Study On Early Weaning Of Beef Calves And Starch Structure In Fattening Diet And Its Application In Beef Cattle

This study aimed at the key points of high-efficiency rearing technology of beef cattle to carry out research on early weaning technique of beef calves and formulation technique of fattening diet for beef cattle.The first experiment evaluated the effects of early weaning on growth performance of both Simmental beef calves and cows and conception rate of cows.Twenty calves with 40 days of age were randomly arranged into two groups(n=10 per group):control group(reared with cows until completely weaned at 4 months of age)and early weaning group(separated from cows and fed milk replacer until completely weaned at 3 months of age).The experiment was lasted until all the calves were 4 months of age.Body weight and body size of calves and body weight and conception rate of cows were measured.The second experiment evaluated the effects of dietary starch amylose/amylopectin ratio on growth performance,rumen fermentation and blood parameters,and carcass characteristics and marbling score,and meat fatty acid profiles and transcriptional changes in the genes involved in gluconeogenesis pathway in Chinese Qinchuan cattle.Forty five cattle were randomly divided into three groups(n=15 per group).The bulls were fed a control diet(middle amylose/amylopectin ratio=0.47)or diets with waxy corn starch(WS)inclusion(low amylose/amylopectin ratio=0.23)or pea starch(PS)inclusion(high amylose/amylopectin ratio=0.60)for 90 days.Blood and rumen fluid samples were collected at 45-day intervals to measure the blood metabolites and rumen fermentation parameters,and longissimus thoracis muscle and liver samples were also collected after slaughter to measure the meat quality and mRNA levels of genes related to gluconeogenesis.Demonstration test on early weaning of beef calves and feeding techniques of cowsDemonstration test of calves:-Feed intake of early weaning group was higher than that of control group.-There were no significant difference in growth performance and body size between two groups.Demonstration test of cows:-Average daily gain of early weaning group was higher than that of control group.-Conception rate of the early weaning group was approximately two times of that of the control group.Study on starch structure in fattening diet and its application in beef cattle-During the whole feeding trial,the average daily gain(ADG)in control and WS showed the trend to be higher than that of PS,while other growth performance and feed intake did not differ among three groups.-Compared with PS,the serum insulin concentration in WS was increased,while compared with control and WS,the serum SOD and T-AOC concentrations in PS were increased at d 45.-Compared with PS,the rumen microbial crude protein contents in control and WS were increased at d 45,but not at other periods.-Compared with PS,the backfat thickness in control and WS were increased,however,marbling score and expression of genes related to gluconeogenesis pathway in liver of three groups did not differ.-Taken together,diet with low or middle amylose/amylopectin ratio increased the backfat thickness,tended to improve ADG,but had no effect on other carcass characteristics,fat content in the LT,and express of hepatic genes related to gluconeogenesis pathway in Chinese Qinchuan cattle.