Production from first-calf beef heifers fed a maintenance or low level of prepartum nutrition and ruminally undegradable or degradable protein postpartum.

Two experiments were conducted in consecutive years to determine the effects of prepartum nutrient level and postpm ruminally undegraded protein intake on nutrient status, milk production, subsequent calf production, and reproductive performance of 126 crossbred, primiparous beef heifers. Prepartum treatments were low nutrient intake (LN) (approximately 2.5 kg of TDN, .5 kg of CP anirnal-l.d-' and maintenance nutrient intake (MN) (5 kg of TDN, 1 kg of CP animat'.d-'), which were fed for 75 d before parturition. Two postpartum protein supplements were formulated to provide 250 g/d of ruminally degradable protein (RD) and one to supply ruminally undegaded protein (UD) at 250 g/d of additional UD CP compared to the RD supplement. Cholesterol was lower (P .11) as a result of L;N, MN, UD, or RD. Postpartum cow weight gain was greatest (P < .01) for UD and LN heifers. The percentage of heifers bred during the first estrous cycle of the breeding season was greater (P < .02) for UD than for RD. Overall, prepartum nutrition did not interact with postpartum protein supplement, nor did it have any effect on postpamUn interval, whereas UD increased cow weight gain postpartum and reduced postpartum interval.