Effect of Particle Length and Sodium Hydroxide Treatment of Wheat Straw on Site and Extent of Digestion by Lambs

Two lamb trials were conducted to determine the effects of particle length (PL; 2.5 vs 10 cm) and sodium hydroxide (NaOH) treatment (0 vs 4%) of wheat straw on dry matter (DM) intake and site and extent of DM and neutral detergent fiber (NDF) digestion. Lambs in the first trial were fed ad libitum once daily. Lambs in the second trail were fed four t imes/d at 6-h intervals and were sacrificed after 7 d of fecal collection to determine site of digestion. For both trials, NaOH increased (P<.05) DM intake and total tract DM and NDF digestibility. Lambs fed 2.5-cm wheat straw once daily had greater (P<.05) DM intake and lower (P<.05) digestibility of DM and NDF than with the 10-cm wheat straw diets. No main effect due to PL was observed for any variable measured when lambs were fed four times daily, but NaOH treatment increased (P<.05) ruminal DM and NDF digestibility and postruminal NDF digestibility. The lO-cm, NaOH-treated straw diet had greater (P<.05) ruminal DM and NDF digestibility than its untreated counterpart . Although not significant (P>.10), lambs fed 2.5-cm, NaOH-treated straw appeared to have a greater percentage of total NDF digestion occurring postruminally than lambs fed untreated straw, suggesting an increased flow of potential ly digestible fiber to the hindgut. This is supported by a shorter ruminal retention time of digesta in lambs fed the 2.5-cm, NaOHtreated straw. Ruminal volatile fa t ty acid concentrations were greater for NaOH-treated straw diets, which reflect the site of digestion results. Results of the present s tudy suggest