EFFECTS OF BARLEY VARIETY AND RESTRICTED VERSUS AD-LIBITUM INTAKE ON RATE, SITE, AND EXTENT OF DIGESTION BY WETHERS FED A HIGH-ENERGY DIET

Twelve ruminally cannulated wethers (four with duodenal cannulas) were used in a replicated 4 x 4 Latin square to investigate effects of bar ley variety and restricted vs ad libitum intake on site, rate, and ext ent of digestion. Diets were based on Ottus (52.7% starch; 0) or Stept oe (56.7% starch; S) barley fed at either 90% of prestudy ad libitum f eed intake (R) or ad libitum consumption (A). Diets were formulated to be equal in starch content (38%). Periods consisted of 10 d for adapt ation followed by 10 d in which fecal, duodenal, ruminal, and in situ collections were made. With the exception of ruminal starch digestion, barley variety did not interact with level of feed intake (P >.26). I ntake of OM was 1,009, 996, 1,124, and 881 g.wether-1.d-1 for O, S, A, and R, respectively. Intake by R wethers of OM and starch was 78% (P < .01) of intake by A wethers. Duodenal flow of OM and ruminal pH were not affected (P > .28) by either intake restriction or barley variety . Although restricted intake did not affect ruminal (P = .84) and duod enal (P =.39) ammonia nitrogen, the O barley had higher (P = .01) rumi nal and duodenal ammonia nitrogen than did S barley. Restricted intake had no effect (P > .30) on rate of ruminal barley digestion, ruminal and total tract starch digestion, or total tract OM digestion. This ma y be due to the rapid digestion rate of barley. Despite reduced fluctu ation in daily OM intake by R wethers, ruminal pH fluctuation was not reduced (P = .99) by intake restriction; however, 0 was higher (P = .0 5) in ruminal pH fluctuation than was S barley. Dynamics of digestion in wethers were not influenced by restricting intake to 78%. Barley va riety influenced ruminal and duodenal ammonia nitrogen and ruminal pH.