Faecal microbial profiles of Angus beef cattle with divergent immune responses

Abstract

Microorganisms inhabiting the gut (gut microbiota) have been shown to influence host immune responsiveness in a variety of species including cattle. The ability of cattle to cope with disease challenges is economically important to the beef industry, for example, disease associated costs in Australia are estimated to reach almost $1 billion Australian dollars (AUD) per annum. Therefore, the aim of this study was to characterise faecal microbiota of beef cattle at weaning and to investigate its association with immune response phenotypes assessed at the same time. Faecal samples were obtained from Angus cattle, phenotyped for cell-mediated and antibody-mediated immune responses at weaning. Immune response phenotypes, as well as an immune index score, were calculated and animals ranked to identify high, medium, and low immune response cohorts (n = 20/cohort). 16S rRNA gene sequence data was used to infer relative abundances and alpha and beta diversity metrics of microbial profiles. Further statistical testing involved a multivariate analysis of variance (MANOVA) to identify individual microbiota whose abundance significantly differed between the high, medium, and low cohorts for each of the immune response phenotypes. Moreover, a regression analysis was undertaken to determine significant associations between phyla or genera and immune response phenotype. A total of six phyla and three genera were found to significantly differ in relative abundances and six phyla and two genera were significantly associated with at least one of the immune response phenotypes. Notably, Bacteroidota, Euryarchaeota, and Proteobacteria may be biologically relevant due to their relationship with gut health and disease. The limitation of the current study was only conducting faecal matter sampling and subsequent immune response phenotyping at weaning stage. Future efforts should be made to explore whether the number of significant differences in faecal microbial profiles increase at a later stage.