The heritability of pH1 in longissimus dorsi muscle in landrace and large white pigs

The susceptibility of a carcass to PSE (pale, soft, exudative muscle) can be assessed by measuring the pH value in the lumbar region of the longissimus dorsi muscle at 45 min post-mortem (pH₁). The effect of breed, station, sex and season on pH₁ was investigated, on a total of 2 775 pig records, including the progeny of 129 Irish Landrace and 126 Large White boars, from two test stations. The heritability of pH₁ and its genetic correlation with other performance characteristics were determined within each breed. Landrace pigs had significantly lower values than Large White pigs, indicating a greater susceptibility to PSE in the former. There was no significant difference between the values for boars, castrates and females. There were marked differences from month to month, but no definite seasonal pattern was present nor was there any apparent long-term trend. The heritability for the Landrace breed was higher than that for the Large White breed, and both values indicate that pH₁ would respond to selection. The genetic correlations between pH₁ and daily gain, food conversion efficiency and backfat (four measurements) were for the most part low and the standard errors relatively high, indicating that there was no strong relationships between pH₁ and these performance characteristics.