The Intensity of MLLT Area Changes and Development of the Selected Body Parts Muscling in Bulls and Heifers of Blonded’ Aquitaine Cattle and its Crossbreeds During Rearing Period

The objective of this work was to determine the effect of sex, breed and birth season of calves on intensity of MLLT (musculus longissimus lumborum et thoracis) area changes and development of the selected body parts in bulls and heifers of Blonde d´Aquitaine (BA) cattle during rearing period. Two generations of bulls (n=63) and heifers (n=68) of Blonde d´Aquitaine (n=61) and crossbreds C×BA (C-Czech Fleckvieh) (n=70) born from December 2004 to June 2006 were evaluated. MLLT area measurements and subjective evaluations of 3 basic body areas muscling (shoulder, back and rump) on live animals were performed at 120, 210 and 365 days of animal age. Statistically significant differences were determined in shoulder, back, and rump muscling in relation to animal sex in favor of bulls at 120 and 210 days of age (P < 0.01 to P < 0.001). Purebred animals achieved significantly higher muscling of rump at 120 days, and muscling of rump and back at 210 days (P < 0.05 to P < 0.001). Statistically significant differences were determined in animals muscling in relation to birth season (P < 0.05 to P < 0.001). Results indicate the best growth ability of purebred bulls born from the end of year to March. Breeders can use this fact as a recommendation for modification of breeding and mating system of beef cattle to achieve better encashment of slaughtered ani-mals.