Question
My mare has been diagnosed with polysaccharide storage myopathy type 1 (PSSM1). I am working through her diet now, and I came across an ingredient called dried distillers grains with solubles. Can a horse with PSSM consume this ingredient without agitating the muscle disease?
Answer
Dried distillers grains with solubles (DDGS) is a corn coproduct of dry-milled ethanol production. Research studies have recommended the use of DDGS as an ingredient in formulated livestock feeds, but the byproduct is deficient or imbalanced in several important nutrients if fed without suitable fortification to animals, including horses.
Kentucky Equine Research conducted a study investigating the potential of DDGS as an ingredient for horse feeds many years ago. This study found that horses readily consumed pellets containing up to 20% high-quality DDGS, and DDGS was potentially a suitable source of protein, fat, and some minerals for mature horses.
Traditionally, this ingredient has been used as a source of moderate-quality protein (approximately 30%) and fat (10-15%), but additional processing to remove corn oil has reduced the fat content of today’s DDGS. The typical mineral profile of DDGS includes an inverted calcium-to-phosphorus ratio and is a moderate to deficient source of some other essential minerals. As a coproduct, the nutrient content of DDGS can be variable due to different extraction procedures, depending on the source, so feed manufacturers should take additional steps to ensure the nutrient profile by chemical analysis when used as an ingredient in horse feeds. This helps ensure that the final feed formula is nutritionally balanced and supplies all essential nutrients to meet nutritional requirements.
Compared to corn, DDGS are lower in nonstructural carbohydrates, so DDGS may be included as an ingredient in feeds low in nonstructural carbohydrates, possibly suitable for a horse diagnosed with PSSM1. Again, DDGS are not suitable to be fed alone as they are not nutritionally balanced but, as part of a well-formulated feed, DDGS can be a suitable feed ingredient.
In addition to nutrient variability, DDGS is a potential source of mycotoxins sometimes found in corn, such as fumonisin. Further, if the original processed corn contains mycotoxins, those mycotoxins will be more concentrated in the DDGS byproduct. It is therefore important that the ingredient is tested for potential mycotoxin contamination before being incorporated as an ingredient in horse feeds. Reputable feed manufacturers that use DDGS as an ingredient should source high-quality DDGS evaluated for nutrient content and mycotoxins.
PSSM1 horses should typically consume diets low in nonstructural carbohydrates. Concentrates intended for these horses should be low in starch and high in fat. A suitable concentrate may contain less than 15% NSC, 10-12% fat, and 11-13% protein.
In collaboration with Dr. Stephanie Valberg, Kentucky Equine Research developed RE-LEVE to provide the optimal energy sources and nutrition for horses diagnosed with tying-up syndrome. Re-Leve helps simplify feeding programs and takes the guesswork out of feeding horses with special nutritional considerations.
