The sensitivity of the hindgut micro-organisims of horses to even modest changes in hay have been highlighted in a French study.
Previous studies have shown that an abrupt change of hay is a major risk factor for equine colic, and disturbances of the microbial ecosystem can lead to colic. However, it was not known if the hay change disturbed the hindgut microbial ecosystem.
The study was conducted by a team from the French science institute, Agrosup Dijon, to determine the effect of yeast supplementation on the hindgut microbiota when horses were subjected to a sudden hay change.
Pauline Grimm and her colleagues determined that changes occurred after the abrupt hay change, even though the two hays were quite similar in composition.
The hay change caused different responses in the cecum and colon, they reported in the journal, Livestock Science.
They found that diet supplementation with the yeast Saccharomyces cerevisiae at a rate of 1 gram a day had no impact on equine hindgut microbiota changes in the study horses.
“Despite the close composition of the two hays, changes were measured after the abrupt hay change, suggesting a sensitive response of the hindgut microbial ecosystem,” the researchers reported.
“Further investigations are needed to evaluate the extent to which hindgut microbial ecosystem disturbances can lead to colic and to understand how yeast could be supplemented to minimize their effect.”
The study used six horses divided into two groups, fed a diet comprising 80 percent forage and 20 percent concentrate.
During each experimental period, one of the two groups was supplemented with 1 gram per day of the yeast in the morning meal. The horses were fed the first hay for four weeks and then the second hay for the next three weeks without an adaption period.
Cecal and colonic samples were collected regularly to test for changes to the horses’ microbial ecosystems.
Testing after the abrupt change indicated a significant increase on day one in Bacteroidetes and a trend for increasing Firmicutes in the cecum, as well as a significant increase in total volatile fatty acids and acetate concentrations in the colon.
After eight days, they noted a significant decrease in colonic Bacteroidetes, as well as a tendency toward an increase of colonic Firmicutes. Cecal pectinolytic bacteria was found to have significantly increased after eight days, and colonic propionate concentrations were significantly higher after 15 days.
Effect of yeast supplementation on hindgut microbiota and digestibility of horses subjected to an abrupt change of hays
P. Grimm, V. Julliand, C. Philippeau, S. Sadet-Bourgeteau
The abstract can be read here.