EFFECT OF AFLATOXIN IN GROWING LAMBS FED RUMINALLY DEGRADABLE OR ESCAPE PROTEIN-SOURCES

Thirty-two crossbred (Suffolk x Rambouillet) wether lambs were used to examine the effectiveness of protein source (soybean meal [SBM] or fi sh meal [FM]) in alleviating decreased performance associated with die tary aflatoxin (AF) in growing lambs. After a 21-d adaptation period t o concentrate diets, lambs were assigned to the following dietary trea tments: 1) SBM, 0 mg of AF; 2) FM, 0 mg of AF; 3) SBM + 2.5 mg of AF/k g diet; or 4) FM + 2.5 mg of AF/kg diet (two lambs/pen; four pens/trea tment). Diets were fed 35 d, at which time AF was removed from the die t (except one pen/protein source) and lambs continued on study for an additional 32 d. On d 67, all lambs were killed and necropsied. Averag e daily gain, feed intake, and gain/feed were similar (P > .10) among lambs fed SBM or FM; however, lambs fed AF had lower (P < .01) feed in takes, daily gain, and gain/feed. Feed intake remained lower (P < .01) after AF was removed from the diet. Aflatoxin elevated(P < .01) aspar tate amino transferase and gamma-glutamyl transferase activities and t otal protein and cholesterol concentrations while decreasing (P < .05) alkaline phosphatase, glucose, cholinesterase, albumin, inorganic pho sphorus, iron, and total-iron-binding capacity. Hematocrit, white bloo d cell count, and prothrombin time increased (P < .01) in lambs fed AF . No AF or protein effects were seen on ruminal VFA, pH, or lymphocyte blastogenesis (P > .10). Serum constituents and hematologic measureme nts remained altered in lambs fed AF throughout the 67-d experimental period; however, they returned to levels similar to those in controls when AF was removed from the diet. Dietary AF decreased lamb performan ce and impaired liver function. No benefits were seen in lamb performa nce when FM was substituted for SBM, either with or without AF.