Effects of Jujube Power and Coated Methionine on Growth Performance, Nutrient Apparent Digestibility, Rumen Fermentation and Serum Biochemical Indexes in Finishing Bulls

The study was conducted to investigate the effects of jujube power (JP) and coated methionine (CMet) in diets on growth performance, nutrient apparent digestibility, rumen fermentation and serum biochemical indexes in finishing bulls. A two-factor completely randomized design was arranged with JP (JP replacing 0 or 15% maize in the diet, JP -/JP +) and CMet (adding 0 or 1. 08 g/kg dry matter to the diet, CMet-/CMet+). Twenty finishing bulls (Simmental×Local) with similar age and body weight were randomly divided into four groups and fed a basal diet, the basal diet +JP, the basal diet +CMet and the basal diet + JP + CMet, respectively, with five replicates of one cow in each group. The feeding test period lasted for 70 d. The pre-trial period lasted for 10 days and the formal trial period lasted for 60 days. The results showed as follows: 1) dietary JP addition significantly improved dry matter intake and average daily gain (P <0. 05); dietary CMet addition only increased average daily gain (P < 0. 05); there was no significant interaction between JP and CMet in growth performance (P >0. 05). 2) Dietary JP addition significantly increased the apparent digestibilites of crude protein, acid detergent fiber and non-fiber carbohydrate (P <0. 05); the increment of apparent digestibilites in organic matter, crude protein and non-fiber carbohydrate were found by adding CMet in the diets (P <0. 05); a significant JP×CMet interaction was found in apparent digestibilites of crude protein and non-fiber carbohydrate (P <0. 05). 3) The significant improvement in the activities of cellodisaccharase and xylanase and the concentration of total volatile fatty acids in the rumen was observed with dietary JP addition (P < 0. 05); pH and ammonia nitrogen concentration in the rumen were significantly decreased and rumen proteinase activity and propionic acid concentration were increased with CMet supplement in the diets (P < 0. 05); there was no significant interaction between JP and CMet in rumen fermentation (P >0. 05). 4) Serum glucose content, total antioxidant capacity and superoxide dismutase activity were significantly increased (P <0. 05) but serum malondialdehyde content was significantly decreased in the dietary JP supplementation (P <0. 05); dietary CMet supplementation showed a significant increment in the serum glucose, total protein contents and total antioxidant capacity (P <0. 05), and a significant decrease in the serum urea nitrogen and malondialdehyde contents (P <0. 05); there was a significant JP and CMet interaction effect on serum malondialdehyde concentration (P <0. 05). In general, compared with the addition of JP and CMet alone, the interaction between JP and CMet failed to significantly promote growth performance of finishing bulls but improve antioxidant capacity by increasing nutrient apparent digestibility.