Development Of Digestive Tract And Its Regulation By Beta-hydroxybutyric Acid In Goats

The development of the digestive tract of goat kids from birth to weaning is critical for the establishment of mature digestion function and healthy growth of adult goats.However,its basic developmental law is not clear,and there is a lack of effective control measures.Therefore,the purpose of this paper is to fit the growth prediction model by exploring the effects of age and dietary factors on the development of the digestive tract of goat lambs,and to ensure a smooth transition from liquid to solid diets by supplementing beta-hydroxybutyric acid(BHBA)to stimulate rumen development.Finally,it provides a theoretical basis for optimizing feeding management and efficient feeding.Firstly,forty-eight female Laiwu Black goats at 8 ages(1,7,14,28,42,56,70,and 84 d;6 goats per group)were selected and killed for anatomical and morphological analysis.The goats experienced the following 4 diet phases:maternal colostrum(d1,d7),maternal milk(d14,d28),maternal milk plus solid diet(d42,d56)and only solid diet(d70,d84).The body size indices,rumen weight,percentage of complex stomach to body weight,crypt depth and muscle layer thickness of jejunum increased over time,whereas the percentage of organs to bodyweight decreased over time.The absolute growth of body weight and carcass weight,the crypt depth of jejunum and ileum of lambs were higher than those fed colostrum and normal milk,and the slaughter rate was the highest in the stage of milk plus starter feeding.At the starter feeding stage,the height of the rumen papilla,the thickness of the lamina propria,the muscle layer thickness and the epithelial thickness were the highest,the crypt depth,the muscle layer thickness and the epithelial thickness of the duodenal were the highest,the colonic mucosa thickness and the villi height and muscle layer thickness of ileal are highest.In conclusion,the solid starter improved digestive tract morphogenesis and growth performance of goat kids.Secondly,based on the body weight,body size,and organ development parameters,the growth curve model of goat kids was fitted.It was found that body weight,body oblique length,tube circumference and rumen weight growth fit the Gompertz model,carcass weight,height and bust circumference fit the Logistic model,slaughter rate,abomasum weight and rumen volume fit the quadratic curve model,rumen p H and the percentage of reticulum fit cubic curve model,and the reticulum weight and omasum percentage fit the Weibull model,while the chest depth,rumen and abomasum percentage fit the MMF model.Model parameters,correlation coefficient(R~2),inflection point,area under the curve vary between different dependent variables.Pearson’s correlation showed that digestive tract development was more correlated with age than body weight,but other variables were more correlated with body weight than with age.In conclusion,the S model and the polynomial model can be used to predict the growth and development of the digestive tract of goat lambs.Thirdly,30 male goats of different ages(1,2,3,6,and 12 months old)were selected to study the effect of age on blood BHBA and related health indicators.The results showed that 12-month-old goats had significantly lower blood concentrations of total protein,globulin,BHBA,Ig A,and Ig M,while the ratio of albumin to globulin was significantly increased compared with 1-to 3-month-old goats.At the same time,blood glucose decreased,and Ig G increased with age in goats.Blood GH and IGF1 were lower in lambs at 1 and 3 months of age than in 12-month-old goats.It was suggested that age has a large effect on blood composition,especially around weaning.Finally,64 1-month-old goat kids(half males and females)were selected to study the effects of BHBA(0,3,6 and 9 g/day)on growth,digestion and organ development.Low-and high-dose BHBA increased feed intake and daily gain compared to control,and low-dose BHBA improved organ development but did not affect nutrient digestibility.At 60 days of age,high-dose BHBA increased serum ratio of albumin to globulin,while middle-dose BHBA decreased serum GH and IGF1.At 90days of age,high-dose BHBA decreased serum TAOC and SOD,and increased serum ceruloplasmin and MDA contents.However,dietary supplementation of BHBA had no effect on serum BHBA content.Overall,low-dose BHBA were positive for growth,organ development and health status,whereas high-dose BHBA may negatively affect antioxidant ability.In conclusion,the digestive development of goat kids is affected by both age and diet,especially the solid starter,which has a significant effect on the morphological development and growth performance of the goat kids.Dietary supplementation with low-doses BHBA improved rumen development and growth performance,whereas high-dose BHBA appeared to increase oxidative stress in goat kids.Low-dose BHBA is suggested to improve growth and development of goat kids safely and effectively.