Absorption and Utilization of Volatile Fatty Acids by the Young Calf

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Abstract
Absorption and utili-zation of volatile fatty acids (VFA) by young milk-fed calves were studied using Na salts of 14C-labeled acids. In 2 trials acetate was administered orally; in 4 later trials, either acetate, pro-pionate, or n-butyrate was administered into the extreme terminal portion of the ileum via a re-entrant fistula, followed several hours later by the same acid administered orally. Radioactivity was measured in expired CO2, ileal digesta, feces and, in 1 experiment, blood. Radioactivity in blood of a week-old calf peaked 90 min. after acetate feeding. In 2 other acetate trials radioactivity in expired CO2 peaked 3 hr. after feeding. Peak activity in expired CO2 appeared in 2 hr. or less after ileal administration. Large amounts of the 14C were eliminated as 14CO2, primarily during the 1st 8 hr. Separate trials with propionate and butyrate indicated they also were efficiently absorbed and used. In all trials, only small amounts of 14C appeared in feces, urine, or ileal digesta. These data indicate that the very young calf can absorb and metabolize VFA, whether the acids are produced in the forestomach or large intestine.