Chemical composition and tenderness of the culinary meat are among the most important characteristics determining the quality and technological value of meat. Those parameters depend on the pre-slaughter factors such as: species, race, sex, and age of animal, as well as on its resistance to stress, its character and tempo of physiological changes occurring in its muscles, degree of muscling, and type of muscle. The Polish Landrace fatteners (36 animals) were slaughtered on the 60^th, 90^th, 120^th, 150^th, 180^th, and 210^th day of life (six animals in each age group). The m. longissimus dorsi –LD and m. semimembranosus – SM (from ham) were chemically analyzed and the following parameters were determined: dry matter/water content, protein content, fat content, and ash content. The muscles were roasted at 180°C to reach the inside temperature of 78°C. Then, the two parameters of the fatteners’ muscles were determined: texture profile and Warner-Bratzler force of cut, using a TA-XT2 texture analyzer (manufactured by a Stable Micro Systems Co.). It was found that in the muscles of older fatteners, the content of protein and fat was higher; also, compared with the younger fatteners, the increase in the force of cut and in the TPA hardness of their muscles was found. The protein level in the LD muscle ranged from 21.0% on the 60^th day of life to 24.9% on the 210^th day of life; whereas in the SM muscle, it was 20.4% and 23.3%, respectively. The fat content in LD ranged from 1.2% to 1.5%. As for LD and SM muscles, the force of cut was comparable and ranged from app. 3.1 kG/cm² on the 60^th day of life to app. 5.8 kG/cm² on the 210^th day of life. The hardness value (TPA) was 54.2 N (LD) and 92.5 N (SM) on the 60^th day of life, and 129.6 N (LD) & 126.0 N (SM) on the 210^th day.