Genetic-diet interactions in the hyperkalemic periodic paralysis syndrome in quarter horses fed varying amounts of potassium: III. The relationship between plasma potassium concentration and HYPP Symptoms
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Six broodmares that were DNA 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 33 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 in two evenly spaced meals per day. The experimental periods were 14 days long, resulting in 28 meals per period. The HYPP Symptoms Index was greater at meal 1 than meal 27 and greater when the horses were fed diet C than diet B. Plasma K+ concentrations at the onset of symptoms were not different by diet or meal and averaged 3.78 mmol/ L. The average time of onset of symptoms was two hours and 33 minutes after the beginning of a meal, which was not different by diet or meal. A regression analysis of 204 paired non-zero HYPP Symptoms Index values and their corresponding plasma K+ concentrations at the same times, from the HYPP H/N horses, resulted in an R2 of .449. While fed diet A, the horses' mean plasma K+ values remained below 3.5 mmol/L, and no symptoms were observed. Generally, an increase in Symptoms Index followed increased plasma K+ concentration when the horses were fed diets B and C at meal 1. At meal 27, the mean HYPP Symptoms Index and average plasma K+ values were lower than at meal 1. However, there were increased plasma K+ concentrations observed in the later post-prandial hours after meal 27, when the horses were fed diet B, that did not correspond to HYPP symptoms. In a pilot study, one horse collapsed into sternal recumbency after meal 1 when her HYPP Symptoms Index was 10 and her plasma K+ concentration was 7.29 mmol/L. This horse spontaneously recovered from the episode. By meal 27, both the peak plasma K+ concentration (4.6 mmol/ L) and the peak HYPP Symptoms Index (1) were smaller in this horse, but they still occurred simultaneously.
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