Interpretive Summary: Effect of hay type on cecal and fecal microbiome and fermentation parameters in horses.
By: Dr. Emily Taylor
Horses rely heavily on volatile fatty acids (VFA) as an energy source via fermentation of structural carbohydrates. These structural carbohydrates can come from both cereal grains and forages. Researchers have come a long way in identifying specific microbial populations needed for optimal fermentation of these structural carbohydrates in the hindgut. However, the cecal microbiome of cannulated horses fed a legume vs. cool-season grass hay has not been reported.
An article recently published in the Journal of Animal Science aimed to quantify the fecal and cecal microbiome of mature horses consuming alfalfa or Smooth Bromegrass hay (Brome). Next-generation sequencing was used for identification, while fermentation parameters, including pH and VFA concentration, were evaluated.
Overall VFA concentration was greater in the cecum of alfalfa-fed horses compared with Bome-fed horses. This could be expected as the NDF value of alfalfa was lower resulting in more readily digestible hay. The relative abundance of Streptococcus, Lactobacillus, and YRC22 were greater in alfalfa-fed horses, which has been related to greater VFA concentrations in previous research. Compartments with increased VFA concentrations generally had a reduced pH. The authors hypothesized that lactate concentrations may have been greater in alfalfa-fed horses, thereby further reducing the pH. Although lactate was not measured in the current study, it was noted in previous research using alfalfa pellets. Hay type had a significant impact on microbial communities within both sampling locations. The cecum had greater levels of Bacteroidetes regardless of hay type, while Firmicutes and the Firmicutes:Bacteroidetes ratio were greater in the feces of alfalfa-fed horses.
In summary, the type of hay, as well as location sites, impacted the microbial communities present and fermentation parameters. In the current study, researchers found that fecal samples were not representative of the cecal microbial community. Therefore, future research relying on information collected from feces to represent the equine hindgut may result in inaccurate assumptions and conclusions.