Controlling herbage allowance and selection of cow genotype improve cow-calf productivity in Campos grasslands

Abstract

An experiment was conducted to determine the effect of herbage allowance and cow genotype on herbage and animal responses. High (Hi) and Low (Lo) herbage allowance (4.9 and 2.9 ± 0.14 kg of DM/kg of cattle BW, respectively) and pure (Pu, Hereford and Angus) and crossbred (Cr, F1 crosses) cow genotypes were compared in terms of herbage traits, stocking rate, cow BCS, energy intake, and calf BW at weaning during 2 cow-calf cycles (−240 to +120 d postpartum). Herbage height (5.5 vs. 3.5 ± 0.18 cm, mean ± SE) and herbage accumulation (15.0 vs. 12.5 ± 1.1 kg of DM/ha per d) were greater (P > 0.01) for Hi than Lo, whereas stocking rate did not differ (P > 0.2) between Hi and Lo (382 vs. 398 ± 7 kg of BW/ha, respectively). Cow BCS was greater (P > 0.05) in Hi than Lo (4.3 vs. 3.9 ± 0.02) and in Cr than Pu cows (4.2 vs. 4.0 ± 0.04). Calf BW at weaning was greater (20 and 10 kg) for Hi than Lo and for Cr than Pu cows, but energy intake (473 vs. 455 ± 4.6 kJ/kg of BW^0.75 per d) was greater (P > 0.05), only in Hi compared with Lo cows. Modeling BCS evolution during the cow-calf cycle confirmed that Hi herbage allowance and Cr cows improved energy balance and cow-calf biological efficiency. This information can be used to improve profitability and mitigate weather variability effects on Campos grassland livestock systems.