Postnatal Growth, Feeding Behavior and Sexual Development of Prenatally Stressed Brahman Bulls

We attempted to manipulate fetal development and performance of Brahman calves by subjecting gestating mothers to prenatal stress or late gestation and early lactation yeast cell wall supplementation. The following objectives were pursued the effect of yeast cell wall supplementation during late gestation and early lactation on cow performance and calf growth and white blood cells. Additionally, the effect of prenatal stress and postnatal temperament on feeding behavior and sexual development at first sperm, puberty and sexual maturity in in post-weaning Brahman bulls.

Pregnant Brahman cows were assigned to a control (n=42; C) or transport group (n=43; PNS, to receive transportation stress during gestation). Bulls were selected at weaning for these studies and temperament was measured. PNS bulls were heavier at first sperm (P=0.04). Control bulls had a greater scrotal circumference per 100 kg of body weight (P=0.05), indicating the PNS bulls had slower development based on body weight at first sperm. Temperamental bulls had a greater (P>0.01) time interval (69.25 ? 10.73 d) from puberty to sexual maturity than calm (27.21 ? 6.05 d) or intermediate bulls (38.60 ? 9.05 d). Additionally, a GrowSafe system was used to record feeding behavior. PNS bulls had a great head-down time per meal and average meal size. Temperamental bulls had a greater number of visits, meal events, head-down time and head-down time per meal than calm or intermediate.

Yeast supplementation did not affect cow prepartum or postpartum performance or the postpartum interval. Calf birth weight was not affected; however, control males on d 14 and weaning tended to be heavier (P=0.08, 0.07, respectively). Treatment did not affect the white blood cell profile of calves on d 0 or 28 (P>0.2).

From the experiments we concluded that yeast cell wall supplementation of late gestating and early lactating cows did not affect cow or calf performance, temperament affected feeding behavior in a bunk feed system; therefore, temperament should be considered in the design of future feeding studies and prenatal stress and postnatal temperament cause delays in sexual development in bulls; therefore, prenatal conditions need to be evaluated and considered when determining potential future reproductive performance.