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Effects of Clinoptilolite on Rumen Fermentation, Digestion and Feedlot Performance in Beef Steers Fed High Concentrate Diets^1,2,

New Mexico State University, Las Cruces 88003

Abstract

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 study effects of CLN on rumen fermentation and digestion. A 5.0% CLN diet was fed in addition to the three diets from the feedlot experiment. Total tract dry matter 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 tract 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 fatty acids and the 2.5% CLN diet produced a greater (P<.05) proportion 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 h postfeeding for the 2.5% CLN diet than for the control or 1.25% CLN diets. At 12 h postfeeding, rumen pH was lower (P<.05) for the 5.0% CLN diet than for the control or 1.25% CLN diets. There were no differences (P>.05) in rumen volume and fluid flow rates among treatments.

¹ Journal Article No. 933 of the New Mexico Agr. Exp. Sta., Las Cruces.

² The authors are grateful to J. K. Elliott, R. E. Estell II, A. L. Goetsch and M. E. Hubbert for assistance with the experiment.