PSIV-15 Influence of genetics on fatty acid profile, vitamin and mineral content of beef from grain and grass-finishing systems

Finishing systems and genetics can affect nutritional profiles. The objectives of this study were to quantify fatty acids (FA), vitamins, and minerals from two different breeds of cattle finished either on grain or on grass. Red Angus (RA, n = 30) and RA x Akaushi (AK, n = 30) were equally assigned to one of the finishing systems: a mixed-species pasture forage (GRASS) or a total mixed feedlot ration (GRAIN) in three replications. Animals were slaughtered between 18 (GRAIN) and 26 (GRASS) months of age, and meat samples were collected between the 11th and 13th rib. FA profiles were determined using microwave-assisted fat extraction, acid-base methylation, and gas chromatography-mass spectrometry (GC-MS) analysis. Vitamin and mineral content were analyzed by commercial laboratory. Overall (µg/g dry), vitamin E (31.05±5.11 vs 17.43±3.07, P < 0.0001), iron (69.28±6.71 vs 47.04±7.64, P < 0.0001), copper (1.56±0.89 vs 0.86±0.9, P = 0.037), zinc (139.57±35.72 vs 110.53±15.4, P = 0.0002), and molybdenum (0.15±0.04 vs 0±0.01, P < 0.0001) were significantly higher in GRASS compared to GRAIN and did not differ by breed. Manganese was significantly higher in GRAIN (0.31±0.07 vs 0.25±0.05, P = 0.0005). Iron was significantly higher in GRASS and differed when comparing AK to RA (73.04±6.9 vs 65.51±3.92, P = 0.018). Regarding FA (mg/100g beef), total n-6 (115.12±55.7 vs 87.43±33.89, P < 0.01) and the n-6:n-3 ratio (8.39±2.66 vs 1.46±0.34, P < 0.0001) were higher in GRAIN, while total n-3 (62.77±30.59 vs 14.39±8.34, P < 0.0001), ALA (35.96±25.6 vs 6.23±5.82, P < 0.0001), and EPA (8.98±2.22 vs 2.01±0.84, P < 0.0001) were higher in GRASS. These results suggest that there are differences in n-3, n-6, n-6:n-3 ratios, ALA, EPA, minerals, and vitamins with results favoring GRASS. Genetics seem to play a minor role in FA profiles and only significantly affected iron content.