PREDICTION OF BREEDING VALUES FOR TENDERNESS OF MARKET ANIMALS FROM MEASUREMENTS ON BULLS

Data were tenderness measures on steaks from 231 bulls (Group II) slau ghtered after producing freezable semen and on 1,431 related steers an d heifers (market animals, Group I) from Angus, Hereford, Pinzgauer, B rahman, and Sahiwal crosses from the Germ Plasm Evaluation project at the U.S. Meat Animal Research Center. Tenderness was assessed through Warner-Bratzler Shear Force (SF), taste panel tenderness (TPT), marbli ng score (MS), and myofibrillar fragmentation index (MFI). For all tra its, as fraction Bos indicus inheritance increased, implied tenderness decreased. Heritability estimates were generally not significantly di fferent from zero. Genetic correlations generally indicated favorable associations among the traits. The range in predicted breeding values of bulls for market animal tenderness was small and from -.34 to .32 k g for market animal shear force. Because of low estimates of heritabil ity for SF or TPT, results from this experiment indicate that selectio n based on tenderness of steaks sampled from intact or late castrate m ales slaughtered following collection of freezable quality semen would not be very effective in improving average tenderness of steaks from steers or heifer progeny. If a mean of heritability estimates reported in the literature of .27 for shear value was assumed for market steer and heifer progeny instead of .02 as found in the present study, then selection based on estimates of shear force in young bulls would be r elatively more effective in improving shear force of market progeny.