Performance, metabolic and hormonal responses of grazing Nellore cows to an energy-protein supplementation during the pre-partum phase.

Abstract

BACKGROUND: Supplementation programs for prepartum beef cows are usually adopted because the nutritional status of the cows upon calving is a main factor impacting reproductive performance of the next production cycle. This study evaluated the effects of 60-d pre-partum energy-protein supplementation on performance, metabolic and hormonal responses during the peripartum phase of grazing beef cows. Thirty-eight pregnant multiparous Nellore cows were assigned to a completely randomized design with two treatments: control (no supplement) and supplementation (1.5&#x2009;kg of energy-protein per d with 30% crude protein, dry matter basis). RESULTS: The supplemented cows had higher ADG pre-partum (P&#x2009;<&#x2009;0.10), but postpartum ADG did not differ between treatments. Supplementation did not affect BCS and calf BW upon calving, on days 45 and 90, milk yield and composition (P&#x2009;>&#x2009;0.10). No differences were found for forage intake and neutral detergent fiber digestibility (P&#x2009;>&#x2009;0.10). The intake and digestibility of CP and OM increased in response to supplementation (P&#x2009;<&#x2009;0.10). An interaction occurred between supplementation and peripartum days for BUN, &#x3b2;HB, T3 and T4, which had higher concentrations for supplemented cows at pre-partum period (P&#x2009;<&#x2009;0.10). Concentration of others blood parameters significantly changed along peripartum days (P&#x2009;<&#x2009;0.10). There was no difference in pregnancy rates and days from calving to conception between treatments (P&#x2009;>&#x2009;0.10). CONCLUSIONS: Providing an energy and protein supplement to grazing Nellore cows over the last 60 d of gestation improved their pre-partum energy balance. However, no post-partum carryover effects were detected.