Symposium Paper: Post-Calving Nutrition and Management Programs for Two-Year-Old Beef Cows

When managed in the same contemporary group, first service conception rates are similar among primiparous and multiparous cows. However, increased postpartum intervals to first estrus (PPI) and decreased pregnancy rates are typical of primiparous cows compared with multiparous cows. Consequently, considerable time, effort, and feed resources go into achieving acceptable pregnancy rates of primiparous cows. Numerous postpartum management and nutritional strategies have been evaluated to improve reproductive performance of primiparous cows. The more extensively studied strategies include early weaning, positive postpartum energy balance, lipid supplementation, undegraded intake protein (UIP) supplementation, and prebreeding bull exposure. Early weaning calves at 6 to 8 wk of age substantially increases pregnancy rates and decreases PPI in primiparous cows. This improvement is mostly due to increased gonadotropin secretion and reduced nutrient requirements of the cow. Postpartum energy restriction increases PPI and decreases conception rate, regardless of parity. In contrast, positive postpartum energy balance reduces PPI, increases conception rate, or does both in primiparous cows. Neither postpartum lipid nor UIP supplementation has consistently improved reproductive performance of primiparous cows. Prebreeding bull exposure decreases PPI and may increase first service conception rate in primiparous cows. Although early weaning and prebreeding bull exposure are effective strategies to improve reproductive performance, managing primiparous cows to calve at a body condition score of ≥6 (1 = emaciated to 9=obese) and providing adequate nutrition postpartum to minimize loss of BW and body condition have the greatest impact on reproductive success. Many of the management interventions discussed in this review need to be evaluated in a systems and economic context.