Foals fed steam-flaked barley in addition to their daily hay rations put on significantly more weight than those fed steam-flaked corn or oats, researchers in China report.
Xiao Bin Li and his fellow researchers noted that there was little objective information concerning the effect of steam-flaked grains on the growth performance and faecal microbiota of foals.
Steam treatment of cereals is a common method to improve starch digestibility and is considered superior to crushing.
The researchers with Xinjiang Agricultural University devised an experiment to determine the effects of different steam-flaked grains on the growth performance and faecal microbiota of foals.
The horses were healthy 5-month-old weaned foals of the Kazakh breed with starting bodyweights around 112.4kg, plus or minus 7.5kg.
The foals, housed individually, were each randomly assigned to one of three groups, fed either corn, oat or barley diets over the 60 days of the experiment. The forage portion of their diet in all cases comprised a 2:1 mix of lucerne and meadow hay.
The hay was fed at a rate of 1.5kg of dry matter per 100kg of body weight per day. The starch from each of the steam-flaked grain feeds was set at 2 grams of starch (dry matter) per kilogram of bodyweight per day.
The horses were turned out each day in dry lot paddocks after feeding.
Faecal samples were collected from the foals for analysis and comparison. Next-generation sequencing was used to learn about the microbial composition of their faeces.
There was a significantly greater increase in the body weight of foals fed barley, compared to either corn or oats, the study team reported in the journal BMC Veterinary Research.
The study team also found significant differences in the diversity of the gut microbiota related to the different diets.
Differences in overall growth, and in faecal microbiota, occurred if either supplementary corn, oat or barley were fed, they said.
“Further studies are required to determine the potential impact of the changes in the microbiota on the health and development of foals fed cereal starch of different sources.”
The study team, discussing their findings, said they had assumed that the three different starch sources would cause differences in growth in the foals.
“The rationale for this assumption is that in plants amylose and amylopectin in the starch granules form dense hydrogen bonds to various degrees that hinder the action of digestive enzymes, and thereby reduce starch pre-ceacal fermentation.
“The higher the ratio of amylose to amylopectin is, the lower is the digestibility of starch.”
Corn, oats and barley contain similar amounts of starch but because of their different amylose-amylopectin ratios and the different size of starch granules, digestibility for horses is different.
Starch that is not digested by enzymes in the horse’s small intestine is transported to the hind gut and is fermented by the residing microbial population, which includes starch-degrading bacteria.
“Their action may cause fundamental changes in the structure of the hind gut flora and result in increasing concentrations of volatile fatty acids and lactic acid.”
The findings, they said, indicate that that varying types of dietary cereal starch could change the structure and diversity of bacterial population in the hind gut of foals.
They said they successfully showed that 2 grams of dry-matter starch per kilogram of bodyweight per day from barley, when added to a routine standard diet, stimulated body weight gain of foals significantly more than did additional starch from corn and oats.
Although research by others suggested that the upper limit of starch digestion in the equine small intestine is between 3.5 and 4 grams of starch per kg of bodyweight per feeding, the researchers decided, given the young age of the horses, to set the rate at 2 grams per kilogram to limit starch bypass to the large intestine.
“In this study, the total daily starch ingestion in the three diet groups appeared on the safe side and did not result in digestive abnormalities,” they said.
The Xinjiang Agricultural University study team comprised Xiao Bin Li, Xin Xin Huang, Chang Jiang Zang, Chen Ma, Kai Xu Chen, Guo Dong Zhao, Qian Li, Xuan Yue Li, Wen Jie Zhang and Kai Lun Yang.
Li, X.B., Huang, X.X., Zang, C.J. et al. Effects of steam-flaked grains on foals’ growth and faecal microbiota. BMC Vet Res 17, 293 (2021). https://doi.org/10.1186/s12917-021-02994-8. The study, published under a Creative Commons License, can be read here.