Effect of age on caecal microbiota of broiler chickens fed diets supplemented with sodium butyrate

A total of 768 chicks Ross 308 (half males and half females) were housed in 16 pens (48 animals/pen); half pens received a control diet, the other half the same diet supplemented with 150 mg microencapsulated Na-butyrate/kg diet. Growth performance was monitored until 45 d of age. At 11 d, 24 d, and 35 d of age, 32 animals per age were slaughtered to sample caecal content. Intestinal microbiota was evaluated by sequencing of V3-V4 region of the rRNA 16S gene using Miseq Illumina. Firmicutes was the most represented phylum, followed by Tenericutes and Proteobacteria; Bacteroidates was the least represented. Out of classes, Clostridia was prevalent, followed by Bacilli and Grammaproteobacteria. The dietary Na-butyrate supplementation did not affect performance: final live weight averaged 3294 and 3266 g in the control and supplemented group, respectively, corresponding to 113 and 112 g/d feed intake, and 1.44 and 1.43 feed conversion ratio. The dietary treatment did not affect the composition or abundance neither the diversity of gut microbiota. Only some OTUs (26) had different distributions according to dietary treatment (P<0.05): some, mostly belonging to Firmicutes phylum and to Clostridiales order, were more abundant in samples from birds fed the control diet; others, such as Tenericutes of the RF39 order, were more present in samples from chickens supplemented with Na-butyrate. On the other hand, microbiota composition significantly changed with age (P=0.001). Among phyla, Proteobacteria and Firmicutes decreased as age increased, whereas Tenericutes increased from 11 to 24 d of age. Among classes, Mollicutes, X4C0d2, Bacterioidia, and Clostridia increased, whereas Grammaproteobacteria decreased with age. Among orders, Lactobacillales, Enterobacteriales, Erysipelotrichales, burkholderiales, Oceanospirillales, Alteromonadales, Pseudomonadales, Pasteurellales, and Unclassified beta Proteobacteria decreased. The biodiversity in each sample and among samples tended to decrease when age increased. The effect on biodiversity among samples was evident using both qualitative analysis (that considers presence/absence of sequences and phylogenetic distances) and quantitative analysis (that considers only sequence abundance). The results of the present study indicate that Na-supplementation did not affect caecal microbiota. On the other hand, bacterial groups of gut community decreased with age and the community became more similar among samples.