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Arachidonic acid in diets for early maturation stages enhances the final reproductive performances of Pacific white shrimp (Litopenaeus vannamei)

Xu, Houguo, Zhang, Yuling, Luo, Kun, Meng, Xianhong, Luan, Sheng, Cao, Baoxiang, Chen, Baolong, Liang, Mengqing, Kong, Jie
Aquaculture 2017 v.479 pp. 556-563
Litopenaeus vannamei, Polychaeta, arachidonic acid, breeding stock, early development, eggs, estradiol, experimental diets, fatty acid composition, fecundity, females, gonadosomatic index, hatching, hepatopancreas, ingredients, males, metamorphosis, nauplii, rearing, salinity, satiety, seawater, shrimp, spawning, squid, tanks
A 70-day feeding trial with Pacific white shrimp (Litopenaeus vannamei) broodstocks was conducted before eyestalk ablation to investigate the effects of arachidonic acid (ARA) in diets for early maturation stages on the final reproductive performances. Three isonitrogenous and isolipidic experimental diets were formulated to contain different ARA levels: the control diet without ARA supplementation (C, 0.87% ARA of total fatty acids (TFA)) and two diets with low (4.65% of TFA, ARA-L) or high ARA (12.39% of TFA, ARA-H) supplementation level. The diets were randomly assigned to 9 tanks of eight-month-old Pacific white shrimp broodstock (30 females and 30 males in each tank). Shrimp were reared in a flowing seawater system and fed to apparent satiation four times daily. At the end of the feeding trial, unilateral eyestalk of the females was ablated to stimulate the gonad maturation. Following the feeding trial (Period I) was a 28-day reproductive evaluation period (Period II), during which all shrimps were fed the same fresh invertebrate ingredients (a mixture of squid and polychaetes). Tissues samples of females were collected at the end of the feeding trial (Period I) and before spawning (ready to spawn) at the reproductive evaluation period (Period II) respectively to measure the gonadosomatic index (GI), hepatopancreas index (HI), estradiol level, and fatty acid composition. The spawning performance and quality of egg and larvae were assayed at Period II. The results showed that compared to the control group, ARA-L increased the GI at Period II while the ARA supplemented diets increased the estradiol synthesis at Period I. The HI was not influenced by dietary ARA level. Compared to the control group, ARA-L but not ARA-H significantly increased the spawning rate, multi-spawning rate, average spawning frequency and fecundity of female shrimp, diameter of fertilized egg, and crude metamorphosis rate of nauplii at 33h post spawning. The hatching rate significantly ranked as follows: C<ARA-H<ARA-L. The dietary ARA supplementation significantly improved the duration of nauplius and zoea larvae in the challenge test with low salinity. The experimental diets significantly affected the fatty acid compositions in hepatopancreas and ovaries of female shrimp, as well as those in fertilized eggs. In conclusion, these results suggested that the ARA supplementation in the diets for early maturation stages enhanced the final reproductive performances of Pacific white shrimp.