EFFECT OF ROASTING ON SITE AND EXTENT OF DIGESTION OF SOYBEAN-MEAL BY SHEEP .2. DIGESTION OF ARTIFACTS OF HEATING

Six mature wethers (BW 72 kg) with ruminal, duodenal, and ileal cannulas were fed a basal (no added soybean meal [SBM]) diet or diets containing unheated SBM or SBM roasted at 165 degrees C for 75, 150, 180 or 210 min in a 6 x 6 Latin square experiment. Concentrations of indicators of heat exposure (NDF, ADF, and ADIN) in SBM increased with increasing roasting time. Organic matter digestion characteristics were not affected (P >.05) by supplementation or roasting of SBM. Daily intakes of NDF, ADF, and ADIN were higher (P <.05) when wethers were fed SBM-containing diets than when they were fed the basal diet and also were higher (P <.05) when wethers were fed diets containing roasted SBM than when fed the diet containing unheated SBM. Roasting time of SBM had a quadratic effect (P <.05) on intakes of NDF, ADF, and ADIN, with the lowest intakes observed for diets containing unheated SBM or SBM roasted for 75 min and the highest intakes observed for diets containing SBM roasted for 180 or 210 min. Disappearance of ADF in the stomach (grams per day) was not affected by supplementation or roasting of SBM. Disappearance of NDF and ADIN in the stomach (grams per day) were higher (P <.05) when wethers were fed SBM-containing diets than when they were fed the basal diet and also were higher (P <.05) when wethers were fed diets containing roasted SBM than when they were fed those containing unheated SBM. Disappearance of NDF and ADIN in the stomach (grams per day) increased (P <.05) linearly with increasing roasting time of SBM. Disappearance of NDF, ADF, and ADIN in the stomach (percentages of intake) were not affected (P >.05) by supplementation or roasting of SBM. Disappearance of NDF, ADF, and ADIN in the total tract (grams per day) were higher (P <.05) when wethers were fed SBM-containing diets than when they were fed the basal diet and also were higher (P <.05) when wethers were fed diets containing roasted SBM rather than those containing unheated SBM. Disappearance of NDF and ADIN in the total tract (percentages of intake) followed trends similar to those expressed as grams per day. It seems that, as concentrations of NDF, ADF, and ADIN in SBM increased due to heating, disappearance of these heating indices in the total tract also increased, the greatest proportion disappearing in the stomach.