INFLUENCE OF DUODENAL SLAFRAMINE INFUSION ON SITE OF NUTRIENT DISAPPEARANCE FROM THE DIGESTIVE-TRACT OF STEERS FED A HIGH-CONCENTRATE

The effect of duodenal slaframine (SF) infusion on site and extent of digestion was determined using four steers equipped with ruminal, duod enal, and ileal cannulas in a 4 x 4 Latin square. A 77% dry-rolled cor n diet was provided in 12 equal portions daily at a DMI of 2.26% BW. S laframine in a .9% saline excipient was infused into the duodenum ever y 12 h with total daily doses of 0, 30, 60, or 90 mu g/kg of BW. Slafr amine infusion had no effect on ruminal pH, ruminal NH3 N, or solids a nd liquids passage rate. Slaframine increased (linear, P < .10) total tract OM and starch disappearance and digestibility and tended to incr ease (linear, P = .14) total tract N digestibility. Ruminal starch dis appearance tended to be decreased (quadratic, P = .16) by SF. Small in testinal OM digestibility was increased (linear, P < .10) but starch d igestibility in the small intestine was not affected by SF. Increased total tract starch digestibility was caused by increased (quadratic, P < .10) starch fermentation in the large intestine. Ruminal feed N dig estibility decreased at the intermediate doses of SF (quadratic; P < . 10). Total N digestibility in the small intestine tended to be increas ed (cubic, P = .13) with 30 and 90 mu g of SF/kg of BW. Decreased rumi nal feed N digestion was compensated for by increased (quadratic, P < .10) small intestinal feed N disappearance for steers treated with int ermediate doses of SF. The potential of SF to increase starch digestio n in the rumen and small intestine seems to be Limited.