HERITABILITIES AND PHENOTYPIC AND GENETIC CORRELATIONS FOR BOVINE POSTRIGOR CALPASTATIN ACTIVITY, INTRAMUSCULAR FAT-CONTENT, WARNER-BRATZLER SHEAR FORCE, RETAIL PRODUCT YIELD, AND GROWTH-RATE

To estimate the heritability (h2) of postrigor calpastatin activity (C A), 555 steers were reared and processed conventionally. Breed-types i ncluded purebreds (Angus [A], Braunvieh [B], Charolais [C], Gelbvieh [ G], Hereford [H], Limousin [L], Pinzgauer [P], Red Poll [RP], and Simm ental [S]), composite populations (MARC I [1/4 C, 1/4 B, 1/4 L, 1/8 H, 1/8 A], MARC II [1/4 S, 1/4 G, 1/4 H, 1/4 A], and MARC III [1/4 RP, 1 /4 H, 1/4 P, 1/4 A]), and F1 crosses (H, A, C, G, P, Shorthorn, Gallow ay, Longhorn, Nellore, Piedmontese, or Salers x H or A). Steers were s erially slaughtered on an age-constant (across breed groups) basis. He ritability estimates for CA, i.m. fat content (IMF), Warner-Bratzler s hear (WBS) force, retail product yield (RPY), and ADG were .65 +/- .19 , .93 +/- .02, .53 +/- .15, .45 +/- .18, and .32 +/- .26, respectively . The genetic correlations (r(g)) of CA with WBS, RPY, and ADG were .5 0 +/- .22, .44 +/- .25, and -.52 +/- .37, respectively. The r(g) of IM F with WBS, RPY, and ADG were -.57 +/- .16, -.63 +/- .15, and -.04 +/- .11, respectively. These h2 and r(g) estimates indicate that it shoul d be possible to select for improvements in CA, IMF, and WBS. However, selection against CA may be a more suitable approach for improving me at tenderness than selection for increased IMF because the level of ge netic antagonism between CA and RPY was not as great as that between I MF and RPY.