
Lowered resistance to diseases and parasites
forage levels (<800–1,000 lb/a) and low palatability may
Increased mortality (toxic plants)
reduce intake, restricting the animals’ ability to meet their
daily dry matter requirements for energy, protein, and other
nutrients.
Protein
Protein is the nutrient most likely to be lacking in summer Reduced appetite
and fall diets when dry forage is plentiful but green forage Reduced growth rate (fetus and calf)
is not adequate. Supplemental protein for wintering cows is Loss of weight
usually the largest cash expense in the yearly costs of main- Inadequate intake of other nutrients
taining a cow. Supplements such as cottonseed and safflower Delayed estrus
oil meal are primary sources. Urea is a non-protein compound Irregular estrus
that ruminants may convert to protein with varying degrees Poor conception rate
of efficiency through the action of microorganisms in the Reduced milk production
rumen. The use of liquid supplements and blocks has increased
drastically over the past few years and will continue to
increase as research provides information in efficient formu-
lations including urea. Proper management procedures
are important when urea is fed to prevent ammonia toxicity
and to enhance urea utilization.
Calcium
Calcium usually is not a serious problem in beef cow diets. Poor growth
It seldom is deficient in California range forage. Depletion of calcium
Swollen, tender joints
Arched back
Stiffness
Deformed legs
Fractures
Phosphorus
Phosphorus may be borderline to definitely deficient in range Decreased appetite
cow diets during summer, fall, and winter periods in California. Chewing wood, bones, and hair
When high-protein and liquid supplements are fed, they Low blood phosphorus
usually supply adequate phosphorus to supplement native Stiff joints and lameness
forage. Decreased milk production
Failure to show estrus
Poor conception rates (open cows)
Retained placenta
Salt (sodium chloride)
Salt should always be provided free choice in loose-pack or Licking and chewing various objects
block form. The placement of salt away from water is a Loss of appetite
common practice for improving stock distribution and Unthrifty appearance
achieving better range utilization. Rough haircoat
Decreased milk production
Reduced gains
Lack of coordination
Weakness
Death
continued on next page
Table 3. Nutrients that have the potential for deficiency in forage on California foothill rangelands
(continued)
.
Nutrient, and potential for deficiency Deficiency symptoms*
Magnesium
Under California conditions grass tetany or hypomagnesemic Uncoordinated gait
tetany often occurs. It is a major problem, especially in Convulsions
lactating cows grazing lush, rapidly growing pastures highly Coma
fertilized with nitrogen during cool foggy or cloudy seasons. Death
Grass tetany can be prevented by providing 8 grams of
magnesium per head per day prior to onset of symptoms.
Magnesium nutrition may be complicated by addition of
urea to the diet.
Potassium
Generally, forages contain more potassium than beef cows Decreased feed intake
require. However, potassium concentration decreases with Decreased milk yield
advancing maturity of forage and can be reduced further Reduced weight gain
by leaching. Muscular weakness
Trace minerals
Deficiencies of trace minerals such as copper, zinc, iodine, Copper deficiency: Change in hair color, rough
and selenium exist in many areas of California. Trace hair coat, depression in weight gain, bone
mineral deficiencies in California are localized, and fractures, and anemic appearance. Cows coming
because their effects can be insidious and substantial, back into estrus due to early embryo death.
producers may want to obtain recommendations from
a local authority such as a Farm Advisor or veterinarian. Iodine: Goiter.
Selenium deficiencies are concentrated in northern
(especially northeastern) California. Selenium can be Selenium deficiency: White muscle disease,
administered as an injection. In deficient areas, selenium retained placentas, reduced gains, unthriftiness,
provided in supplement blocks has generally proved and diarrhea.
ineffective at the 30 ppm level.
Vitamin A
Vitamin A deficiencies occur in beef cow herds in California. Watery eyes
A cow stores up a several-months’ supply in her liver during Night blindness
the adequate green feed period, but this supply can be Scouring
depleted rapidly in a lactating cow.Vitamin A deficiencies Respiratory infection
may also occur in fall calves during dry years or in young Poor conception
cows. Supplemental vitamin A should be provided by: Abortion-shortened gestation period
1. addition to a protein supplement; Birth of dead, weak, or blind calves
2. intramuscular injection (1 million IU will last 3 months); Retained placentas
3. addition to a mineral mix. Uncoordinated calves
Poor conception rate
*Source: Merck and Co. 1998.
Balancing Beef Cow Nutrient Requirements and Seasonal Forage Quality on Annual Rangeland 5
ANR Publication 8021
Figure 2 compares forage protein content for a normal year to that for years
when the fall rains are delayed (dry fall) or the rainy season ends earlier than usual
(early dry season). These two examples result in an extended dry season character-
ized by reduced protein content in the available forage. Figure 3 compares monthly
forage protein for a normal year and for years when early fall rains result in an early
green season or extended spring rains result in a long green season. These two exam-
ples result in a longer than normal green season with higher protein contents in the
forage. Mountain meadows and irrigated pasture are two common forage alterna-
tives that are used by ranches on annual rangeland to provide summer green forage
(Figures 4 and 5). While protein content in a typical Central Valley irrigated pasture
will usually exceed cow protein requirements throughout the summer, the protein
contents of mountain meadow forage may not be adequate in the late summer and
early fall.
Balancing Beef Cow Nutrient Requirements and Seasonal Forage Quality on Annual Rangeland 6
ANR Publication 8021
Normal Year
Long Green Season
Cow-Calf (Spring Calving)
Cow-Calf (Fall Calving)
25
20
15
10
5
0
Stage of Maturity
J F MAM J J A S O N DJFMAMJJASOND
Protein (%)
late spring rains result
in a long green season
early fall rains result in
early green season
late rains result in
a dry fall
early dry season shortens
spring growing season
Normal Year
Long Dry Season
Cow-Calf (Spring Calving)
Cow-Calf (Fall Calving)
Protein (%)
Stage of Maturity
J F MAM J J A S O N DJFMAMJJASOND
5
0
10
15
20
25
Figure 2.
Examples of annual range-
land forage protein for a
normal year, a year with a
dry fall, and a year with an
early dry season, with cow
protein requirements for
fall- or spring-calving cows
superimposed.
Figure 3.
Examples of annual range-
land forage protein for a
normal year, a year with an
early green season, and a
year with a long green sea-
son, with cow protein
requirements for fall- or
spring-calving cows super-
imposed.
In addition to seasonal changes in forage quality, forage nutrient concentration
can also vary greatly across the landscape. Forage dries sooner on south-facing
slopes. Springs, seeps, and swales may remain green longer than surrounding vege-
tation. Nutrient concentration is higher in leaves and twigs from woody vegetation
than in surrounding dry forage.
Balancing Beef Cow Nutrient Requirements and Seasonal Forage Quality on Annual Rangeland 7
ANR Publication 8021
Protein (%)
Month
25
20
15
10
5
0
J F M A M J J A S O N D J F M A M
J
J
A S O
N D
Mountain Meadow Cow-Calf (Spring Calving) Cow-Calf (Fall Calving)
Mountain Meadow
Cow-Calf (Spring Calving)
Cow-Calf (Fall Calving)
Protein (%)
Month
25
20
15
10
5
0
Irrigated Pasture-CV
Cow-Calf (Spring Calving)
Cow-Calf (Fall Calving)
J F M A M J J A S O N D J F M A M J J A S O N D
Figure 5.
Example protein content for a
Central Valley cool-season irri-
gated pasture, with cow protein
requirements for fall- or spring-
calving cows superimposed.
Figure 4.
Example protein content for a
mountain meadow, with cow
protein requirements for fall- or
spring-calving cows superim-
posed.
Ruminant animals are selective grazers and seek out and remember the location
of nutrient-rich patches. Consequently, they usually select a higher-quality diet than
that represented by forage samples collected by hand. The comparisons illustrated
here are only examples of forage protein content that can in reality vary widely in
time and space. Consequently, each operation must develop its own unique range
livestock nutrition program.
Balancing Beef Cow Nutrient Requirements and Seasonal Forage Quality on Annual Rangeland 8
ANR Publication 8021
LITERATURE CITED
Merck and Co. 1998. Merck veterinary manual, 8th edition. Whitehouse Station, NJ:
Merck and Co.
Momont, P. A., and R. J. Pruitt. 1999. Condition scoring of beef cattle. In J. R. Adams
and M. W. Stellmon, coord. eds., Cow-calf management guide. Moscow, ID:
College of Agriculture, University of Idaho.
National Research Council. 1984. Nutrient requirements of beef cattle, 6th edition.
Washington, DC: National Academy of Sciences.
ADDITIONAL READING
Adams, J. R., and M. W. Stellmon, coord. eds. 1999. Cow-calf management guide.
Moscow, ID: College of Agriculture, University of Idaho.
Bruce, B., R. Torell, and B. Kvasnicka. 1999. Nutritional management of beef cows
in the Great Basin. Reno: University of Nevada, publication EB-99-01.
FOR MORE INFORMATION
You’ll find detailed information on many aspects of livestock and range management
in these titles and in other publications, slide sets, and videos from UC ANR:
Beef Rancher’s Software Package, publication 21460
California Range Brushlands and Browse Plants, publication 4010
Monitoring California’s Annual Rangeland Vegetation, publication 21486
To order these products, visit our online catalog at http://anrcatalog.ucdavis.edu.
You can also place orders by mail, phone, or FAX, or request a printed catalog of
publications, slide sets, and videos from
University of California
Division of Agriculture and Natural Resources
Communication Services
6701 San Pablo Avenue, 2nd Floor
Oakland, California 94608-1239
Telephone: 1-800-994-8849 or (510) 642-2431, FAX: (510) 643-5470
e-mail inquiries: danrcs@ucdavis.edu
An electronic version of this publication is available on the DANR Communication Services website at
http://anrcatalog.ucdavis.edu.
Publication 8021
©2001 by the Regents of the University of California
Agriculture and Natural Resources. All rights reserved.
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This publication has been anonymously peer reviewed for technical accuracy by University of California
scientists and other qualified professionals. This review process was managed by the ANR Associate Editor
for Natural Resources.
Balancing Beef Cow Nutrient Requirements and Seasonal Forage Quality on Annual Rangeland 9
ANR Publication 8021
