Intestinal microbes are especially important to herbivores, as mammals are unable to process plant-based food without them. In horses, this takes place in the colon and the cecum, which have abundant and diverse microbiota. Antibiotics and sudden dietary changes can disturb the equine gut microbiota, even to a fatal degree.
“An enormous amount of research has been conducted on the human microbiota in the Western world, but there is limited corresponding information on domestic livestock. And yet, their welfare and health are at least as important, since human, animal and environmental health are closely linked, particularly through microbes,” underlines doctoral candidate Aleksi Husso, of whose doctoral thesis the research article forms a part.
Bacterial DNA detected in the foal gut immediately after birth
Researchers at the Faculty of Veterinary Medicine investigated the early development of the gut microbiota in foals in collaboration with the Sahara Stud in Keuruu, central Finland.
“The gut of newborn foals already contained small amounts of microbial DNA from a range of bacteria. For the time being, it remains unclear whether there are microbes in the gut already before birth, or whether they sneak in there in conjunction with birth,” says University Lecturer Mikael Niku, the project’s principal investigator.
“In one way or another, the mare’s microbiota probably has an impact on the development of the immune system already before birth,” Niku surmises on the basis of prior research.
There were similarities between the microbial samples of newborn foals and the dams’ faecal and vaginal microbiota. One day after birth, a considerable number of bacteria had already settled in the gut, but at this point the microbiota remained very simple.
“In some foals, the gut contained Escherischia coli or Streptococcus bacteria almost exclusively. These bacteria are a frequent cause of problems for foals. In spite of this, the foals stayed perfectly healthy. In other words, the abundance of these bacteria is not necessarily harmful, as long as the intestinal immune system keeps them in check,” says Niku.
In week-old foals, the microbiota was already bearing a closer resemblance to typical gut microbiota. However, the bacterial species present were largely different from those found in adult horses, probably due to dietary differences. Even one week after birth, there were indications of the mare’s vaginal microbiota in the foal gut microbiota.
For the first time anywhere in the world, the study thoroughly investigated the oral and vaginal microbiota of mares. In contrast to humans, the vaginal microbiota of mares contained very few lactobacilli. The mare oral microbiota was dominated by the Gemella genus of bacteria, also commonly found in the human mouth.
Challenge in studying small numbers of bacteria
Veterinarian Petra Huhti and her colleagues collected microbial samples from foals immediately after birth, one day later and a week after birth. To prevent microbes from the sampling environment contaminating the results, the samples were taken directly from within the foals’ rectum. For comparison’s sake, the microbiota of the mares was also studied. Bacterial DNA was extracted from the samples at the Faculty's laboratory located in Viikki to determine the amount and types of bacteria found in the samples. Traditional culture techniques are not well suited to studying gut bacteria, as they often survive only inside the gut. By employing DNA analysis techniques, even such bacteria can be identified.
Bacteria living in the environment and their remains, which are found everywhere, make it difficult to reliably investigate the microbiota of newborn animals even with these methods. Bacterial DNA can be found even in laboratory reagents considered sterile, and in sterilised equipment. To be on the safe side, the researchers extracted bacterial DNA also from unused sampling tools and excluded the microbes found in them from the analyses of the animal samples.
Husso, J. Jalanka, M. J. Alipour, P. Huhti, M. Kareskoski, T. Pessa-Morikawa, A. Iivanainen & M. Niku (2020) The composition of the perinatal intestinal microbiota in horse. Scientific Reports 10:441. DOI: 10.1038/s41598-019-57003-8