Effects Of Zinc And Cellulose Enzymes Complex On Lactation Performance And Rumen Fermentation On Dairy Cows

The objective of this study was to investigate the effects of coated zinc(CZn)and cellulose enzyme complex(CEC)on milk performance and rumen fermentation in dairy cows.In the first experiment 32 Holstein dairy cows were blocked by parity,daily milk yield and days in milk and randomly assigned to 4 treatments with 0,10,20 and 30 mg Zn/kg dry matter as CZn addition.In the second experiment,32 Holstein dairy cows were blocked by parity,daily milk yield and days in milk and arranged into four groups using a 2 × 2 factorial design.Supplementary CZn(0 or 20 mg Zn/kg dry matter)and CEC(0 or 2 g/kg dry matter)were mixed into daily ration.Dry matter intake and fat-corrected milk yield increased quadratically with increasing CZn addition.Digestibility of dry matter,organic matter,ether extract,neutral detergent fiber and acid detergent fibre increased linearly following CZn addition.Rumen p H,propionate proportion and ammonia N concentration decreased linearly but total volatile fatty acids concentration and acetate to propionate ratio increased linearly.Activities of carboxymethyl-cellulase,cellobiase,xylanase,pectinase and protease as well as copies of total bacteria,fungi,protozoa,methanogens,Ruminococcus albus,Ruminococcus flavefaciens,Fibrobacter succinogenes,Butyrivibrio fibrisolvens,and Prevotella ruminicola increased linearly but Ruminococcus amylophilus decreased linearly with increasing CZn addition.Serum insulin-like growth factor-1 and total antioxidant capacity activity increased linearly and quadratically,and glucose,triglyceride,growth hormone,insulin,glutathione peroxidase and superoxide dismutase increased quadratically following CZn addition.Significant CZn × CEC interaction was observed for serum growth hormone,insulin-like growth factor-1 and total antioxidant capacity activity.Dietary CEC or CZn addition increased feed efficiency but did not affect milk performance.Digestibility of dry matter,organic matter and ether extract increased with CEC or CZn addition.Ruminal p H decreased but total volatile fatty acids concentration and acetate to propionate ratio increased with CEC addition.Supplementation with CZn did not affect rumen fermentation parameters.Populations of total bacteria,F.succinogenes and P.ruminicola were increased due to CEC or CZn addition.Activities of cellobiase,xylanase as well as R.albus,R.flavefaciens,Rb.amylophilus were increased with CZn addition.Serum malondialdehyde concentration was decreased by CEC or CZn addition.The data indicated that supplementation with CZn at 20 mg Zn/kg dry matter improved milk performance,rumen fermentation and nutrient digestibility,and that CEC or CZn addition increased nutrient digestibility and the combined addition of CEC and CZn was more efficient in increasing serum hormone concentrations and antioxidant capacity activity than CEC or CZn addition alone.