VOLATILE FATTY ACID PRODUCTION IN THE HINDGUT OF SWINE

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Abstract
Volatile fatty acid (VFA) production was determined using a continuous cecal isotope infusion system. In experiment 1, a control diet (diet 1) containing 12.9 MJ digestible energy (DE) per kilogram, 2.3% nitrogen and 4.8% crude fiber (CF) was fed to four pigs fitted with cecal cannulac. In experiment 2, the same control diet plus two diets (diets 2 and 3) containing, respectively, 27.3 and 52.07 alfalfa, 10.9 and 9.1 MJ DE. 9.9 and 15.0% CF were fed. In experiment 1, pigs were fed 2.7 kg daily of diet 1 in 24 equal feeds. In experiment 2, pigs were fed 2.4 kg daily of the three diets in three equal feeds at 8-h intervals. Following a 15-wk adaptation to diet 3, VFA production rates were again determined (exp. 3). In experiment 1, average VFA concentrations, in cecal fluid, were 79.1, 33.0 and 9.9 mmoles/L while VFA molar percentages were 64.8, 27.1 and 8.1 for acetate, propionate and butyrate, respectively. Net production rates for acetate, propionate and butyrate, respectively, for pigs fed diet 1, were 42.6, 14.3 and 4.9 mmoles/h. The average contribution of VFA to the maintenance energy requirement of the pig was calculated as 19.7%. In experiment 2, total VFA concentrations for pigs fed diets 1 and 2 were not significantly different. Pigs fed 15% CF had significantly lower total VFA concentrations than those fed diet 2. No significant dietary differences were observed in VFA production rates. However, pigs fed the 10% CF diet tended to have the highest production rates, with intermediate levels for pigs fed diet 3. The energy contribution of VFA for pigs fed 5, 10 and 15% CF was calculated as 10.1, 15.5 and 11.1% of the maintenance energy requirements, respectively. Following a 15-wk adaptation period to the high fiber diets, there was no evidence of increased VFA production.