Date Available


Year of Publication


Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation


Agriculture, Food and Environment


Animal and Food Sciences

First Advisor

Dr. Laurie M. Lawrence


Foals are born lacking a functional microbial community in their gastrointestinal tract (GIT). However, these microbes quickly colonize after birth. Factors influencing the process of microbial colonization and health of the foal’s gastrointestinal tract, such as milk yield and composition, are not well understood. Milk contains non-lactose carbohydrates termed “oligosaccharides”, which serve as prebiotics in human neonates and may serve a similar function in foals. Three animal studies were conducted to evaluate factors influencing mare milk and digestive health in the foal. In experiment 1, bacteria were enumerated and identified in foal feces and the utilization of different carbohydrates by bacterial isolates were evaluated. The results indicated that microbes change rapidly in the foal’s GIT and that the pioneer species are able to utilize carbohydrates found in milk. Experiment 2 compared milk yield and composition, including oligosaccharides, of mares fed concentrates either high or low in nonstructural carbohydrate (NSC). In turn, the influence of milk composition on foal diarrhea and microbial colonization was investigated. A method was developed to analyze milk oligosaccharides, which were highest 12 h after birth and decreased by 7 d postpartum. Feeding the high NSC concentrate increased milk yield, driven by an increase in lactose synthesis. Maternal diet did not affect foal bacteria, but the incidence of diarrhea was related to the amount of lactobacilli, lactate-utilizing bacteria, and cellulolytic bacteria. Experiment 3 explored relationships between mare milk yield, forage intake and consumption of maternal feces by foals, and fecal bacteria. A novel method for detecting coprophagy was developed. Foals from low milk producing mares consumed more fiber compared to foals from high producing mares. All foals consumed maternal feces during the first 3 wk of life. Mare feces appear to provide fiber for foals and also serve as a source of inoculum, aiding in microbial colonization, particularly for cellulolytic bacteria. By understanding the factors capable of influencing the development of the foal’s GIT, improved management strategies to optimize foal growth and GI health may be possible.

Digital Object Identifier (DOI)

Funding Information

United States Department of Agriculture, Agriculture Research Service. Specific Cooperative Agreement. 2014-2015