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Polysaccharide Storage Myopathy Explained

Tuesday, November 14, 2017 - 6:00pm to 7:00pm
Event Type: 

On November 14th, 2017 Michigan State University veterinarian Dr. Stephanie Valberg will present a webinar explaining Polysaccharide storage myopathy (PSSM) a muscle disease in horses.  The FREE webinar will take place at 7 pm EDT and is sponsored by My Horse University, an online horse management program, based out of Michigan State University Extension.


Fiber and the Horse

Forages as hay or pasture make up the major share of the horse's daily intake. The energy and nutritive value of forages varies considerably and to a large extent is determined by the fiber content and fiber quality. Fibrous carbohydrates, also known as structural carbohydrates, are not digested in the small intestine but rather are digested by billions of bacteria in the hindgut. Some of the end products of bacterial fermentation include substances called volatile fatty acids (VFA) which are absorbed from the hindgut and used as a valuable source of energy. Feeds that contain structural carbohydrates are pasture, all types of hay, sugar beet pulp, soybean hulls and oat hulls.

Why is fiber beneficial?

  • Fiber provides a source of calories for horses.
  • Forage helps keep the gut full  
  • Fiber soaks up and holds water in the horse’s gut which acts a reservoir when horses need it.

There is not an exact requirement for fiber but diets that don’t provide enough fiber can cause major problems such as colic, dehydration, boredom and others.

Horses consuming pasture
ISU Horses Consuming Pasture

Horses should be fed a minimum of 1.5% of its bodyweight in fibrous feeds per day. This is equivalent to 1.5 lb./100 lb. bodyweight (equivalent to 15 lbs./day for a 1,000 lb. horse). At this level, horses can keep their gut full and have plenty of feed to chew on. Many horses will consume 2% of their bodyweight in forage per day. The type of forage used in horse feeding should be carefully selected so that appropriate levels of energy and nutrients are provided. Knowing the components of the forage or fibrous feed will allow an owner to feed the best grain mix to meet any deficits in the fibrous feed.


Nutrition for the Gestating and Lactating Mare

A mare's gestation or pregnancy is approximately 340 days (11 months). Special attention must be given to the diet of the pregnant mare from conception to foaling. During the first eight months of pregnancy, the foal does not gain much weight. In fact, the fetus at the 7th month may only weigh between 8.8 and 16.5 lbs. Many mares are able to obtain enough calories and protein from high quality forages such as alfalfa/grass hay mix. Fresh pasture is also a source of nutrients for the pregnant mare. The equine fetus grows linearly during the second half of gestation and will gain 75% of its final birth weight between mid and late gestation. Birth weight of the foal is expected to be 8-10% of the mare’s initial body weight. Gestational weight of the mare is expected be 12-16% of a mare’s initial weight.