Meeting Nutritional Requirements of Developing Heifers
A majority of the factors that affect the attainment of puberty in replacement heifers can be managed through nutrition. When developing a feeding program, there are several factors that should be considered to ensure that puberty is reached prior to the breeding season, allowing heifers the opportunity to maximize their reproductive potential.
First a producer must estimate pounds of gain needed to reach percentage of mature weight at puberty. Studies have shown that different breeds of cattle reach puberty at different stages of maturity. Specifically, British cattle should weigh at least 65 percent of mature body weight, and Brahman cross cattle should weigh at least 70 percent of mature body weight. .
A diet should then be developed to help heifers reach the average daily gain necessary to reach puberty at the beginning of the breeding season. Energy (TDN) and protein will be the two main nutrients that will be considered when balancing a ration, while not overlooking the importance of vitamins and minerals.
If there are sizable differences in the size and weight of heifers, they should be sorted into feeding groups so that feeding programs can be specifically targeted to that group of heifers. Monitoring growth with periodic weighing will tell how well heifers are growing on specific rations. Thin or over-conditioned heifers should be avoided. Visual appraisal of heifer body condition can also be important in making adjustments to the feeding program. Research has indicated that over-conditioning replacement heifers can impair future milking ability and, if continued, could also result in increased calving difficulty.
While it is well established how much heifers need to gain during the development phase, research has shown that the time and rate of gain can be altered. Typically heifers are fed to gain at a consistent rate throughout the development phase; however research has shown that heifers gaining 2.5 lbs. the last 60 days compared to those gaining 1.5 lbs. throughout the entire period had no difference in reproductive performance while reducing feeding costs. If altering the time and rate of gain is something producers are considering, heifers should be weighed at least 60 days prior to the breeding season to ensure benchmarks are being met and puberty will be attained.
Ionophores have proven to be a useful tool in many heifer diets. Feeding an ionophore alters the microbial population of the rumen and will improve feed efficiency. If properly used it can increase gains of replacement heifers and has been shown to help decrease the age at which puberty is reached by 14 to 28 days.
Developing a successful feeding program for a herd of replacement heifers is critical for their future reproductive success. While it seems like a complex feat to tackle, by planning ahead and understanding the benchmarks that must be met, and how to manage the attainment of puberty, producers can help secure their success.