The relationships among lumbar region width, back muscling and musculus longissimus lumborum et thoracis area in Blonde d’Aquitaine bulls and heifers during rearing period

Abstract. The objective of this study was to determine the predictive value of lumbar region width, measured with a tape (WT) and Wilkinson’s trammel (WW), and the ultrasounded musculus longissimus lumborum et thoracis (MLLT) area in the 1st lumbar vertebra, and back muscling (BM) in bulls and heifers of the Blonde d’Aquitaine (BA) breed during the rearing period for selection of breeding animals, concentrating on the MLLT area and muscling. Two generations of bulls (n=63) and heifers (n=68) of BA breed (n=61) and crossbreds Czech Pied Cattle × Blonde d’Aquitaine (C×BA) (n=70) born between December 2004 and June 2006 were included in the investigation. Measurements of the WT, the WW, the MLLT area and subjective judging of the BM were performed at 120, 210 and 365 days of age. The effects of lumbar region width in the 1st lumbar vertebra level, the level of back muscling and that of the MLLT area were used to determinate the relationships among dependent variables at the given ages of the animals. Better muscling of the back or a larger MLLT area during the entire period of rearing was determined in relation to a wider lumbar region (P<0.05–0.001), whereas more significant results were detected during measurement of the WT. Direct dependencies were confirmed by evaluation of the MLLT area at 210 and 365 days in relation to the BM at the same age (P<0.05–0.01). The trend of dependence between the MLLT at 210 and 365 days of age was stated, a larger MLLT at 210 days of age predicted a larger MLLT at 365 days of age, from 2.58 cm² to 6.21 cm². The values of the WT and the WW at 120, 210, and 365 days and level of the BM at 210 and 365 days of age can be also considered objective and acceptable characteristics for the selection of animals aimed at the MLLT area at the same age.