Fecal Microbial Communities of Nellore and Crossbred Beef Calves Raised at Pasture

The intestinal microbiota has been shown to play an essential role in maintaining health and susceptibility to diseases. In food animals, the intestinal microbiota is crucial as its composition might be related to performance, likely because different species of bacteria have different capacities to ferment feedstuff. Many factors can impact the intestinal microbiota composition, which restrain microbiota studies in research facilities. Among other factors, age, diet, and management have been shown to affect the microbiota of cattle, and there is increasing evidence that genetics might also be important. In the present study, we used high-throughput DNA sequencing to evaluate the longitudinal changes in the fecal bacteria of beef calves with two different genetic compositions (purebred and crossbred Nellore). All calves were raised together in the same pasture, which minimized factors of variance in the study. Results showed that the microbiota of calves changed according to their age but differently according to their genetic background, indicating that the genetic composition is essential in the colonization and maturation of the bovine intestinal microbiota. This study aimed to investigate the effect of age and genetics on the fecal microbiota of beef calves. Ten purebred Nellore (Bos taurus indicus) and ten crossbreed 50% Nellore-50% European breed (Bos taurus taurus) calves co-habiting on the same pasture paddock had fecal samples collected on days five (5 d), 14 d, 28 d, 60 d, 90 d, 180 d, 245 d (weaning) and 260 d after birth. All calves were kept with their mothers, and six Nellore dams were also sampled at weaning. Microbiota analysis was carried out by amplification of the V4 region of the 16S rRNA gene following high-throughput sequencing with a MiSeq Illumina platform. Results revealed that bacterial richness increased with age and became more similar to adults near weaning. Differences in microbiota membership between breeds were found at 60 d and 90 d and for structure at 60 d, 90 d, 245 d, and 260 d (p < 0.05). In addition, crossbreed calves presented less variability in their microbiota. In conclusion, the genetic composition significantly impacted the distal gut microbiota of calves co-habiting in the same environment, and further studies investigating food intake can reveal possible associations between microbiota composition and performance.