Effects of prepartum supplementation levels on the performance and metabolic responses of Nellore cows in a grazing system

Abstract

This study aimed to evaluate the effects of prepartum supplementation levels on the productive and nutritional performance and metabolic responses of Nellore cows in a grazing system. Forty-four pregnant Nellore cows multiparous with an initial mean gestation time of 230 days, average initial body weight (BW) of 541 ± 19 kg, and body condition score (BCS) of 5.5 ± 1.7 were used and distributed in a completely randomized design, with four treatments and 11 cows per treatment. The treatments evaluated consisted of four supplementation levels in the prepartum period with a duration of 60 days, according to the following scheme: 0.0 (Control = CON); 0.5 (LOW); 1.0 (Medium = MED) and; 1.5 (High = HIG) kg per animal day-1 of supplement. The supplement was composed of wheat meal and urea, and formulated to contain 22% of crude protein (CP). A positive linear effect (P < 0.05) was observed on the intake of CP and CP:digested organic matter (DOM) ratio as supplementation levels were increased. In addition, a quadratic effect (P < 0.05) was detected on the intake of neutral detergent fiber corrected for ash and protein (apNDF), digested neutral detergent fiber, and DOM with increasing supplementation levels in the prepartum period, in which MED cows had higher intakes compared to CON, LOW, and HIG cows. Prepartum supplementation levels did not affect (P > 0.10) the average daily gain in the prepartum or postpartum periods and, BCS of the dams, and BW of calves at birth or 45 days of age. In the prepartum period, supplementation levels did not affect (P > 0.10) the blood concentrations of total proteins, albumin, globulins, glucose, cholesterol, triglycerides, non-esterified fatty acids, and beta-hydroxybutyrate in the experimental cows. In conclusion, the provision of 1.0 kg of supplement per animal per day during the last 60 days of pregnancy improves prepartum nutritional performance and postpartum milk production of grazing beef cows.