Genetic parameter estimation for traits related to the immune system against sheep red blood cells in Japanese quail.

1. Improving resistance against disease is important in the animal and poultry industry. Besides drugs and vaccines, genetic selection for improved immune systems may be an effective approach.2. Traits related to the immune system were studied in a 938 pedigreed Japanese quail population infected by sheep red blood cells (SRBC). Besides body weight at 35 d of age (BW35), weight of the gizzard (G), liver (Li), lungs (Lu), bursa (Bu), spleen (S), heart (H), and digestive track (D) and length of ileum (I) and caecum (C) were recorded. Total antibody (TA), mercaptoethanol-resistant (IgG), mercaptoethanol-sensitive titres (IgM), the number of monocyte (M), basophil (B) and eosinophil (E) and the ratio of heterophil to lymphocyte (H/L) were measured. Co-variance components were estimated via Gibbs sampling using GIBBS3F90 software. Five univariate animal models, including simple forms, were used for genetic parameter estimations, and the best model was determined by the deviance information criterion (DIC). Genetic and environmental correlations were estimated using a bivariate animal model.3. Direct heritability estimates for internal organs ranged from 0.06 (Lu) to 0.57 (G) and for immune system traits from 0.05 (IgM) to 0.17 (IgG). Negative genetic correlations were found between BW35 and internal organs (-0.22 to -0.80).4. Including one of the internal organs, such as the spleen, in the selection index improved the immune response in heavier birds. Additionally, because of the moderate heritability of IgG (0.17) and its effect on lasting immunity, selecting for higher IgG concentration may improve the resistance of Japanese quail against pathogens.