Effect of slaughter weight and/or age on histological characteristics of pig longissimus dorsi muscle as related to meat quality.

The effect of increasing both weight and age or age alone through feed restriction on muscle longissimus dorsi histological characteristics were studied in relation to fresh and cooked meat quality. Starting at 83 days (32 kg) 80 crossbred Duroc × (Large White×Landrace) barrows were allotted within litter to 4 experimental groups (A100, R100, A130, R130). Pigs were fed either ad libitum (A) or were restricted 30% (R) and slaughtered either at 100 kg or 130 kg. Muscle fibres were classified as βR, αR or αW according to Ashmore and Doerr (1971)(Ashmore, C.R., & Doerr, L. (1971). Comparative aspects of muscle fibre types in different species. Experimental Neurology, 31, 408-418.). Percentages (PC), cross-sectional areas (CSA) and relative areas (RA) of each fibre type were evaluated. Phenotypic correlations between histological traits showed that RA of a particular fibre type depends essentially on its numerical abundance. Increasing weight together with age led to enlargement of βR and αW muscle fibres, without changing muscle histochemical profile. When age was increased at the same weight (restriction), higher RA of βR fibres was observed. Low, but significant correlation between loin eye area and CSA was observed, but not within experimental group. The phenotypic correlations between histological and meat quality traits were generally low. This material showed some significant correlations suggesting that increasing PC or CSA of overall αW fibres can be beneficial for water holding capacity of fresh meat and juiciness of cooked meat. ©