Acetate and propionate production in the cecum and proximal colon of lambs [Fed a forage, hay or high corn, concentrate diet]

A modified single-injection isotope dilution technique measured acetate and propionate production rates in the cecum and proximal colon of 14 lambs fed a forage (hay) or high corn (concentrate) diet. The modified isotope dilution appeared to have merit. Volatile fatty acid pool sizes were stable and apparently absorption of fermentation products occurred to prevent end product inhibition. Propionate pool sizes were greater (P less than .01) while acetate pool sizes were not significantly greater when lambs received the concentrate diet. Apparent acetate production was higher (P less than .05) in lambs fed the concentrate diet than in forage-fed lambs (239.4 vs 189.5 mmol/d, respectively). Apparent propionate production was also greater (P less than .01) when lambs were fed the concentrate diet rather than the forage diet (431.4 vs 180.7 mmol/d, respectively). These results indicate that acetate and propionate produced in the cecum and proximal colon may be a considerable source of energy and glucose precursors for the growing lamb.