Iron and selenium supplementation of sheep

Iron deficiency and a possible interaction between iron and selenium were investigated in lambs raised under an intensive management system. Trial 1 compared 2 levels of iron dextran treatment, 0 and 500 mg Fe, using 35 lambs injected once at birth. Trial 2 involved 66 lambs and 3 levels of iron: 0, 250, and 500 mg. A third trial was replicated 3 times, using a total of 121 lambs, in order to determine if the iron treatment response was limited by the marginal Se status of the lambs. Treatments were control, +1.5 mg Se, +500 mg Fe, and 1.5 mg Se + 500 mg Fe. The parameters measured included hemoglobin, hematocrit, weight, plasma iron, and a plasma profile (Ca, P[sub i], glucose, BUN, total protein, albumin, AP, LDH and AT). Additionally, plasma Se, plasma protein fractions and disease resistance were measured in Trial 3. Injection of 500 mg Fe significantly (P<0.05) increased hemoglobin from 2 to 11 weeks of age in Trial 1, and from 1 to 8 weeks in Trial 3. While iron dosages of either 250 or 500 mg prevented the depression of hemoglobin from birth to 30 days, plasma iron and hemoglobin (P<0.05) were significantly higher at 4 weeks in lambs receiving 500 mg Fe. In all studies, a significant proportion of control lambs were anemic at 3-4 weeks of age. Preliminary information was provided on the effect of iron deficiency and other factors (breed, sex, rearing, birth weight and growth rate) on the lamb plasma profile at 4 weeks. The data indicate that iron deficiency affects plasma metabolites similarly in lambs and humans. P[sub i], glucose, cholesterol, total protein, alkaline phosphatase and aspartate transaminase responded linearly to iron dosage. Many parameters were also significantly correlated with plasma iron. The interaction of iron with selenium was significant (P<0.05) only for plasma selenium levels. Plasma selenium at 4 weeks was increased in lambs injected with selenium and not injected with iron. Means were 0.085 ppm (control), 0.086 ppm (+Fe), 0.107 ppm (+Se) and 0.088 ppm Se(+Fe+Se), with 18 to 20 lambs per treatment. Disease resistance was assessed by susceptibility of lambs to sore-mouth; hemagglutination titer to a chicken RBC antigen; and gamma globulin levels from 2 to 6 weeks. Selenium but not iron treatment influenced susceptibility of lambs to soremouth. The response of lambs to antigenic challenge from chicken RBC's was also increased (P