Gone with the wind: Horse flatulence under scrutiny in lab experiment

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Adding psyllium plant fiber to a horse’s diet decreases their production of methane gas, a study reveals, although the researchers caution against its use as a long-term supplement for healthy horses.

Psyllium is derived from the seed and husks of the Plantago species. It has a range of uses, including as a bulk-forming laxative in humans. It has a reputation for promoting bowel regularity without increasing flatulence.

Researchers Kanber Kara and Erol Baytok, from Turkey’s Erciyes University, noted that psyllium is also considered an effective laxative feed supplement, used as a supportive measure to prevent constipation in horses considered at-risk. In some countries it has been used in commercial feed additives for digestive problems in horses.

Kara and Baytok set out to determine what effect the addition of psyllium to horse diets had on their methane emissions.

The pair, in research to be published in the Journal of the Faculty of Veterinary Medicine Istanbul University, noted that 50-60% of global methane emissions came from agriculture and livestock, especially dairy cattle, beef cattle and sheep. They noted 1986 research that estimated that the share of horses in animal-derived methane was 0.5% to 3% globally.

Adult horses produce about 18 kilograms of methane annually, compared with 35 to 55 kg a year produced by dairy cattle. It was therefore important to determine the methane concentrations produced by horses, they said.

The pair conducted a laboratory experiment to assess methane production and digestion parameters using horse feces as the inoculum. They assessed the effect of adding no psyllium (the control group), then 5 grams per kilogram of dry matter, repeating the experiment with increasingly higher psyllium doses (10g, 20g and 40g/kg of dry matter).

Total gas and methane production was determined, as well as metabolisable energy, organic matter digestion, ammonia nitrogen, the presence of short chain fatty acids and pH values.

Total gas production decreased in linear fashion by up to 28% as the psyllium ration was increased. In other words, gas production decreased as psyllium use increased.

The inclusion of psyllium in the horse ration decreased methane production by up to 35%, they found. However, the supplementation also impacted on levels of metabolisable energy, organic matter digestion and short chain fatty acids.

The addition of psyllium at the rates used in the study did not influence ammonia nitrogen levels nor pH.

They said although psyllium reduced methane emission, it was found to have adverse effects on digestibility of the horse ration in the laboratory setting.

Further investigations were warranted to better understand the effects of psyllium supplementation by doing laboratory-based or in-horse (in vivo) digestion studies to determine the effects of lower doses of psyllium than those used in the current study.

“Consequently,” they said, “it is considered that constipation and methane production in horses can be decreased by feeding [a] psyllium supplemented diet.”

However, they concluded, it was not useful in the long-term for healthy horses due to negative effects noted in the laboratory experiments on gas production, metabolisable energy and short chain fatty acid values.

Kara and Baytok are both with the Department of Animal Nutrition and Nutritional Diseases, within the Faculty of Veterinary Medicine at Erciyes University.

Effect of Different Level of Psyllium Supplementation to Horse Diet on in vitro Fermentation Parameters and Methane Emission, by Kanber Kara and Erol Baytok, is to be published in the Journal of the Faculty of Veterinary Medicine Istanbul University.

An in-press version of the research can be read here

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