Crossbred steers (n = 136) were used to assess breed differences in growth performance, carcass characteristics, fatty acid composition (total lipids and phospholipids), and palatability attributes of longissimus muscle. A multiple regression model was applied to crossbreeding data to estimate genetic differences between Simmental and Red Angus at the same level of backfat finish (10 mm). Simmental spent 71 more (P < 0.001) days on feed to acquire the same degree of backfat thickness as Red Angus, had heavier (P < 0.001) slaughter weights, larger (P = 0.002) longissimus muscle area, and increased (P = 0.023) lean yield. Average daily gain did not differ (P = 0.297) between breeds. Simmental were less (P = 0.012) efficient in converting feed to gain than Red Angus. Generally, there were few breed differences in palatability attributes for longissimus and semitendinosus muscles, with the exception of increased (P < 0.05) beef flavor scores for Simmental beef vs Red Angus beef across both muscles. For total lipids, concentrations of myristoleic acid (14:1), palmitoleic acid (16:1), and vaccenic acid (18:1n-7), along with n-6 to n-3 fatty acid (n-6:n-3) ratio, were greater (P < 0.05) in Simmental than Red Angus. In contrast, concentrations of margaric acid (17:0), eicosapentaenoic acid (20:5n-3), and total n-3 polyunsaturated fatty acids (n-3 PUFA) were greater (P < 0.05) in Red Angus than Simmental. For phospholipids, Simmental had lower (P < 0.05) amounts of 20:5n-3, docosahexaenoic acid (22:6n-3), and n-3 PUFA, with a greater (P = 0.017) n-6:n-3 ratio. Activity of delta9-desaturase enzyme in the conversion of palmitic acid (16:0) to 16:1 was greater (P = 0.001) in total lipids from Simmental as compared with Red Angus. A genetic basis for fatty acid differences is suggested, although the biological and practical significance needs to be demonstrated.

Effect of management strategy on growth performance, carcass characteristics, fatty acid composition, and palatability attributes in crossbred steers. Can. J. Anim. Sci. 82: 49-57. Crossbred steers (n = 136) were used to evaluate the effect of management strategy on growth performance, carcass characteristics, and fatty acid composition and palatability attributes of beef. Management strategies included: (1) high grain (75% high moisture corn) finishing (HG), or (2) backgrounding with restricted feeding of an alfalfa silage ration for 112 d, followed by HG until slaughter (BKG). Steers were slaughtered at 8-10 mm ultrasound backfat. Backgrounding increased (P < 0.001) days on feed and decreased (P < 0.01) days on grain, average daily gain and longissimus muscle area compared with the HG regime. Slaughter weight, intramuscular fat content, and marbling score were unaffected (P > 0.10) by management strategy. Longissimus muscle palatability attributes and shear force did not differ (P > 0.10) between management strategies, whereas BKG increased (P < 0.03) softness, overall tenderness, chewiness, and rate of breakdown scores, and decreased (P < 0.09) juiciness scores in semitendinosus muscle. Backgrounding increased (P < 0.05) conjugated linoleic acid (CLA), total monounsaturated fatty acids, and ω3 polyunsaturated fatty acid (PUFA), and decreased (P < 0.05) total saturated fatty acids (SFA), and ω6 PUFA content of beef. While the change in quantitative and qualitative fatty acid composition of beef is in line with current dietary recommendations for humans, the magnitude of these changes was minimal. (1) finition avec une ration riche en grains (maïs à 75 % d'humidité) (RG) ou (2) semi-finition par alimentation rationnée avec de l'ensilage de luzerne pendant 112 jours suivi d'une RG jusqu'à l'abattage (SF). Les animaux ont été sacrifiés quand la couche de gras dorsal, mesurée aux ultrasons, atteignait 8 à 10 mm d'épaisseur. La semi-finition augmente (P < 0,001) le nombre de jours d'engrais et diminue (P < 0,01) le nombre de jours de finition au grain, le gain quotidien moyen (GQM) et la superficie du longissimus dorsi, comparativement aux animaux soumis au régime RG. Le poids à l'abattage, la proportion de gras intramusculaire et le persillage ne sont pas affectés (P > 0,10) par la méthode d'élevage. Les propriétés gustatives du longissimus dorsi et la résistance du muscle au cisaillement ne varient pas (P < 0,10) avec la stratégie d'élevage, mais la SF améliore (P < 0,03) la souplesse, la tendreté globale, la masticabilité et la rapidité de désagrégation de la viande tandis qu'elle diminue (P < 0,09) la jutosité du muscle semi-tendineux. La semi-finition augmente (P < 0,05) la concentration d'acide linoléique conjugué, d'acides gras mono-insaturés totaux et d'acides gras poly-insaturés ω3 alors qu'elle diminue (P < 0,05) la concentration d'acides gras saturés totaux et d'acides gras poly-insaturés ω6 du boeuf. Bien qu'elles aillent dans le sens des recommandations formulées pour l'alimentation humaine, les modifi...