Carbohydrate digestion and absorption studies in the horse.

This study investigates how horses digest and absorb certain types of carbohydrates to gain insight into equine nutrition and potential dietary restrictions. The researchers found that adult horses are lactose intolerant but can absorb a glucose: galactose mixture, while all horses rapidly break down the sugars sucrose and maltose.

Study Objective and Methodology

• The purpose of the study was to assess the horse’s ability to digest and absorb soluble carbohydrates.
• To understand this, the researchers conducted a series of oral disaccharide tolerance tests, followed by tolerance tests with the separate monosaccharides. These tests were conducted on horses of various ages.

Findings and Observations

• Lactose, a type of sugar, did not increase plasma glucose levels in horses older than three years and caused them to pass softer faeces. This result indicates that adult horses are intolerant to lactose- they can’t effectively digest or process this sugar.
• However, the adult horses were able to absorb a mixture of glucose and galactose without affecting their faecal consistency, implying their ability to process these monosaccharides (simple sugars).

Conclusion and Implications

• The findings imply that dietary lactose intolerance in horses isn’t connected to the horse’s monosaccharide transport systems (how a horse absorbs simple sugars), but rather their inability to break down lactose into its components.
• The study noted that horses of all ages could digest and process sucrose (a sugar formed from glucose and fructose) and maltose (a sugar formed from two glucose molecules) quickly. These sugars’ digestion patterns closely mirrored those of the individual simple sugars that make them up.
• The researchers found that galactose was absorbed at a similar rate to glucose, but a higher dose was necessary to result in elevated blood galactose levels.
• The results from this study may have clinical utility- an oral lactose tolerance test could be used to identify small intestinal damage in young horses with diarrhea. If a young horse continues to eat lactose after damage to the intestine, it could exacerbate their symptoms and condition.