The effect of milk replacer composition on the intestinal microbiota of pre-ruminant dairy calves

Dietary approaches, designed to stimulate the growth and establishment of beneficial gut microbiota, instituting healthy gut function in pre-weaning (neonatal) animals, are of growing importance. The impact of prebiotic compounds, such as milk oligosaccharides, promoting the growth of beneficial groups of gut bacteria, is becoming increasingly apparent. By employing Illumina MiSeq sequencing of bacterial 16S rRNA, this study aims to characterize the establishment of the gastrointestinal microbiota in dairy calves given two different milk replacer (MR) diets after colostrum feeding. Each MR (Volac Enerlac/Volac Heiferlac), has different levels of whey protein phospholipid concentrate and whey permeate due to differences in manufacturing processes, and thus are expected to contain differing amounts of both free and conjugated milk oligosaccharides. A total of 10 dairy calves, 5 in each group, were assigned to one of the two MR diets. Freshly voided fecal samples were taken at 0, 1, 2, 4 and 7 weeks post-partum. The relative abundance of Bifidobacterium was significantly higher at week 1 in the fecal microbiome of calves fed Heiferlac compared to Enerlac. Similarly, Heiferlac feeding also stimulated the propagation of a Faecalibacterium prausnitzii-related species, with a significantly higher abundance at week 1 in Heiferlac-fed vs Enerlac-fed calves. These commensal bacteria are widely regarded as probiotic organisms that confer a health benefit on the host through stimulation of host immunity, reduction of gastrointestinal inflammatory responses and protection from pathogen invasion. Our findings suggest that the composition of bovine milk replacers can have significant effects on the establishment of the gut microbiota in pre-weaned (neonatal) dairy calves. Better understanding of milk-microbiota-host interactions in early life will inform targeted interventions to increase growth and reduce mortality in young animals