Changes in carcass composition of pigs with various lean percentage

The objective of the paper was to provide information on carcass composition of pigs with respect to the total content of lean as taken into account in the new system of slaughter animal grading. Solution to the above problem relied on a batch fattening schedule practised in the Czech Republic conditions. A set of pigs was followed in which test fattening from 30 kg of live weight to slaughter lasted 130 +/- 3 days. Carcass analysis first consisted in cutting the left side of pork into separate parts. Except the head and trotters, these parts were dissected into lean, fat, bones, skin and other tissues, i.e. ligaments, arteries, veins, etc. A crucial step was that the animals were graded into five classes according to the lean percentage in their carcasses, as follows from the basic EUROP-system scale. The best class involved pigs with the lean percentage higher than 55%, the worst class those with the lean percentage lower than 40%. The span of both values was divided into classes with an interval of 5%. The average weight of the side of pork was different in the particular classes, which is evident from the relationship between grading criterion and slaughter weight. If the weight of side of pork with the highest lean percentage is taken as 100%, then at a gradually decreasing lean percentage the respective values in other classes are 105.4%, 113.2%, 123.0% and 118.5%. Data on the particular slaughter parts were not in correspondence with this trend. Eg. the relations between the classes were described by the values 100.0%, 96.0%, 95.9%, 94.6% and 82.5% for ham with bone. On the contrary, these values were 100.0%, 131.8%, 174.7%, 228.0% and 251.0% for the weight of backfat with skin. Lack of uniformity of slaughter part formation in relation to slaughter weight can be documented by the values of correlation coefficients between the lean percentage in the whole carcass and the portion of more or less fatty parts that were always negative, and mostly very high. On the other hand, data on similar assessment of parts with a high lean percentage as well as parts with a high bone portion were positive. Detailed analysis of the carcass parts confirmed the worsening of results describing also the composition of the most valuable lean cuts. Eg. the meat percentage in loin decreased from the best grading class to the worst grading class as follows: 74.7 +/- 0.800%, 72.3 +/- 0.415%, 69.5 +/- 0.290%, 66.6 +/- 0.435% and 64.4 +/- 0.639%. Advantages of slaughter animal grading according to the lean percentage in the whole carcass were demonstrated. Hence the data acquired can quantify the differences in pig carcass composition with respect to varying lean percentage. In general terms, the results make it possible to focus on animal growth uniformity. This applies particularly to the animal health sector and to the breeding sector.