Effect of Varying Levels of Postpartum Nutrition and Body Condition at Calving on Subsequent Reproductive Performance in Beef Cattle23

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Abstract
Multiparous, spring-calving beef females (n = 355) were utilized during three production years to study the effects of postpartum nutritional management on subsequent fertility and calf production. At critical times in the production cycle, a body condition score (BCS), using a numerical score ranging from 1 = emaciated to 9 = extremely fat, was assigned to each animal. Cows were maintained prepartum to calve with BCS 4 to 7. Following parturition cows were allotted to 1 of 4 nutritional regimens: high (H), moderate (M), low (L) or low-flush (LF). Postpartum nutritional management had no effect on interval to estrus (ITE) or interval to pregnancy (ITP). However, mean ITE was 61 vs 49 d (P<.01) and mean ITP was 90 vs 84 d (P<.05) for cows calving with BCS ⩽4 or ⩾5, respectively. Body condition at calving was the most important factor influencing early return to estrus and pregnancy. High levels of nutrition in the postpartum period did not increase cumulative percent in estrus or pregnant if cows calved in BCS ⩾5. Within BCS ⩽4 at calving, cumulative percent exhibiting estrus by d 20, 40 and 60 of the breeding period was higher when cows were in the H, M, and LF groups. Cumulative percent pregnant by 20 d after breeding was not affected by nutritional management. However, more cows in the H, M, LF groups that calved with BCS ⩽4 became pregnant by 40 and 60 d after breeding when compared with similar cows in the L group (P<.05). Within BCS ⩽4 at calving, cows that lost weight early in the postpartum period and were flushed had a higher first service pregnancy rate than similar cows in the L group (P<.06). Cows that were fed to lose weight throughout the first 30 d of breeding (L) weaned lighter calves than cows that maintained (M) or gained (H) weight, or that were flushed (LF) during the postpartum period (P<.01). Copyright © 1986. American Society of Animal Science . Copyright 1986 by American Society of Animal Science

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