In situ evaluation of dried distillers grains (DDG) and of diets containing different levels of DDG inclusion replacing soybean meal, urea and corn, and development of alternative methods to estimate in vivo digestibility of diets

This study aimed to evaluate ruminal in situ degradation of diets containing different levels of dried distillers grains (DDG) replacing soybean meal, urea and corn and the effect of these diets on in situ ruminal degradation of DDG, and to propose alternative methods to estimate in vivo digestibility of diets. Four rumen-cannulated Nellore bulls were used in a 4 × 4 Latin square design, for both in situ incubation and in vivo digestibility. We evaluated the following treatments: diet without DDG (D0) or containing 150 (D150), 300 (D300), or 450 g/kg (D450) of inclusion. For in situ evaluation, DDG was incubated in all animals, and diets only in those fed with the same diet that would be incubated. To estimate in vivo digestibility, three days of total feces collection were performed in each period. Data was analysed in PROC MIXED, PROC NLIN and PROC REG of SAS (version 9.4, SAS Institute Inc., Cary, NC, USA). There was no effect of diet on the in situ degradation parameters of the DDG (P > 0.05). However, for the diets, the readily soluble fraction (parameter "a") (P