Effects of fertilization and yeast culture supplementation on growth performance and nitrogen balance in Nellore young bulls

We aimed to evaluate the effects of nitrogen (N) fertilization in tropical pastures and yeast culture (YC) supplementation on intake and digestibility, N use efficiency, and growth performance of Nellore young bulls during their growing phase. Treatments: 1) protein–energy supplementation at 0.3% body weight (BW) with YC (fertilized pasture 100 kg N ha-1 year-1), 2) protein–energy supplementation at 0.3% BW without YC (fertilized pasture 100 kg N-1 ha-1 year), 3) protein–energy supplementation at 0.3% BW with YC (unfertilized pasture), and 4) protein–energy supplementation at 0.3% BW without YC (unfertilized pasture). The experiment lasted 112 days and involved 60 Nellore young bulls (initial BW: 230 ± 10 kg) in a completely randomized design in a 2×2 factorial arrangement (Factor A: with/without fertilization; Factor B: with/without YC supplementation). Animals fed YC-supplemented diets consumed 145 g day-1 more crude protein, showed an additional average daily weight gain of 130 g day-1, and retained 20.4% more N (p<0.005) than animals fed diets without YC. Protein–energy supplementation at 0.3% of BW with YC addition effectively increased N retention in grazing Nellore young bulls and improved their growth performance. N fertilization in tropical pasture-based beef cattle systems, improved forage digestibility and animal production per unit area.