Effects Of Different Manganese Sources On Growth Performance,Fecal Bacterial Community And Serum Indexes Of Calves

During the calf’s weaning,the gastrointestinal digestive system has undergone a complete change from liquid feed to solid feed,and there may be differences in nutritional demand.Manganese is an essential trace element for all animals,which can promote skeletal system development,carbohydrate and lipid metabolism,and other functions.This experiment investigated the effects of adding different manganese sources in the basal diet on growth performance,fecal microbiome,and serum indexes of calves pre and post-weaning.Fifteen Holstein heifer calves(6-week-old,82.71±1.35 kg,mean ± standard error)were randomly designed into three groups(5 each):(1)no extra Mn supplemented(CON),(2)20 mg Mn/kg(dry matter basis)in the form of chelates of lysine and glutamic acid in a mixture 1:1(LGM),(3)20 mg Mn/kg(dry matter basis)in the form of MnSO4.All calves were weaned at eight weeks of age.The experiment lasted 28 days(14 days before and 14 days after weaning).Chapter 1:Effects of different manganese sources on growth performance,nutrient apparent digestibility and fecal mineral element concentration of calves.Body size indexes of calves were measured 14 days before weaning(d-14),one day before weaning(d-1),and 14 days after weaning(d 14).The increases in body height,body length,chest girth,cannon circumference,hip height,and hip width of calves were calculated before weaning(d-14 to d-1),after weaning(d-1 to d 14),and during the whole period(d-14 to d 14).The feces of calves were collected at d-1,1 day after weaning(d 1),three days after weaning(d 3),seven days after weaning(d 7),and d 14 to determine the apparent digestibility of nutrients and the concentration of fecal mineral elements.The study results are as follows,(1)Mn supplementation increased body length and chest girth at d-1 and d 14,and hip height after weaning and the whole period.LGM increased daily gain of post-weaning and entire period chest girth(P<0.05).MnSO4 increased feed to gain ratio after weaning and full life and cannon circumference at d 14(P<0.05).(2)CP’s apparent digestibility was not affected by time,and other indexes were affected by time,manganese source,and interaction of day and manganese source(P<0.05).(3)The rectal temperature of calves in the MnSO4 group was the highest at d 14(P<0.05)and significantly higher than that of the other two groups(P<0.05).(4)Fecal contents of iron(Fe),phosphorus(P),and manganese(Mn)in the LGM group were lower than those in the MnSO4 group(P<0.05).Chapter 2:Effects of different manganese sources on facal microbiome of calves.Fecal samples were collected aseptically at d-1,d 1,d 3,d 7,and d 14 to investigate the effects of different manganese sources on the fecal microbiome of calves.The study results are as follows,(1)the Chao 1 index and Shannon index of fecal bacteria in LGM and MnSO4 groups decreased in d 1 but increased after weaning.(2)The PCoA results indicated that the LGM group was distinctly separate from the CON and MnSO4 groups during the experimental period.(3)Bacteroidota and Firmicutes were calf’s the dominant fecal microbial community.(4)Significant differences(P<0.05)were observed in the relative abundance of two phyla(Proteobacteria and Spirochaetota)and eight genera(Alloprevotella,Prevotellaceae UCG-001,Clostridia UCG 014,RF 39,UCG-010,Pseudomonas,Ralstonia and Treponema)in three groups.Chapter 3:Effects of different manganese sources on serum enzyme activities,antioxidant and immune capacity and serum mineral element concentration of calves.In this experiment,blood was collected from the jugular vein of calves at d-1,d 1,d 7,and d 14 days by vacuum collection vessel without anticoagulant to explore the effects of different manganese sources on serum enzyme activity,antioxidant capacity,immune capacity and serum mineral element content of calves.The study results are as follows,supplementation of manganese in calf diets increased the activities of d-1 and d 1 alanine aminotransferase(ALT)and alkaline phosphatase(ALP)and increased the activities of arginase(ARS)and glutamine synthetase(GS)throughout the trial period(P<0.05).(2)Day effect observed in the ALT,ARS,and GS activity.The ALT of calves in CON and LGM groups was the lowest at d-1,and the ARS activity of calves in the three treatment groups was the highest at d-1.Still,the GS was the lowest at this time point and the highest at d 7.(3)The supplementation of manganese significantly increased the total antioxidant capacity(T-AOC)and the activity of manganese superoxide dismutase(MnSOD)(P<0.05).(4)The immune capacity of calves was not affected by the interaction of day and treatment(P>0.05)but was significantly affected by day and treatment factors(P<0.05),the immunoglobulin A(IgA),immunoglobulin G(IgG)and immunoglobulin M(IgM)of calves in the Mn supplemental group were higher than those in the CON group.The interleukin-6(IL-6)of calves in the CON group were higher than those in the supplementation of Mn group during the whole experiment period.(5)The concentration of serum Fe in the CON group was higher than that of the supplementation of the Mn group,and the serum copper(Cu),calcium(Ca),P and magnesium(Mg)were not affected by day,treatment,or the interaction factors between day and treatment(P>0.05).In conclusion,additional Mn increased feed intake after weaning and during the whole period,body length and chest girth of calves at d-1 and d 14,and hip height post-weaning.Compared with the MnSO4 group,calves in the LGM group had higher post-weaning daily gain,chest girth,and apparent digestibility at d 14,lower excretion of Fe,P,and Mn,and more stable fecal microbiota.Adding 20 mg/kg LGM to the diet containing 158.82 mg/kg Mn is beneficial to the growth of calves and environmental protection.