Supplementation levels for pre-weaning grazing beef heifers during the rainy-dry transition season

Abstract

This study was undertaken to examine production performance, pasture and milk intakes and nutrient digestibility in heifers supplemented with different levels of energy in a creep-feeding system on Urochloa decumbens Stapf pastures during the rainy-dry transition season. Fifty-one heifers with predominant Nellore genetic composition (average initial age and weight: 120 days and 133.4 ± 3.12 kg) and their respective dams were used in an evaluation of production performance, intake, and diet digestibility. Four treatments were evaluated, namely, MM - mineral mixture; T250 - 0.250 kg of supplement per head per day; T500 - 0.500 kg of supplement per head per day; and T750 - 0.750 kg of supplement per head per day, totaling three groups with 13 animals each and one group with 12 animals. All supplements were balanced to provide 100 g of CP animal-1 day-1. LIPE® and chromium oxide were used as external markers to estimate fecal excretion and individual DM and supplement intakes, respectively, whereas iNDF was used as an internal marker for pasture DM intake. Production performance did not differ between the supplemented and unsupplemented animals. Total DM intake and pasture DM intake were higher in the group supplemented with concentrate, and the same was observed for the digestibility of DM and NDFap consumed by the animals. The average cow milk yield was 5.33 kg/day, with average protein and fat contents of 3.51% and 4.85%, respectively. In conclusion, compared to the use of mineral mixture only, multiple supplementation at different levels containing 100 g of CP does not significantly improve performance in lactating beef heifers grazing on Urochloa decumbens Stapf and supplemented during the rainy-dry transition season.