Effects of dietary iron on performance and mineral utilization in lambs fed a forage-based diet

Twenty-four lambs, averaging 29 kg, were used to determine the effect of supplemental dietary Fe on performance and Cu, P, Zn and Mn utilization. Treatments consisted of supplemental Fe at 0, 300, 600 or 1,200 mg/kg diet as ferrous carbonate. The basal diet contained 154 mg Fe/kg diet and consisted of 90% Coastal bermudagrass pellets, 9.45% group corn, .5% sodium chloride and .05% vitamin mix. Lambs were slaughtered after having ad libitum access to diets for 98 to 121 d. Dietary Fe did not affect lamb gain or feed intake. Supplemental Fe increased Fe concentrations in liver (P less than .01), spleen (P less than .01) and bone (P less than .10), but not in kidney and muscle. Serum Fe concentrations and percentage transferrin saturation in serum were increased (P less than .01) by supplemental Fe at 28 and 84 d, but not at the termination of the study. Plasma Cu was decreased (P less than .01) at 56 d, whereas serum ceruloplasmin activity was reduced (P less than .01) at 28 d in lambs fed 1,200 mg Fe/kg diet compared with lambs fed 600 mg Fe/kg diet. Lower levels of Fe (300 and 600) reduced (P less than .01) ceruloplasmin by 56 d and plasma Cu by 84 d compared with controls. Liver Cu also was decreased (P less than .05) by supplemental Fe. Plasma P was decreased slightly (P less than .10) by 28 d and significantly (P less than .01) at the other sampling dates by supplemental Fe.(ABSTRACT TRUNCATED AT 250 WORDS)