Effects of clinoptilolite on rumen fermentation, digestion and feedlot performance in beef steers fed high concentrate diets.

In a 148-d feedlot experiment, 48 crossbred steers were fed a 70% sorghum diet with clinoptilolite (CLN), a natural zeolite, substituted at 0, 1.25 and 2.5% of the diet dry matter. No differences (P>.05) were detected in average daily gain, feed intake (dry matter and organic matter) and feed efficiency among treatments. Negative correlations (P<.05) between fecal starch and fecal pH were detected on d 0, 37 and 66 of the feeding period. Four rumen-cannulated steers were used in a 4 x 4 Latin square design to s tudy effects of CLN on rumen fermentat ion and digestion. A 5.0% CLN diet was fed in addit ion to the three diets from the feedlot experiment. Total tract dry mat ter digestibility was higher (P<.05) for the 1.25% CLN diet than for the 2.5 and 5.0% CLN diets, but not different from the control diet. Ruminal digestion of dry matter , organic matter, starch and crude protein tended to be higher for CLN diets, while the opposite occurred in intestinal digestion. Total t ract starch digestion was higher (P<.05) for the 1.25% CLN diet than for the 5.0% CLN diet, but not different (P>.05) from the control or 2.5% CLN diets. The CLN-supplemented diets tended to produce higher levels of total volatile fa t ty acids and the 2.5% CLN diet produced a greater (P<.05) propor t ion of propionic acid than other diets. The 5.0% CLN diet had the lowest (P<.05) rumen ammonia concentration at 3 h postfeeding; at 6 h postfeeding, 2.5 and 5.0% CLN had lower (P<.05) ammonia levels than the control diet and at 9 h postfeeding, 2.5 and 5.0% CLN ammonia levels were lower (P<.05) than the other diets. Rumen pH was lower (P<.05) at 6