88 Factors influencing mare milk composition and yield and foal digestive health

Abstract The microbial community that colonizes the gastrointestinal tract within the first few days of life can have significant impacts on the health of the foal. For example, proliferation of pathogens can lead to neonatal diarrhea. The factors influencing the establishment of the normal microbiome, which can provide pathogen resistance, are not well understood. This research aimed to evaluate factors influencing foal gut health including changes in foal fecal bacteria, mare milk composition and yield, and utilization of milk components by fecal bacteria from foals. We hypothesized that the maternal diet would alter milk yield and composition and as a result, will influence microbial colonization in the foal. To evaluate dietary influence on milk composition, mares (n = 16) were fed forage and either a concentrate with high nonstructural carbohydrate (NSC) or low NSC. Milk yield and composition were evaluated and relationships with foal fecal bacteria and diarrhea were explored. In addition, fecal samples collected from foals were used to enumerate select bacterial groups and isolate and identify carbohydrate-utilizing bacteria. We found that feeding mares a high NSC concentrate increased synthesis of milk carbohydrates and daily milk yield compared to mares fed a low NSC concentrate (P < 0.05). Microbes isolated from foal feces were capable of utilizing carbohydrates, such as lactose and galactooligosaccharides, as early as 12 h after birth. High milk producing mares had foals with fewer cellulolytic bacteria (P < 0.001). Foals with >1 bout of diarrhea had fewer cellulolytic bacteria (177 viable cells/g feces) compared to foals with no diarrhea (10,000 viable cells/g feces; P < 0.001). Fecal lactobacilli and lactate-utilizing bacteria were positively related to bouts of diarrhea (r=0.745 and r=0.555, respectively; P < 0.05). The gastrointestinal microbiome is changing rapidly in the foal and milk yield and composition appear to play an important role. The neonatal period may provide an opportunity to influence the microbiome and prevent gastrointestinal upsets.