Production and quality of ryegrass pasture with different nitrogen fertilization levels and its influence in the performance of lambs

The effect of nitrogen levels (0, 75, 150, and 225 kg ha-1) in broadcast application on the production and quality of ryegrass pasture as well as lamb production was evaluated. Thirty-six matrices and 60 lambs were maintained in continuous grazing for 112 days. A randomized complete block design with a factorial arrangement 4 (nitrogen levels) x 6 (evaluation dates) for forage evaluation, and 4 (nitrogen levels) x 7 (evaluation dates) for animal performance with 3 replications was used. Forage mass production was positively influenced by nitrogen fertilization, which had increase of 32% compared to the absence of fertilization. Animal stocking and weight gain of lambs had increase of 136% with application of 225 kg ha-1 of nitrogen compared to no application of nitrogen. Crude protein and mineral material increased whereas acid detergent fiber, neutral detergent fiber and dry mass decreased, which maintained the quality of forage longer. The highest ruminal disappearance rate of neutral detergent fiber and dry mass occurred with application of 150 kg ha-1of nitrogen. The results of this study, nitrogen fertilization enables the use of ryegrass as exclusive source for animal feed, because it provided increase in production and quality of forage as well as animal gain.