Effects Of Ruminal Degradable Starch Levels On Growth Performance,Blood Parameter And Immunity In Young Dairy Goat

With the continuous breeding of livestock,whose production performance has constantly improved,energy and other nutrients demand of ruminants is also gradually increased.In order to meet the energy demand of ruminants,dietary starch level is often increased in practice.However,the degradation of large amounts of starch in rumen not only causes energy loss,but also rumen acidosis,which is harmful to animal health.Therefore,regulating the rumen degradation rate of dietary starch is of great significance for guaranteeing the energy supply efficiency of starch and animal health.Corn which is rich in starch is the most commonly energy feed for dairy goats.Comminution of corn could change the contact area between corn starch granules and rumen microbes and improve the rumen degradation rate of corn starch.The experiment chose grinding corn and whole grain corn to control the rumen degradation rate of starch to study the effects of rumen degradable starch?RDS?on growth performance of dairy goats,and the change of blood parameter and immune function,exploring the potential mechanism of effect of RDS on the metabolism and health of ruminant,and providing the scientific basis for practice.Experiment 1:The effects of RDS on growth performance and rumination time of dairy goatsIn this experiment,40 weaning lambs with similar body condition?13.6±0.23 kg,3months old?were randomly divided into two groups,respectively named the low rumen degradable starch?L-RDS?group and the high rumen degradable starch?H-RDS?group,each group had 20 goats.The pre-feeding period was one week,and the experimental period was 28 weeks?dairy goats grew from 3 to 10 months old?.Growth performance,body size parameter and rumination time of goats were measured in experiment period.Comparing with H-RDS group in 3-6 months old goats,average daily weight gain was increased?P<0.05?,feed weight ratio were decreased?P<0.05?,and chest and abdominal girth tend to increased?P<0.1?in L-RDS group.The body height of goats aged 6-10 months showed an increasing trend?P<0.1?in L-RDS group when compared to H-RDS group.In the whole experimental period?3-10 months?,there are increasing trends in body height and chest circumference?P<0.1?after feeding the L-RDS diet,but had no significant effect on ruminant time of dairy goats?P>0.05?.The results showed that appropriate reduction of RDS level on similar nutrition diet could improve the growth performance of dairy goats aged 3-6months and promote the growth of body height and chest circumference.Experiment 2:The effects of RDS on blood parameter and immunity of dairy goatsThe growth performance of dairy goats aged 3-6 months old were increased in the experiment 1.On the basis of this,the blood parameter,hormones and immunity indexes of dairy goats were measured in Experiment 2 to detect the different performance of the metabolism and immunity level of goats to explore the potential mechanism.At 11^thh week and 27^th week,serum samples were collected before morning feeding and after morning feeding for 2 h,4 h,6 h and 8 h to measure blood parameter.Part of the serum before morning feeding was taken to measure the blood hormone and immunity indexes.Dairy goats were slaughtered at 12^th week and 18^th week,and liver tissues were collected to detect the mRNA expression of inflammatory cytokines.In L-RDS group,the triglycerides and low-density lipoprotein concentration in blood were increased?P<0.05?and the content of total cholesterol were significantly increased?P<0.01?,the level of blood urea nitrogen was significantly reduced?P<0.01?in 6-month-old goats compared to H-RDS group.However,there was no significant effect on blood enzymes?glutamic-oxalacetic transaminase and glutamic-pyruvic transaminase?and hormones?insulin,growth hormone,insulin-like growth factor 1??P>0.05?.In 10 months old goats,the level of glutamic-pyruvic transaminase and insulin in blood were reduced?P<0.05?,and the level of urea nitrogen was significantly reduced?P<0.01?when fed L-RDS diet compared to H-RDS diet.For immunity index,The content of albumin in blood were increased?P<0.01?,and globulin in blood were decreased?P<0.05?when fed L-RDS diet in dairy goats aged 6 months old than H-RDS diet.The content of globulin in blood tended to decrease in L-RDS group?P<0.1?in 10 months old dairy goats.Combined with the age of 6 months and 10 months,the ratio of albumin to globulin in blood of dairy goats fed L-RDS diet were significantly increased?P<0.01?compared to H-RDS diet.There was no effect on TNF-?,LBP,IL-6,IgG?P>0.05?in blood,and inflammatory cytokines in the liver?P>0.05?in L-RDS group.The results showed that appropriate reduction of RDS level on similar nutrition diet may promote lipid and microbial protein synthesis,improve amino acid balance,and improve nitrogen and energy utilization efficiency in weaning dairy goats?3-6 months?.In conclusion,with the same dietary nutrition level,appropriate reduction of RDS level may improve the synthesis of lipid and rumen microbial protein in dairy goats aged 3-6months,improve the balance of amino acids,improve the utilization rate of energy and nitrogen,and promote the growth and development of dairy goats aged 3-6 months.