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Iron and selenium supplementation of sheep

University of British Columbia

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<0.05) by Se treatment at birth, even though by the time of initial challenge at k weeks, plasma Se was only slightly higher in the Se-injected lambs (0.098 ppm vs. 0.086 ppm). Iron had little effect on titer, except in selenium-treated lambs. Although iron treatment enhanced gamma globulin production at 6 weeks of age, iron may be more crucial to cellular rather than humoral immunity. This study consistently demonstrated a dramatic response of blood hemoglobin to iron treatment, but also indicated that other aspects of iron deficiency may be more important than anemia. Marginal deficiencies of both iron and selenium may affect lamb health, and thus have an economic impact on intensive sheep production systems.

Text

2010-04-20

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http://hdl.handle.net/2429/23923

Animal Science

University of British Columbia

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