Effects of prepartum protein nutrition and birth weight on basal metabolism in bovine neonates.

Recipient beef heifers, pregnant with single demi-embryos, were paired to according to identical twin or full-sib embryo. Within pair, recipient heifers were assigned to one of two isocaloric diets containing a control or restricted level of protein (91 vs 55% of National Research Council recommendations) on d 190 of gestation. Following parturition, calves were weighed, fed 1 liter of colostrum, dried and placed in a metabolic chamber at 5 h of age for an 8-h determination of heat production (HP). Maternal body weight gains (P less than .001) during the last trimester and body condition scores at parturition (P less than .05) were reduced in heifers fed the protein-restricted diet. Calves born to heifers fed the protein-restricted diet had 11.4% lower (P less than .05) HP than calves born to control heifers (43.7 vs 49.3 kcal.kg-1.d-1). Birth weights, respiratory quotients and rectal temperatures of newborn calves were not significantly affected by prepartum protein restriction. Within treatment groups, the relationship between HP and weight was described by the equation: HP (kcal/d) = 2.30 wt1.86. The allometric exponent of 1.86 +/- .26 implied that weight-specific metabolic rate was higher rather than lower in larger weight calves. We concluded that the thermogenic ability of neonatal calves may be compromised by prepartum protein restriction and(or) small birth weights.