Association between Single Nucleotide Polymorphisms of the Major Histocompatibility Complex Class II Gene and Newcastle Disease Virus Titre and Body Weight in Leung Hang Khao Chickens

The aim of the present study was to investigate the effect of single nucleotide polymorphisms in the major histocompatibility complex (MHC) class II gene on resistance to Newcastle disease virus and body weight of the Thai indigenous chicken, Leung Hang Khao (Gallus gallus domesticus). Blood samples were collected for single nucleotide polymorphism analysis from 485 chickens. Polymerase chain reaction sequencing was used to classify single nucleotide polymorphisms of class II MHC. Body weights were measured at the ages of 3, 4, 5, and 7 months. Titres of Newcastle disease virus at 2 weeks to 7 months were determined and the correlation between body weight and titre was analysed. The association between single nucleotide polymorphisms and body weight and titre were analysed by a generalized linear model. Seven single nucleotide polymorphisms were identified: C125T, A126T, C209G, C242T, A243T, C244T, and A254T. Significant correlations between log titre and body weight were found at 2 and 4 weeks. Associations between single nucleotide polymorphisms and titre were found for C209G and A254T, and between all single nucleotide polymorphisms (except A243T) and body weight. The results showed that class II MHC is associated with both titre of Newcastle disease virus and body weight in Leung Hang Khao chickens. This is of concern because improved growth traits are the main goal of breeding selection. Moreover, the results suggested that MHC has a pleiotropic effect on the titre and growth performance. This mechanism should be investigated in a future study.