Horses fed a diet of high-energy forage have more stable gut bacteria than those on higher carbohydrate diets, Swedish researchers have found.
The researchers from the Swedish University of Agricultural Science also found fewer less desirable bacteria species in the gut of horses on a high-forage diet.
Diets rich in readily fermentable carbohydrates, fed traditionally to meet the increased energy requirements of the performance horse, are associated with several gastrointestinal disorders that involve disturbances to gut micro-organisms, the researchers noted.
However, these changes are poorly understood, said the study team, led by Professor Jan Erik Lindberg.
The researchers set up an experiment involving six mature standardbreds in training. The horses, all geldings, were fed two different diets, each for a period of 29 days, and their dung was collected weekly for analysis.
One diet, called F, comprised early cut timothy/meadow fescue haylage, while the other, named diet C, comprised a late-cut timothy/meadow fescue (50% of dry matter) and feed concentrate (35.8 per cent starch, 50 per cent dry matter), comprising 82 per cent oats, 14 per cent soy bean meal, 2.7 per cent wheat bran and 1.4 per cent sugar.
Both diets were supplemented daily with vitamins and minerals, including salt. Ground chalk was added to the concentrate diet.
The amount of forage fed ranged from 13-17.4 kg a day on diet F and 6.3-8.4 kg a day on diet C, according to horse size.
The concentrate was divided into three equal meals a day.
The diet which provided the most stable guts bacteria was Diet F.
“Diet F resulted in a microbial composition that was more stable between sampling periods,” the authors wrote. The samples also had lower lower counts of undesirable gut bacteria, specifically members of the Streptococcus bovis/equinus complex.
The researchers also noticed Lactobacillus ruminis was present in all horses on diet C and not in horses on diet F. Diet C also resulted in the increase in members of the Clostridial family.
The gut of horses is adapted to the continuous grazing of a fibre-rich diet, they said.
The researchers said their findings provided an opportunity to develop feeding strategies that supported equine health and welfare.
The changes in the faecal microbiota that resulted from carbohydrate inclusion warranted further investigation, they said.
Equine vet. J. (2009) 41 (1) 00-00