The effect of zeolite on digestibility and feedlot performance of Mehraban male lambs given a diet containing urea-treated maize silage

A naturally occurring zeolite (Anzymite(TM)) was added to a diet containing 350 g maize silage per kg ( which was treated with 10 g urea per kg ( fresh weight)), 375 g barley and 275 g alfalfa hay per kg. Effect of inclusion of zeolite (0, 30 and 60 g/kg diet) on diet digestibility, ruminal fluid acidity and ammonia concentration, blood urea nitrogen level, and feedlot performance was studied in Mehraban ram lambs. The diets were given ad libitum. Digestibility coefficients of dietary dry matter and crude protein were significantly increased by zeolite (P < 0.05). The diet containing 30 g zeolite per kg had higher neutral-detergent fibre digestibility compared with the control (P < 0.05). Over all sampling times, the ruminal fluid of the sheep given the 30-g/kg zeolite diet had the highest and those given the 60-g/kg zeolite diet had the lowest pH values (P = 0.03). Before feeding, ruminal ammonia concentration was low for all treatments (4 to 8 mg/dl). At 4 h after feeding, the control diet had the lowest ruminal ammonia concentration (5.5 mg/dl) which was significantly lower than the values for zeolite diets (35 to 39 mg/dl). Blood urea nitrogen ( BUN) level increased post feeding for all diets. At 4 h post feeding, the level for the control diet was significantly higher than for the zeolite diets, but at 6 h post feeding, the level of BUN was higher with 60 g zeolite per kg diet. Daily dry-matter intake for the 60 g zeolite per kg diet was significantly higher than for the control. Backfat depth in the 60 g zeolite group was significantly less than the control group. Pelvic and pericardial fats were significantly higher for the zeolite groups. Fat-tail weight in the 60 g/kg of zeolite group was significantly higher than in the 30 g zeolite and control groups. The findings indicated that, in spite of some improvements in digestibility and rumen fermentation pattern, addition of zeolite to the diet of feedlot Mehraban lambs, under the conditions of this experiment, was not advantageous.