Growth and carcass characteristics of crossbred and straightbred Hereford steers. II. Carcass measurements and composition

Abstract

The effect of sire breed on the growth and development of carcass characteristics was examined in 104 steer carcasses, over the weight range of c. 300 to 600 kg liveweight. The carcasses were obtained from 28 straightbred Hereford, 27 Brahman x Hereford, 23 Simmental x Hereford and 26 Friesian x Hereford steers, which were grown on pasture and slaughtered in four groups when the Herefords weighed c. 270, 370, 470 and 570 kg liveweight. Changes in carcass characteristics with weight were examined by using the linear form of the allometric equation (log10Y = log10A+blog10X). As liveweight increased, the proportion of carcass in the body increased (b = 1.152). At the same liveweight, Brahman cross steers had heavier carcasses than the Hereford steers, which were heavier than either the Simmental or Friesian cross steers (P < 0.05). Fat thickness at the 12th-13th rib site, and kidney and channel fat weight both increased at a proportionally faster rate than carcass weight (b = 1.511 and 1 567 respectively). At the same carcass weight, Hereford and Brahman cross carcasses had a greater fat thickness than Simmental and Friesian cross carcasses (P i 0.05). Differences between sire breeds in kidney and channel fat weight were not significant (P > 0.05). C:rcass length and eye muscle area increased at a proportionally slower rate than carcass weight (b = 0.268 and 0.466 respectively). At the same carcass weight, Friesian cross carcasses were longer, and Simmental cross carcasses had a larger eye muscle area than the other breed crosses (P < 0.05). As total side weight increased, the proportions of subcutaneous and intermuscular fatAincreased (b = 1.554 and 1.535 respectively), and the proportions of muscle and bone decreased (b = 0.938 and 0.676 respectively). At the same side weight, the Hereford and Brahman cross carcasses had more subcutaneous fat than the Simmental and Friesian cross carcasses (P < 0.05). The Hereford carcasses had more intermuscular fat than the Simmental cross carcasses, which had more muscle than the other breed crosses (P < 0.05). Friesian cross carcasses had more bone than the Simmental crosses, with Brahman cross and Hereford carcasses having the least bone (P < 0.05). Brahman cross carcasses had a higher conformation score than the Simmental cross and Hereford carcasses, the Friesian cross carcasses having the lowest (P < 0.05). Samples of the M. longissimus from Brahman cross carcasses had a higher Warner-Bratzler shear force than samples from the other breed crosses (P < 0.05).