Effect of protein source and level of urea supplementation on performance and rumen fermentation dynamics in feedlot lambs

Abstract

determine to what extent it can replace a natural protein source without negatively affecting feedlot performance and rumen fermentation dynamics of lambs. The treatments were 0% urea (control), 0.42% urea, 0.83% urea, 1.25% urea and 1.66% urea. Experiment one was a feedlot study and experiment two a rumen fermentation and digestibility study. Results from experiment one showed that there was a linear decrease in dry matter intake as the levels of urea increased. The 0% urea treatment had the highest average daily gain (0.309kg/lamb/day) and the 1.66% treatment had the best feed conversion ratio of 5.63. The higher inclusion of natural protein in the 0% and 0.42% urea treatments resulted in higher cold carcass weight. In experiment two the dry matter, organic matter, crude protein and energy apparent digestibility coefficients were lower for the 0% urea compared to the 1.66% urea. The 1.25% urea treatment had the lowest average rumen pH of 5.35, and the 0% urea had the lowest average rumen ammonia nitrogen concentration of 13.09. The results suggest that urea can be included up to 1.66% of total diet dry matter in finishing lamb diets without having a depressed dry matter intake, growth performance, digestibility and fermentation of certain rumen parameters of sheep.