2006 Annual Report 4d.Progress report. This project is a Specific Cooperative Agreement between USDA-ARS, Cropping Systems Research Laboratory, Livestock Issues Research Unit, Lubbock, TX, and Texas Tech University. Additional details of research can be found in the report for the parent CRIS 6208-32000-004-00D, "Development and Interpretation of Animal Well-Being Indicators to Assess Management Systems". The objective of the research associated with this Specific Cooperative Agreement is to evaluate alternative management practices that can be implemented to improve the health, productivity, and overall well-being of beef cattle. Preliminary research has evaluated non-traditional nutritional supplements as potential modulators of the immune system in beef cattle. To date, the animal component for three preliminary studies has been completed. The first study was conducted to develop an immune challenge model in finishing beef cattle. From this study, an appropriate endotoxin dose was obtained for future work, and development of an indwelling rectal probe was initiated. A series of modifications were made to the rectal probe after the initial study, and a working model has been tested within a related research project. Two additional studies were conducted to determine the potential benefit of feeding non-traditional nutritional supplements either prior to shipment or after shipment on the performance and health of weaned beef cattle. In the first study, 168 head of weaned beef cattle from the USDA-ARS Sub Tropical Agricultural Research Station beef cattle facility were supplemented with a product that contained active dried yeast and B-complex vitamins for at least 21 days prior to shipment. These cattle were then shipped to the USDA-ARS Grazinglands Research Laboratory in El Reno, Oklahoma, where they were maintained until slaughter. Preliminary data indicate that the pre-shipping supplementation altered aspects of the innate immune system of these cattle. In the second study, 200 head of stocker calves were purchase in Okalahoma City, Oklahoma, and shipped to the West Texas A&M University beef cattle feedlot facility. Upon arrival, these cattle were given either a typical feedlot ration or a ration supplemented with the previously mentioned product plus the addition of sucram which is a high intensity flavoring mixture. Preliminary data from this work indicates that both the innate and adaptive components of the immune system in these cattle were altered in a beneficial manner.