Effects Of Protein Level And Vitamin E In Broodstock Diets On Reproductive Performance Of Monopterus Albus

This study investigated the effects of dietary protein level and vitamin E on the reproductive performance of Monopterus albus, including gonadosomatic index(GSI), absolute fecundity, relative fecundity, spawning quantity, spawning performance, hatching rate and larval quality, and determined the dietary protein and vitamin E optimum requirements of broodstock Monopterus albus. Two series of experiments were conducted with One-Way grads design. In cultured trial-1, six isocaloric(16 MJ kg~-1) diets containing Ⅰ 25%, Ⅱ30%, Ⅲ35%, Ⅳ40%, Ⅴ45% and Ⅵ50% crude protein were prepared. The diets were fed to broodfish reared to satiation once a day for 165 days. In feeding trial-2, six diets containing Ⅰ 0mg·kg~-1, Ⅱ50mg·kg~-1, Ⅲ125mg·kg~-1, Ⅳ200mg·kg~-1, Ⅴ275mg·kg~-1 and Ⅵ350 mg·kg~-1 dietary vitamin E were used. The diets were fed to broodfish reared to satiation once a day for 175 days. Female broodstocks were divided into six treatments with triplicate groups, which was the same as cultured trial-1. The experimental results were as follows.1. The results showed that the absolute fecundity, spawning quantity, hatching rate, larval weight gain and survival rate of groups Ⅰ,Ⅱ,Ⅲ and Ⅳ were significantly increased with an increase in the protein levels in broodstock diets(P<0.05), and those of groups Ⅴ and Ⅵ were significantly decreased(P<0.05). The absolute fecundity, spawning quantity, hatching rate, larval weight gain and survival rate of group Ⅳ were significantly higher than those of groups Ⅰ ,Ⅱ and Ⅵ(P<0.05). The GSI, relative fecundity and egg diameter of each groups were not significantly different(P>0.05).2. Synchronously, final body weight of female broodstocks of each groups was significantly different(P<0.05), and ovary weight, absolute fecundity and spawning quantity followed similar trends as final body weight, which showed that the increase of absolute fecundity and spawning quantity was possibly associated with the weight gain of female rice field eels.3. The analysis showed that the first fecundity/absolute fecundity ratio per female was highest from females fed with 40% protein, which revealed that 40% dietary protein possibly promoted the ovary development and egg maturation.4. The results showed that the GSI, spawning performance, hatchability and larval quality of groups I , II, III and IV were significantly increased with the improvement of VE concentration in diets (PO.05), and those of groups V and VI were increased, but no significant difference(P>0.05). The GSI, spawning performance, hatchability, larval weight gain and survival rate of group IV were significantly higher than those of groups I , II, III(P<0.05), but there was no significant difference among groups IV, V, VI(P>0.05).5. The results indicated that vitamin E concentration of egg was increased with the increase in dietary vitamin E concentration. Vitamin E concentrations in eggs reflected dietary vitamin E concentration and ranged from 207.41 mg-kg"1 dry matter( I ) to 295.16 mg-kg'1 dry matter(VI)(P<0.05).6. The SOD activities in ovaries of groups IV, V and VI were significantly lower than those of groups I , II and III(P<0.05), and MDA contents of groups IV, V and VI were also significantly lower than those of groups I , II and III(P<0.05). Though the SOD activities in ovaries of groups I , II and III were high, peroxidation still took place because of deficiency in Ve, so MDA contents in ovaries of groups I , II and III were high, resulting in very low hatchability of groups I , II and III.7. In summary, optimum level of protein in broodstock diets has been shown to readily mend the growth, greatly improve absolute fecundity, spawning quantity and larval quality, which in turn significantly improve reproductive performance of Monopterus albus. The performance was found to be best with an increase in dietary protein level up to 40%, as group IV.8. This experiment demonstrated that Ve supplemented in the diet of female broodstock could improve the reproductive performance of Monopterus albus. It also indicated that vitamin E optimal supplementation of Monopterus albus was 200mg-kg"' in broodstock diet.