THE EFFECTS OF AGE AT SLAUGHTER, GENOTYPE AND FINISHING SYSTEM ON THEORGANOLEPTIC PROPERTIES AND TEXTURE OF BULL BEEF FROM SUCKLED CALVES

An experiment was devised to examine the effect of animal age at slaug hter, within genotype and finishing system, on bull beef eating qualit y characteristics to assess the 15 month age limit imposed for bulls a t slaughter by the Meat and Livestock Commission specification for imp roved beef eating quality. The experiment teas a factorial design usin g bulls of two crossbred genotypes (Aberdeen Angus X and Charolais X), offered two diets (silage-based and barley-based) and slaughtered at two abattoirs. Bulls were slaughtered from approximately 10 months of age on seven dares (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 s laughter date and at each abattoir the first four commercial steers wh ich followed the bulls on the slaughterline and met the United Kingdom (UK) modal carcass specification R 4L were selected as abattoir, slau ghter date and industry representative controls. At 48 h post mortem s amples of m. longissimus lumborum; m. biceps femoris; and m. semimembr anosus were recovered from all bull and steer carcasses, vacuum packed and stored at 2 OC for a further 12 days before freezing and subseque nt 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 silag efed Angus X bulls; barley-fed Angus X bulls; silage-fed Charolais X b ulls; and barley-fed Charolais X bulls, respectively (s.e.d. = 0.08; P < 0.05). Age at slaughter had no significant effect on beef tendernes s from young bulls in this study. Similarly, no significant difference s in beef tenderness either between genotypes or diets were detected. Bulls, however, produced meat which had lower mechanical shear force v alues (10.2 v. 11.9 kg for m. biceps femoris; P < 0.001) and was consi dered to be more tender (P < 0.001), less flavoursome (P < 0.001) and more acceptable (P < 0.01) than that produced by steers. It was conclu ded that beef aged fro 14 days post mortem and recovered from young bu lls which have achieved high growth rates can be at least as good as t hat representative of the UK standard product. The 15-month age limit for bulls ensures that commercially produced bulls achieve high lifeti me growth rates and will produce beef of a quality comparable with tha t achieved in this study.