Including immune-neuroendocrine variables in welfare studies: is itworth the effort?

NAZAR, F N; MARIN R. H.; CORREA S. G.

Simposio; The fourth Animal Welfare Science Symposium 2019; 2019

Individual susceptibility to environmental challenges, sometimes overlookedin population level studies, may be one of the reasons underlying a poor/lowanimal welfare. Safeguarding the five-freedoms has been proposed as a strategyforensuring good/elevated welfare. This core concept in the area implies that animalsshould have guaranteed freedom from: i) hunger and thirst, ii) discomfort, iii)pain, injury or disease, iv) freedom to express normal behaviour,and v) freedomfrom fear and distress. Many concepts on these freedoms such as discomfort,fear, distress, injuries and diseases are evidencesof the immune-neuroendocrine(INE) system functioning. This physiological system is quintessentiallyresponsible for registering environmental challenges, processing theirinformation and, orchestrate an appropriate response. The reactions could varyinthe organism, covering a wide spectrum of possibilities ranging from local inflammation(injuries) to systemic stressresponses (distress). The anatomical substrate ofthe INE system are four well-known axes: the Hypothalamic-Pituitary-Adrenalaxis (underlying the stress response), the Sympathetic-Adrenal axis (involvedin immediate fight or flight responses), the Vagus-Cholinergic way (sensing andcontrolling inflammation in the peritoneal cavity) and the Microbiota-Gut-Brainaxis (communicational path startinginthe part of the exterior that is internal).Animals may show no obvious indicators of poor welfare, but their differentialsusceptibilities relies on the INE macrosystem. An example can be given bymeans of a study performed in poultry species. Immune-neuroendocrine phenotypes(INPs) stand for population subgroups differing in INE interactions. Whilemammalian INPs have been characterized thoroughly (ratsand humans), avian INPswere only recently described in Coturnixcoturnix (quail). We characterized INPs in Gallus gallus (a domestic laying hen strainsubmitted to a very longhistory of strong selective breeding pressure) and evaluated whether asocialchronic stress challenge modulates the individuals? interplay affecting the INPsubsets anddistribution. Afterchronic stress, an increment of about 12% in eachpolarized INP frequency was found at expenses ofa reduction in the number of birdswith intermediate responses. The observed inter-individual variation suggestthat, even aftera considerable selection process, the population is stillprepared to deal with a varietyof challenges. Nevertheless, these results implythat not all birds would respond in the same wayto the same challenge. Stresspromoted disruptive effects, leading to a more balanced INPsdistribution, whichrepresents a newsubstrate for challenging situations.This new substrate iscomposed by birds differentially prepared to deal with a) diverse kind ofcommon/expectable challenges such as, vaccination, transport, experimenterpresence, as well as b) various unexpected (i.e.: pathogenic) events. Thisaspect of their physiological characterization would be key in their welfareassessment.INE system could then be consideredan indicator of which birds wouldbe prone to welfare negative consequences in different scenarios according to thenature of each challenge.