Quality improvement of spotted babylon (Babylonia areolata) broodstock with highly unsaturated fatty acid-supplemented feed

Abstract

This study was designed to study effects of fatty acids and arachidonic acid on reproductive performance of hatchery-reared broodstock spotted babylon, Babylonia areolata. The study was divided into two experiments. The first experiment, a 120-day feeding trial was conducted to evaluate reproductive performance, egg and larval quality and egg fatty acid composition in spotted babylon broodstock fed natural food (fresh meat of carangid fish, Selaroides leptolepis,) and four experimental formulated diets containing 5% or 15% of dietary lipid from tuna oil (TO) and a mixture of tuna oil and soybean oil (MO) (ratio 3:2) labeled as 5%TO, 15%TO, 5%MO and 15%MO respectively. Using trash carang resulted the lowest levels of in 20:5n-3, 22:6n-3 and 20:4n-6 fatty acids compared to those of all experimental diets. The highest content of total fatty acids was found in the 5%TO diet. The best reproductive performance were found only for females fed the 5%TO diets, but egg and larval quality showed no variability among females fed. No significant differences were observed in survival duration in the starvation tolerance test for females fed trash fish or any of the experimental diets. However, the fatty acid profile of egg capsules was significantly affected by the dietary treatments. The levels of major fatty acids (20:5n-3, 22:6n-3 and 20:4n-6) in egg capsules produced from females fed diets containing 5% tuna oil (5%TO) was significantly higher than those females fed trash fish or other experimental diets. We therefore conclude that formulated diets with fish oil resulted in successful reproduction and high essential fatty acids in egg capsules comparable to the use of trash fish. The second experiment studied on the effects of arachidonic acid in broodstock diet on spawning performance, egg and larval quality and fatty acid composition of eggs from broodstock spotted babylon (B. areolata). A formulated diet containing similar compositions was supplemented with five levels of arachidonic acid (20:4n-6, ARA); 0% (1), 0.4% (2), 0.8% (3), 1.2% (4) and 1.6% (5) ARA, respectively. Results showed that spawning quality (total number of spawning and monthly spawning frequency) were affected by ARA supplementation. The total number of spawning and monthly spawning frequency throughout the experiment increased with an increased supplemented of ARA levels. Females fed on diet 5 had the highest total number of spawn (25.5), followed by the diet 4 (23.0), diet 3 (22.0), basic diet (17.5) and diet 2 (15.5). While the egg quality (number of fertilized eggs in capsule, length and width of egg capsules, egg incubation time and hatching rate) were not affected by ARA supplementation. For larval quality, ARA did not enhance tolerance to low salinity stress and starvation test together with increasing the levels of dietary ARA in B. areolata broodstock. These results indicated that high level of dietary arachidonic had a positive effect on spawning performance of B. areolata broodstock and high level of arachidonic improved spawning performance but not for egg and larval quality and fatty acid composition of egg capsules.