Breed effects on growth performance, carcass characteristics, fatty acid composition, and palatability attributes in finishing steers

Crossbred steers (n=136) were used to assess breed differences in growth pe rformance, carcass characteristics, fatty acid composition (total lipids an d phospholipids), and palatability attributes of longissimus muscle. A mult iple regression model was applied to crossbreeding data to estimate genetic differences between Simmental and Red Angus at the same level of backfat f inish (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 increase d (P = 0.023) lean yield. Average daily gain did not differ (P = 0.297) bet ween breeds. Simmental were less (P = 0.012) efficient in converting feed t o gain than Red Angus. Generally, there were few breed differences in palat ability attributes for longissimus and semitendinosus muscles, with the exc eption of increased (P < 0.05) beef flavor scores for Simmental beef vs Red Angus beef across both muscles. For total lipids, concentrations of myrist oleic acid (14:1), palmitoleic acid (16:1), and vaccenic acid (18:1n-7), al ong 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 ac ids (n-3 PUFA) were greater (P < 0.05) in Red Angus than Simmental. For pho spholipids, Simmental had lower (P < 0.05) amounts of 20:5n-3, docosahexaen oic acid (22:6n-3), and n-3 PUFA, with a greater (P = 0.017) n-6:n-3 ratio. Activity of Delta (9)-desaturase enzyme in the conversion of palmitic acid (16:0) to 16:1 was greater (P = 0.001) in total lipids from Simmental as c ompared with Red Angus. A genetic basis for fatty acid differences is sugge sted, although the biological and practical significance needs to be demons trated.