Horse diets should take into account the fermentation factor, findings suggest

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"There is a need to evaluate the fermentation of diets, rather than predicting from the values of pure ingredients."
Sport-horses diets are designed to ensure maintenance, work and, in some cases, growing requirements.

High-performance horses are often fed high-performance diets, calculated with precision based on nutritional values, but fresh research in Chile suggests it may not be that simple.

Horses are hindgut fermenters. “It is therefore important to determine the postgastric nutritive value of their feedstuffs and diets,” Mónica Gandarillas, Juan Pablo Keim and Elisa María Gapp wrote in their paper just published in the journal Animals.

“Horses are involved in diverse equestrian disciplines that increase their digestible energy and nutrient requirements,” the trio, with the Austral University of Chile, noted. “Therefore, highly balanced nutrient and energy diets are required.”

Sport-horses diets are designed to ensure maintenance, work and, in some cases, growing requirements.

The researchers noted that, in other animal species, it has been shown that the fermentation of diets can result in different values than those expected from pure ingredients.

The researchers set out in a laboratory-based experiment to evaluate the gas production and volatile fatty acid concentrations of mixtures of different forages and concentrated foods, which are representative of the traditional diets of high-performance horses.

In their experiment, they used three forages (alfalfa hay, mature grass hay, and a mix of the two) and three concentrates that are typical in horse diets.

The concentrates or grains used were a mix of oat grain and wheat middlings and two commercial concentrates: One was a starch-based concentrate composed of wheat bran, oats, soybean meal, corn, molasses, vegetable oil and salt; and the other a concentrate that included soluble fibre ingredients, composed of barley, oats, corn, wheat, triticale (a wheat-rye hybrid), rice, wheat middlings, dehydrated fruit and carrot, alfalfa, linseed, molasses, sunflower oil, and/or soybean meal.

Nine different diet treatments were designed. The nine treatments included the combination of 70% (on a dry matter basis) of the three hay forages and 30% of three grains or concentrate sources, resulting in nine experimental diets.

They were particularly interested in any associative effects, exploring the interactions of the fermentation reactions using them in a combination of 70% of forage and 30% concentrates.

Each sample was treated with digestive enzymes, inoculated with horse feces and incubated.

They found that the concentrates and grains produced higher levels of gas production and volatile fatty acids than forages when evaluated alone.

“When experimental diets were incubated, gas production parameters and volatile fatty acid concentrations of forage–concentrate mixtures had unexpected differences from the values expected from the fermentation of pure ingredients, suggesting the occurrence of associative effects,” they reported.

The gas production after 96 hours of incubation was higher in the mixtures of the different forages that included oat bran, they found.

When comparing the pH values, the mixtures containing alfalfa obtained higher values.

“Our results indicate that there is a need to evaluate the fermentation of diets, rather than predicting from the values of pure ingredients,” they concluded.

Gandarillas, M.; Keim, J.P.; Gapp, E.M. Associative Effects between Forages and Concentrates on In Vitro Fermentation of Working Equine Diets. Animals 2021, 11, 2212. https://doi.org/10.3390/ani11082212

The study, published under a Creative Commons License, can be read here

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