Carbohydrate fermentation in the large intestine of lambs

In one of two experiments, six 4-mo-old wethers fitted with ileal and cecal cannulas were fed three levels of concentrate (0, 40 or 80% corn) with forage in a replicated 3 X 3 Latin square design. Chromic oxide was fed as a marker. Quantities of starch recovered at the ileum and digested in the large intestine increased (P less than .05) with increased starch intake. Quantities of acid detergent fiber (ADF) recovered at the ileum increased with increased ADF intake; however; ADF digestion (grams) in the large intestine was highest (P less than .05) when the 80% corn diet was fed. Cecal total VFA concentrations, butyrate molar proportions and lactic acid concentrations were highest (P less than .05), and cecal acetate to propionate (C2:C3) ratios and pH values were lowest, in lambs fed 80% corn. In Exp. 2, 14 wethers (4-mo-old) were fed a forage (alfalfa hay) or a concentrate (80% corn) diet containing chromic oxide as a marker. Digesta grab samples were obtained by surgical procedure. The amounts of starch recovered at the abomasum and ileum and the amounts digested in the rumen, small intestine and large intestine were greater (P less than .05) when lambs were fed the concentrate. Large intestinal total VFA concentrations and butyrate molar proportions were higher (P less than .01) when the concentrate diet was fed; pH values were lower (P less than .01). Lambs fed the concentrate diet had lower (P less than .01) large intestinal and ruminal C2:C3 ratios of VFA.