Effects of feeding lasalocid and monensin on digestive tract flow and partial absorption of minerals in sheep.

: Fifteen wethers (average BW 45.0 kg), fitted with abomasal and ileal cannulas, were fed a 70% concentrate diet alone or supplemented with 23 ppm of lasalocid or 23 ppm of monensin, DM basis. Wethers were fed 398 g of DM twice daily during a 10-d preliminary period, a 10-d total collection period, and a 6-d digesta collection period. During the total collection period, feed, feces, and urine were collected daily and composited. During the digesta collection, abomasal and ileal digesta and feces were collected at 12-h intervals, advancing 2 h each day, and composited. Feeding lasalocid and monensin increased (P < .01) urinary Mg excretion 17% and 19%, respectively. Lasalocid and monensin did not alter Ca and P metabolism. Feeding lasalocid decreased (P < .05) urinary excretion of Na 29%, whereas feeding monensin tended (P < .10) to increase it, compared with sheep fed the control diet. The effects of lasalocid and monensin were different for several variables compared with controls. Lasalocid and monensin altered absorption at different sites, overall absorption, and retention of minerals in sheep.