PREDICTION OF THE PERCENTAGE OF LEAN CUTS IN PIGS USING SOME CARCASS MEASURES

Prediction of the percentage of lean cuts and/or lean meat in pigs is based on exploitation of some carcass measures. Apparatuses record particularly backfat thickness and/or muscle thickness to estimate the amount of meat by means of ultrasound or optic probes or by means of a graduated ruler. The objective of experiments was to evaluate the level of relationships between backfat thickness and percentage of valuable lean cuts (spare rib, shoulder, loin and ham) in the pigs of the Large White - BU (n = 522) and white Pork breed - BM (n = 178), in the crossbreds Belgian Landrace x Duroc (LB x D), so called synthetic line - SL (n = 223) and hybrids of the cross combination (BU x BM) x SL (n = 163). At the same time, regression equations were used to calculate the percentage of valuable lean cuts (CMC). Backfat thickness was determined at three spots of the side of pork as well as the eye-muscle area, in the pigs BU, BM and SL in test conditions (feed mix with the contents of 17.2 % crude protein) after slaughter. Technological analysis enabled to determine the percentage of valuable lean cuts, and simple correlation coefficients were calculated between the investigated parameters (Tabs. I to IV). Statistically highly significant relationships were determined between CMC arid backfat thickness at the first vertebra (r = -0.57 to -0.69). the coefficient r = 0.55 to 0.65 was calculated for the relationship between the percentage of valuable lean cuts and the eye-muscle area. This regression equation was constructed for the BU breed (live weight 100 kg, even representation of both sexes) from the given measures: Y = 58.448 - 0.4433 . HS 3, where Y - estimate of the percentage of valuable lean cuts, HS 3 - backfat thickness at the first sacral vertebra (mm). The equation for die BM breed was as follows: Y = 55.1271 - 0.3340 HS 3 and its form for the pigs of the synthetic line (LB x D crossbreds) is this: Y = 57.7659 - 0.3819. HS 3. The estimate of the CMC percentage was most successful in the pigs with the percentage ranging from 46 to 50 %. The reliability of prediction was decreasing in the expressly meat types (above 52 %) and/or in fatty types (below 44 %). The accuracy of the calculation did not improve when another parameter (eye-muscle area) was used. In the hybrid pigs (live weight 113.96 kg) raised in practical farming conditions (feed mix with the content 12.9 % CP) there were statistically significant correlations between the CMC percentage and backfat thickness above the middle of the second thoracic vertebra (r = -0.67) and between the CMC percentage and backfat thickness above the m.g.m. (r = -0.62). The coefficient r = 0.48 was calculated for the relationship between the eye-muscle area and CMC percentage. Regression equation for the estimate of valuable lean cuts had this form: Y = 59.1437-0.2999. HS 1, where Y - estimate of the percentage of valuable lean cuts, HS 1 - backfat thickness measured above the middle of the second thoracic vertebra (mm). The results of the experiments have confirmed that the use of carcass measures (particularly backfat thickness) can help to estimate the percentage of valuable lean cuts with relatively high accuracy.