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Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 7/15/2014 Publication Date: 12/10/2015 Citation: Carroll, J.A., Sanchez, N.C. 2015. Overlapping physiological responses and endocrine biomarkers that are indicative of stress responsiveness and immune function in beef cattle. Journal of Animal Science. 92(12):5311-5318. Interpretive Summary: This review discusses the stress response and immune system interaction, a topic that has been a focus of our research group for several years. The interaction between stress and the immune system is very complex and dynamic. While it is understood that chronic stress can have serious consequences on the health and well-being of livestock, it is less clear whether or not periodic short-term or acute stress can affect animal health. In order to understand whether or not acute stress can influence immune function, it is necessary to take a multidiciplinary approach to understand the effects of stress on various body systems. In this review, we discuss the response of physiological, endocrine, immune, and metabolic parameters to an acute stress challenge (induced by corticotropin releasing hormone) or in response to an acute inflammatory challenge (induced by a lipopolysaccharide challenge to mimic an E. coli infection). Research from our laboratory has demonstrated that these two challenges produce specific responses, which may be as unique as the stressor itself. However, as the parameters assessed all increased in response to both challenges, although differing in magnitude and temporal pattern, the data also imply that assessing the immune status or stress responsiveness of an animal using only a single time point may not be an accurate depiction of the animal's overall health. Further, differences observed could potentially be more reflective of a stress response associated with animal processing/handling. Development of methods to effectively attenuate potentially detrimental effects of various stressors encountered by livestock depends on understanding these unique stressor- and immunological-specific responses. Technical Abstract: Acknowledgement that modern livestock production systems impose stress upon animals has been accepted by the scientific community and producers. As the economic burden has increased for livestock producers, expectations for animal performance have increased, thus placing more strain upon the entire production system. Whether or not periodic exposure to stress within the production system jeopardizes the well-being of animals continues to be an area of debate largely due to the inability to accurately quantify the magnitude and severity of the stress response on other biological systems. Adding to the confusion is the fact that activation of the stress axis can be both beneficial as well as detrimental on the body depending upon the duration of the stress response and the frequency at which an animal is exposed to stressful stimuli. Few would argue against the fact that continuous long-term stress inhibits livestock productivity and overall well-being. Less clear is whether or not occasional exposure to acute stress jeopardizes the productivity and well-being of livestock. To fully appreciate the complexity associated with activation of the stress axis and the overall biological impact on the body, one must delve deep into the scientific literature and examine the science in an unbiased manner. It’s imperative to appreciate and understand that activation of the stress axis is an essential survival mechanism necessary to maintain homeostasis during biologically challenging times. Acute activation of the stress axis leads to repartitioning of energy to organs and tissues essential for coping with stress, redirection of blood flow from the peripheral to large muscle groups, decreased digestive function, and priming of the immune system to prepare for subsequent infections. Conversely, chronic activation of the stress axis disrupts digestive function, causes catabolism of muscle tissue, and suppresses overall immune function, thus making an animal more susceptible to disease. But what parameters are needed to distinguish periods of acute stress from chronic stress, and what biological markers are the best indicators of "stress" in an animal? While there are a plethora of physiological responses and endocrine biomarkers that can be quantified, there has yet to be an integrative tool identified that has been readily embraced by scientists and producers as an effective and efficient indicator of the magnitude of stress that an animal is experiencing. |
