| A total of sixty-four newborn healthy Holstein male calves at the age of 4 days were randomly selected and divided into 8 treatment groups according to the principle of similar body weight using a 2×2×2 factorial design.Group A(weaning on day 35,Starch31.5%,Ordinary ingredient)and group B(weaning on day 35,Starch31.5%,Curing ingredient),group C(weaning on day 35,Starch24.5%,Ordinary ingredient),group D(weaning on day 35,Starch24.5%,Curing ingredient),group E(weaning on day 42,Starch31.5%,Ordinary ingredient),group F(weaning on day 42,Starch31.5%,Curing ingredient),group G(weaning on day 42,Starch24.5%,Ordinary ingredient),group H(weaning on day 42,Starch24.5%,Curing ingredient).All treatment groups were fed the same granule during the growth period(66 to 180 days of age).The paper aimed to explored the effects of different weaning age,starch level and starter ingredient on the growth performance,blood parameters,rumen development and microbial flora of calves,and provide theoretical basis for scientific feeding management and rational application of ration preparation of calves.The specific research content is divided into the following three aspects:Experiment 1: The effects of weaning age,starch level and starter ingredient on growth performance of calves.The results showed that the dry matter intake of the groups(A,B,C,D)that weaning on day 35 were significantly higher than that of groups(E,F,G,H)that weaning on day 42(P<0.05).The diarrhea rate of ordinary ingredient of starter groups(A,E,C,G)was significantly lower than that of curing ingredient of starter groups(B,F,D,H)(P<0.05);For the body weight of calves on days 35 and 42,the groups(E,F,G,H)that weaning on day 42 were significantly higher than those groups(A,B,C,D)that weaning on day 35(P<0.05).During the periods of 4～35 days and 4～42 days,the average daily gain groups(E,F,G,H)that weaning on day 42 were significantly higher than those groups(A,B,C,D)that weaning on day 35(P<0.05),and the average daily gain of ordinary ingredient of starter groups(A,E,C,G)were significantly higher than that of curing ingredient of starter groups(B,F,D,H)(P<0.05);The average daily gain of groups(A,B,C,D)that weaning on day 35 were significantly higher than those groups(E,F,G,H)that weaning on day 42 during the periods of 36～60 days and 43～60days(P<0.05).Experiment 2:Experiment 2:Effects of weaning age,starch level and starter ingredient on blood indexes of calves.The results showed that: on day 35,the concentrations of ALB and BUN in blood in groups(A,B,C,D)that weaning on day 35 were significantly higher than those groups(E,F,G,H)that weaning on day 42(P<0.05)and the concentrations of GLU in groups(E,F,G,H)that weaning on day 42 was significantly higher than those groups(A,B,C,D)that weaning on day 35(P<0.05).On day 42,the concentrations of BUN in blood in groups(A,B,C,D)that weaning on day 35 was significantly higher than those groups(E,F,G,H)that weaning on day 42(P<0.05).On day 35,the concentrations of Ig G in groups(E,F,G,H)that weaning on day 42 was significantly higher than those groups(A,B,C,D)that weaning on day35(P<0.05)and Ig G in 31.5% starch groups(A,B,E,F)was significantly higher than that in24.5% starch groups(C,D,G,H)(P<0.05).On day 42,the concentration of Ig M in groups(A,B,C,D)that weaning on day 35 was significantly higher than those groups(E,F,G,H)that weaning on day 42(P<0.05),however,opposite results of the concentration of Ig A and Ig G were found(P<0.05),and Ig A and Ig M in 24.5% starch groups(C,D,G,H)was significantly higher than that in 31.5% starch groups(A,B,E,F)(P<0.05).On day 90,the concentrations of Ig G in groups(E,F,G,H)that weaning on day 42 was significantly higher than those groups(A,B,C,D)that weaning on day 35(P<0.05).Experiment 3: Effects of weaning age,starch level and starter ingredient on rumen development of calves.The results showed that: on day 60,rumen p H value in groups(A,B,C,D)that weaning on day 35 was significantly higher than those groups(E,F,G,H)that weaning on day 42(P<0.05),and acetic acid concentration in rumen in groups(E,F,G,H)that weaning on day 42 was significantly higher than those groups(A,B,C,D)that weaning on day 35(P<0.05).At phylum level,13 and 15 phyla of rumen microorganisms were identified on day 60 and 120,respectively.Bacteroidetes was the dominant phylum on day 60,however,Firmicutes was the phylum on day 120.Synergistetes was only detected in group H on day 60.Tenericutes was detected in group B,C,E and G,TM7 was detected in group F,Spirochaetes was detected in group E and G on day 120,and Cyanobacteria was detected in group B and D.At genus level,129 genera were detected in the rumen on day 60 and 74 genera were detected on day 120.Prevotella was the most abundant on day 60 and the abundance was more than 45% in the all treatment groups.On day 120,Prevotella was the most abundant in groups A(19%),B(23%),D(36%),F(22%)and H(21%),and Succiniclasticum was the most abundant in groups C(21%),E(8%)and G(9%).On day 60,Chao1 richness,Shannon diversity and Simpson diversity in groups(E,F,G,H)that weaning on day 42 were significantly higher than those groups(A,B,C,D)that weaning on day 35(P<0.05),and Chao1 richness and Shannon diversity curing ingredient of starter groups(B,D,F,H)were significantly higher than those in the normal structure groups(A,C,E,G)(P<0.05).On day 120,Chao1 richness of calves in groups(A,B,C,D)that weaning on day 35 was significantly higher than that in groups(E,F,G,H)that weaning on day 42(P<0.05),which was contrary to the results on day 60.Conclusion: In this experiment,it is recommended that the weaning age of the calf is 35 days,the starch level of the starter is 24.5%,and the main raw material is corn and soybean meal with common structure. |
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