Calcium propionate supplementation alters the ruminal bacterial and archaeal communities in pre- and postweaning calves

The aim of this study was to determine the effect of calcium propionate (CaP) on rumen microbiota, fermentation indicators, and weight gain in calves both pre- and postweaning. Twenty-four newborn calves were randomly divided into 4 groups (2 × 2 factorial treatment arrangement): either pre- (90 d) or postweaning (160 d), and either without or with dietary CaP supplementation (5% dry matter). The CaP supplementation increased the body weight and rumen weight of the calves and lowered NH₃-N concentration in the rumen. Microbiota composition was characterized by sequencing the amplicons of the bacterial and archaeal 16S rRNA genes. The CaP supplementation decreased the relative abundance of the phylum Bacteroidetes but tended to increase that of Proteobacteria. In addition, CaP supplementation decreased the diversity of bacteria and archaea in the rumen compared with the calves fed the control diet. Linear discriminant analysis of the rumen microbiota revealed that Succinivibrionaceae and Methanobrevibacter were enriched in the CaP group postweaning. A correlation was also present between the acetate to propionate ratio and the species that acted as co-occurrence network hubs, including Succiniclasticum, Treponema, and Megasphaera. In conclusion, CaP supplementation can improve body weight gain and rumen growth and alter the ruminal microbiota in calves both pre- and postweaning.