Beef production from Holstein–Friesian bulls and steers of New Zealand and European/American descent, and Belgian Blue×Holstein–Friesians, slaughtered at two weights

Abstract Various strains of Holstein–Friesian cattle have been imported into Ireland in recent years. The objective of this study was to evaluate for beef production the male progeny of New Zealand (NZ) and European/American (EU) Holstein–Friesians, and Belgian Blue×Holstein–Friesians (BB). The NZ animals were imported from New Zealand as embryos which were implanted into Irish heifers. The EU animals were the progeny by artificial insemination (AI) of high genetic merit Irish cows and high genetic merit European/North American-bred bulls. The BB animals were the progeny both by AI and natural mating of Belgian Blue bulls and Holstein–Friesian cows on commercial farms. A total of 96 spring-born male cattle (32 per genotype) were reared from calfhood to slaughter. They spent their first summer together at pasture and they were then blocked on weight to a 3 genotypes (NZ, EU and BB)×2 production systems (bulls and steers)×2 slaughter weights (550 and 630 kg) factorial experiment. After slaughter, carcasses were measured and the ribs joint was dissected into subcutaneous fat, intermuscular fat, muscle and bone. For NZ, EU and BB, respectively, mean daily gains from arrival to slaughter were 773, 822 and 850 (S.E.D. 9.8) g, mean carcass weights per day from arrival were 425, 459 and 528 (S.E.D. 3.8) g, mean kill-out proportions were 496, 508 and 554 (S.E.D. 2.8) g/kg and mean carcass weights were 284, 302 and 339 (S.E.D. 3.0) kg. Carcass conformation score, carcass fat score, fat depth and m. longissimus area did not differ significantly between NZ and EU, but BB had higher values for carcass conformation and m. longissimus area and lower values for the fatness indicators. Compared with NZ, EU had more muscle and bone and less fat in the ribs joint, while BB had more muscle and less fat and bone than the dairy strains. Bulls had significantly higher slaughter and carcass weights per day from arrival than steers and also had a higher proportion of muscle and a lower proportion of fat in the ribs joint. Delaying slaughter increased slaughter and carcass weights but there was no significant effect on ribs joint composition. It is concluded that EU were slightly superior to NZ for beef production and BB were considerably superior to both dairy strains. Rearing as bulls rather than as steers improved carcass traits and retaining animals to a heavier slaughter weight improved carcass compactness with little effect on rib joint composition.