Nitrogen balance in Holstein steers grazing winter oats: effect of nitrogen fertilization

SÁNCHEZ CHOPA, FEDERICO; NADIN, LAURA BEATRIZ; AGNELLI, LORENA; KUHN DA TRINDADE, JULIO; GONDA, HORACIO LEANDRO

ANIMAL PRODUCTION SCIENCE

CSIRO PUBLISHING

Lugar: Collingwood; Año: 2015

1836-5787

The present study evaluated the effect of nitrogen (N) fertilization of winter oats on whole-animal N balance (N intake, N excretion in urine and feces, N retention), partition of urinary N (purine-N derivatives and urea-N) and average daily gain (ADG) in grazing steers. The experimental area was divided in two plots (10 steers/plot), and samples were obtained in two periods (1 plot/period).The experimental area was divided in 2 plots, and each plot in 10 strips. Twenty Holstein steers (161.3 ± 7 kg of initial body weight) grazed, for 51 days, individual strips of fertilized (100 kg N/ha; N100) and non-fertilized (N0) winter oats during daylight (10 h/d). The daily individual grazing paddock was adjusted to offer 6 kg DM of green leaf?100 kg BW-1?d-1. Chemical composition of the herbage and N diurnal variation were estimated by collecting 3 samples per paddock at 8:30, 13:30 and 18:30 h, twice on each sampling period. Forage intake and in vivo digestibility were estimated by the n-alkane technique. Individual N intake was estimated using n-alkane data, the ingestive behavior data and the diurnal variation of the chemical composition of the forage. N fertilization increased N content (P