Effects of dietary inulin and animal density on cortisol regulation and stress responses in pigs

density on cortisol
regulation and stress responses in pigs.
Siegien, Pawela. Gillis, Margota. Li, Jiahenga. Dufourny, Sandrineb. Comer, Lukec.
Wavreille, Joséb. Schroyen, Martinea. Bindelle, Jérômea.
a. Precision Livestock and Nutrition Laboratory, TERRA Teaching and Research Centre, Gembloux Agro-Bio Tech, University
of Liège, 5030 Gembloux, Belgium
b. Animal production unit, Walloon Agricultural Research Centre, 5030 Gembloux, Belgium
c. Nutrition & Animal Microbiota EcoSystems Lab, Animal and Human Health Engineering, KULeuven, 3001 Leuven,
Belgium
Abstract
Cortisol is a key glucocorticoid hormone involved in the physiological stress response
of animals. Regulating cortisol secretion is crucial for animal welfare and growth
performances. The hypothalamic–pituitary–adrenal (HPA) axis plays a central role in
this regulation.
Inulin is a prebiotic that promotes beneficial gut microbiota including Lactobacilli and
enhances intestinal health. Short-chain fatty acids (SCFA) obtained through microbial
fermentation exert anti-inflammatory and gut barrier–protective effects. Through the
gut-brain axis, prebiotics acting on the intestines can have influence on the brain
including the HPA axis.
In this study, we focused on the effects of inulin on cortisol secretions in saliva and
deposits in hair, illustrating respectively an acute stress response and chronic stress
levels. We compared 4 growth environments of pigs by differing animal density crossed
with a diet containing or not inulin. Animal mixing at weaning and at the beginning of the
fattening stage served as a social stressor for acute stress responses. Saliva samples
were collected using oral polypropylene swabs, before and after stressor exposure to
assess stress responsiveness, and hair samples were obtained with a razor at the end of
post-weaning and 5 weeks after the start of fattening. A salivary cortisol ELISA kit
(Salimetrics, State College, PA, USA) was used for both saliva and hair samples for
cortisol quantification. Data were analysed using a Four-Parameter Logistic (4PL)
calibration curve.
Inulin reduced basal salivary cortisol levels at the second stressor exposure (P<0.05).
Moreover, hair cortisol levels showed an interaction between animal density and diet,
with diet effects varying by density (P<0.05), indicating that environmental and dietary
factors jointly influence chronic stress.
We conclude that, in addition to its well-established intestinal health benefits, inulin
may serve as a promising dietary strategy to enhance animal welfare by modulating
circulating cortisol levels and influencing stress responses in pigs.