The effects of age at slaughter, genotype and finishing system on the organoleptic properties and texture of bull beef from suckled calves

Abstract

An experiment was devised to examine the effect of animal age at slaughter, within genotype and finishing system, on bull beef eating quality characteristics to assess the 15 month age limit imposed for bulls at slaughter by the Meat and Livestock Commission specification for improved beef eating quality. The experiment was a factorial design using bulls of two crossbred genotypes (Aberdeen Angus × and Charolais ×), offered two diets (silage-based and barley-based) and slaughtered at two abattoirs. Bulls were slaughtered from approximately 10 months of age on seven dates (ages) at 6-week intervals. Bulls given barley were slaughtered on date numbers 1 to 5 (43 to 67 weeks of age) and bulls given silage on date numbers 2 to 7 (49 to 79 weeks of age). On each slaughter date and at each abattoir the first four commercial steers which followed the bulls on the slaughterline and met the United Kingdom (UK) modal carcass specification R 4L were selected as abattoir, slaughter date and industry representative controls. At 48 h post mortem samples of m. longissimus lumborum; m. biceps femoris; and m. semimembranosus were recovered from all bull and steer carcasses, vacuum packed and stored at 2°C for a fiirther 12 days before freezing and subsequent assessment by a 12 member taste panel and texture analysis using a Warner Bratzler shear jig.Bulls achieved high growth rates during the finishing period averaging 1·22, 1·55, 1·41 and 1·98 kg/day for silage-fed Angus × bulls; barley-fed Angus × bulls; silage-fed Charolais × bulls; and barley-fed Charolais × bulls, respectively (s.e.d. = 0·08; P < 0·05). Age at slaughter had no significant effect on beef tenderness from young bulls in this study. Similarly, no significant differences in beef tenderness either between genotypes or diets were detected. Bulls, however, produced meat which had lower mechanical shear force values (10·2 v. 11·9 kg for m. biceps femoris; P < 0·001) and was considered to be more tender (P < 0·001), less flavoursome (F < 0·001) and more acceptable (P < 0·01) than that produced by steers.It was concluded that beef aged for 14 days post mortem and recovered from young bulls which have achieved high growth rates can be at least as good as that representative of the UK standard product. The 15-month age limit for bulls ensures that commercially produced bulls achieve high lifetime growth rates and will produce beef of a quality comparable with that achieved in this study.