饲料蛋白水平对双齿围沙蚕生长、体组成及养殖底质总氮的影响

Effects of dietary protein level on growth performance,body composition of Perinereis aibuhitensis and total nitrogen in cultural substances

以白鱼粉为蛋白源,制备6种蛋白水平分别为25%、28%、31%、34%、37%和40%的等能饲料,饲养初始体重为(24.7±0.9)mg的双齿围沙蚕(Perinereis aibuhitensis),每种饲料设3个重复,每个重复100 ind沙蚕,连续饲养60 d,测定沙蚕生长性能、体组成及养殖底质的总氮。结果表明,双齿围沙蚕的存活率不受饲料蛋白水平影响;末均重和特定生长率先随饲料蛋白水平显著升高,而饲料系数和日摄食率则先随饲料蛋白水平显著下降,当饲料蛋白水平达到31%以上时均开始趋于稳定;蛋白质效率则始终随饲料蛋白水平升高而显著下降。沙蚕的粗蛋白先随饲料蛋白水平显著升高,当饲料蛋白含量达到31%以上时趋于稳定;体水分及灰分含量随饲料蛋白水平显著升高,而体脂含量随饲料蛋白水平显著下降。当饲料蛋白水平超过34%时,养殖底质总氮含量随饲料蛋白水平显著升高,并且饲料蛋白水平越高,养殖底质总氮的升幅越大。根据饲料蛋白水平与双齿围沙蚕特定生长率的折线方程分析,双齿围沙蚕饲料的最适蛋白含量为31.61%。

The clamworm Perinereis aibuhitensis, a commercially important marine benthic polychaetes in intertidal zones, is in the greatest demand in domestic and foreign markets. Due to over-harvesting and deteriorated environment, the natural resource of P. aibuhitensis has been exhausted gradually and can not meet market demands. With the development of modem breeding technology, P. aibuhitensis has become an important aquacuhural species in the coastal areas of China. The optimal level of dietary protein in diets is important for the growth of aquatic animals and maintenance of good aquacultural environment. However, to date, there has been no reports on specific protein feed demand of P. aibuhitensis. The purpose of this study is to estimate the optimal dietary protein level for P. aibuhitensis to provide scientific basis and guidance for the development of its special, efficient and environmental-friendly compound feed. The P. aibuhitertsis larvae used were obtained from one batch of fertilized eggs hatched in seawater （ salinity 24‰）. The larvae were dug out from sediments and placed in clean seawater （salinity 24‰） to empty their guts. Finally, 1 800 healthy individuals with an average weight of （24. 7 ± 0. 9 ） mg were selected and randomly distributed to 18 polyethylene tanks （61 cm × 41 cm× 25 cm, culture tanks ） with soil for feeding experiments. The soil in each culture tank was 10 cm thick, and the soil was collected from the intertidal zone and washed with tap water to remove salts, organic matter and other impurities and then immersed with seawater （ salinity 24‰） to become water-saturated soil. The white fish meal was used as only protein source to formulate six isoenergetic diets with various protein levels daily （ 8： 00 am and 19： 00 pm） 2% -3% of the body weight, （25%, 28% 31%, 34%, 37% and , each diet had 3 replicates. The feeding 40% ）. The larvae were fed twice amount was equal to 1% -2% and respectively. While feeding, 100-120 ml of fresh water was spread on the surface of the soil to replenish the evaporated water and soften the feed. After 1.5 - 2 hours, the feed residue was cleaned up. The light period was 14 hours： 10 hours （light： dark）, and the temperature was maintained at 25 - 28 ℃. After 60 days of culture, the growth performance, body composition of the clamworms and total nitrogen in cultural substance were studied. The results showed that there was no significant difference in survival rate （SR） of clamworms among six treatments （ P 〉 0.05 ）. With increasing dietary protein from 25% to 31%, the final average weight （FAW） and specific growth rate （SGR） were significantly improved, whearas daily feed intake （DFI） and feed conversion ratio （FCR） decreased significantly （ P 〈 0.05 ）. Protein efficiency ratio （PER） decreased significantly with increasing dietary protein levels （ P 〈 0.05 ）. Crude protein of clamworms upgraded significantly when dietary protein levels increased from 25% to 31% and then kept stable （P 〈 0.05 ）. Moisture and ash of clamworms elevated significantly with the increase in dietary protein level （P 〈 0.05 ）. Crude fat content of clamworms showed a reverse trend compared to body moisture content. Total nitrogen in cultural substances increased significantly when the dietary protein exceeded 34%, and the higher the dietary protein content, the greater the increasing extend of cultural substances total nitrogen. According to the broken-line model analysis based on SGR and dietary protein level, it is indicated that dietary protein requirement for clamworms is 31.61%.