HERITABILITY ESTIMATE OF HYPERTROPHIC CARDIOMYOPATHY IN PIGS (SUS SCROFA DOMESTICA)

The purpose of this study was to evaluate the heritability of hypertro phic cardiomyopathy (HCM) in pigs and the relation between HCM and hea rt measurements, pathologic features, and growth to provide references for HCM line development. A total of 353 on-farm tested gilts (female s) and boars (males) from 74 sire families were randomly selected from a single breeding farm where HCM was prevalent, Hearts were collected after animals were slaughtered. Heart length, width, and weight, hear t-to-body weight ratio, and thickness of the cranial, middle, and caud al portions of the ventricular septum, left and right ventricles, and apex were measured, Cardiac hypertrophy and myocyte disorganization, m yocardial and endocardial fibrosis, and intramural coronary arterial o cclusion were used as criteria for HCM. Growth traits were evaluated f rom average daily body weight gain, ultrasonically determined backfat thickness, loin-eye area, and performance selection index. Heritabilit y of the disease was estimated by treating it as a threshold trait. Th e prevalence of HCM in three studied breeds was 5.26 in Duroc, 22.98 i n Landrace, and 5.56% in Yorkshire pigs. The value in Landrace pigs wa s significantly (P < 0.001) higher than that in the other pigs. There was no significant difference between sexes. In general the heart of p igs with HCM was heavier, wider, longer, and thicker than that of clin ically normal pigs. Backfat was the only growth trait with a differenc e (P < 0.05) among pig breeds. The HCM pigs were leaner than normal pi gs. Leaner pigs may have a higher risk of HCM. Heritability of HCM was >0.30 for all three breeds, but the standard errors of these estimate s were high because of limited sample size, in particular for the York shire and Duroc breeds. The preliminary results of this study indicate that HCM in pigs is moderately heritable; thus development of a high- HCM incidence line by selection is possible.