Genetic-diet interactions in the hyperkalemic periodic paralysis syndrome in quarter horses fed varying amounts of potassium: IV. Pre-cecal and post-ileal absorption of potassium and sodium

During an experiment to determine the genetic-diet interactions in genetica lly predisposed Quarter Horses, biphasic symptoms of Hyperkalemic Periodic Paralysis (HYPP) were observed when the HYPP H/N broodmares were fed the hi gher potassium rations.' The cause of those symptoms was assumed to be: 1) the difference in absorption times of the highly absorbable potassium citra te in the concentrates and the potassium contained in the cells of the grai ns and hays in the rest of the rations, 2) partial absorption of potassium in the small intestine followed by no absorption from the cecum and further absorption in the large colon or 3) a combination of both of the above exp lanations. Since previously cannulated ponies were available in this labora tory, an experiment was designed to determine which of those possibilities was the most likely. Three ponies, weighing an average of 132 kg, with posterior-ileal cannulas were used in a 3x3 Latin square experiment to determine the amounts of pota ssium and sodium that would be absorbed pre-cecally and post-ilealy. The po nies were fed the same rations as the mares in the previously described exp eriment (see part I), which provided approximately 1, 1, 1.9 and 2.9% potas sium by weight as fed, Samples of water, feces, ileal contents and blood we re collected. Water, feed, ileal and fecal samples were analyzed for sodium and potassium concentration, Apparent absorption of potassium prior to the cecum was 97% when the ponies were fed the low potassium diet and 98% when they were fed the higher pota ssium diets. Three percent and 2% of the potassium was absorbed from the hi ndgut when the ponies were fed the low potassium diet and the higher potass ium diets, respectively, Nine percent and 16% of sodium was absorbed pre-ce cally when the ponies were fed the low potassium diet and the higher potass ium diets, respectively. Ninety-one and 84% of the sodium was absorbed from the hindgut, when the ponies were fed the low potassium diet and the highe r potassium diets, respectively for 99-100% total absorption of both sodium and potassium from all diets. These results indicate that the potassium from the three diets was absorbed pre-cecally, and that the process took up to nine hours, resulting in bi-p hasic HYPP symptoms in the HYPP H/N mares in the companion experiment, This information can be used to better understand the relationship between diet ary potassium, plasma KC concentration and HYPP symptoms.