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Microbiota of the Neonatal FoalBy Kentucky Equine Research Staff · May 18, 2017

During the first few weeks of a foal’s life, the development of a diverse and healthy microbiota occurs. The microbiota, or population of beneficial microorganisms such as bacteria and protozoa, plays a major role in the proper function of the immune system and will serve to protect the foal from harmful pathogens as it matures. The microbial population is influenced by environment and diet. Most discussion surrounding the equine microbiota involves mature horses, and a closer look at a foal’s hindgut inhabitants provides interesting insight.

Foals are born with a sterile gut, but microbial colonization begins the first day of life. Some researchers found that meconium, the foal’s first feces after birth, is not sterile, while others report that it is. Differences may be attributed to the mare or sample collection techniques.

Nevertheless, changes in the bacterial community measured in feces were detected sequentially between days 0-2, days 2-10 and days 10-30 (birth to one month of life), at which point the changes stabilized1. Colonization proceeds rapidly, with a mature microbial complement present by six weeks of age. Additional study is needed to determine exactly which species of bacteria are becoming established in the gut during the first month of life.

Because of the rapid changes in the foal’s microbiota, probiotic supplementation may have a different effect on young horses, especially neonates, compared to their mature counterparts. While there are many probiotics that the U.S. Food and Drug Administration considers safe, the probiotic population in the young horse’s gut may be more sensitive to manipulation2.  Such manipulation could potentially lead to imbalances that cause digestive upset, such as diarrhea or colic. In addition, research to date shows that probiotics are not likely to improve growth, development, or feed utilization in young horses that are consuming a balanced diet3. Therefore probiotic use in neonates is not recommended.

A healthy and diverse microbiota will support immune function, vitamin and energy production, and fiber digestion throughout life.

1Faubladier, C., S. Sadet-Bourgeteau, C. Philippeau, E. Jacotot, and V. Julliand. 2014. Molecular monitoring of the bacterial community structure in foal feces pre- and post-weaning. Anaerobe. 25:61-66.

2Schoster, A., J.S. Weese, and L. Guardabassi. 2014. Probiotic use in horses – what is the evidence for their clinical efficacy? Journal of Veterinary Internal Medicine. 28:1640-1652.

3Weese, J.S. 2002. Probiotics, prebiotics and synbiotics. Journal of Equine Veterinary Science. 22(8):357-360.