OBJECTIVE APPROACH TO SLAUGHTER PIG CLASS IFICATION IN THE SLOVAK-REPUBLIC

The proportion of lean cuts was determined using detailed carcass anal ysis and separating lean cuts with a knife in a set of 120 pigs divide d into four groups according to the breed and/or cross combination (1. White Pork x Duroc x Yorkshire, 2. Landrace x Hampshire x synthetic l ine, 3. Landrace x Duroc x Yorkshire, 4. White Pork). The pigs were fa ttened in current husbandry conditions, receiving commercial feed mash es until the live weight of about 110 kg. The average proportion of le an cuts in the set evaluated was 52.69 per cent out of the weight of s ides of pork, with the values ranging from 38.11 to 68.29%. The portio n of valuable lean cuts (ham, loin, spare rib, shoulder) was 49.86% ra nging from 39.54 to 61.43% (Tab. I). Various spots for measuring backf at thickness and lean meat that may be usable for the calculation of l ean cut percentage were also tested. High correlations were found out between the portion of lean cuts and backfat thickness above the middl e point of the musculus gluteus medius (MGM) - r = -0.847, and backfat thickness measured laterally between the 3rd-4th last but one thoraci c vertebra - r = -0.736 (Tab. II). Accuracy of determining the lean cu t percentage was also tested for the use of regression equation applie d in Germany, regression equation conceived by the manufacturer of cla ssification instruments UNI-FOM-89 and our own regression equation con structed 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 lea n cut portion in pig carcasses spots of measuring backfat and meat thi ckness 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 meas uring above the middle point of MGM. The portion of lean cuts in pig c arcasses should be calculated in this way: a) for the basic spot of me asuring 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 i n mm; b) for the substitute spot of measuring above the middle point o f 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.