EFFECT OF MC4R POLYMORPHISM ON PHYSIOLOGICAL STRESS RESPONSE IN PIGS
Melanocortin-4 receptor (MC4R) is a G-protein coupled receptor predominantly expressed in hypothalamic regions which are known for their roles in feeding behavior, energy homeostasis and HPA axis regulation. In this study, we analyzed the effect of a missense mutation (Asp298Asn) in the porcine MC4R gene on physiological stress response and carcass composition in pigs of two crosses: A (♀ Duroc x ♂ Swedish Landrace) x ♂ Pietrain (n=25) and B (♀ Swedish Landrace x ♂ Large White) x ♂ Pietrain (n=21). All pigs included in this study were heterozygous (Nn) for the stress syndrome gen. Blood samples were collected before loading and at exsanguinations to measure cortisol, lactate, glucose, serum enzymes activity and some haematological parameters. Because only one pig with AA genotype was observed, there was no indicated effect of this genotype on investigated parameters. The heterozygous (AG) pigs showed a lower increase (P<0.05) in CK and AST activity after exsanguinations as well as trend towards lower increase (P<0.10) in cortisol and lactate levels and higher increase (P<0.10) in RBC and haemoglobin content. Higher increase (P<0.05) in LDH activity was observed in GG homozygous pigs from group B, but not in pigs from group A. In addition, the heterozygous (AG) pigs had a higher backfat thickness and lower estimated lean (P<0.05) than homozygous (GG) pigs. These results may support a possible role of the MC4R Asp298Asn polymorphism in the genetic basis of stress response and economically important traits in pigs.