|Carroll, Jeffery - Jeff Carroll|
|Welsh Jr, Tom|
Submitted to: American Meat Science Association Conference Reciprocal Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 7/11/2008
Publication Date: 7/15/2008
Citation: Carroll, J.A., Berg, E., Vann, R., Randel, R., Welsh Jr, T. 2008. The connection between animal stress and meat production: Uncoupling of the growth hormone/insulin-like growth factor 1 axis. Proceedings of the 61st American Meat Science Association Reciprocal Meat Conference, Muscle Biology/Molecular Biology Section, June 22-25, 2008, Gainesville, Florida. p. 1-6.
Interpretive Summary: This manuscript reviews the connection between animal stress and meat production as it related to the uncoupling of the hormones that regulate growth in domestic livestock. While numerous factors can be identified that contribute to the growth and overall performance of domestic livestock, in general, genetics, nutrition, environment, medication, and stress are five categories that represent some of the more commonly recognized and manageable inputs that continue to be of significant interest to scientists and producers. The economic importance of the detrimental impacts that stress can have on animal growth and performance continues to be downplayed/overlooked due to a lack of understanding regarding the regulation of stress in animals and the connection to animal productivity. While the debate among animal scientists concerning the definition and quantification of "stress" as it relates to animal productivity and well-being is ongoing, there is little doubt that an increased appreciation and understanding of the effects of "stress" on livestock production has emerged throughout the scientific community and with livestock producers. In recent years, livestock producers have become more knowledgeable with regard to understanding the influence of stress on animal production, and have been proactive in implementing changes to reduce various types of stress to increase productivity and overall well-being in their animals.
Technical Abstract: For decades, researchers have demonstrated that "stress" can have detrimental effects on the immune system. However, what had not been distinguished until recently are the divergent effects of "acute" stress associated with subclinical immunological burdens on the animal versus long-term or "chronic" stress associated with disease and severe pathogenic challenges. Livestock experience numerous environmental, managerial, and nutritional stressors throughout the production cycle that could potentially inhibit overall productivity and well-being due to stress-induced immunosuppression. Typically, sick animals experience a period of anorexia, thus requiring nutrient repartitioning and nutrient sparing to liberate nutrients for the production of proteins such as the pro-inflammatory cytokines and acute phase proteins that are critical for re-establishing homeostasis. Activating and maintaining an immune response is essential for survival; however, there is an associated energy cost to the animal during a time when incoming nutrients are limited due to the animal’s anorexic behavior. Creating and maintaining a febrile response alone is very energy intensive. It has been estimated that there is approximately a 10 to 13% increase in metabolism for every degree of body temperature increase associated with an immune response. While the energy liberating effects of growth hormone (GH) are well recognized, the significance of elevated GH during times of sickness-induced anorexia may be more profound due to its stimulatory actions on immune cells. The currently available literature supports the possibility that the uncoupling of the growth axis during periods of immunological stress in domestic livestock extends beyond a simple nutritional influence and warrants continued investigation to further elucidate this complex bi-directional communication pathway. Further understanding of the bi-directional communication within the body will undoubtedly continue to be unveiled as new research tools become available and as researchers develop multi-disciplinary teams to pursue the complexities associated with the regulation of animal growth, performance, and meat quality.