Feed restriction enhances the depressive effects of erythromycin on equine hindgut microbial metabolism in vitro.

This research explores how the antibiotic erythromycin, when combined with a restricted diet, can affect the metabolic activity of gut microbes in horses, potentially contributing to a serious digestive disease called equine typholocolitis.

Context and Purpose of the Research

• Equine typholocolitis is a severe diarrheal illness in horses that can lead to high mortality rates. Certain factors may increase the risk of developing this disease, such as the dental application of the macrolide antibiotic, erythromycin, and feed restriction.
• The study aims to understand how the combination of these factors may alter microbial metabolism in the horse’s hindgut, potentially giving rise to equine typholocolitis.

Research Methods

• The experiment utilized a colon simulation technique, or Cositec, which helps evaluate the biochemical parameters of microbial metabolism in an in vitro setting.
• The production rates of acetate, propionate, and butyrate were measured. These substances are quantitative parameters of microbial fermentation – a crucial aspect of a horse’s digestive health.
• The researchers applied erythromycin and reduced the amount of fermentable substrate to test their separate and combined effects on hindgut microbial metabolism.

Findings

• Applying erythromycin largely decreased the production rates of propionate.
• When the quantity of fermentable substrate was reduced to 30%, the detrimental effects were even more pronounced.
• The effects of feed restriction on the production rates of short-chain fatty acids (SCFAs) were exacerbated when combined with erythromycin application.
• Independently of erythromycin, feed restriction alone completely halted the rate of butyrate fermentation within two days of implementation.

Implications

• The significant reduction in butyrate fermentation rate could potentially be a pathophysiological factor for the onset of acute typhlocolitis.
• The findings underscore the potential risks associated with the combination of erythromycin use and feed restriction in horses, highlighting the importance of careful management of these factors to prevent the manifestation of equine typholocolitis.