Colour of subcutaneous adipose tissue and M. longissimus dorsi of high index dairy and beef × dairy cattle slaughtered at two liveweights as bulls and steers

The objectives of this study were (a) to compare muscle and adipose tissue colour of male progeny of two strains of high genetic merit Friesian cows (New Zealand [NZF] and Irish [DAF]) with those of beef (Belgian Blue) × dairy (Holstein-Friesian) [BBHF] male progeny; (b) to compare bulls and steers (gender) of these genotypes and (c) to examine the effects of slaughter weight (SW) on these quality traits. Bulls (n=48) and steers (n=48) of the three genotypes were grown to nominal target liveweights of 550 kg (light) and 630 kg (heavy). Adipose tissue from the NZF genotype was more yellow (P<0.05) than from DAF or BBHF, regardless of gender or SW. For longissimus dorsi (LD) pH, bulls and heavy animals had higher pH (P<0.05) than steers or light animals, respectively, while NZF and BBHF bulls had higher pH than steers. LD muscle from the BBHF genotype had lighter colour (P<0.05) and lower haem pigments (P<0.01) than NZF or DAF progeny. There was no difference in muscle `Lʹ value between light bulls and steers but heavy bulls had darker muscle than heavy steers. There was an interaction between genotype, gender and SW for LD redness. Thus, NZF animals were most red when slaughtered as light or heavy bulls, but there were no differences between genotypes slaughtered as light or heavy steers. These data demonstrate differences in colour of beef, especially from progeny of NZF, which produced the most yellow adipose tissue and the most red muscle tissue.