Vitamin B12 Requirement of Weanling Pigs II. Performance on Low Levels of Vitamin B12 and Requirement for Optimum Growth

Abstract

Six sets of 4 litter-mate pigs, three barrows and three gilts, were individually fed and watered ad libitum from weaning to 100 lb. live weight, confined in wire-floored wooden crates. The pigs were fed a fortified corn-soybean oil meal ration containing 80 mg of a combination of antibiotics per pound of ration. To this ration were added 0, 2, 4, and 6 µg of crystalline vitamin B₁₂ per pound. The addition of vitamin B₁₂ to the basal ration produced significantly greater gains to either 75 or 100 lb. live weight. There was practically no difference in the average daily gains of the pigs on the 4- and 6-µg levels of vitamin B₁₂. Vitamin B₁₂-deficient pigs on the basal ration exhibited a dramatic response to the intraperitoneal injection or oral feeding of crystalline vitamin B₁₂, or both. Vitamin B₁₂ also significantly increased feed efficiency. There were no significant differences in hemoglobin or red and white blood cell counts of pigs fed different levels of vitamin B₁₂. The pigs fed the basal ration had the lowest level of total nitrogen and the highest level of urea in the blood. The amount of blood urea decreased as the amount of vitamin B₁₂ in the ration was increased. There was a tendency for the livers of the pigs to become lighter in weight as the amount of vitamin B₁₂ fed was increased; however, the amount of vitamin B₁₂ per gram of liver and total vitamin B₁₂ per liver increased. Urinary vitamin B₁₂ assay values were inconsistent, thereby indicating a difference among pigs in their ability to synthesize this nutrient. Differences in the amount of vitamin B₁₂ per gram of feces were small. The total amount varied with the total feces voided. Assay of intestinal contents from 12 pigs showed synthesis of vitamin B₁₂ or vitamin B₁₂-like substances in the lower part of the digestive tract of the pig. These results indicate that the vitamin B₁₂ requirement of the weanling pig for efficient weight gain is at least 4 µg per pound of total ration when added to a corn-soybean oil meal ration containing a combination of antibiotics for partial control of intestinal microflora.