Factors Affecting Ultrasound Intramuscular Fat Content in Musculus Longissimus Dorsi of Beef Bulls Estimated with Bia Pro Plus Software / Czynniki wpływające na ultrasonograficzną ocenę udziału tłuszczu śródmięśniowego mięśnia najdłuższego grzbietu buhajów mięsnych

The aim of the study was to determine the effect of ultrasound gain level, chemical composition and histological structure of musculus longissimus dorsi on pre-slaughter ultrasound evaluation of intramuscular fat content in m.l.d. of beef bulls. The study was conducted on 217 young bulls of six breeds: Red Angus, Charolais, Hereford, Limousin, Salers, and beef type Simmental. Measurements were conducted with an ultrasound system Aloka SSD-500 at five gain levels (90, 85, 80, 75, 70). After slaughter the content of intramuscular fat, total protein, connective tissue and muscle fibre type and diameter of m.l.d. were determined. Ultrasound evaluation of the intramuscular fat depended on the actual intramuscular fat and the total protein content (P<0.01) in most of the measurements. The correlation between actual and ultrasound measurement of intramuscular fat content ranged from 0.2 to 0.36, and was highly significant for most of the ultrasound gain levels. There were highly significant (P<0.01) and significant (P<0.05) negative correlations between the total protein and ultrasound fat content (r = -0.17 to -0.31). The connective tissue percentage showed a significant effect on the ultrasound fat measurements at gains of 75 and 85. Ultrasound intramuscular fat content was positively correlated with the connective tissue in the m.l.d. at gain levels of 75 and 85 and the average ultrasound intramuscular fat measurement (r = 0.16, 0.20, 0.16). Highly significant and significant correlations between each ultrasound measurement were observed.