Nutrition for Developing Replacement Heifers


M. H. Poore


Adequate heifer development is a key to profitable beef production. Unfortunately, due to the perceived high cost of developing heifers, many young females have a slow start in life and this impacts their lifetime productivity. The nutritional program for heifers need not be based on expensive purchased feeds, and target gains can be met easily with no, or only minimal, energy and protein supplementation. The improved profitability of calving heifers at 2 years old as compared to 3 years old has been long proven, but some producers continue to calve 3 year olds rather than provide the nutrition needed for a successful 2 year-old program. The nutritional development program is divided into stages of development which include; pre-weaning, weaning, weaning to breeding, breeding to first calving, first calving to second breeding, and the second post-calving period.

Pre-Weaning

Good management of the replacement heifer starts before birth. When producing replacement females is one of the goals of the producer, the cows should have been bred to produce offspring with a high level of maternal merit. In general for our area, they should be expected to have a mature weight of 1100 lbs, should be above average (but not excessive) in their potential for milk production, and should be near the industry standards for breed composition and carcass traits. A good development program includes starting with animals that have a high level of genetic merit.

The cow should be in good body condition (BCS 6.0) at calving which will result in a thrifty calf, and will increase the level of colostrum produced. This will improve general thrift of the calf throughout its early life. The growing calf should receive adequate nutrition to maintain a body condition of 5.0 - 6.0, which will result in an adequate weaning weight, but which will not result in an overly-fat heifer. Fat heifers have reduced milk production later in life and this condition should be avoided. While creep feeding is rarely ever recommended due to high cost and minimal returns, it is still done in some situations. This practice may result in excessively fat heifers and should be discouraged. The heifer needs to weigh at least 450 lbs at 8 months to continue through the cycle and meet the target weights without needing a high level of nutrition.

Weaning

Weaning is a time of stress, and it is a time when heifer calves can fall behind in their development. The weight loss and nutritional stress of weaning can be overcome by a good weaning program. Get the calves started on some very high quality hay as soon as they are weaned, and start them on a palatable grain mix providing the recommended level of trace minerals and an ionophore. The grain mix should contain some molasses and can contain grains and oil seed meals, or byproduct commodities. A proven formula of this type is shown in Table 1. Feeding an ingredient the calves may know how to eat (like whole cottonseed) can also help to get them to the feed bunk quickly. I like to feed high quality square baled hay in the feed troughs, and feed about 1 lb/head of the grain mix and 1 lb/head of whole cottonseed the first day. This is then increased 2 lb/head/day grain and 2 lb/head/day cottonseed, and the program continues for 4 weeks. The calves are then turned to high quality pasture, and the growing program is initiated. During the "preconditioning period" is the ideal time to complete all the vaccinations needed, depending on the program developed for the specific producer.

Post-weaning

The post weaning period goes from the end of the weaning phase to the time the heifers are bred. The growth rate during this phase should be calculated to allow heifers to reach their target weight for breeding. The growth rate can be accelerated during this period so that heifers behind in development can catch up, but the gain should not exceed 2 lb/day. Table 2 shows target weights and gains for heifers at various stages of development. The ages listed are based on the first day of the calving season, so the heifers will mostly be younger than the ages listed. These weights are shrunk weights, and are based on average body condition. Animals can be behind in their development at any point and still catch up. The most critical point is that heifers be at the desired weight for breeding, which is approximately 65% of their mature weight. At this weight, most of the heifers will have attained puberty.

The daily gain of heifers will need to be about 1.25 lb/day during this stage, and while this can often be achieved with pasture alone, typical hay or average pasture rations will require supplementation with concentrate. The supplement may need to provide protein, energy or both, and the hay should be analyzed to determine which is needed. During wintering, grazing on small grain, ryegrass, or fescue pastures will result in adequate gain. A mineral mix containing an ionophore may be used to stimulate performance if forage quality is marginal compared to the heifer's requirements.

Table 3 shows the protein, energy and mineral requirements of heifers at their different stages of development. The requirements given are from the NRC 1984 values. There is a new Beef NRC (1996) but it will take several years to develop a feel for how the new approach to determining requirements will work out.

Breeding to Calving

Heifers need to gain only about .8 lb/day from the time they are bred up until calving, and this is usually achieved on pasture alone. Again, while it seems easy to achieve this performance goal, the heifers should not be turned out and ignored before calving. The producer should take steps to improve the body condition of heifers to be 6-7 pre-calving, and should pay extra attention to mineral and vitamin A nutrition during the last trimester. If heifers are in thin body condition they should be placed on a higher level of nutrition. It is difficult to improve their condition as they approach calving, and it is especially difficult after they calve. Improving condition will improve their colostrum production and quality, will decrease their post-calving anestrous period, and will increase the livability of their calves. Some producers starve heifers to reduce birth weight, but this is not recommended. A high quality trace mineralized salt (containing zinc, copper sulfate and selenium) will generally meet their mineral requirements, while a formula containing an ionophore may be useful if attempting to improve body condition.

Calving to Rebreeding

If a well-developed heifer that calves in good body condition loses condition rapidly after calving, she still will have a less than desirable reproductive rate. Often, calving in the southeast occurs during the winter, and often the heifer faces the lowest quality forage of the year post-calving. The producer should have a well developed plan to provide the lactating first-calf heifer the highest quality hay or pasture available, and should be prepared to provide a grain supplement at a level to maintain body condition above 5.0. Heavy-milking heifers are especially prone to rapid weight loss and resulting reduced chance of cycling. While heifers are not very prone to grass tetany, it is still a good idea for the producer to use a high magnesium mineral supplement with adequate trace minerals 30 days prior to and during the first 6 months of lactation, as would be recommended for the older cows. A high quality trace mineralized salt can be used at other times. Trace mineral needs and specifications in supplements are given in Table 4.

Second Calving

When the heifer is preparing for her second calf she reaches about 90% of her mature body weight. She should be in a body condition of 5-6, and should maintain a body condition of 5 or better after calving. The heifer is still growing at this stage, especially with later maturing breeds, so they will still need a slightly higher level of nutrition than the mature cows. In general, however, if milk production is moderate and forage quality is high, the 3 year old cows can be managed successfully with the mature cows. Some producers may find it easier to group the 3 year olds with the 2 year olds, but either way it is difficult to specifically target nutrition to this group. The mineral supplement should be a high magnesium formula with adequate trace minerals, and should be provided 30 days prior to and during the first 6 months of lactation.

Summary

The development program for heifers is divided into a number of stages. Providing heifers with nutrition to meet the target gains and weights indicated will result in a high level of fertility and calf health. Providing heifers with a good start will improve the overall profitability of the beef operation, and ensuring growth is not excessive will prevent the decreased lifetime productivity related to fat heifers.

Table 1. A palatable concentrate mix for use in weaning calves to be fed at 1 to 4 lb/head/day
Ingredient % lb/ton
Ground corn 41 820
Soybean meal 5 100
Wheat midds or soyhulls 41 820
Molasses 5 100
Limestone 1 20
Complete mineral1 7 140
1Four lbs of this grain mix will provide .277 lb mineral/head/day. This is the maximum feeding rate for a mineral with 1440 g/ton ionophore. The mineral percentage of the mix should be adjusted according to the label of the product being used.

Table 2. Target weights and gains for developing replacement heifers (1996 Beef Cattle NRC).
Stage of development Age, months Target weight, lbs % of mature Target gain lbs/day
Weaning period 8 450 41 1.75
Post-weaning to breeding 9 500 45 1.25
Breeding to calving 14 684 62 .8
Calving to rebreeding 23 880 80 .4
Second breeding season 27 927 84 .4
Second calving 36 1012 92 .2

Table 3. Requirements of developing replacement heifers, 1100 lb mature size, according to the 1984 Beef Cattle NRC
Age, months DM, lb/d CP, % TDN, % Nem,
Mcal/lb
Ca, % P, %
8 - - - - - -
9 12.0 10.0 65 .68 .34 .22
14 14.5 8.2 59 .58 .25 .20
23 19.2 10.4 63 .64 .32 .23
27 20.0 10.2 62 .63 .31 .22
36 22.0 10.7 60 .61 .32 .24

Table 4. Trace Mineral Requirements of Growing Heifers
Mineral 1984
NRC1
1996
NRC
NCSU Rec.
from Suppl.2
Recommended Level in
TM Salt3
4 oz mix4 Maximum Tolerable5
Copper 8 ppm 10 ppm 15 ppm6 .50 % .13 % 100 ppm
Zinc 30 ppm 30 ppm 20 ppm .72% .18% 500 ppm
Selenium .2 ppm .1 ppm .3 ppm .01% .0026% 2 ppm
Manganese 40 ppm 40 ppm 20 ppm .72% .18% 1000 ppm
Iodine .5 ppm .5 ppm .3 ppm .01% .0026% 50 ppm
Cobalt .1 ppm .1 ppm .2 ppm .0072% .0018% 10 ppm
1Required concentration in the diet on a dry basis from either the 1984 or 1996 Beef Cattle NRC
2General recommendation from NCSU on how much of each trace mineral should be provided by the mineral mix, based on the analysis of NC forages.
3Consumed at 1 oz/hd/day.
4Supplement with target intake of 4 oz/day per animal unit.
5Maximum level that can be tolerated in the diet.
6Recommend 10 ppm for British breeds and 15 ppm for continental breeds


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Last modified March 1998
EAH Webmaster, Department of Animal Science, NCSU