Abstract: The gut morphology and function in newborn lambs changed dramatically during suckling period. However, the growth and development of the composition and structure of gut microbiota (GM) were less clear. This experiment was conducted to study the changes and characteristics of the composition of GM in one-month-old Hu lambs. Healthy sucking lambs without antibiotic therapy history were randomly selected in neonatal period (3 days old, d03), suckling period (10 days old, d10), creep feeding period (15 days old, d15) and pre-weaning period (30 days old, d30), in addition, another 10 healthy weaned lambs at age of 60-day old (60 days old, d60) which was weaned between 43～45 days old were selected as controls, 10 lambs in each group. Rectal feces samples were collected to study the changes of the composition, structure and predicted potential function of GM by 16S rRNA. The results showed that, the number of OTU of lamb GM showed an increasing trend within one month age, but it was still extremely significantly lower than that in weaned lambs (P<0.01). The α-diversity of GM within one month age was first decreased and then increased, but it was still significantly lower than that in weaned lambs (P<0.05). The β-diversity of GM in d03 and d10 groups respectively showed an extremely significant independent distribution, but it was extremely grouped together with d15 and d30 lambs (P<0.01), and extremely independent distribution in d60 lambs (P<0.01). The relative abundance of Bacteroidetes, Spirochaetes, Lentisphaerae, Elusimicrobia, 5-7N15, CF231, Ruminococcus, Treponema and Butyricimonas in GM of one month old lambs showed an increasing trend, whereas Firmicutes, Bacteroides, Lactobacillus and Veillonella showed a decreasing trend with age growth. The carbohydrate metabolism of GM was significantly higher, while the amino acid metabolism and energy metabolism were significantly lower of lambs aged 3~15 days than that in weaned lambs (P<0.05). It is concluded that the composition, structure and predicted material metabolism function of GM in one month old lambs showed significantly dynamic changes, the richness and diversity of GM in weaned lambs are significantly increased. The changes of GM and their potential functions present a “watershed-like” characteristics of lambs aged 15~30 days, the association of this characteristic with the introduction of solid feed is worth further studying.

Key words: Hu sheep, one month-old sucking lamb, gut microbiota, composition and structure, function prediction