EFFECTS OF SELECTION FOR HIGH MILK-YIELD AND GROWTH ON CARCASS AND MEAT QUALITY TRAITS IN DUAL-PURPOSE CATTLE

To study the correlated responses of selection for high milk yield on beef production characteristics, growth rate, roughage intake, carcass and meat quality traits were measured on 78 (n = 22 sires) Norwegian (NRF) dual purpose cattle bulls from genetic lines for high (HL) and l ow (CL, control) milk production level. The genetic lines were establi shed by use of progeny-tested sires from the NRF selection programme, which were preselected for growth rate in performance test. The bulls were fed two concentrate levels (HC, high; LC, low), and slaughtered a t 550 kg live weight. Contrasts between the genetic lines and feed lev els were estimated by REML. The HL bulls had a higher growth rate and roughage intake than the CL bulls, and were younger at slaughter. No i mportant differences in carcass quality were observed between the HL a nd the CL. The HL bulls had a lighter meat colour and a lower content of intramuscular fat in the m.l. dorsi than the CL bulls. HC bulls had a slightly higher dressing % and higher fleshiness scores, carcass fa t level and intramuscular fat content in m.l. dorsi compared to LC bul ls. Selection for high milk yield did not have unfavourable effects on commercial carcass quality in this study. Differences in retail cut p roportions indicated a lower stage of maturity of the HL bulls at slau ghter. As the r(g), between milk and beef production traits generally seem to be low, this was probably mainly caused by the higher genetic growth potential in the HL. The similarity in commercial carcass quali ty between the lines suggested that improvements in carcass quality in dual purpose cattle is difficult to obtain if selection mainly is lai d on milk production and growth traits. The present study also confirm ed the hypothesis that selection for high growth rate may lead to phys iological changes in the musculature which can have unfavourable effec ts on the overall eating quality of beef. (C) 1997 Elsevier Science B. V.