Pistachio by-product as an alternative forage source for male lambs: Effects on performance, blood metabolites, and urine characteristics

Thirty-two Kermanian male lambs (5-6 months of age and 23.73 ± 2.20 kg BW) were used to determine the effects of feeding sun-dried pistachio by-product (PBP) on growth performance, nutrients digestibility, blood metabolites, and urine characteristics over a 4-months period. Lambs were randomly allocated to one of four experimental diets containing 0 (DM basis; 0PBP), 10 (10PBP), 20 (20PBP), and 30% of PBP (30PBP), substituted with alfalfa hay and wheat straw. Experimental diets were fed twice daily in two equal portions as pelleted total mixed rations. Lambs were weighed at the beginning of trial and the end of each month over the experimental period. Blood and urine samples were also collected monthly. Eight Kermanian castrated rams (48.35 ± 2.81 kg BW) placed in metabolic cages were used in a replicated 4 × 4 Latin square design during four 3-week periods to evaluate nutrient digestibility in response to feeding experimental diets. Dry matter intake (DMI) and average daily gain (ADG) reduced linearly (P = 0.001) with increasing the amount of PBP in the diets. The lambs fed 30PBP, had the lowest daily DMI and ADG, which were lower (P < 0.01) than the control group (1549 g/d vs. 1063 g/d and 195.7 g/d vs. 129.4 g/d, respectively). Feed conversion ratio increased linearly and it was greater (P < 0.05) in 30PBP than the control group (13.82 vs. 7.96). Plasma activities of circulating enzymes including alanine aminotransferase and aspartate aminotransferase as indicators of liver function were not affected by experimental diets. Blood urea nitrogen responded quadratically (P = 0.001) and decreased in lambs fed 30PBP in comparison with lambs fed the control diet (13.52 vs. 16.21 mg/dl). Urine characteristics including pH, specific gravity, and the counts of white and red blood cells and also epithelial cells were not different across experimental diets. Apparent total tract digestibility of DM and CP reduced linearly (P < 0.01) with increasing the amount of PBP in the experimental diets; however, ether-extract and ash digestibility were not affected by diets. Results indicate that using PBP to replace alfalfa hay and wheat straw up to 20% of dietary DM had no negative effects on feed intake and growth performance in Kermanian male lambs.