“In situ” ruminal degradation kinetics of feed ingredients in feedlot Nellore cattle fed high concentrations of crude glycerin

Abstract

The objective of this study was to evaluate the inclusion of up to 30% crude glycerin (CG) in feedlot Nellore cattle diets and its effects on in situ ruminal degradability of dry matter, organic matter, crude protein, neutral detergent fiber, and acid detergent fiber from the feed ingredients maize, sunflower meal, soybean hulls, and maize silage. Five permanently rumen-cannulated Nellore steers (approximately 400 kg BW and 24 months old) were used for ruminal incubations. Animals were randomly assigned to one of the five treatments: G0 - (control), no CG inclusion in the diet; G7.5 - 75 g CG/kg dietary dry matter (DM); G15 - 150 g CGL/kg dietary DM; G22 - 220 g CG/kg dietary DM; and G30 - 300 g CG/kg dietary DM. Data were analyzed as a Latin square design 5 × 5. Contrasts were performed observing the significance of linear and quadratic models and significance of control treatment × glycerin treatments. Crude glycerin did not affect most of degradation parameters of DM and OM of tested ingredients, with exception of effective degradation of DM of maize silage, which was linearly decreased with the inclusion of CG (P = 0.02). The CG quadratically affected fermentation rate of CP of sunflower meal, with the greatest values 8.36 and 9.05, respectively for treatments G15 and G22.5. The degradation parameters of NDF of all the ingredients tested were linearly decreased with the inclusion of CG (P < 0.01). The inclusion of up to 30% crude glycerin in Nellore cattle diets changes “in situ” ruminal degradation kinetics of feed ingredients, highly impairing fiber fraction use.