Effects of Precalving Feed Level on Birth Weight, Calving Difficulty and Subsequent Fertility

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Abstract
Two studies were conducted to determine effects of precalving feed level on calf birth weight, calving difficulty and subsequent fertility of the dam. Pregnant dams were held in drylots and fed a low (3.2 or 3.4 kg TDN) or high (6.3 or 6.4 kg TDN) daily feed level for 90 days before calving. Rations fed in drylot immediately postcalving ranged from 7.6 to 8.6 kg TDN content. Lactating dams grazed common pastures after the drylot phase and were bred by artificial insemination during a 45-day breeding season. High gestation feed levels increased calf birth weights (P<.10 to P<.05) but had no significant effects on either incidence or severity of calving difficulty (all P>.10). Dams receiving the high feed levels before calving had shorter postpartum intervals (P<.05 to P<.01), greater numbers exhibiting estrus before the breeding season (P<.01) and tended to have a higher fall pregnancy rate (P≅.10). A negative relationship between day of year calved and length of the postpartum interval was noted (P<08 to P<05). Copyright © 1978. American Society of Animal Science . Copyright 1978 by American Society of Animal Science.

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