The decreased rate and extent of protein degradation in the rumen as observed due to feeding of tannin-rich feeds could lower ammonia concentrations in the rumen and hence urea N excretion in urine. The tannins shift the site of N metabolism from rumen to the lower digestive tract and large intestine. Shifting excretion pattern of nitrogen from urine to feces and formation of tannin—protein complex are beneficial environmentally. We aimed to evaluate if tannin rich diets (pistachio hull (PH) as a tannin source) manipulate intake, digestion, excretion and retention of nitrogen in Balochi male lambs. Three male lambs (35 ± 2 kg live weight) equipped with ruminal cannula were randomly assigned into a changeover 3 × 3 design. Treatments were: 1) control (alfalfa), 2) 15% alfalfa+15% PH that provided 10.59 g/kgDM tannin, and 3) 30% PH that provided 18.28 g/kgDM tannin. Statistical analysis was performed using the MIXED procedure of SAS (P < 0.05). As tannin was increased in the diets, the nitrogen intake linearly and quadratic was decreased, rumen N-NH3 concentration linearly was decreased, and nitrogen excretion from urine and digested nitrogen linearly were decreased. Nitrogen excretion from fecal linearly and quadratic and retained nitrogen linearly were increased, by increased of dietary tannin. Thus, effects of tannins to reduce the degradation of protein in the rumen and nitrogen excretion from urine and to increase the nitrogen excretion from fecal and retained nitrogen due to N metabolism in the large intestine could have important role to improve nitrogen efficiency in lambs.

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