Most spring calving herds are preparing to wean this year’s calf crop in the coming weeks. At this time, select groups of heifers will enter into a management stage designed to turn them into productive replacement cows. This stage of production represents significant economic investment to the producer, and how well a group of heifers is managed can significantly influence their productivity and profitability in future years.
The goals of a heifer development program should include producing healthy, functional heifers that calve at an appropriate age, raise a healthy calf and rebreed early the next season.
Producers should start by targeting heifers to calve at approximately 24 months of age. Heifers that calve much earlier often lack the opportunity to fully grow and develop themselves and are more likely to have difficulty come calving time. Those that calve much later are less economically efficient and do not provide as timely a return on investment for the producer. Additionally, heifers should be scheduled to start their breeding season at least one cycle (21 days) ahead of the cowherd and should reach puberty two cycles (42 days) ahead of their breeding season, as conception rates will be higher on the third cycle as compared to the first. Heifers that breed one cycle earlier than the cowherd will, in turn, calve earlier providing two advantages. Heifers calving prior to the cowherd can more easily receive special observation and assistance as necessary. Moreover, an earlier calving means more time to resume normal cycling and to rebreed for the next season. With these goals in mind, heifers should begin puberty around 12-13 months of age in preparation for breeding at 15 months.
Genetics and nutrition are the two primary factors affecting age at puberty. Larger framed cattle with more continental breeding are likely to cycle later. Heifers should weigh approximately 60 percent of mature body weight at breeding and 80-85 percent at calving maintaining a body condition score of 6. To achieve these goals, heifers should be weighed at weaning and calculations performed to arrive at the desired rate of daily gain.  From there, rations can be designed to provide the energy and protein levels necessary for the required Average Daily Gain.
Replacement heifers should also be placed on an appropriate herd health program that allots for basic immunizations and parasite control and, in particular, includes proper vaccination against reproductive diseases.
As yearlings, heifers should be evaluated for reproductive soundness and maturity. Ideally, a yearling weight, reproductive tract score and pelvic measurement should be obtained. The information collected will allow producers to cull heifers that do not meet minimum criteria, eliminating those animals most likely to present difficulty in breeding, calving and overall performance.
Darren Loula, DVM, is a large animal veterinarian at Fair Grove Vet Service in Fair Grove, Mo.


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