| The present study was to explore the interaction between starch and sodium butyrate(SB)on growth performance,and health status,during preweaning period and weaning transition period,and to provide scientific basis for the use of SB in different starch levels of calves.A two factor design was used to explore the interaction between starch(27 vs.37%)and SB(0 vs.0.5%)on Holstein calves.A total of 120 preweaning Chinese Holstein calves(60 males and 60 females)with similar age(15.98 ± 1.75d)and body weight(41.72± 2.81kg)were selected and divided into 12 groups(5 males and 5 females in each group).Low starch,low starch + SB,high starch,and high starch + SB were fed respectively.No hay was provided for calves,but drinking water freely.The calves fed pasteurized whole milk twice a day(a total of 4.4L).Seven weeks of preweaning and 3 weeks postweaning were included.The other feeding and management conditions were the same except for the different diets.Experiment 1: Interaction of starch and SB on growth performance and blood indexes of Holstein calvesThis experiment was conducted to study the interaction of starch level and SB on growth performance,blood biochemical indexes,and growth related hormones before weaning.The results showed that:(1)starch level affected dry matter intake(DMI)(P <0.01),weaning weight(P = 0.01),and preweaning average daily gain(ADG)(P < 0.05),but SB in starter had no effect(P > 0.05),but starch and SB showed an interaction on weaning weight(P = 0.062)and ADG(P < 0.05).SB and starch levels did not affect the feed to weight ratio(P > 0.05),but showed the same trend as weaning weight and ADG in body length(P = 0.052),body length index(P = 0.108)and chest circumference index(P =0.01).(2)Starch level affected blood cholesterol(P < 0.05),triglyceride(P = 0.096),urea nitrogen(P < 0.05),and β-hydroxybutyric acid(P < 0.10),which was also reflected in the addition of SB;they had an interaction on blood glucose(P = 0.10),total protein(P <0.05),total cholesterol(P < 0.05),and urea nitrogen(P < 0.10).(3)Low starch had higher blood concentrations of GH(P < 0.05),IGF-1(P < 0.05),and GLP-2(P = 0.059);the addition of SB increased the concentrations of GH(P < 0.05),IGF-1(P < 0.05),and GLP-2(P = 0.059)in both high or low starch(P < 0.05),but there was no interaction between starch and SB(except GLP-2 at 2-week-old).Therefore,low starch starter has higher growth performance,starch and SB have interaction,that is,adding SB in low starch starter can reduce growth performance,adding SB in high starch starter can improve growth performance;blood index shows that adding SB in high starch starter is more advantageous to metabolism;adding SB in starter can improve the growth and development related hormones,no matter in high or low starch condition.Experiment 2: Interaction of starch and SB on health status of preweaning calvesThe interaction of starch and SB on the health status of Holstein calves was studied through the health scores(ears,eyes,nose,and feces)and the incidence of diarrhea.The results showed that:(1)low starch had better feces(P < 0.05);interaction on ear score(P <0.05).(2)there was an interaction on the diarrhea rate and diarrhea frequency(2-4 week),diarrhea frequency calculation in the whole preweaning period(P < 0.05),the trend was the same as weaning weight and ADG.Therefore,starch with low SB is more healthy.Experiment 3: Interaction of starch and SB on weaning stress of weaning transition calvesIn this study,the effects of dietary starch level and SB on weaning stress of Holstein calves were analyzed by measuring growth performance,diarrhea,serum cortisol,and acute phase protein.The results showed that:(1)low starch had higher DMI(P = 0.077),and SB increased ADG(P < 0.05)and hay DMI(P < 0.05)within 3 weeks after weaning.(2)Low starch had lower diarrhea rate(P < 0.05).(3)Low starch had lower cortisol concentration,while SB decreased cortisol concentration in low starch,but increased it in high starch,showing interaction(P < 0.01);however,SB increased the concentration of C-reactive protein(P < 0.01),amyloid A(P < 0.01)and haptoglobin(P = 0.10),with a lower increase in low starch.Therefore,the weaning stress of calves fed low starch diet was less,and the addition of SB in low starch diet was more advantageous to weaning.In summary,the addition of sodium butyrate into the starter with high starch is beneficial to the growth and health of lactating calves.The addition of sodium butyrate into low-starch starter has less weaning stress and can reduce stress responses. |
