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New Mexico State University

Nutrition for the Beef Cow

Guide B-213

Larry Foster, Extension Livestock Specialist

Nutrition plays a key role to ensure that each cow gives birth to a strong, healthy calf and rebreeds every year within approximately 80 days of year. An inadequate nutrition program may result in a low percent calf crop, late calving and decreased weaning weights. Too much supplementation can lower profits because of excess costs and perhaps decreased longevity of cows in the herd.

New Mexico cows primarily graze on the range year-round, with the bulk of the calves born in early spring. A mature cow in average condition can lose 10-15 % of her body weight from weaning to just after calving and still reproduce satisfactorily if she gets ample feed in the spring to initiate estrus early in the breeding season.

The state is often dry in the spring, when ample nutrition is critical for cows to breed. Supplementation becomes crucial in years when the quantity and quality of forage is low. Achieving a short calving season of 45-60 days may be difficult to maintain because of frequent droughts. Under New Mexico conditions, it is probably more practical to plan for a 70-100-day breeding season. In either case, planned breeding and calving seasons are essential for intensive cow herd management.

When calves are sold at weaning, more emphasis is needed on management and nutrition to increase weights than when calves are carried over and sold as yearling feeders. Earlier birth dates, a short calving period and a higher milking cow all help produce heavier weaning weights on calves. These also require more feed and emphasize the need for a well-planned nutritional program.

STAGE OF PRODUCTION

A cow's nutrient needs are largely determined by her stage of production. A production cycle, or cow year, can be divided into four stages: (1) calving to breeding--70-80 days; (2) breeding to weaning--approximately 120 days; (3) mid-gestation--approximately 100 days; (4) late gestation--60-70 days.

Calving to breeding. This is the most critical period with regard to a cow's nutritional requirements. She is producing milk at her highest level 3-4 weeks postpartum through breeding, while her reproductive system is recovering from her past pregnancy. Cows that lose weight during this period have lower first-service conception rates than cows that gain some weight. Lower first-service conception rates result in longer calving intervals. A cow's weight loss at this time also decreases the weaning weight of the calf.

Breeding to weaning. Milk production declines during this period, lessening a cow's nutritional requirements. She generally gains weight (with summer grass), and the most serious effect of poor feed is lowered weaning weights. Nutrition rarely affects the developing fetus at this stage.

Mid-gestation with the calf weaned. In this stage a cow requires little other than enough feed to maintain her own weight. Requirements for the fetus are small in terms of nutrient requirements. Cows entering this stage in average or better condition can lose weight (up to 10-15% of post-calving weight) without damage. Cows can use lower quality feeds during this period without affecting production.

Late gestation. The total liveweight of a pregnant cow in late gestation includes the maternal weight plus the fetus and associated components (membranes and fluids). During this period, the fetus and associated components gain approximately one pound per day. Thus, a cow must gain nearly a pound a day just to maintain her own maternal weight during late gestation. Cows losing weight during this period take longer to start cycling after calving and may have lowered conception rates. If supplementation is needed, it should begin during this period to ensure the birth of strong, healthy calves and early rebreeding of cows.

AGE OF COWS

Nutrient requirements of young developing heifers differ from those of older cows, so they should be handled separately until good grass is available. Because they are still growing, yearling heifers need higher percentages of protein, energy, calcium, and phosphorus in their diets than older cows, both before and after calving. Further, older cows may force younger heifers away from feed, which is another reason for separation. Yearling heifers, two-year-old bred heifers and thin older bred cows might be handled together to avoid numerous small groups of cattle.

NUTRIENT REQUIREMENTS

Nutrient requirements during various production stages of heifers calving as two-year-olds and cows calving as three-year-olds and older are shown in table 1. Range cattle are seldom fed a complete ration; thus, to decide what supplement to feed, one must estimate the dry matter intake on the range as well as the quality of forage.

Table 1. Nutrient requirements of heifers and cows
(percentage of ration dry matter)

			Calving 
			to breeding	Mid		Late. 
			aver. milk1	Pregnancy2	Pregnancy3
________________________________________________________________________
Heifers-calving as 2's			
  Protein (%)		9.5 - 10.8	8.0		8.5 - 9.0
  TDN (%)		63 - 65		48 - 52		52 - 58
  Calcium (%)		.34		.20		.20 - .23
  Phosphorus (%)	.24		.20		.20 - .23

Cows-calving as 3's or older
  Protein (%)		9.6		7.0		7.9
  TDN (%)		56 - 58		48 - 49		50 - 54
  Calcium (%)		.28 		.18		.26
  Phosphorus (%)	.22		.18		.21
________________________________________________________________________
1.Heifers fed the higher levels of protein and TDN should gain .5 lb daily; 
cows should gain some weight.
2.Heifers should make some gain; cows will usually lose weight on lower levels 
of TDN.
3.Heifers fed higher levels should gain .5 lb daily in addition to fetal weight gain;
 cows should gain fetal weight.

Table 2. Approximate daily dry matter intake of beef cows and yearling heifers1

________________________________________________________________________
Cow		Mid			Late
Weight2		Gestation		Gestation		Lactating
________________________________________________________________________
(lbs)		(lbs)			(lbs)		(lbs)
 700		14.0			15.0		18.5
 800		15.0			16.0		20.0
 900		16.5			17.5		21.5
1000		18.0			19.0		23.0
1100		19.0			20.0		24.0
1200		20.0			21.0		25.0
1300		21.5			22.5		26.0
1400		23.0			24.0		27.0
________________________________________________________________________
1.Fed rations meeting nutrient requirements shown in table 1.
2.Fall weight taken near time calves are weaned.

Table 2 shows the estimated dry matter intake for different weights of cows and heifers.

Samples of stored forage such as hay can be analyzed, making it possible to estimate supplemental needs fairly accurately. Analyzing forage for grazing livestock is much more difficult, however, because of the variation of forage available and the animal's preference for the most nutritious plants or plant parts.

Unfortunately, no single range supplement will do the job for all ranchers all the time. Supplemental programs should be varied, depending on the class, condition, age and reproductive status of the animal to be fed as well as the quality and quantity of forage available. In different years, different supplements may be needed in varying amounts.

Most cow herds are grazed yearlong in New Mexico. Some general guides for supplementing these herds are based on current understanding of nutritional requirements, previous experience, and research for developing programs. These guides, which you can use in developing your supplement program, include the following:

Energy Nutrition

  • Winter range and low-quality harvested forages usually provide adequate energy for bred mature cows, if the range or forages are available in adequate quantities. Under these conditions, protein is more likely to be deficient with yearling heifers likely to be deficient in both energy and protein, generally needing to be supplemented.
  • hen grass is in short supply during or following a drought, energy is most likely to be deficient. A supplement containing more energy relative to the protein should be fed, e.g., a 20% protein "high energy" supplement.
  • Feeding plant protein supplements with low-quality forage may improve energy nutrition of the cow more than feeding small amounts of grain. Supplemental protein increases digestibility and intake of low-quality forages and supplies some supplemental energy, whereas small amounts of grain without protein supplementation tend to cause decreased forage digestibility and intake.
  • Grain fed as a supplement to high-quality, high-protein hays or to low-quality forages that are adequately supplemented with protein improves energy nutrition of the animal. Where severe shortages of forage exist, grain can be fed to meet energy requirements, as long as 3-5 pounds of forage are fed for each cow daily.

Protein Nutrition

  • Protein is most apt to be limited in New Mexico for growing cattle or lactating cows during the spring and early summer. Data from studies at Fort Stanton Experimental Range indicate that mature cows do not need supplemental protein, provided there is adequate variety and supply of forage. Drought years are an exception--growing cattle and first-calf heifers should be supplemented during the dormant season and drought.
  • Protein is needed to provide adequate nitrogen for the functioning of rumen bacteria. Protein supplementation can increase the digestibility and intake of low quality forages, so that the energy provided in these forages is used more efficiently.
  • Protein supplements, including legume hay, appear to be as effective when fed two or three times weekly as when fed daily. When these supplements are fed less frequently, timid cows are more likely to get their share, because greater amounts are fed at one time and "boss" cows have fewer opportunities to consume more than their share of the feed. Also, cows may graze more when supplemented at 2- and 3-day intervals.
  • Cottonseed meal and alfalfa (as a supplement) are two of the better supplemental sources for protein.

Mineral Nutrition

  • Phosphorus is the only mineral that is consistently deficient for range cows in New Mexico. It is deficient nearly year-round except during periods of rapid lush growth of new grass in July and August.
  • Supplemental phosphorus can be provided in a protein supplement, a mineral supplement, or a salt-mineral mix. A commercial mineral mix should contain a minimum of 6% percent phosphorous and should be fed with no other salt available to insure adequate phosphorus intake. A mixture of 45% salt, 50% phosphorus source and 5% cottonseed meal makes a good mix. Phosphorus sources include dicalcium phosphate, bonemeal and defluorinated rock phosphate, all offering similar amounts of phosphorus for beef cattle.
  • In areas of New Mexico where crested wheatgrass is prevalent, magnesium supplementation is needed for prevention of grass tetany.
  • Trace minerals are seldom needed but are usually supplied at low cost in commercial supplements.
  • Calcium:phosphorus ratios are not the problem in beef cattle that they are in non-ruminants. Normally there is little to worry about unless the calcium-to-phosphorus ratio exceeds 3:1 in a supplement (three times as much calcium as phosphorus). Amounts are listed on the feed tag.

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Written:March 1993
Last Modified:
Placed on Server: Nov. 20, 1995