LIVEWEIGHT GAIN AND CARCASS CHARACTERISTICS OF BULLS AND STEERS FARMED ON HILL-COUNTRY

Liveweight gain and carcass and meat characteristics of Friesian bulls (n = 40) were compared with those of Hereford x Friesian bulls (n = 4 0) and Friesian x (Hereford x Angus) steers (n = 40). The cattle were grazed together on hill country from about 4 months, and were slaughte red either at c. 20 months (the heaviest animals at that time) or c. 2 8 months. Growth rates of the two bull groups were similar, and for bo th, were significantly higher than for the steer group. The Hereford-c ross group of bulls had a higher dressing-out percentage (50.0) than e ither of the other groups (49.0), and their carcasses were 3.5% shorte r than those of the Friesian bulls at the same weight. Kidney and pelv ic fat weight and percentage intramuscular fat were similar for the tw o bull groups, but fat depth was greater for the Hereford-cross bulls. All measures of fatness were significantly greater for the steer grou p, but their mean rib-eye area was less than for the Hereford-cross bu lls (63.2 versus 69.7 cm(2)). Beef from bulls had a higher mean ultima te pH (6.11 versus 5.64), and an associated darker colour and shorter sarcomere lengths. After adjustment to a constant pH, these difference s were no longer apparent, but bull beef had a higher pH-adjusted cook ing loss (27.1 versus 24.5%). The results were consistent with the sug gestion that the increased shear force associated with an increase in ultimate pH from 5.5 to about 6.2 resulted in part from some muscle co ntraction. Meat from the 28-month group had higher Warner-Bratzler she ar values and a darker colour after adjustment for differences in pH.