| Early weaning is a commonly used technique in intensive mutton sheep farming mode.Early weaning can easily lead to lamb stress,poor lamb resistance,and increased incidence,which is not conducive to lamb growth and development.At present,probiotics are developing rapidly and are widely used in feed additives.This study aimed at the problem of digestive tract development of early-weaned lambs by feeding a bacillus subtilis compound feed(BS compound)to evaluate its effect on gastrointestinal development,and provided a theoretical basis for early-weaning of lambs.45 newborn healthy male lambs(double lambs)with similar body weight were randomly divided into three experimental treatment groups,namely,the early weaning at day of 45 group(EW45),the early weaning at day of 45+bacillus subtilis compound(EW45+BS)group and the normal weaning at day of 60 group(NW60).Four animals randomly selected from each group were sacrificed for sampling on the day of weaning.The remained lambs were reared to 75 days,in which another 4 lambs randomly selected from each group were sacrificed forsampling as that on the day of weaning.The aforementioned 3 group’s then suffixed with-75 each as EW45-75,EW45+BS-75,and NW60-75.Samples of gastrointestinal tissues,blood,visceral organs and feces were collected at the weaning time and at day 75 for measuring growth and development,digestion and absorption indicators,blood physiological and biochemical parameters and inflammatory factors,and for the analysis of gut microbiota changes by 16s rRNA.The results are as follows:1.The body weight and visceral organs of slaughtered lamb were weighed.At different weaning time point the stomach organ coefficient of EW45+BS group was significantly lower than the NW60 group(P<0.05),and the hormone levels of GH and INS in EW45 group were significantly lower than the NW60 group(P<0.05);At age of day 75 The body weight of EW45+BS group was significantly higher than that of NW60 group(P<0.05).The kidney organ coefficient of EW45 + BS group was significantly higher that of NW60 group(P<0.05).2.Techniques of histology,ELISA and Western Blot were applied to detect the histological morphology of rumen and intestine,the digestive activity of enzymes in the small intestine,and the expression level of glucose transfer protein 2(GLUT2).At different weaning time point the number of Ruminal papilla per unit area in the EW45+BS group was significantly higher than the EW45 group(P<0.05).The villi height of duodenum and ileum in EW45 group were significantly higher than that in NW60 group(P<0.05).The villi height of the mid-jejunum in EW45+BS group was significantly higher than that in NW60 group(P<0.05),and lipase、amylase、maltase、invertase and protease activity was significantly higher than the NW60 group.At age of day75 the villi height of duodenum and front jejunum in EW45+BS group was extremely higher than that in NW60 group(P<0.01),the digestive enzyme activity in different segments of the small intestine in lambs of EW45+BS group was significantly increased when compared with those of EW45 group.The expression of GLUT2 in the jejunum of EW45+BS group was significantly higher than the NW60 group(P<0.05).3.Blood physio-biochemical measurement and ELISA were used to detect blood physio-biochemical indexes and immune factors.At different weaning time point the blood physiological parameters in EW45 group were closer to that in NW60 group,and the RBC and IL-6 contents of the EW45+BS group were significantly lower than of NW60 group(P<0.05)and the cholesterol and triglyceride were significantly higher than that of NW60 group(P<0.05);At age of day75 the blood biochemical parameters of the EW45+BS group were closer to those of NW60 group than those of EW45 group were.HGB and RBC of the EW45 and EW45+BS groups were extremely significantly higher than those of NW60 group(P<0.01).4.16S rRNA high-throughput Sequencing technology were applied to analyze of V3 and V4 variable regions of gut microbiota using stool samples.At different weaning time point,Alpha and Beta diversity of gut microbiota in EW45 and EW45+BS groups was not significantly different from that of NW60,but the levels of Bacillus,RF39 and Mollicules are still different.At age of day75 Prevotella in EW45+BS group was extremely significantly higher than that in NW60 group(P<0.01).The results showed that supplementary of the bacillus subtilis compound could increase the height of the intestinal villi of the lamb,increase the activity of digestive enzymes in the intestine,promote the absorption of sugar in the intestine,improve blood physiological functions,and improve the flora in the small intestine of lamb,increase the number of beneficial bacteria.Bacillus subtilis compound could be supplied as a beneficial feed additive to improve the growth and development of gastrointestinal tract for early weaned lambs. |
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