Tannins could affect rumen parameters such as pH, NH3-N and microorganisms. The low rate and extent of protein degradation in the rumen by feeding tannin-rich feeds could lower rumen ammonia concentration. There are many reports indicating inhibitory effect of tannins on rumen protozoa. We aimed to determine the effects pistachio hull (PH) as a tannin source in the diet on rumen pH, N-NH3 concentration, and protozoa content in Balochi male lambs. Three male lambs (35 ± 2 kg live weight) equipped with ruminal and abomasual cannula were randomly assigned into a changeover 3 × 3 design with 3 treatments: 1) control (alfalfa), 2) 15% alfalfa+15% PH and 3) 30% PH (DM basis). Rumen fluid pH was measured immediately before and every 30 min up to 8 h after the a.m. feeding. Also, rumen fluid was collected from the anterior dorsal, anterior ventral, medium ventral and posterior dorsal and posterior ventral locations within the rumen at 0, 1, 2, 4, 6 and 8 h after the 0800 h feeding for determination of NH3-N concentration and protozoa count. Data were analyzed as a repeated measurement design using PROC MIXED of SAS (P < 0.05), assuming the model included treatment, time, and time × treatment as fixed effects and animal as random effect. Rumen fluid pH was not affected by PH content of diet, although tended to increase as the amount of dietary PH increased. Dietary PH content resulted in a decrease in the rumen N-NH3 concentration. Protozoa content of rumen was not affected by the amount of PH in the diets, although a tendency to decrease was observed when dietary PH amount increased.

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