The Dynamics Of Bacterial Communities In Sows Milk

Breast milk provides not only all the nutrients and immunologic active compounds for the viability and health of offspring,but also abundant bacteria.The milk microbiota contributes to the “initial” intestinal microbiota of infants and also plays a crucial role in modulating and influencing neonatal health.However,the milk microbiota of sows has yet to be systematically investigated.The goal of the present study was to characterize variations in bacterial diversity and composition in sow milk over the duration of lactation using a high-throughput sequencing approach.In the present study,milk samples(n=130)were collected from 30 healthy landrace-yorkshire hybrid sows at 8 different time points,and microbial profiles were analysed by 16 S ribosomal RNA(rRNA)sequencing using the Illumina MiSeq platform,and analysis of bioinformatics were applied to investigate the dynamic changes of bacteria in sows milk was analyzed.The correlation between routine nutrients and relative abundance of bacteria in sow milk was analyzed;to explore the reasons of the dynamic changes of the milk bacteria.These results lay the groundwork for further studies exploring milk replacement and probiotics to reduce weaning stress for piglets during the transition to food.The main result are as follow:(1)At the phylum level,a total of 12 taxa were identified in the sow milk samples.Firmicutes(mean relative abundance: 52.73%),Proteobacteria(25.44%),Actinobacteria(8.25%),Bacteroidetes(8.16%),Fusobacterium(2.99%),and Tenericutes(1.10%)were dominant bacterial phyla in the sow milk samples.These dominant bacterial phyla accounted for 98.68% of the total sequence in the milk samples.At the genera level,a total of 212 taxa were identified.Unclassified Ruminococcaceae(4.91%),Streptococcus(4.57%),unclassified Clostridiales(4.66%),Lactobacillus(3.56%),unclassified Lachnospiraceae(3.12%)and Corynebacterium(3.11%)were the most abundant genera in our samples.(2)The amounts of Streptococcus,Bifidobacterium and Staphylococcus genera were 4.49,3.94 and 3.62 in log-transformed 16 S rDNA gene copy number per milliter of sample by using qPCR,respectively.(3)The composition and diversity of the sows' milk microbiota significantly changed in different stages of lactation(P<0.05).The relative abundance of microbiota was fluctuating changes in the first five days of lactation,but relative stable after seven days.In addition,the diversity of microbiota in colostrum(0~5 days)is lower than that of the transitional and mature milk samples(6~21days).(4)There was a significant correlation between the relative abundance of milk microbiota and the content of routine nutrients(P<0.05).Caulobacteraceae,Pseudomonas,Peptoniphilus,Enterococcus,Comamonas,Comamonadaceae,Clostridiu significantly positively corelated with the lactose and protein content(0.4??<0.6),but significantly negatively correlated with fat content(-0.6??<-0.4).Prevotella,Leptotrichia,p-75-a5,Weeksellaceae,Fusobacterium,Oscillospira significantly positively correlated with fat content(0.4??<0.6),but significantly negatively correlated with lactose and protein content(-0.6??<-0.4).(5)There were high linear relationship between the 23 dominant genera,and the beneficial bacteria may have a certain inhibitory effect on harmful bacteria.Among them,Oscillospira,prevotella,Lactobacillus and Bactaeroidia had positively correlated with each other.Helcococcus had negative correlation with Oscillospira,Lactobacillus,Ruminococcaceae and other beneficial bacteria.(6)A total of 37 functional gene families were identified through Phylogenetic Investigation of Communities by Reconstruction of Unobserved States(PICRUSTs).Membrane transport,amino acid metabolism and carbohydrate metabolism were the most abundant functional categories in sow milk communities.The function of the relative abundance of the gene family was fluctuation change in the first five days of lactation,to stabilize after the seven days of lactation.(7)The relative abundance of 19 bacteria genus were correlated with the daily weight gain of piglets,and the relative abundance of 21 bacteria genus were correlated with the weaning weight of piglets.Three beneficial bacteria,such as Lactobacillus,Propionibacterium and Sphingobium,were positively correlated with the weight of piglets.In summary,there were abundant microbiota in the milk of landrace-yorkshire hybrid sows,and some of which were significantly related to the weight of piglets.Lactation stage influenced microbial composition and diversity,which may be related to the fluctuation of nutrients in colostrum.