Written by Dr. Jim White and Mike John
Thursday, 01 March 2012 20:40
Feed them right early and have them at breeding weight in time
The goal for selecting replacement heifers is simple—you want them to conceive, calve early in the calving season, provide adequate milk production and produce a calf every year. But much of what makes a good replacement heifer begins long before you begin to eye the keepers. Dam nutrition has distinct and long-term implications for replacement heifers.
Heifer development is influenced by how the cow carrying the heifer was fed prior to the heifer being born. While you are familiar with the challenges of calf vigor born to dams calving thin, you might not know about studies that show how appropriate protein supplementation to late-gestation cows has a lasting effect on heifers.
Work at the University of Nebraska looked at the effects of nutrition of dams on growth and reproductive performance of their heifer calves. One group of last-trimester cows got a pound of 40-percent protein supplement three times a week, the control group didn’t. In the study, cows were managed similarly during calving and breeding. The research lasted three years—long enough for researchers to get a good look at the effects of feeding an appropriate protein supplement to late-gestation cows. Results showed that supplementing cows with protein during late gestation made for heavier heifers at weaning and breeding. Moreover, the heifers from protein-supplemented dams had higher pregnancy rates and earlier calving dates.
Aside from successful nutrition during gestation, pre-weaning management of heifer calves influences lifetime productivity. Heifers should be programmed to calve early during their first calving season. They will tend to calve early and wean heavier calves throughout their lifetime. Poorly developed heifers will fail to conceive or will calve late the first year and wean lighter calves.
Many of the heifers that calve late will be open after a limited breeding season.
With that in mind, there are several goals to work toward when developing heifers. Hopefully they will: 1) reach puberty by 12 to 14 months of age; 2) achieve high percentage for conceiving early in the breeding season; 3) be structurally large enough to minimize dystocia.
Due to the record-high value of feeder heifers and the high cost of developing replacement heifers, it makes sense to pay attention to genetic factors when selecting and breeding replacement heifers.
As stated above, selecting potential replacements from heifers born early in the calving season will make it easier to assure that they do the same when they calve.
Along those lines, the cost of using proven AI sires can be justified in the immediate added value of offspring from the insemination. And, it will pay in other ways in the future. One way this practice proves its future value is that heifers that conceive to AI have proven their ability to conceive early under a process that often has a lower conception rate than natural service. Odds are high that she will continue to do so in future years. Plus, bull calves from the AI services should be heavier and have predictable performance based on high accuracy EPDs. There are also well-documented advantages for multi-generational “stacking” of those predictable traits in future replacement heifers.
Feeding Replacement Heifers
Develop a ration geared toward adequate growth, not fattening. Given typical weaning ages, medium-frame heifers need to gain about 1.5 pounds per head daily from weaning to breeding. Large-framed continental breeds and crosses need to gain more than 1.5 pounds daily. Puberty is a function of both age and weight, so rate of gain can vary during the development period. Just make sure heifers reach the desired weight and appropriate body composition before breeding time.
To ensure that all heifers reach these weights before breeding, feed them separately from the cow herd. If possible, sort according to size. Smaller heifers require a more nutrient-dense diet and a higher rate of intake to attain target weights in the same timeframe as larger heifers. Remember that feeding replacement heifers similarly to terminal heifers will push the replacements heavier than they need to be—a costly proposition these days. Moreover, heifers that gain too fast have a tendency to have lower lifetime productivity, another costly proposition.
To determine the average daily gain needed for a group of heifers, subtract their average weight from the desired weight at breeding, and then divide by the number of days of feeding before the start of the breeding season.
Most heifers need to gain 1 to 1.5 pounds per day during the feeding period. Nutrient requirements for growing heifers to gain at these rates are listed in the nearby at right. These requirements are based on neutral conditions. Housing and other environmental conditions drastically influence the energy requirement of the animals.
Many combinations of feeds can be used for growing heifers—as long as intake and nutrient composition are appropriate. If you have to allow for error, it is better to overfeed protein than to overfeed energy. Heifers need to be grown rapidly but not fattened, so better-than-average forage should be offered. If heifers are on stockpiled pastures, they should be fed at least four to five pounds of Trendsetter Developer per head daily to attain the recommended weight gains; two to four pounds per head per day is the lower end of the feeding rate. Often, the feeding program can be divided into one of four scenarios: 1) the operation has a forage base; 2) the operation also has grain storage; 3) the operation uses grain co-products; 4) the operation uses corn or sorghum silages to develop heifers.
Taking periodic measurements of animal weight and height are helpful in determining if heifers are growing at the proper rate. Some cycling, estrus activity should be observed in the heifers by six weeks prior to the breeding season. If you don’t see estrus activity six weeks or so prior, it’s likely that the heifers are smaller than they need to be. If that’s the case, you have roughly a month to get enough weight on them so they will be cycling at breeding. If the situation arises in which you need to put on weight on a deadline, feed Full Throttle or Cattle Charge at two percent of bodyweight per head per day along with free-choice forage.
Dr. Jim White is ruminant nutritionist for MFA Incorporated. Mike John is director of MFA’s Health Track program.