Ruminant Nutrition: Beef: Forages and Grazing

The objective of this study was to evaluate self-fed byproducts on pasture reared finishing cattle. Major effects studied were animal performance, carcass traits and fatty acid (FA) profile with specific emphasis on conjugated linoleic acid (cis-9, trans-11–18:2; CLA). Eighty-two crossbred yearling steers were utilized in a 2 × 2 factorial design with implanted and non-implanted cattle fed either Diet 1: corn/dried distillers grain with solubles (DDGS) or Diet 2: soyhulls/DDGS. Self-feeders were available to cattle that continually grazed cool-season grasses at 5.6 animals/ha. Ribeye facings were extracted for lipid content and esterified for FA analysis by gas chromatography. Data presented is from the first year of this 2 year trial, which second year data has yet to be analyzed. Average daily gains (ADG) over the entire trial of cattle fed Diet 1 were greater (1.59 kg/d vs. 1.52 kg/d, P = 0.09) compared with cattle fed Diet 2. Diets did not affect dressing percentage, yield grade or quality grade. As expected, implanted cattle gained faster (1.66 kg/d vs. 1.46 kg/d, P < 0.0001) than non-implanted cattle. No differences were observed among implant treatments relative to marbling scores (1031.0 vs. 1016.0, non-implanted vs. implanted, respectively, P = 0.29). However, percentage of cattle grading low choice or better was higher in non-implanted cattle (77.5% vs. 47.6%, P = 0.005). Cattle fed Diet 2 did have greater CLA levels (0.66 g/100g FA vs. 0.44 g/100g FA, P < 0.0001). However, supplementation of byproducts does lead to reduced levels of CLA when compared with grass-finished cattle. Neither diet nor implant treatments had an effect on total lipid, total saturated fatty acid (SFA), polyunsaturated fatty acid (PUFA) or monounsaturated fatty acid (MUFA). In conclusion, pasture reared cattle perform comparably to feedlot cattle in the yard and on the rail when supplemented with byproducts. As well, greater CLA levels can be achieved especially when fed a low starch diet such as soyhulls.