Effects Of Supplemental Zinc On Performance And Blood Physiological And Biochemical Parameters In Lactating Cows

The objections of this study were to determine the effects of different levels of zinc on production performance , nutrient digestibility,blood physiological and biochemical parameters in Chinese Holstein lactating cows. Trial one: Eight primiparous Holstein cows were selected in a replicated 4x4 Latin squar design to determine the effects of supplemental zinc on performance,nutrient digestibility, blood biochemical parameters. Treatments involved the control group A(basal diet); B(basal plus Zn2OmgIkgDM); C(basal diet plus Zn 40mg/kg); D(basal diet plus Zn 60 mg/kg). The results were listed as below: (1) The apparent digestibility of dry matter, crude protein, EE,ADF and NDF tended to be higher for supplemental zinc treatments, but no significant difference(p>0.05). (2) The treatments of supplemental zinc siginificantly increased the milk yeild (p<0.05), but no significant difference betwen them; The treatments of supplementing zinc had no effects on milk protein and fat percentage (p>O.05); The zinc contents of milk were significantly increased with zinc levels being increased(p<0.05), and it showed a positive correlation betwen them (r=0.9720, pO.O5),3 .85%(p>0.05)and 1 0.34%(p.O.O5) when supplementing 800mg/kg Zn to diet. (2) There were no significant difference on hemoglobin and packed cell volume among the four treatments (p>O.05), but the content of hemoglobin and packed cell volume tended to be decreased by supplementing 800mg/kg zinc(p>0.05); The high levels of dietary Zn masterly increased the zinc content of the milk(p<0.0 1). (3) High dietary zinc masterly increased the zinc content of blood serum (p0.05). The high levels of dietary zinc did not affect the contents of K, Ca, Na albumen and urea nitrogen of blood serum..