2013 Annual Report
1a.Objectives (from AD-416):
The objective of the research associated with this Specific Cooperative Agreement is to evaluate the potential influence of cattle temperament, transportation, and disease challenge on the productivity and overall well-being of cattle during critical stages of the production cycle. The research will include, but not be limited to, evaluating the potential influence of temperament, transportation, and disease challenge on regulation of the growth, stress, and immune systems of cattle and production efficiency following these stressors. The critical stages of the production cycle to be studied involve the movement of cattle through the production system as cattle are moved from the ranch to a stocker location and again to the finishing feedlot.
1b.Approach (from AD-416):
Calves will be selected based on an assigned temperament score measured at weaning. Temperament score will be calculated based upon an average of exit velocity (EV) and pen score (PS). Exit velocity is an objective measurement that records the rate (m/s) at which cattle exit a working chute. Pen score is a subjective measurement based upon an animal's reactivity to a human entering the pen. Following temperament classification, calves will be subjected to various management practices, such as transportation and a simulated disease challenge, which are known to cause stress in livestock and have negative impacts on health, productivity, and well-being. Animal health and productivity will be monitored prior to and following these stressors to determine if an animal's temperament is associated with, or predictive of, how that animal copes with and recovers from the particular stress. A large-scale study will be implemented where yearling heifers that had been evaluated for temperament will be selected using the 32 calmest and 32 most temperamental from a population of over 125 heifers in a single calf crop. These heifers will be further stratified equally into equal subsets of 16 calm and 16 temperamental animals which will be transported for a 12-hour period followed with an overnight rest and then transported again for 12 hours back to the point of origin. The remaining subsets of 16 calm and 16 temperamental heifers will remain at the point of origin and not receive any transportation stressor. After return to the point of origin each subset of 16 heifers will be divided equally into subsets of 8 animals with one subset of 8 receiving an LPS challenge to simulate disease and the remaining subset will not be challenged to simulate the lack of disease stress. The animals will be then placed in Grow Safe equipped feeding facilities and feed consumption will be monitored for a 2-week recovery period followed by a 70-day feeding and growth period to calculate residual feed intake in these animals as well as all standard measurements of feed efficiency and growth. The heifers will be weighed at the beginning of the study and at each point of transportation and challenge, and body weights will be collected at 7-day intervals throughout the feeding period. Blood samples will be collected for endocrine and immune function measurements appropriately throughout the experimental period. These data should allow for determination of the economic losses due to transportation, temperament, and disease challenge. The involvement of the cytokines and mRNA for the cytokines will allow for better basic understanding of immune function following stressors in yearling beef females. Further small-scale studies will be designed following the large-scale study to further examine basic endocrine and immune function in stressed beef animals.
The overall focus and objective for this project is to evaluate potential influences of dietary supplementation, temperament, transportation, and disease challenge on the health, productivity, and overall well-being of yearling cattle. Previous collaborative research from our group has demonstrated that the inclusion of yeast cell wall products in the diet of feedlot cattle can increase feed intake, maintain feed intake during periods of heat stress, alter blood metabolites, enhance immune function, and increase overall growth performance during stressful periods. Additionally, past collaborative work has demonstrated that prenatal transportation stress can cause epigenetic effects that result in an altered postnatal stress response, as well as altered immune function in these calves. Therefore, during this past year, researchers evaluated the potential health and performance benefits to newborn calves whose dams were provided a yeast supplement during the last 80 days of gestation as a means to prime the immune system of the unborn calf. Results from this study indicated that providing the yeast supplement did not alter any parameters associated with calf performance from birth to 28 days of age. However, additional laboratory work is being conducted to evaluate blood parameters to determine whether or not the treatment altered any markers associated with immune function.