Effect of energy nutrition in the last third of gestation in beef cows on the productive and reproductive performance of their progeny

Doctoral thesis abstract

Abstract

The present thesis evaluated the impact of restrictive and non-restrictive energy nutrition in beef cows in the last third of gestation on the productive and reproductive performance of the progeny. In addition, the effect of consumption of low-energy diets in pregnant cows in the last third of gestation on their own productive and reproductive variables was considered. Thirty-one multiparous, fixed-time inseminated, gestating British cows were assigned on day -90 (day 0 = calving) to two levels of energy intake relative to maintenance requirements until calving: i- 125 % (ALTO; n = 15) and ii- 75 % (BAJO; n = 16). At calving, energy-restricted cows had higher concentration of non-esterified fatty acids (AGNE) (P < 0.01) and lower insulin concentration (P < 0.03) relative to unrestricted cows. During lactation, restricted cows had lower body condition (P < 0.05) and lower AGNE concentration (P = 0.05) with respect to non-restricted cows. Milk production was not significantly affected (P > 0.05) by energy restriction. Regarding the characteristics evaluated in placentas, they were not affected by the treatments. Live weight (BW), morphometry and calf behaviour at birth were not significantly affected by the treatments. In contrast, energy restriction of cows affected PV at weaning (P < 0.05) and daily liveweight gain (GD) at weaning (P < 0.05) of (F1). From weaning to puberty, the GD and PV of the (F1) was not affected by the treatments. Similarly, the variables of (F2) were not affected by the treatments. In the present study, the undernourished cows mobilized body reserves and maintained milk production. Energy-restricted cows mobilized pre- and postpartum body reserves sufficient to supply fetal and milk production demands. Possibly, breeding cows grazing native range may develop similar resilient mechanisms, at least for the conditions of the present work. Specifically, there was no evident effect on calf growth and development parameters.