Effect of dried distillers’ grains on nutrients digestibility and nitrogen metabolism of Nellore cattle fed non-forage diets

ABSTRACT This study was carried out to evaluate the effects of corn dried distillers’ grains (DDG) levels in non-forage diets by in vitro, in situ (0 to 50%), and in vivo (0 to 40%) trials on kinetic parameters of gas production (GP) on rumen-degradable protein (RDP) and rumen-undegradable protein (RUP) as well as on nitrogen (N) metabolism in Nellore cattle. For in vitro and in situ studies, three rumen cannulated Nellore males with body weight of 340.48 ± 22.22 kg were used. For the in vivo study, five non-castrated male Nellore cattle with an initial body weight of 355.20 ± 35.28 kg and 24 ± 3 months old were used to evaluate the effect of increasing DDG levels in non-forage diets on N metabolism by a 5 × 5 Latin square design. Experimental diets were based on ground corn, cottonseed cake, urea, mineral supplement, and increasing levels of DDG replacing ground corn. The DDG levels caused a linear decrease in GP and in vitro dry matter digestibility. The DDG presented a lower dry matter digestibility (DMD) and RDP and higher RUP than corn grain and cottonseed cake, making DDG diets present lower DMD and RDP than control. The DDG levels linearly increased the intake of crude protein, neutral detergent fiber, and ether extract, whereas non-fiber carbohydrates intake decreased and tended to decrease the DMD and organic matter digestibility. The DDG levels caused a linear increase in N intake and in total, fecal, and urinary N excretion, which was the major N excretion route, causing a quadratic drop in retained N and caused a quadratic effect on alanine aminotransferase. In contrast, triglycerides were cubically affected, and total blood protein increased. Thus, DDG levels negatively affect in vitro and in situ digestibility, increasing N intake but increasing urinary N excretion.