Nutritional content is not the only thing to be considered when assessing the suitability of feedstuffs for horses. Hygienic quality is also an important factor.
Feeds that are produced or stored under conditions that are less than ideal may be damaged through bacterial or fungal growth. Such feeds can cause health problems in the horses to which they are fed.
Dr Petra Wolf and her colleagues at the Institute of Animal Nutrition, part of Hannover`s University of Veterinary Medicine, have been reviewing the results of tests for hygienic quality carried out on horse feed. The study was based on samples submitted to the institute for testing between 2000 and June 2005. During that time they examined 766 samples. These were mostly roughage, although some concentrate and mixed feed samples were also submitted.
Speaking at the recent Equine Nutrition Conference in Hannover, Wolf explained that much can be learned about the sample of feed by careful "sensory control" - an assessment of the smell, appearance, and texture. For example, a heavy dusty appearance, or a mouldy odour, is often associated with a heavy mould contamination.
A full laboratory examination includes assessment of bacterial content. Some species of bacteria are normally present, but other species always indicate spoilage. If the bacterial contamination occurs early in the production of the feedstuff , it may no longer be possible to culture the bacteria. However, the presence of lipopolysaccharide (LPS, endotoxin -a breakdown product of the cell wall of certain bacteria) is an indication of poor hygienic quality. They also assess mould and yeast content, and look for parasites.
The scientists analysed the type of health problems that prompted a detailed assessment of the hygienic quality of feedstuffs . Colic and poor performance were the most common, with 211 cases each. Less common reasons included liver damage, coughing and allergy.
Generally, poor hygienic quality was seen most commonly in roughage samples. Cereals were less commonly affected. Commercial mixed feeds were the least likely to show signs of poor hygienic quality.
Over half of the samples submitted from horses with colic or respiratory disease showed poor hygienic quality. Food from coughing horses was often affected with mould (62%) and LPS (63%).
Lipopolysaccharides were particularly high in feed fed to horses with a history of poor performance, raised liver enzymes or indigestion.
Wolf pointed out that these findings did not reflect the true extent of the situation in practice because the samples were only taken from feeds that were thought to be causing a problem. But they do give an indication of the type of problems that can arise when horses are fed food of poor hygienic quality.
She suggested that veterinarians should be able to assess the hygienic quality of feedstuffs offered to horses (especially in cases of colic and respiratory disorders). In particular, the roughage should receive close attention, even if only used as bedding material.
Reference: A survey on the hygienic standard of feeds for horses associated with diseases. Petra Wolf, Manfred Coenen, Josef Kamphues. Proceedings Equine Nutrition Conference. Pferdeheilkunde. (2005) 21, 24 - 25..