Effect of live yeast culture supplementation on apparent digestibility and rate of passage in horses fed a high-fiber or high-starch diet.

The research paper investigates the impact of live yeast culture supplementation on two main diets for horses – high-fiber (HF) and high-starch (HS). The researchers analyzed the differences in digestibility and the overall impact on horse nutrition.

Methodology

• The study used eight crossbred male horses, with their ages averaging at 12 and body weight at around 305 kg. These horses were used in pairs and the study was structured with a 4 x 4 Latin square design.
• Four different diets were prepared: a high-fiber diet based on dehydrated alfalfa (HF+0), a high-starch diet based on barley and wheat bran (HS+0), and modified versions of these two diets supplemented with Saccharomyces cerevisiae, a type of yeast (HF+SC and HS+SC).
• The yeast was top-dressed on the feed pellets at a rate of 10g per day, distributed among two daily meals.
• Each horse’s diet was followed by a 10-day period of total fecal collection to measure digestion and passage rate.
• Some elements of the feed and fecal matter were bound to specific markers to allow the researchers to estimate retention time in the digestive tract.

Findings

• The high-starch (HS) diet demonstrated greater digestibility of dry matter (DM), organic matter (OM), and crude protein (CP) compared to the high-fiber (HF) diet. This was found regardless of the yeast supplementation.
• However, acid detergent fiber (ADF) digested better in the high-fiber (HF) diet.
• The cellulolytic activity, which refers to the breaking down of cellulose, was lower in the high-starch diet than in the high-fiber diet.
• Supplementation with yeast improved the digestibility of acid detergent fiber (ADF). It also encouraged the intake of dry matter (DM) and neutral detergent fiber (NDF), but had no impact on the mean retention time of solid digesta.
• There was no significant interaction observed between the diet type and yeast supplementation; the beneficial effects of yeast were largely the same whether the diet was high in starch or fiber.

Conclusion

This research suggests that supplementary yeast can help to improve cellulose digestion in horses, potentially enhancing the nutritional status of the animals. The boost to horses’ nutritional status was seen regardless of whether they consumed a high-fiber or a high-starch diet, and the supplementation did not affect the speed at which digesta moved through the digestive tract.