Nutrients digestibility, microbial protein synthesis and rumen and blood parameters in sheep feeding grape pomace treated with Neurospora sitophila

Abstract

Context Agricultural by-products such as grape pomace (GP), could form an important component of ruminant diets. Aims The present study aimed to evaluate the effects of treating GP with Neurospora sitophila on chemical composition, digestibility, nitrogen balance, rumen, and blood parameters. Methods Twenty-four adult Kermani rams were allocated to one of three treatments arranged as a completely randomised design for a 26-day period. The first 21 days were for adaptation, and the last 5 days were for sample collection. The animals were placed in individual cages equipped with a urine–faeces separator. They were fed with (1) a basal diet without GP (control), (2) a basal diet with 20% of untreated grape pomace (UGP), and (3) a basal diet with 20% of N. sitophila-treated grape pomace (TGP). Key results Treating GP increased the percentages of crude protein (CP), lignin and rumen-degradable protein (RDP; P < 0.01), but decreased rumen-undegradable protein (RUP; P < 0.05) and total phenols and tannins (P < 0.01). Nutrient digestibility in the TGP- and UGP-supplemented groups was lower than that in the control group (P < 0.05). The mean excretion of allantoin (P < 0.05), xanthine plus hypoxanthine (P < 0.01), total purine derivatives (P < 0.05), and microbial protein synthesis (P < 0.05) were lower in the sheep fed UGP than in the control group. The acetate (P < 0.01), propionate and total volatile fatty acids (P < 0.05) in rumen fluid were the highest in the control group. The UGP-supplemented group had a higher rumen pH and a lower NH3-N concentration than did other groups, 1.5 h after feed intake. Also, blood glucose and urea nitrogen in animals fed UGP were lower than in those in other groups (P < 0.05). Conclusions Treating of GP with N. sitophila fungus increases the CP and RDP and reduces the adverse effects of GP on ruminal kinetics. Implications The GP that has been exposed and treated with N. sitophila may provide a suitable supplementary feed for ruminants when incorporated into diets at rates of up to 20%.