Genetic-diet interactions in the Hyperkalemic Periodic Paralysis syndrome in Quarter Horses fed varying amounts of potassium: I. Potassium and sodium balance, packed cell volume and plasma potassium and sodium concentrations
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Six broodmares that were genetically tested to be heterozygous (H/N) and six broodmares that were tested to be homozygous negative (N/N) for Equine Hyperkalemic Periodic Paralysis (HYPP), that were descendents of the same stallion, were used in a replicated 3x3 Latin square experiment to determine the genetic-diet relationships in the HYPP syndrome. 1 The mares were fed rations consisting of 65 % pelleted concentrate and 35% Coastal Bermuda grass hay that provided 1.1 (diet A), 1.9 (diet B) and 2.9% (diet C) potassium. The experimental periods were 14 days long, resulting in 28 meals per period. At meals 1 and 27, blood samples were taken every 30 minutes for 12 hours and every 10 minutes from 2 to 5 hours post-feeding. Total urine and fecal collections were made on the last 4 days of each period. Water, feed and fecal samples were analyzed for sodium and potassium content. Blood was analyzed for packed cell volume (PCV) and plasma potassium (K+) and sodium (Na+) concentrations. Apparent absorption of potassium was 99.8% across all diets, and potassium was excreted principally in the urine. More potassium was retained when the horses were fed diet B than diets A or C. Apparent absorption of sodium was 99.6% with no difference by diet. Neither potassium nor sodium balances were affected by HYPP status. There was no post-prandial pattern of plasma K+ concentration seen when the horses were fed the low potassium diet. When fed the higher potassium diets, they had greater plasma K+ values and exhibited a post-prandial peak at 2 to 5 hours after feeding. This peak occurred in all of the horses, meaning that plasma K+ cannot be used as a diagnostic aid for the presence of the HYPP mutation. By meal 27, some adaptation had occurred resulting in lower plasma K+ values when the horses were fed the higher potassium diets. The horses had increased plasma K+ concentrations throughout the post-prandial period while fed diet B compared to diet A, agreeing with the positive potassium balance seen in this experiment. The HYPP H/ N horses had lower plasma Na+ concentrations in the early post-prandial hours and continuously greater PCV values than the HYPP N/N horses.
Journal of Equine Veterinary Science
author list (cited authors)
Reynolds, J. A., Potter, G. D., Greene, L. W., Wu, G., Carter, G. K., Martin, M. T., ... Erkert, R. S.
complete list of authors
Reynolds, JA||Potter, GD||Greene, LW||Wu, G||Carter, GK||Martin, MT||Peterson, TV||Murray-Gerzik, M||Moss, G||Erkert, RS