Horse nutrition: Prebiotics may do more harm than good
Prebiotics are only able to help stabilise the intestinal flora of horses to a limited degree. Before they can reach the intestines, commercially available supplements partially break down in the animals' stomachs, which can lead to inflammation of the stomach lining. This was discovered by researchers at Martin Luther University Halle-Wittenberg (MLU) and the University of Veterinary Medicine Hannover (TiHo). The team therefore suggests preparing prebiotic food supplements so that they don't take effect until they reach the large intestine. The study appeared recently in the journal PLOS ONE.
Prebiotics are often added to horse feed in order to stabilise the horse's health. They are indigestible fibres that can stimulate the growth and activity of certain beneficial bacteria in the large intestine. "Horses have a relatively small, non-diverse core microbiome and are therefore very susceptible to digestive disorders," explains Professor Annette Zeyner, head of the animal nutrition group at MLU. However, according to the scientist, insufficient research has been conducted on whether the use of prebiotics actually does produce the desired effects. Her research group explored this question in partnership with Professor Gerhard Breves' lab from TiHo.
For the study, the team investigated the effect of feeding Jerusalem artichoke meal (JAM) on horses. This is a typical prebiotic for horses. In addition to their normal feed, six animals received JAM containing high amounts of certain carbohydrates, so-called fructo-oligosaccharides (FOS) and also inulin. Another group of six horses received a placebo with their normal feed. The researchers then analysed the balance of bacteria in the digestive tract of the animals of both groups. It was discovered that the prebiotics were already being fermented in the stomach by the microorganisms naturally living there -- i.e. they were taking effect much too early. "The fermentation process leads to the formation of organic acids that -- unlike in the large intestine -- can damage the mucous membrane of the horse's stomach," says Maren Glatter, a member of Zeyner's group and lead author of the study.
However, the bacterial diversity of the entire digestive tract did increase, which probably also produces the desired protective effect. "Still, the prebiotics are probably more harmful than beneficial when used in their present form," Zeyner surmises. Instead, the substances must be treated so that they arrive in the large intestine in one dose in order to have a positive effect on the intestinal bacteria living there without stimulating overactivity.
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New insight into bacterial infections found in the noses of healthy cattle.
New research led by academics at the University of Bristol Veterinary and Medical Schools used the 'One Health' approach to study three bacterial species in the noses of young cattle and found the carriage of the bacteria was surprisingly different. The findings which combined ideas and methods from both animal and human health research could help prevent and control respiratory diseases.
Cattle, like humans, harbour a wide range of bacteria in their noses, microbes which are normally present and probably necessary for health like those that live in the gut. However, some species of these bacteria do cause serious illness at times, particularly when infection becomes established in the lower respiratory tract within the lungs.
The research team took nasal swabs at intervals during the first year of life, to detect their presence and measure their abundance using a DNA-detection technique called quantitative polymerase chain reaction (qPCR) that targeted genes found in three bacterial species well-known for their ability to cause respiratory disease in cattle: Histophilus somni, Mannheimia haemolytica and Pasteurella multocida.
The researchers found the carriage patterns of the three bacteria differed remarkably. Pasteurella was found in most of the animals, large numbers of bacteria were usually present, and the bacteria stayed in the nose for weeks or months. Histophilus was present in up to half the animals, usually in smaller numbers and the periods it was present were shorter. Mannheimia was rarely found although the numbers detected, when present, varied widely.
These differences are of interest because the numbers of bacteria and their duration of carriage are likely to influence their spread among healthy cattle and the likelihood of causing severe respiratory disease.
Amy Thomas, lead author who carried out the research as part of her PhD studies in Clinical Veterinary Science, said: "These techniques and results offer a way forward in understanding why and how apparently healthy cattle harbouring these bacteria may go on to develop respiratory illness and should help in finding new ways to prevent it."
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Professor Mark Eisler, co-author and Chair in Global Farm Animal Health at the Bristol Vet School, added: "These studies are particularly important because cattle are known to contribute to greenhouse gas emissions and improving how their diseases are controlled will help mitigate climate change. Also, reducing the use of antimicrobials that treat respiratory diseases in cattle should help reduce the increasing global threat of antimicrobial resistance in animals and humans."
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