A review of unlikely sources of excess carbohydrate in equine diets

Abstract

Introduction Equines suffering from laminitis, insulin resistance, Equine Metabolic Syndrome, Cushing’s, osteochondrosis, and equine polysaccharide storage myopathy ( EPSM) require restriction of sugar, starch and/or fructan, which is collectively called Non Structural Carbohydrates (NSC). While there is a great deal of scientific literature in plant science journals regarding factors effecting NSC content of feed and forage, the information is not convenient to veterinarians. The nomenclature that plant scientists use may be unfamiliar to veterinarians, as well as the concepts central to plant physiology. Attempts by some veterinarians to give advice regarding more appropriate feed choices and pasture management practices to owners of carbohydrate intolerant equines may be based on incorrect assumptions, and incomplete understanding of the mechanisms governing NSC concentration in forage. This review is necessary to dispel some frequent misconceptions regarding NSC content of forage. Some forage that may be intuitively perceived as low in feed value, such as dead grass and weeds, may actually be high enough in NSC to trigger symptoms in susceptible animals. Grass founder has always been blamed on ‘lush’ grass. The term ‘lush’ is generally considered to mean green, vigorous, and well hydrated. Advice given by veterinarians on methods to avoid ‘lush’ grass may actually increase NSC concentration. This review will demonstrate how brown, dead or dying, desiccated grass can have surprisingly high levels of NSC, and explain the concepts of plant physiology that govern NSC accumulation in grass. This may explain onset of some previously mysterious cases of endocrinopathic laminitis, or worsening of symptoms in other diseases involving carbohydrate intolerance. There are some common misconceptions about the relative levels of Non Structural Carbohydrate (NSC) in horse feeds. While most horse owners recognize that molasses and grain are high in sugar and starch, they do not realize that excess NSC may be found in other portions of horse rations. This review of the NSC content of the non-grain portion of equine rations may provide practitioners and caretakers with information to fine-tune the diets of CHO intolerant equines.