Location: Livestock Issues Research
Project Number: 6208-32000-007-04
Start Date: Jan 01, 2010
End Date: Dec 31, 2014
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.