By Randie Culbertson, Iowa State University
Postpartum interval (PPI) is the time between calving and rebreeding, and plays a significant role in herd reproductive efficiency. A cow's reproductive success is determined by her ability to produce a live calf, resume estrous, and rebreed within a 365-day window. Minimizing PPI can increase the reproductive success of any cow herd. The following are factors and management strategies that can influence PPI.
- Calf presence. The suckling activity of a calf can inhibit the release of hormones needed for a cow to resume estrous post-calving. Short-term calf removal 48 to 72 before breeding has been shown to hasten the resumption of estrous and increased pregnancy rates. Removing calves may not be feasible for some operations, in addition to potential influence on overall calf performance.
- Body Condition Score. Nutrition plays a critical role in PPI. The postpartum interval will increase when a cow’s nutritional requirements are unmet. Cows with a low body condition score (BCS) will have longer PPI as she has fewer body stores. A cow will prioritize nutrients for providing for the calf on the ground before she allocates those resources for the resumption of estrous. Maintaining cows at a body condition score (BCS) between 5 and 6 through calving to rebreeding can minimize PPI and increase breeding success.
- Age. Heifers have longer PPI than older cows. First, calf heifers are still growing when they calve and will prioritize growth over reproduction, resulting in a longer PPI. Feeding first calf heifers separately from the mature cows can help to minimize anestrus. Breeding heifers 2 to 3 weeks before the rest of the herd can provide the heifer a little more time to recover from calving and resume estrous.
- Dystocia. Dystocia can lead to increased PPI. Minimizing dystocia through the use of calving ease bulls, proper heifer development, and calving assistance when needed can all help reduce dystocia and PPI.
- Bull stimulation. The presence of a bull has been shown to decrease PPI. Cows exposed to bulls 40 days after calving have demonstrated the best results. Fence line exposure is as effective as having bulls mixed in with the cow herd.
- Estrous synchronization. The use of progestin estrous synchronization protocols will initiate estrous cycles, and timed AI protocols have been shown to increase the proportion of anestrous cows to cycle and become pregnant.
Source: Iowa State Univeristy