Bacterial colonization of the equine gut; comparison of mare and foal pairs by PCR-DGGE

Authors: EARING, JENNIFER - University Of Kentucky; DURING, ANDREW - University Of Kentucky; Gellin, Gloria; LAWRENCE, LAURIE - University Of Kentucky; Flythe, Michael

Submitted to: Advances in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/8/2012
Publication Date: 6/1/2012
Citation: Earing, J.R., During, A.C., Gellin, G.L., Lawrence, L.M., Flythe, M.D. 2012. Bacterial colonization of the equine gut; comparison of mare and foal pairs by PCR-DGGE. Journal of Applied Microbiology. 2:79-86.

Interpretive Summary: Horses, like all animals, are born without the symbiotic microbes that occupy the gastrointestinal tracts of mature animals. As grazing animals, horses rely on these microbes to fully utilize the grasses and other fibrous feeds that they consume. Foals begin eating plant-based feeds soon after birth and by weaning they must be capable of existing on plant-based feeds alone. Thus, colonization of the foal’s gastrointestinal tract must occur between birth and weaning. To evaluate the time course of microbial colonization of the gastrointestinal tract, the feces of nine mare and foal pairs were sampled from the day of parturition until 12 weeks of age. Samples were analyzed by polymerase chain reaction amplification of the bacterial 16S ribosomal gene and denaturing gradient gel electrophoresis (PCR-DGGE). This procedure provides a means of assessing the diversity of microbial population. The feces of day (d) 0 foals produced very few visible bands on the gels suggesting few bacteria were present at birth, and three of the samples produced no bands. The number of bands increased during the first 4 days of life, and by d 14 the gels produced from the foals and mares were similar. When the PCR-DGGE profiles were compared with appropriate software the similarity between mare and foal pairs was not different than the similarity among mares. These results are consistent with the idea that foal’s gastrointestinal tract is sterile at birth, that colonization proceeds rapidly, and a mature microbial community is present in the first few weeks of life. Knowledge of the normal succession of microbes in the equine gastrointestinal tract is essential to understanding the events that result in the establishment of pathologic microbes that result in gastrointestinal disease.

Technical Abstract: Horses, like all animals, are born without the symbiotic microbes that occupy the gastrointestinal tracts of mature animals. As grazing animals, horses rely on these microbes to fully utilize the grasses and other cellulosic feeds that they consume. Thus, colonization of the foal’s gastrointestinal tract must occur between birth and weaning. The feces of nine mare and foal pairs were sampled from the day of parturition until 12 weeks of age, and the samples were analyzed by polymerase chain reaction amplification of the bacterial 16S ribosomal gene and denaturing gradient gel electrophoresis (PCR-DGGE). The gels from feces of day (d) 0 foals had no or very few ( = 3, n = 6) bands, which indicates that few bacteria were present. The number of bands increased during the first 4 days of life, and by d 14 the foals and mares had similar numbers of bands ( = 28, n = 23). Some bands were present in young foals, but not in mares or in foals on d 42 or d 84, which indicated succession of bacterial species. When the PCR-DGGE profiles were compared with Dice’s algorithm, all mare-foal pairwise similarities on d 14 and later were as great as the pairwise similarities between mares. These results are consistent with the idea that foals are born sterile, colonization proceeds rapidly, and a mature microbial community is present in the first few weeks of life.