Feeding ryegrass silage to horses affects their systemic metabolic pathways, especially involving lipid metabolism, researchers in China report.
Yiping Zhu and his fellow researchers have described a study in which they explored the effects of feeding ryegrass silage on the equine fecal microbiota and blood metabolite profile of 12 horses.
The study team noted that silage is often fed to horses in China and other areas in the world. Occasional disturbances, such as a soft or loose stool, have been reported when it is introduced as a feedstuff.
Knowledge about the impact of feeding silage on horse health is still limited, they said.
In their study, reported in the journal Frontiers in Microbiology, the 12 healthy horses were split into two groups and fed either ryegrass silage or ryegrass hay for eight weeks, with a daily maintenance ration of 2% of body mass on a dry matter basis.
Before the study, all horses had been kept in individual stalls and fed with mainly commercial hay and a small amount of home-made corn-based concentrates formulated locally.
Each horse spent a week being acclimatized to their new diets.
Throughout the eight-week feeding phase, the average body condition score and body weight of each horse did not change significantly. Weekly physical exams proved unremarkable and no clinical abnormalities were noted during the feeding trial.
High-throughput sequencing was applied to analyze the fecal microbiota in samples taken before and after the feed trial, while a liquid chromatography-tandem mass spectrometry-based metabolomics technique was used to obtain metabolite profiles from blood samples to determine some of the effects of the diets on equine intestinal and systemic health.
The researchers found that the silage-fed horses had significantly different fecal microbiota and blood metabolomes from the hay-fed horses.
The results showed that, in the silage-fed group, Verrucomicrobia was significantly less abundant, which plays an important role in maintaining the mucus layer of the hindgut.
Rikenellaceae and Christensenellaceae were markedly more abundant in the silage group. Rikenellaceae, they noted, may be associated with some gut diseases and obesity.
Both diets led to significant changes in fecal microbiota, they reported, with both also showing a significant impact on the composition of blood metabolites.
The metabolomics analysis showed that ryegrass silage feeding significantly affected lipid metabolism and might increase the risk of insulin resistance.
Some specific gut bacterial taxa-related metabolites were strongly correlated with altered gut microbes, which they said added more evidence to the diet-fecal microbiota-health relationship
The results, they said, suggest that silage could cause significant changes in the horse fecal microbiota and might be associated with metabolic dysfunctions, such as insulin resistance and lipid metabolic abnormality.
Studies measuring levels of blood insulin and lipid in horses fed silage will provide more evidence of the association, they suggested.
The authors said their findings may promote understanding of the impact of silage on horse health and facilitate making a more scientific diet plan for horses, especially those with metabolic disorders such as insulin resistance and hypertriglyceridemia.
The full study team comprised Yiping Zhu, Xuefan Wang, Bo Liu, Ziwen Yi, Yufei Zhao and Jing Li, all with the Equine Clinical Diagnostic Center, part of the College of Veterinary Medicine at China Agricultural University in Beijing; Liang Deng, with the College of Animal Husbandry and Veterinary Medicine at Shenyang Agricultural University; and Reed Holyoak, with the College of Veterinary Medicine at Oklahoma State University.
Zhu Y, Wang X, Liu B, Yi Z, Zhao Y, Deng L, Holyoak R and Li J (2021) The Effect of Ryegrass Silage Feeding on Equine Fecal Microbiota and Blood Metabolite Profile. Front. Microbiol. 12:715709. doi: 10.3389/fmicb.2021.715709