GENETIC-VARIATION IN THE HUMORAL IMMUNE-RESPONSE IN ATLANTIC SALMON (SALMO-SALAR) AGAINST AEROMONAS-SALMONICIDA A-LAYER

Antibody responses to Aeromonas salmonicida A-layer were analysed in f amily material of Atlantic salmon (Salmo salar), consisting of 791 fis h belonging to 34 full-sib groups within 12 paternal half-sib groups. The fish were immunized twice and blood samples were collected three t imes. Significant increase in antibody titre from first to second, and from second to third sampling, was observed. Genetic variation in ant ibody titres was observed at the three samplings with estimated herita bilities ranging from 0.16 to 0.20, and a significant heritability est imate was recorded in the antibody response after the second immunizat ion (h(2) = 0.16). Moderate to high genetic (r = 0.5-0.72) and phenoty pic (r = 0.29-0.57) correlations were found between the titre values a t different samplings, and between selected titres and titre increases . Production parameters, such as mean slaughter weight and mean surviv al rate were obtained for fish which were reared commercially in the s ea, and which belonged to the same full-sib groups as those analysed f or A. salmonicida A-layer antibodies. No significant correlation betwe en the mean antibody titre to A. salmonicida A-layer in this study and mean slaughter weight and survival rate in full-sib family material i n the sea was observed.