Factors influencing beef eating quality - 1. Effects of nutritional regimen and genotype on organoleptic properties and instrumental texture

An experiment was conducted to determine if growth rate, as affected by lev el of feeding, during a 10-or 20-week period prior to slaughter could influ ence the tenderness and palatability of beef from young (approx. 14 months old at the start of experiment) steers. Steers, comprising 18 Aberdeen Angu s (AA), 18 Charolais (CH) and 18 Holstein (HO) purebreds, were allocated, w ithin genotype, to one of three levels of feeding: (a) moderate ((M/M) 750 kJ metabolizable energy (ME) per day per kg M-0.75), (b) high ((H/H) 1050 k J ME per day per kg M-0.75) both for 20 weeks; or (c) moderate for the firs t 10 weeks followed by high for the remaining 10 weeks (M/H). The steers we re slaughtered at a fixed age (approx. 19 months old) and samples of m. lon gissimus lumborum (from all three genotypes) m. vastus lateralis and m. bic eps femoris (from AA and CH only) separated, vacuum packed and stored at 2 degreesC for both 7 and 14 days before freezing. These cuts were subsequent ly assessed by a 12 member taste panel and texture analysis performed using Volodkevitch-type jaws. Growth rafts during the final 10 weeks of the experimental period differed between dietary regimen (M/M = 0.87; M/H = 1.25; and H/H = 1.02 kg/day; s.e .d. = 0.08; P < 0.001). Steers offered the M/M level of feeding grew more s lowly (0.97 kg/day) than those offered the M/H and H/H level of feeding (1. 20 kg/day; s.e.d. = 0.06; P < 0.001) over the entire 20 week experimental p eriod. In spite of these differences in growth rate, there were no consiste nt effects on beef tenderness and general palatability. Mean growth rates f or CH, HO and AA steers were 1.21, 1.13 and 1.03 kg/day (s.e.d. = 0.06; P < 0.05). Beef samples front AA steers consistently scored better for various sensory attributes than those from CH and HO steers; this may have been du e, in part, to level of carcass fatness and rate of carcass cooling post mo rtem. Accounting for factors such as genotype within the experimental desig n and slaughtering animals at a relatively constant age reduced the varianc e associated with each sensory attribute to 0.6 of that observed in commerc ial practice. The data suggest that there is little opportunity to improve beef eating quality by increasing growth rate by dietary means in steers pr ovided that moderate levels of gain (equivalent to the UK average) are main tained.