Owners of horses with allergies are often encouraged to steam their hay. Steaming hay binds dust and fungal spores, making them less likely to be inhaled; it also kills potentially harmful microorganisms.
Recent research from Martin Luther University Halle-Wittenberg (MLU) has shown that steaming hay may affect the digestibility of protein in the hay. The steam causes a chemical reaction that damages the proteins and makes them harder to digest in the small intestine – and they cannot be digested in the large intestine.
This can lead to a nutrient deficiency that can cause a plethora of issues, including the impairment of growth or muscle development. Proteins are made up of amino acids; not enough of them can be an issue for young horses, which need amino acids to grow, and lactating mares, which need amino acids to produce milk.
A team of scientists led by Dr. Annette Zeyer examined samples of multiple types of hay gathered in central Germany. The steamed hay samples had increased rates of proteins that had been damaged. According to the study, steaming hay reduced the amount of protein that can be absorbed by the small intestine by nearly 50 percent; lysine in particular was affected, with less than 50 percent available for absorption after steaming.
It can be difficult to identify horses lacking proper amino acid amounts; the symptoms are vague. They may have impaired muscle development, or a dull and shaggy coat. “Hunger hair” is also often seen, where individual hairs in the horse’s coat are long.
The scientists suggest that owners of horses being fed steamed hay ensure that their diets are balanced. Supplementation with a protein-rich compounded feed or yeast and soybean meal may be necessary.
Read more at Equine Science Update.