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Effect of Vitamin B₁₂ Status on Performance of the Lactating Ewe and Gluconeogenesis from Propionate

Department of Animal Science, Cornell University, Ithaca, NY 14853-0281

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ABSTRACT

Ewes fed a diet containing .06 ppm cobalt prior to and after parturition were used to examine effects of hydroxycobalamin supplementation upon production of milk. Four ewes were assigned to each of three treatments after hand milking at 3 wk postpartum. At 7 wk postpartum, B₁₂ concentrations in liver were enhanced in the group receiving intramuscular injections of 200 µg on alternate days (750 ng/g wet liver) relative to low groups that received 20 and 0 µg on alternate days (190 and 200 ng/g wet liver). Following 1 wk of treatment, B₁₂ enhanced ewes had greater daily intake of feed and increased live weight. Vitamin B₁₂ status was without significant effect on production of milk, total solids, fat, and solids-not-fat at 4, 5, and 6-wk milkings; however, production of milk protein was increased for B₁₂-enhanced ewes. After lactations were terminated and feed intakes standardized, slices of liver obtained from B₁₂-enhanced ewes incorporated 2-carbon 14-labeled propionate into glucose at rates greater than did slices from low B₁₂ ewes. Subclinical changes affecting production may occur in lactating sheep when B₁₂ status is at the lower end of what usually is considered the normal range.