Effect of aflatoxin in growing lambs fed ruminally degradable or escape protein sources

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Abstract
Thirty-two crossbred (Suffolk × Rambouillet) wether lambs were used to examine the effectiveness of protein source (soybean meal [SBM] or fish meal [FM]) in alleviating decreased performance associated with dietary aflatoxin (AF) in growing lambs. After a 21-d adaptation period to concentrate diets, lambs were assigned to the following dietary treatments: 1) SBM, 0 mg of AF; 2) FM, 0 mg of AF; 3) SBM + 2.5 mg of AF/kg diet; or 4) FM + 2.5 mg of AF/kg diet (two lambs/pen; four pens/treatment). Diets were fed 35 d, at which time AF was removed from the diet (except one pen/protein source) and lambs continued on study for an additional 32 d. On d 67, all lambs were killed and necropsied. Average 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 intakes, daily gain, and gain/feed. Feed intake remained lower (P < .01) after AF was removed from the diet. Aflatoxin elevated (P < .01) aspartate amino transferase and gamma-glutamyl transferase activities and total protein and cholesterol concentrations while decreasing (P < .05) alkaline phosphatase, glucose, Cholinesterase, albumin, inorganic phosphorus, iron, and total-iron-binding capacity. Hematocrit, white blood cell count, and prothrombin time increased (P < .01) in lambs fed AF. No AF or protein effects were seen on ruminai VFA, pH, or lymphocyte blastogenesis (P > .10). Serum constituents and hematologic measurements 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 performance and impaired liver function. No benefits were seen in lamb performance when FM was substituted for SBM, either with or without AF.

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