Carbohydrate digestion in the stomach of horses grazed on pasture, fed hay or hay and oats.

This research examines how different feed types—pasture, hay, or a combination of hay and oats—affect carbohydrate digestion in the stomach of horses. It found there are deviations, based chiefly on the diet, in the degradation of various substances such as starch, sugars, and different types of fiber like fructans, hemicellulose, and cellulose, which could influence the stomach’s microbial makeup and the horse’s overall bodily response.

Study Setup and Methodology

• Twenty-four horses were divided into different dietary groups: some grazed on pasture all day (PST), others fed on unlimited hay (HAY), and two groups given unlimited hay and oats in varying amounts.
• The horses were fed their allocated rations for at least 34 days.
• Post euthanasia, the researchers sampled the digesta—contents of the digestive tract—from two different regions of the horse’s stomach.
• The concentration of various substances in the feed and gastric digesta was analyzed, using acid insoluble ash as a marker for matter that is indigestible in the stomach.

Key Findings

• The concentration of oat starch in the gastric digesta reduced significantly in horses fed oats (OS1 and OS2 groups). The reduction was more in the group fed a lower amount of oats (OS1).
• Simple sugars like glucose, fructose, and sucrose disappeared more from the gastric digesta in the PST, HAY, and OS1 groups than in the OS2 group. In fact, sucrose was completely cleared in the PST and HAY groups.
• The researchers noticed a significant reduction in fructans (a type of fiber) in the PST and HAY groups, especially in one region of the stomach (PNG). No reduction was observed in the high-starch diet group (OS2).
• There was some evidence of fiber breakdown in the PST group.

Implications

The study concludes that the type of feed directly impacts the digestion of carbohydrates, with different substances being broken down differently based on the diet. This, in turn, could trigger changes in the stomach’s microbial community, potentially impacting the overall health and well-being of the horse. The exact effects of these changes, however, are not explored in this specific study and may be subject to further research.