Effects Of Different Zinc Sources On The Performance,zinc Metabolism And Rectal Microorganism Of Newborn Calves

This objective of the present study was to evaluate the effects of zinc oxide or zinc methionine on growth performance,diarrhea,immune function,blood indexes,zinc metabolism and fecal microorganism of newborn calves,which might provide a reference basis for the application of zinc in calves.The specific contents are as follows:Experiment 1: The objective of this study was to explore the effects of different doses of Zinc Oxide on the growth performance,diarrhea,serum and fecal zinc content of newborn calves,and select the best dose.30 newborn Holstein calves were randomly divided into 5 groups,6 cows in each group.Each group of calves was added 0,26,52,104 and 156 mg Zinc Oxide per day(equivalent to 0,20,40,80 and 120 mg zinc,respectively).The test was carried out at the end of the calf 14 days after birth.The results showed that:(1)Dietary zinc supplementation had no significant effect on the growth performance of calves,adding 80 mg/d zinc significantly reduced the diarrhea rate of calves(P<0.05).(2)The content of zinc in calf serum was highest when 80 mg/d zinc was added into the diet.(3)Dietary zinc supplementation resulted in a linear rise in the content of zinc in calf feces(P<0.01)Experiment 2: The objective of this study was to evaluate the effects of zinc oxide or zinc methionine on growth performance,diarrhea,blood hormone and immune indexes of calves.Thirty-six Chinese Holstein newborn calves were randomly assigned to 3 groups of 12 calves.The treatments were as follows: no addition(control group);457 mg/d of zinc methionine(equivalent to 80 mg/d of zinc)was added to each calf;104 mg/d of zinc oxide(equivalent to 80 mg/d of zinc)was added to each calf.The whole experiment lasted for 14 days.The results showed that:(1)Compared with the control group,dietary supplementation of zinc methionine significantly increased the average daily gain(P<0.05),but decreased the incidence of diarrhea of calves(P<0.05).(2)Oral administration of difference zinc sources significantly reduced the concentration of insulin in serum(P<0.05).(3)Compared with zinc oxide group,the concentration of serum insulin-like growth factor-1 tended to increase in zinc methionine group(0.05≤P<0.1).(4)The content of immunoglobulin IgG and IgM in the serum of calves fed zinc oxide was significantly higher than that in control group(P<0.05).Experiment 3: The objective of this study was to evaluate the effects of adding zinc oxide or zinc methionine on zinc metabolism in calf diet.Test design is the same as experiment 2.The feces and blood samples of 14-day-old calves were collected.The contents of zinc and other mineral elements in blood and feces were determined by inductively coupled plasma mass spectrometry,and the contents of zinc related hormones in serum were measured.The results showed that:(1)Dietary supplementation of 80 mg zinc significantly increased zinc content in serum of calves(P<0.01),while zinc content in calf serum of zinc oxide group was between zinc methionine group and control group.(2)Dietary supplementation of different zinc sources had no significant effect on the zinc content in feces of calves(P>0.05).(3)Dietary supplementation of zinc oxide or zinc methionine did not significant effect on enzymes related to zinc metabolism in the serum of calves(P>0.05).Experiment 4: The objective of this study was to explore the effects of different zinc sources on the rectal microorganisms of newborn calves.Test design is the same as experiment 2.Rectal contents samples were collected at d 1,3,7,and 14 after the calves were born,and rectal contents microbial diversity was determined using high-throughput sequencing technology.The results showed that:(1)The community structure of rectal contents microorganisms of calves at different ages was significantly different(P<0.05).Zinc oxide and zinc methionine did not affect on rectal contents community structure(P>0.05).(2)The metabolic function of calves was not significantly influenced by zinc oxide or zinc methionine(P>0.05),and the metabolic function of calves changed significantly with ages.(P<0.05).In summary,supplementation of zinc methionine to the diet increased the growth performance of calves.Adding zinc oxide helped to enhance immunity.The addition of zinc oxide and zinc methionine increased zinc absorption.The rectal microorganisms of calves changed significantly with ages,which were not affected by dietary zinc supplementation.