Genetic analysis of the number of pyloric ceca in brown trout salmo trutta and the rainbow trout salmo gairdneri 2. effect of the genotype rearing environment and feeding on expression of the characteristic in the rainbow trout
Chevassus, B.; Blanc, J.M.; Bergot, P.
Annales de Genetique et de Selection Animale 11(1): 79-92
Four factors liable to affect the within and between-population variability of the number of pyloric ceca in rainbow trout (S. gairdneri) were studied. After 6 mo., no variation due to age was observed even after transferring the fish from 1 fish farm to another. Rearing of fish from the eyed-stage in 2 fish farms with very different mean temperatures (8.degree. C and 16.degree. C) induced a large difference between the mean number of pyloric ceca (55.5 at 8.degree. C, 51.0 at 16.degree. C). At 8.degree. C, S. gairdneri fed a polyholoside-rich diet had 2.7% more pyloric ceca than fish fed a high-protein diet. No effect was detected at 16.degree. C. Study of the progenies of crosses between parents having a known number of ceca showed a high correlation (r = 0.92) between the mean of the parents and the mean of the progenies. A high estimate was obtained for heritability (h2 = 0.53 .+-. 0.07) and the non-additive genetic variance was quite low. The conjoined effect of those different factors was analyzed and described by a linear additive model. It is apparently possible to obtain, by a 2 way selection, strains with different numbers of ceca. The effect of this trait on other quantitative ones such as growth rate or nutritional parameters can be analyzed.