| This study was devided into three stages which included 24 months of feeding trials and slaughtering trials.40 Xianan cattle were divided into five treatment groups:A,B,C,D and E.The trial design of each stage was as follows: early fattening:6-12-month-old,6 months,Group A-E fed with 4.61、4.91、5.22、5.52、5.82MJ/Kg net energy diet respectively;middle fattening: 12-18-month-old,6 months,fed the same medium-term fattening diet;late fattening: 18-30-month-old,12 months,fed the same fattening-late diet.The study’s purpose was to investigate the effects of energy levels in the early fattening period on the growth performance,nutrient digestibility,blood metabolites,meat quality,rumen fermentation,and flora structure of Xianan cattle in middle and late fattening stages and provide technical basis for the choosing of feeding mode and feed preparation.The study was divided into five parts:The effects of energy levels in the early fattening period on the daily weight gain and feed intake of Xianan cattle in early、middle and late fattening stages.On the first and last day of each experimental period,the cattles were weighed on an empty stomach before morning feeding.Then the average daily weight gain of each cattle was calculated.Three days before the middle and late stages of fattening,15 cattles,each group with 3 cattles were randomly selected which aimed to acquire the ADFI.The results showed that:(1)In the early fattening period;Compared with group A,the daily weight gain of groups C,D and E increased by 24%,25%,and 42%;Compared with group B,the daily weight gain of group E were increased by 27%,the difference was significant(P<0.05);(2)In the middle period of fattening,the daily weight gain of the group A,D,and E were significantly higher than that of group B(P<0.05);Dry matter intake,group B was significantly lower than group A,C and E(P<0.05);(3)In the late fattening period,the daily weight gain of groups A and E was significantly higher than that of group B(P<0.05);there was no significant difference in dry matter intake between five groups(P >0.05).The effect of energy levels in the early fattening period on the digestibility of nutrients in Xianan cattle during the middle and late stages.On the last three days of two stages,15 cattles,each group with 3 were randomly selected to determine the nutrients digestibilities.The results showed that:(1)Mid-term fattening;the dry matter,crude protein,crude fat,and ADF digestibility of the group B,C,and D were all improved to a certain extent compared with group A,but the difference was not Significant(P> 0.05);Energy utilization rate: The total energy intake of group A was higher than the other four groups,the difference in fecal energy excretion was not significant(P> 0.05),and the difference in digestive energy of each group was not significant(P>0.05)),The total digestibility of group A and E was lower than the three groups of B,C and D,but the difference was not significant(P>0.05).(2)Late fattening;There was no significant difference in nutrient digestibility among the five groups(P>0.05);energy utilization rate: there is no difference in digestive energy of the five groups,There was no difference in total digestibility(P>0.05).The influence of energy levels in the early fattening period on the blood indexes of mid-and late-stage fattening of Xianan cattle.When the two stages were completed,the blood was collected and relevant indicators were measured.The results showed that:(1)The middle period of fattening;Blood immune indicators: the Ig G content in the A and D groups was significantly lower than that in the group E(P<0.05),The content of Ig M and Ig A gradually increased with the increasing of energy level,but there was no significant difference(P>0.05);Blood hormone index:the IGF-1 content in group B was significantly lower than those in group C and D,and the IGF-1 content in group E was significantly lower than that in group D(P<0.05),There was no difference in growth hormone and insulin content in each group.The insulin content in group A was higher than the other four groups,but the difference was not significant(P>0.05).Blood antioxidant index: There was no significant difference between MDA and SOD in each group(P>0.05).The content of glutathione peroxidase in group A was significantly lower than those in group B,C,and D(P<0.05);Blood biochemical indicators: the content of high density lipoprotein cholesterol in group A was significantly lower than those in group D,at the same time,the HDL of group B and C was significantly lower than group D and E(P<0.05);With the increasing of the dietary energy level,the total protein content showed an upward trend,but there was no significant difference between the groups(P> 0.05).(2)The late period of fattening;Blood immune indicators: There was no significant difference in Ig G,Ig M,Ig A content in each group(P>0.05);Blood hormone indicators: The content of IGF-1 in group C was significantly higher than those in group D and E,and the content of IGF-1 in group B was significantly higher than that in group E(P<0.05);Blood antioxidant indexes: The total antioxidant capacity of group A was significantly lower than those of group C and E,and the total antioxidant capacity of group B and D were significantly higher Lower than group C(P <0.05);There was no significant difference in the content of malondialdehyde and glutathione peroxidase in each group(P>0.05);Blood biochemical indicators: There was no significant difference in each group(P>0.05).The the effects of energy levels on the rumen VFA and flora structure in the late fattening period of Xianan cattle.When the experiments finished,all cattles were slaughtered and rumen fluid was collected to determine the content of VFA and the structure of the rumen flora.The results showed that:(1)the rumen acetic acid content in group A and E was significantly higher than that in group B(P<0.05);the content of isovaleric acid in groups A,D,and E was significantly higher than that in group B,and the content of isovaleric acid in group C was significantly lower than group E(P<0.05).(2)There were 1883 OTUs in group A,of which 264 were unique and there were 1813 OTUs in group E,of which 194 are unique.There were 1619 crossed by the two groups.There was no significant difference in Chao and Ace indexes betwee group A and E(P> 0.05).At the same time,there was no difference in Simpson and Shannon indexes.The four indexes meaned that there was no significant difference in the rumen flora richness and diversity.Bacteroidetes and Firmicutes were dominant flora of two groups of which the sum exceeded 90%.At the genus level,bacterial flora in the top 10 had no differences between the two groups.The effect of energy levels in the early fattening period on the meat quality of Xianan cattle.After part 4,the longest dorsal muscle was taken to determine related meat quality indicators.The results showed that: the shear force value of group A was significantly higher than that of group B,C,and E(P<0.05),The p H of group D was significantly lower than that of group A,B,C,and E,and the p H of group B was significantly higher than those of groups A,C,and D(P< 0.05);the yellowness of group E was significantly higher than the other four groups;Other indicators had no significant difference between the groups(P>0.05).To sum up:(1)there were no significant differences in daily gain,nutrient digestibility,rumen fermentation function and microbial flora between a and e groups of Xianan cattle in the middle and later period.Therefore,the production of Xianan cattle could be carried out by means of straight-line fattening or hanging rack fattening.(2)The high energy level in the early stage can improve the immune index and meat quality of Xianan cattle. |
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