SERUM IRON LEVELS IN FARMED ATLANTIC SALMON - FAMILY VARIATION AND ASSOCIATIONS WITH DISEASE RESISTANCE

Serum samples from previous experiments were utilized to study the var iation between sib families in serum iron concentration, and the assoc iation between serum iron concentration in the sib group and survival in challenge tests with vibriosis, furunculosis, cold water vibriosis or bacterial kidney disease (BKD) in farmed Atlantic salmon. In the fi rst experiment, fish that died from vibriosis had significantly higher serum iron concentration prior to the challenge test than surviving f ish. No significant variation was found in serum iron concentration be tween 34 full-sib families or between 12 half-sib families, but a non- significant suggestion of negative correlations (r = -0.25, P = 0.15; r = -0.35, P = 0.27), was observed between least square means of serum iron concentration and survival rates from vibriosis in the sib famil ies. Sexually maturing fish had significantly higher serum iron concen trations and lower survival rates than immatures. In the second experi ment, 23 full-sib families showed a significant variation in serum iro n concentration, and a non-significant suggestion of a negative correl ation (r = -0.34, P = 0.12) of about the same magnitude as in the firs t experiment was observed between full-sib least-square means for seru m iron concentration and the survival rate of parallel full-sib famili es in a challenge test with cold water vibriosis. The corresponding co rrelations between serum iron levels and survival rates in challenge t est with furunculosis and BKD were both close to zero. The results fro m the two experiments taken together suggests that families with incre ased levels of serum iron may be more suceptible for Vibrio infections .