Lean and fat growth patterns of beef bulls were described with respect to average daily body weight gain and body weight. The variables were studied on a natural scale and after adjusting for degree of maturity within a breed. Size-scaling rules and the ratio of body weight to estimated mature weight were used. The data, collected in Denmark, represented progenies of Red Danish and Danish Friesian cows. These cows were randomly inseminated with semen from Angus, Charolais, Gelbvieh, Piedmontese, South Devon, Brown Swiss, Red Belgium, Blue Belgium, Red Danish or Danish Friesian bulls. Bull calves were allotted at 70 d of age to three slaughter weights (320, 440 and 560 kg) and three feeding levels (ad libitum, 85 and 70% of ad libitum on an energy basis). Linear partial regressions of daily lean gain and daily fat gain on body weight, daily body weight gain and the interaction were estimated. The small breed (Angus) was the highest in daily fat gain and the large breeds (Charolais, Piedmontese and Blue Belgium) the lowest. The other breeds were intermediate. Breed rankings were reversed for daily lean gain. Interactions between body weight and daily body weight gain were important only among medium size/dual purpose breeds for prediction of daily fat gain. Size-scaling did not decrease the importance of this interaction. The interaction was significant in only 2 of 20 cases after adjustment of both y- and x-variables by the ratio of live weight to mature weight. Regardless of the method used, breed group differences in carcass composition still existed after adjusting for degree of maturity.
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Korver et al. (1987) studied this question.