Genetic co-variation between resistance against both Caligus rogercresseyi and Piscirickettsia salmonis, and body weight in Atlantic salmon (Salmo salar)

• We evaluated genetic co-variation for disease resistance traits and body weight.
• Heritabilities for SRS and Caligus resistance were 0.18 and 0.1, respectively.
• Heritability for body weight was 0.4.
• Genetic correlations among these traits ranged between − 0.32 and − 0.02.

Infectious and parasitic diseases are recognized worldwide as primary causes of economic losses in salmon production. Piscirickettsia salmonis and Caligus rogercresseyi are the main diseases affecting the Chilean salmon aquaculture. In this study, we used data from experimental challenges against P. salmonis and C. rogercresseyi in full- and half-sibs from 118 families belonging to a Salmo salar breeding nucleus. Resistance against P. salmonis (SRS) was defined as the day of death of each fish and C. rogercresseyi resistance (CAL) was measured as the parasite load. We also measured body weight (BW) in full-sibs of the tested fish. We used a multi-trait animal model to estimate (co)variance components and to calculate genetic parameters. For BW we included contemporary group (sex*tank) as factor and age as a covariate. In addition, tank was included as a factor and weight at the end of test as a covariate for SRS and CAL. The estimated heritabilities for BW, SRS and CAL were 0.4 (± 0.05), 0.18 (± 0.03) and 0.1 (± 0.03), respectively. The genetic correlations between BW–SRS, BW–CAL and SRS–CAL were − 0.19 (± 0.12), − 0.32 (± 0.14) and − 0.02 (± 0.17), respectively. The levels of genetic variation and the magnitude of the genetic correlations between resistance to P. salmonis, C. rogercresseyi and body weight found in the present study demonstrate the feasibility for the improvement of these traits simultaneously by means of selective breeding.