OBJECTIVE APPROACH TO SLAUGHTER PIG CLASSIFICATION IN THE SLOVAK-REPUBLIC

The proportion of lean cuts was determined using detailed carcass analysis and separating lean cuts with a knife in a set of 120 pigs divided into four groups according to the breed and/or cross combination (1. White Pork x Duroc x Yorkshire, 2. Landrace x Hampshire x synthetic line, 3. Landrace x Duroc x Yorkshire, 4. White Pork). The pigs were fattened in current husbandry conditions, receiving commercial feed mashes until the live weight of about 110 kg. The average proportion of lean cuts in the set evaluated was 52.69 per cent out of the weight of sides of pork, with the values ranging from 38.11 to 68.29%. The portion of valuable lean cuts (ham, loin, spare rib, shoulder) was 49.86% ranging from 39.54 to 61.43% (Tab. I). Various spots for measuring backfat thickness and lean meat that may be usable for the calculation of lean cut percentage were also tested. High correlations were found out between the portion of lean cuts and backfat thickness above the middle point of the musculus gluteus medius (MGM) - r = -0.847, and backfat thickness measured laterally between the 3rd-4th last but one thoracic vertebra - r = -0.736 (Tab. II). Accuracy of determining the lean cut percentage was also tested for the use of regression equation applied in Germany, regression equation conceived by the manufacturer of classification instruments UNI-FOM-89 and our own regression equation constructed from the parameters of an experimental set :of 120 pigs (Tabs. IV and V). It was found out that for a qualified estimate of the lean cut portion in pig carcasses spots of measuring backfat and meat thickness should be determined like this: a) basic spot of measuring - 6 to 8 cm laterally from the line of the median section at the level of the 3rd-4th last but one thoracic vertebra; b) substitute spot of measuring above the middle point of MGM. The portion of lean cuts in pig carcasses should be calculated in this way: a) for the basic spot of measuring where an instrument is to be used the calculation will employ the regression equation of this form: % of meat = 54.456 - 0.75027. S + 0.21181. F, where S = backfat thickness in mm, F = flesh thickness in mm; b) for the substitute spot of measuring above the middle point of MGM in the section line measure by hand and calculate the portion of lean meat by means of this equation: % of meat = 68.2928 - 0.8263. S, where S = backfat thickness above the middle point of MGM in mm.