Effects Of Weaning Stress And Supplementation Of Resveratrol And Bacillus Licheniformis On Gastrointestinal Development And Microbiota In Lambs

Weaning is an unavoidable event in the growth and development of lambs.With the development of large-scale sheep farming,weaning age is often earlier than the natural growth period due to considerations of improved production efficiency.Early weaning is accompanied with lactation termination,dietary changes,separation from ewes and environment transformation.These drastic changes stagnate the growth rate and leading to increased susceptibility of young animals to disease.Therefore,investigation of the weaning stress mechanism and nutrition manipulation will be of great importance to improve the early raring technology of lambs.This study was conducted to evaluate the effects of early weaning and oral supplementation of Resveratrol（RSV）and Bacillus licheniformis（BL）on growth performance,nutrient digestibility,serological parameters,rumen fermentation and microbiota,intestinal epithelial tissue structure and intestinal microbiota of lambs.The main results are as follows.1.Effects of weaning stress and oral supplementation resveratrol or Bacillus licheniformis on growth performance,nutrient digestion and utilization,and blood parameters of lambsA total of 120 neonatal Hu lambs averaged 3.82±0.46 kg of body weight（BW）were randomly divided into 4 groups,including CON group（lambs were conventional weaned at 49 day of age）,EW group（lambs were early weaned at 21 days of age）,RSV group（early weaned lambs were supplemented with 10 mg/kg BW resveratrol）,and BL group（early weaned lambs were supplemented with 60 mg/kg BW Bacillus licheniformis with≥4.0×10⁹ CFU/g live bacteria）.Each group had 3 replicates with 10lambs in each replicate.From day 7 of age,all lambs were offered pelleted starter.The body weight（BW）of each lamb was recorded weekly.The intake of starter was measured by each pen daily.The digestion trial was carried out during d 56 to 63,and blood sample was collected on d 26,35 and 63.The experiment lasted 63 d.The results showed that weaning stress had a significant effect on lambs’performance.After weaning,the average daily gain（ADG）decreased significantly at the first week after weaning and reached normal levels since the third week.The lambs’diarrhea rate was increased due to weaning stress.Oral supplementation of resveratrol and Bacillus licheniformis had no significant effect on starter intake,ADG and diarrhea rate of lambs before and after weaning（P>0.05）.Early weaning on d 21 promoted the rumen development rapidly and did not affect the development of the internal organs of lambs.There was no difference in the serum immunity,antioxidant and inflammation of lambs by early weaned or feed additives,and these indicators fluctuated with the increase of age,and 14 days after weaning may be the period for the recovery of weaning stress.2.Effects of weaning stress and oral supplementation of resveratrol and Bacillus licheniformis on rumen fermentation and microbiotaLambs were slaughtered and sampled on d 26,35 and 63,respectively.Rumen pH,volatile fatty acids（VFA）and NH₃-N concentrations were measured.Samples of rumen contents were collected and sequenced using 16S rDNA technique.The results showed that the rumen pH and NH₃-N concentrations.The rumen Total VFA concentrations of EW group was increased at d 26 and d 35,but rumen pH,NH₃-N and Total VFA concentrations of the lambs were no difference among the groups on d63.Early weaning led to a significant decrease in rumen microbiota richness and diversity in the short-term（P<0.05）,and led the rumen microbiota to shift at the phylum and genus levels.The relative abundance of rumen Syntrophococcus and Dialister which are fiber digesting bacteria were increased significantly on d 26 due to weaning stress.There was no significant difference in rumen fermentation parameters and rumen microbial communities by supplementation of resveratrol and Bacillus licheniformis.Supplementation of resveratrol increased the abundance of Selenomonas 1 on 26 d and Megasphaera on 35 d,and supplementation of Bacillus licheniformis increased the relative abundance of Bifidobacterium and Selenomonas 1on 35 d.Some of the rumen bacteria composition evolved with the increase of age.The number of significantly different bacteria caused by age were more compared with weaning.The similarity of the rumen microbiota composition was increased with the increase of age and 35 d may be the node of rumen microbiota evolution.3.Effects of weaning stress and oral supplementation of resveratrol or Bacillus licheniformis on the intestinal morphology,mucosal immunity and microbiota of lambsAt 26,35 and 63 d of age,the jejunal tissue,contents and mucosa of the middle jejunum section of lambs were collected.The results showed that there was no significant difference in the jejunum villus height,the number of lymphocytes and goblet cells and the concentration of sIgA of lambs among groups（P>0.05）.Early weaning did not affect the microbial richness of the jejunum contents in lambs,just reduced the microbial diversity on 35 d.Some genus level bacteria have changed mainly occur at 5 days after weaning.After early weaning,the relative abundance of Lactobacillus decreased,while Olsenella and Syntrophococcus increased on the intestinal content bacteria of lambs.Supplementation of resveratrol or Bacillus licheniformis had a specific effect on the intestinal bacteria of lambs and some of the genera have changed.Feeding Bacillus licheniformis significantly increased the relative abundance of Sharpea and Bifidobacterium in the jejunum content of lambs on 26 d.jejunal The jejunum contents microbiota succeeded with age and tended to be stable,and closed to the composition of adult animal microbiota at 35 days.The richness and diversity of the lamb jejunum mucosa microbiota were decreased due to early weaning.There was no significant effect on the microbial composition of phylum taxa by early weaning,but the abundance of genera lactobacillus in the lamb jejunum mucosa decreased in on 26 d by early weaning.Supplementation of resveratrol had no significant effect on the lamb jejunum mucosa microflora,while feeding Bacillus licheniformis affected the abundance of some bacteria on d 26 and d35.Some genera bacteria of the jejunum mucosa of lambs changed significantly with age,especially the abundance of Lactobacillus decreased significantly with age.In summary,weaning stress response was most obvious in the first week after weaning and the growth performance began to recover from the third week.The lambs’rumen and intestinal microbiota were transferred at the phylum and genus levels in the short term due to early weaning.Dietary changes brought about by age and weaning are the main factors that determined the rumen microbiota and fermentation parameters.The significant decrease in intestinal beneficial bacteria Lactobacillus is an important cause of lambs’diarrhea after weaning.The changes in the rumen and intestinal microbiota are adaptations to the changes in feed and environment,and 35 d is the node for the recovery of weaning stress and the stable establishment of gastrointestinal microbiota.Under the conditions of this experiment,oral supplementation of resveratrol or Bacillus licheniformis in the early life of age had no significant effect on the growth performance,and had a specific effect on the rumen and intestinal microflora composition of lambs.