Histological structure of the musculus longissimus lumborum et thoracis in pigs with the same ryanodine receptor genotype (CC) in relation to carcass indicators

The aim of this study was to investigate the histological structure of the longissimus muscle in pigs in relation to carcass value indicators. A total number of 16 pigs of about 101.28 kg average live weight were used. The animals were raised at a Fattening and Carcass Value Experimental Station (FCVES) of Slovak University of Agriculture in Nitra in equal conditions, receiving a standard diet fortified with vitamin-mineral mixture, and they were slaughtered in an experimental abattoir of FCVES. Samples from the musculus longissimus lumborum et thoracisi (MLLT) for histological evaluation were taken within 30 minutes post mortem, immediately frozen in liquid nitrogen and stored at a temperature of -20°C. In the experimental abattoir of FCVES feeding indicators, and indicators of meat quality and carcass value were examined. Samples were processed histochemically and single types of muscle fibres were differentiated according to reactions on SDH on the basis of Vacek's (1974) method. Nikon microscopic system, Pixelink digital camera and LUCIA software for image analyses for the morphometric analysis of MLLT structure were used. The highest abundance of white and the lowest abundance of intermediate muscle fibres was obtained in the analyzed musculus longissimus lumborum et thoracisi of pigs. Red muscle fibre abundance was only slightly higher than intermediate muscle fibre abundance. Concerning the average muscle fibre diameter, the highest values in white and the lowest values in red muscle fibres were found. Positive correlations of white muscle fibre abundance with loin meat weight, thigh meat weight, carcass length, ribcase length, hot right half weight, valuable meatiness parts in kilograms, thigh weight, thigh percent in the half-carcass and MLLT area weight were obtained. In the case of all fat content and weight indicators negative correlations were obtained except loin fat weight. Red muscle fibre content showed positive correlations with shoulder fat weight, neck meat weight, neck fat weight, head weight, thigh fat weight, average backfat thickness and MLLT area. Correlation coefficients between white muscle fibre diameter and shoulder meat weight, thigh meat weight, carcass length, ribcase length showed weak positive correlations. An increase in the white muscle fibre diameter corresponds with an increase in loin meat weight, valuable meatiness parts in kg, valuable meatiness parts in percents, thigh weight, thigh percent in the half-carcass weight and MLLT area. Concerning the red muscle fibre diameter weak positive correlations were obtained in relation to neck meat weight, thigh meat weight, thigh weight and moderate positive correlations to shoulder meat weight, loin meat weight, valuable meatiness parts in kilograms and percents, thigh percent in half-carcass and MLLT area.