The substitution of fishmeal and fish oil with vegetable ingredients, poses potential challenges to achieving optimal fish broodstock nutrition. This study aim to assess the impact of dietary changes during gonadal maturation on reproductive efficiency and embryo quality in S. salar females, for optimizing the management of this species. Four diets were employed (Diet 1: marine ingredients; Diet 2: partial substitution of marine origin meals and oils by terrestrial animal and plant sources and, two commercial Atlantic salmon broodstock diets (Diet 3 and 4).
Each diet was administered to 30 females and 10 males S. salar for six months. At spawning, zootechnical parameters, oocyte quality and, embryo survival and quality of embryonic development at 280 accumulated thermal units (ATU), were measured. The results indicated a higher incidence of maturation for groups fed Diets 1 (22 females (73%)) and 2 (20 females (67%)) during the earlier periods compared to the commercial diets (16 females (53%) Diet 3 and 15 females (50%) Diet 4)) (Figure 1). A significant positive correlation (p<0.001) was observed between spawn mass and total fecundity (Table 1). Regarding embryonic development, no statistically significant differences were found between the diets in terms of fertility. However, when considering embryo survival at 280 ATU, statistically significant differences were observed exclusively among the commercial diets (Diet 3 62.6% and Diet 4 85.6%). Zootechnical parameters assessed, including weight, length, K-factor, and GSI, no significant statistical differences were observed between the diets. However, a trend was observed where commercial diets tended to exhibit higher weight and length compared to the experimental diets. Furthermore, Diet 1 displayed a significantly higher HSI compared to the other diets.
Low maturation rate and subsequent decrease in the number of spawned females observed in the groups fed commercial diets may be attributed to a potential nutrient imbalance. It is noteworthy that these diets had higher gross energy content compared to the other experimental diets. This finding aligns with existing knowledge that low protein diets in carnivorous fish can extend maturation time, reduce reproductive performance, and decrease ovulation frequency.