2008 Annual Report 1a.Objectives (from AD-416) The objective of this cooperative research project is to determine time-series differences in blood urea nitrogen and cortisol concentration levels in varying genotypes and genders of stocker cattle to determine the usefulness of these blood parameters as indicators of adaptation to and animal performance on cool-season and warm-season forages. 1b.Approach (from AD-416) Differences in blood urea nitrogen and cortisol concentration levels in varying genotypes and sex of stocker cattle will be determined in cattle grazing both warm-season and cool-season forages. Relationships of these parameters to time of adaptation to novel forages and to grazing animal performance will be determined using multiple linear regression. Standard laboratory procedures will be used in estimating serum cortisol and blood urea nitrogen. 3.Progress Report In the southern Great Plains region, wheat pasture is a predominant cool-season forage for stocker cattle. Poor gains during the adaptation period on this forage reduce profits. Cortisol, as a measure of stress, and blood urea nitrogen may be implicated. Blood samples for the second year of the project from cattle adapting to wheat pasture and cattle on mixed rations were collected. Failure of a laboratory freezer resulted in the loss of samples from two years of collection. Subsequent samples taken were also lost through freezer failure. An alternative project of evaluation of sensory characteristic and fatty acid profiles of meat from six sire breeds was substituted as an interim project. Three rib samples from 64 finished heifers and steers from Bonsmara, Brangus, Charolais, Gelbvieh, Hereford and Romosinuano sires were collected in the fall of 2007 and winter of 2008 and shipped to the University of Arkansas. Results are pending. The ADODR monitors the activities of this agreement through meetings, telephone calls, and email messages.