Digestibility of nitrogen fraction in bovines feed with nitrogen from different ration sources

Abstract

The present research work has been carried out with the aim to study the digestibility of nitrogen fractions, in animals fed with different nitrogen sources rations. The diets were supplied to Holstein steers with abomasal cannulas, with eight months of age and average weight of 187 kg, in a total of 21 animals selected at random. The experimental rations were constituted by 40% roughage (Rhodes grass hay) and 60% concentrate (corn, cotton seed meal, yeast, urea, molasses and minerals) by concentrate mixture. The utilized treatments were: RA (ration with cotton seed meal); RL (ration with yeast); RU (ration with urea). The amount of nitrogen (N) intaked in grams per day (g/day) in relation of metabolic weight (g/kgLW0.75) did not display significant differences (P > 0.05) with the change of nitrogen source of diets. Also the N present in abomasum (g/day) did not display significant differences (P > 0.05). The N apparent digestibility was superior (P < 0.05) in RU diet (53.61%) when compared to RA and RL diets (46.66 and 46.37%, respectively). RA and RL diets, despite presenting the largest amount of NNA in the abomasum (71.75 and 72.38 g/day respectively) in relation to RU diet (P < 0.05), were the ones that present the largest amounts eliminated in feaces as well (37.74 and 41.20 g/day, respectively). This fact contributed for the amounts absorbed of NNA by the intestine (g/day), which did not present significant differences between the diets (P > 0.05). The protein sources of diets intervened on the nitrogen apparent digestibility.