In order to study the effects of two kinds of clinoptilolites (calcic and potassic) on ruminal parameters, four fistulated mature male sheep were used in a change over design as balanced latin squre. The formulated diets included: 1) Control, 2) Control + 4% calcic clinoptilolite, 3) control + 4% potassic clinoptilolite and 4) control + 2% calcic and 2% potassic clinoptilolite. The experiment was comprised of four periods. Each period included adaptation (two weeks) and sampling (one week). Sampling was made from ruminal fluid for measurement of pH, ammonia nitrogen, total volatile fatty acids (tVFAs), ruminal total and cellulolytic bacterial population as well as from ruminal fungi population at 0, 3, 6 and 10 hours after morning feeding. The results showed that calcic clinoptilolite increased pH, tVFAs and ruminal cellulolytic bacterial population significantly (P<0.05), but its effect on ruminal total bacteria and fungi population was not significant. Calcic clinoptilolite also decreased ruminal. ammonia nitrogen at 3 hours after feeding, and in general its concentration in ruminal fluid had a lower fluctuatin while with calcic clinoptilolite. Effect of potassic clinoptilolite on the mentioned parameters was not significant. In general the results indicated that using 4% calcic clinoptilolite changes ruminal parameters for increasing animal performance.
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