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.