Rebreeding performance of the first calf heifer has major economic consequences. This classification of breeding animal is often the most challenging to manage for reproductive efficiency, primarily because this animal is not only subject to the stresses of calving and lactation for the first time but she is also still growing. Failure to rebreed after birth of the first calf is one of the primary reasons for culling in a beef cattle operation in the Western United States. There is a considerable amount of money invested in this animal and high replacement rates can greatly decrease the profitability of a beef cattle operation.
A sound herd health program is an essential part of any reproductive management system. Cattle are susceptible to a variety of diseases which are detrimental to reproduction. All herd health programs should be implemented under the supervision of a qualified, licensed veterinarian. A relationship exists between poor nutrition and increased incidence of herd health problems. Several vitamins and minerals are necessary for immune system function and nutrient deficiencies in these areas can result in an increased susceptibility to disease.
Breed heifers to calve earlier than the cow herd
Properly developed and managed beef heifers generally have a 20-30 day longer postpartum interval (interval from calving until fertile estrus) than older cows. The practice of breeding virgin heifers 20-30 days earlier than the cow herd will allow the heifer additional time to return to estrus and rebreed with the older cows the next year. It is important to manage these heifers separately for two reasons; 1) earlier calving will likely mean that pastures are not available as soon and additional nutrients will need to be supplied, and 2) nutrient requirements (% of ration) are higher for 1st calf heifers than for mature cows. Breeding heifers early will be of no benefit if they are not properly managed after calving.
Minimize the postpartum interval
The period from calving until the cow conceives is a very critical period in a cow's production cycle, minimizing this time period is critical for maximizing reproductive and economic efficiency of a beef cattle operation. Cows that cycle early in the breeding season have more opportunities to become pregnant during a limited breeding season. Keeping other factors constant such as genetics, age of dam and nutrition, cows conceiving early in the breeding season will have older calves that will have heavier weaning weights. The length of breeding season will influence uniformity of calves and their value at weaning. In order to have a successful, short breeding season, it is vital that cattle cycle and conceive early in the breeding season. The ability to minimize the postpartum interval is limited by uterine involution, which is the time needed for repair of the reproductive tract so another pregnancy can be established. Uterine involution generally occurs within 30 days postpartum and does not generally limit cyclicity; however, factors such as malnutrition, disease and calving difficulty will delay normal involution.