Deactivation of tannins in raisin stalk by polyethylene glycol-6000 effect on feed intake, digestibility, and nitrogen retention in sheep

Abstract

An experiment was conducted to assess the effects of polyethylene glycol (PEG-6000) and urea on feed intake, nitrogen retention, and nutrient digestibility in sheep fed raisin stalk. Sixteen male fat-tailed Sanjabi sheep (26 ± 0.66 kg) were randomly assigned to one of 4 dietary treatments: raisin stalk (control; RS), raisin stalk supplemented with 3% urea and 4% molasses (RSU3%); 5% urea and 7% molasses (RSU5%); or 5% urea, 7% molasses plus 5% PEG (RSU-PEG) per DM of raisin stalk. The urea and molasses were dissolved in distilled water and then mixed into a solid ingredient. Polyethylene glycol was also sprayed onto the diet with a solution of PEG in distilled water (5 g/10 mL). The results indicated that feed intake, DM digestibility, average daily gain, and nitrogen retention significantly increased due to incorporation of molasses, urea, and PEG-6000, which may be associated with the inactivation of TEPH and TET. The digestibility of CP increased from -20.5% to 78.6%, and nitrogen retention in the PEG group was significantly higher than that in the other groups (P < 0.05). No significant effect of urea alone was observed in the average daily gain. The negative effects of tannin on DM intake and N retention were alleviated when animals received molasses with 5% urea + 5% PEG.