Skip to main content Accessibility help

Pig cognitive bias affects the conversion of muscle into meat by antioxidant and autophagy mechanisms

  • Y. Potes (a1), M. Oliván (a2), A. Rubio-González (a1), B. de Luxán-Delgado (a1), F. Díaz (a2), V. Sierra (a1) (a2), L. Arroyo (a3), R. Peña (a3), A. Bassols (a3), J. González (a4), R. Carreras (a4), A. Velarde (a4), M. Muñoz-Torres (a5) and A. Coto-Montes (a1)...


Slaughter is a crucial step in the meat production chain that could induce psychological stress on each animal, resulting in a physiological response that can differ among individuals. The aim of this study was to investigate the relationship between an animal’s emotional state, the subsequent psychological stress at slaughter and the cellular damage as an effect. In all, 36 entire male pigs were reared at an experimental farm and a cognitive bias test was used to classify them into positive bias (PB) or negative bias (NB) groups depending on their decision-making capabilities. Half of the animals, slaughtered in the same batch, were used for a complete study of biomarkers of stress, including brain neurotransmitters and some muscle biomarkers of oxidative stress. After slaughter, specific brain areas were excised and the levels of catecholamines (noradrenaline (NA) and dopamine (DA)) and indoleamines (5-hydroxyindoleacetic acid and serotonin (5HT)) were analyzed. In addition, muscle proteasome activity (20S), antioxidant defence (total antioxidant activity (TAA)), oxidative damage (lipid peroxidation (LPO)) and autophagy biomarkers (Beclin-1, microtubule-associated protein I light chain 3 (LC3-I) and LC3-II) were monitored during early postmortem maturation (0 to 24 h). Compared with PB animals, NB pigs were more susceptible to stress, showing higher 5HT levels (P<0.01) in the hippocampus and lower DA (P<0.001) in the pre-frontal cortex. Furthermore, NB pigs had more intense proteolytic processes and triggered primary muscle cell survival mechanisms immediately after slaughter (0 h postmortem), thus showing higher TAA (P<0.001) and earlier proteasome activity (P<0.001) and autophagy (Beclin-1, P<0.05; LC3-II/LC3-I, P<0.001) than PB pigs, in order to counteract the induced increase in oxidative stress, that was significantly higher in the muscle of NB pigs at 0 h postmortem (LPO, P<0.001). Our study is the first to demonstrate that pig’s cognitive bias influences the animal’s susceptibility to stress and has important effects on the postmortem muscle metabolism, particularly on the cell antioxidant defences and the autophagy onset. These results expand the current knowledge regarding biomarkers of animal welfare and highlight the potential use of biomarkers of the proteasome, the autophagy (Beclin-1, LC3-II/LC3-I ratio) and the muscle antioxidant defence (TAA, LPO) for detection of peri-slaughter stress.


Corresponding author



Hide All

Members of Research team: cellular Response to Oxidative Stress (cROS).



Hide All
Adeola, O, Ball, RO, House, JD and O’Brien, PJ 1993. Regional brain neurotransmitter concentrations in stress-susceptible pigs. Journal of Animal Science 71, 968974.
Arnao, MB, Cano, A and Acosta, M 2001. The hydrophilic and lipophilic contribution to total antioxidant activity. Food Chemistry 73, 239244.
Arroyo, L, Carreras, R, Valent, D, Pena, R, Mainau, E, Velarde, A, Sabria, J and Bassols, A 2016. Effect of handling on neurotransmitter profile in pig brain according to fear related behaviour. Physiology & Behavior 167, 374381.
Bauer, EP 2015. Serotonin in fear conditioning processes. Behavioural Brain Research 277, 6877.
Berridge, CW and Waterhouse, BD 2003. The locus coeruleus-noradrenergic system: modulation of behavioral state and state-dependent cognitive processes. Brain Research Reviews 42, 3384.
Caballero, B, Sierra, V, Oliván, M, Vega-Naredo, I, Tomás-Zapico, C, Álvarez-García, O, Tolivia, D, Hardeland, R, Rodríguez-Colunga, MJ and Coto-Montes, A 2007. Activity of cathepsins during beef aging related to mutations in the myostatin gene. Journal of the Science of Food and Agriculture 87, 192199.
Caballero, B, Tomas-Zapico, C, Vega-Naredo, I, Sierra, V, Tolivia, D, Hardeland, R, Rodriguez-Colunga, MJ, Joel, A, Nevo, E, Avivi, A and Coto-Montes, A 2006. Antioxidant activity in Spalax ehrenbergi: a possible adaptation to underground stress. Journal of Comparative Physiology 192, 753759.
Carreras, R, Mainau, E, Rodríguez, P, Dalmau, A, Manteca, X and Velarde, A 2015. Cognitive bias in pigs: individual classification and consistency over time. Journal of Veterinary Behavior 10, 577581.
Conus, S and Simon, H-U 2008. Review: cathepsins: key modulators of cell death and inflammatory responses. Biochemical Pharmacology 76, 13741382.
Coto-Montes, A, Boga, JA, Rosales-Corral, S, Fuentes-Broto, L, Tan, DX and Reiter, RJ 2012. Role of melatonin in the regulation of autophagy and mitophagy: a review. Molecular and Cellular Endocrinology 361, 1223.
de Gonzalo-Calvo, D, Neitzert, K, Fernandez, M, Vega-Naredo, I, Caballero, B, Garcia-Macia, M, Suarez, FM, Rodriguez-Colunga, MJ, Solano, JJ and Coto-Montes, A 2010. Differential inflammatory responses in aging and disease: TNF-alpha and IL-6 as possible biomarkers. Free Radical Biology & Medicine 49, 733737.
European Union 2007. Amendments to the treaty on European Union and to the treaty stablishing the European community. Official Journal of the European Communities 50, 1271.
European Union 2010. Directive 2010/63/EU of the European Parliament and of the Council of 22 September 2010 on the protection of animals used for scientific purposes. Official Journal of the European Communities L276, 3379.
Garcia-Macia, M, Sierra, V, Palanca, A, Vega-Naredo, I, de Gonzalo-Calvo, D, Rodriguez-Gonzalez, S, Olivan, M and Coto-Montes, A 2014. Autophagy during beef aging. Autophagy 10, 137143.
Houbak, MB, Ertbjerg, P and Therkildsen, M 2008. In vitro study to evaluate the degradation of bovine muscle proteins post-mortem by proteasome and mu-calpain. Meat Science 79, 7785.
Jorgensen, A 2013. Oxidatively generated DNA/RNA damage in psychological stress states. Danish Medical Journal 60, B4685.
Lana, A and Zolla, L 2015. Apoptosis or autophagy, that is the question: two ways for muscle sacrifice towards meat. Trends in Food Science & Technology 46, 231241.
Landsheer, J and van den Wittenboer, G 2015. Unbalanced 2 x 2 factorial designs and the interaction effect: a troublesome combination. PLoS ONE 10, e0121412.
Li, Q, Zhang, M, Chen, YJ, Wang, YJ, Huang, F and Liu, J 2011. Oxidative damage and HSP70 expression in masseter muscle induced by psychological stress in rats. Physiology & Behavior 104, 365372.
Logue, SF and Gould, TJ 2013. The neural and genetic basis of executive function: attention, cognitive flexibility, and response inhibition. Pharmacology Biochemistry and Behavior 123, 4554.
Maribo, H, EWrtbjerg, P, Andersson, M, Barton-Gade, P and Mùller, AJ 1999. Electrical stimulation of pigs- effect on pH fall, meat quality and Cathepsin B+L activity. Meat Science 52, 179187.
Mendl, M, Burman, OHP, Parker, RMA and Paul, ES 2009. Cognitive bias as an indicator of animal emotion and welfare: emerging evidence and underlying mechanisms. Applied Animal Behaviour Science 118, 161181.
Mora, F, Segovia, G, Del Arco, A, de Blas, M and Garrido, P 2012. Stress, neurotransmitters, corticosterone and body-brain integration. Brain Research 1476, 7185.
Nakhaee, A, Shahabizadeh, F and Erfani, M 2013. Protein and lipid oxidative damage in healthy students during and after exam stress. Physiology & Behavior 118, 118121.
Ouali, A, Gagaoua, M, Boudida, Y, Becila, S, Boudjellal, A, Herrera-Mendez, CH and Sentandreu, MA 2013. Review: biomarkers of meat tenderness: present knowledge and perspectives in regards to our current understanding of the mechanisms involved. Meat Science 95, 854870.
Phillips, AG, Vacca, G and Ahn, S 2008. A top-down perspective on dopamine, motivation and memory. Pharmacology Biochemistry and Behavior 90, 236249.
Piekarzewska, A, Sadowski, B and Rosochacki, SJ 1999. Alterations of brain monoamine levels in pigs exposed to acute immobilization stress. Zentralbl Veterinarmed A 46, 197207.
Poletto, R, Cheng, HW, Meisel, RL, Garner, JP, Richert, BT and Marchant-Forde, JN 2010. Aggressiveness and brain amine concentration in dominant and subordinate finishing pigs fed the beta-adrenoreceptor agonist ractopamine. Journal of Animal Science 88, 31073120.
Poletto, R, Cheng, HW, Meisel, RL, Richert, BT and Marchant-Forde, JN 2011. Gene expression of serotonin and dopamine receptors and monoamine oxidase-A in the brain of dominant and subordinate pubertal domestic pigs (Sus scrofa) fed a beta-adrenoreceptor agonist. Brain Research 1381, 1120.
Rubio-Gonzalez, A, Potes, Y, Illan-Rodriguez, D, Vega-Naredo, I, Sierra, V, Caballero, B, Fabrega, E, Velarde, A, Dalmau, A, Olivan, M and Coto-Montes, A 2015. Effect of animal mixing as a stressor on biomarkers of autophagy and oxidative stress during pig muscle maturation. Animal 9, 11881194.
Sabria, J, Torres, D, Pasto, M, Peralba, JM, Allali-Hassani, A and Pares, X 2003. Release of neurotransmitters from rat brain nerve terminals after chronic ethanol ingestion: differential effects in cortex and hippocampus. Addiction Biology 8, 287294.
Salim, S 2014. Oxidative stress and psychological disorders. Current Neuropharmacology 12, 140147.
Yeates, JW and Main, DC 2008. Assessment of positive welfare: a review. Veterinary Journal 175, 293300.


Type Description Title
Supplementary materials

Potes supplementary material
Figures S1-S2

 Word (4.1 MB)
4.1 MB


Altmetric attention score

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...


Usage data cannot currently be displayed