Effects of a silage diet on the gut bacteria of horses explored in study

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The Lachnospiraceae family was statistically more abundant in horses fed hay, while it was the least abundant in horses fed silage.
The Lachnospiraceae family was statistically more abundant in horses fed hay, researchers said, while it was the least abundant in horses fed silage. (File image)

The abundance of a key bacterial family that inhabits the equine gut fell away significantly in horses fed silage, when compared to those given hay or grass, researchers found.

The decline seen in the abundance of Lachnospiraceae in horses fed silage was a significant finding, according to the researchers, as it may indicate inflammatory changes, as revealed by previous studies on humans.

Other than that, the silage diet did not generate any other apparent imbalance within the equine fecal microbiota in comparison with the other two common forages.

“Further investigation is necessary to look at whether the decrease of Lachnospiraceae in the intestinal microbiota is correlated with a compromised gastrointestinal health of horses that are fed silage in the long term,” the study team said.

Lachnospiraceae are found in the gut of many mammals. In humans, the Lachnospiraceae have shown an ability to convert lactate to butyrate, which is critical in the maintenance of healthy intestines and the reduction of the risk of intestinal inflammation.

Lachnospiraceae are also involved in the production of short-chain fatty acids (SCFA), which act as growth factors for a healthy gut lining.

Yiping Zhu and his colleagues, in a study reported in the journal Animals, said horses are hindgut fermenters characterized by a complex family of microorganisms — the microbiota — mostly comprising anaerobic microorganisms that facilitate the digestion of a high-fiber diet.

The intestinal microbiota also affects the host’s immune system, influences the animal’s metabolism, and helps in the detoxification of harmful substances.

Therefore, any disruption to it can have major consequences on overall health.

Diet, they noted, can have a significant effect on the intestinal microbiota, with changes capable of triggering the likes of colic, metabolic syndrome and laminitis.

“There is evidence that changes in dietary patterns alter the colonic microbiota, subsequently leading to changes in colonic pH and fermented products, and some of these changes may predispose horses to colic,” they said.

“Understanding the impact of different dietary patterns on the intestinal microbiota will help to reveal connections between diet and the overall health of horses.”

In their study, the researchers investigated the effects of three different forage feeds — grass, silage, and hay — on the fecal microbiota of horses.

The study involved 36 healthy horses at the Guanzhong Stud farm in Shanxi province, China.

They were divided into three groups, with one group put on a grass diet (local pasture ryegrass), another receiving ryegrass silage, and the third receiving only second-cut ryegrass hay.

Fecal samples were collected after eight weeks from each horse and analyzed using high throughput sequencing to learn more about the bacteria present.

The authors described a range of changes in bacterial composition between the diets.

The Lachnospiraceae family was statistically more abundant in horses fed hay, while it was the least abundant in horses fed silage.

Streptococcaceae species, considered a core microbial component in equine intestinal microbiota, were present in significantly lower quantities in the feces from horses fed pasture grass as compared to those from horses fed hay or silage.

The Oscillospiraceae was another bacterial family with significantly different levels between groups. It was the most abundant in horses managed on pasture and least abundant in the hay group, which indicated that its presence could have been influenced by different diets.

“This study revealed some characteristic findings on the fecal microbial composition in horses that were given each type of diet and showed significant differences between the groups,” the study team said.

For the first time, baseline information has been established on the fecal microbiota of horses fed silage, they said.

They hoped that the information could be used to help balance the intestinal microbiota in horses that are fed mainly silage in combination with other types of forages in order to maintain intestinal health.

The authors noted that the body condition score of all the horses did not change and their body weight remained relatively stable throughout the feeding trial.

Throughout the trial, physical examinations were unremarkable for each horse, and no clinical abnormalities were observed.

The study team said more studies are warranted to further define the impact of the silage diet on equine intestinal health.

The study team comprised Yiping Zhu, Xuefan Wang, Shulei Chen and Jing Li, all with the College of Veterinary Medicine at the China Agricultural University in Beijing; Liang Deng with the College of Animal Husbandry and Veterinary Medicine at Shenyang Agricultural University; and Chunyan Zhu, with the Shanghai Center of Agri-Products Quality and Safety.

Zhu, Y.; Wang, X.; Deng, L.; Chen, S.; Zhu, C.; Li, J. Effects of Pasture Grass, Silage, and Hay Diet on Equine Fecal Microbiota. Animals 2021, 11, 1330. https://doi.org/10.3390/ani11051330

The study, published under a Creative Commons License,  can be read here

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