23 Current progress in the Agricultural Research Service Beef Grand Challenge: A large-scale genetics by environment by management evaluation project

The Agricultural Research Service (ARS) Beef Grand Challenge is a cooperative, multidisciplinary effort evaluating differences in performance of genetic lines across production environments representative of different geographical regions. Weaned spring-born calves (n = 120 per location), representing natural service matings to Angus, Hereford, Simmental, Charolais, or indicus-composite (Beefmaster or Brangus) bulls from the U.S. Meat Animal Research Center Germplasm Evaluation program in south central Nebraska, are sent to wheat pasture (central Oklahoma) and winter range (eastern Montana), and weaned fall-born calves (n=40 per location) are sent to summer grazing on shortgrass prairie (northeastern Colorado) and southern mixed-grass rangeland (western Oklahoma). All cattle are fed a finishing ration representative of the region that approximately matches energy content across locations. Each calving season has a matching counterpart of calves that remain in Nebraska on a calf-fed drylot program (receiving ration followed by longer finishing ration). Breeds and sires are represented equally, to the extent possible, at each location. To detect differences in breed effects at each location and average over yearly variation, the study is being replicated for 4 years. Weights, stress measures, carcass composition (marbling, yield grade, quality grade, etc.), steak tenderness and steak fatty acid composition are collected from each location. Additionally, rumen metagenomic composition, metagenomic samples, preharvest food safety samples, and feed intake measures are collected at some locations. Grazing impacts and supplemental range feeding are also being evaluated. One year of sampling has been completed, with numeric differences observed for marbling and tenderness as well as growth performance among locations. Statistical differences will be evaluated when replicate years are collected. The USDA is an equal opportunity provider and employer.