| Plectropomus leopardus has a very high economic value for its nutritional anddelicious flesh, gorgeous body color, and broad market prospect. However, the studyon feed and light color of this fish in industrial culture was blank, and none researchhad reported the interact effect of feed’s protein level, lipid level, and protein sourceon farming fish.This paper designed a three-factor experiment, and investigated the effect of feed’sprotein and lipid level combined with protein source on growth performance, skinpigment content, water environment and metabolism of juvenile Plectropomusleopardus in recirculating culture. Meantime, it has studied the effect of light color, asingle factor, on culturing the fish. The paper aimed at providing reference forproducing specific feed for Plectropomus leopardus and its light regulation inrecirculation culture.The experiment was directed by eco-nutrition, physiology, and biochemistryknowledge, and had two main parts. Part1has designed eight (1-8#) compound feedformulated by two protein level(46%,50%or P46, P50), two lipid level (8%,10%orL8, L10) and two protein source which contain pigment (vegetal, animal protein orVPP, APP). Then, it investigated the effect of different feed on juvenile Plectropomusleopardus (64.2±1.1) g in recirculating culture. Part2has studied the effect of fourdifferent light colors [red, blue, dark, and day-night (D-L) light] on culturing juvenilePlectropomus leopardus. We got the following experimental results by94days trial,measuring of physiology index, and statistic analysis.1. The survival rate of trial fish between different nutritional treatment had nosignificant difference (p>0.05), and the average survival rate is92.71%. Each fish of1#(P46L8VPP) have eaten1.04g everyday, and have significantly increased by18.2%-36.8%(p<0.05). The trial fish exhibited better growth performance feedingwith P46, L10and APP interaction (4#) feed. Weight gain rate significantly increased by17.4%-34.1%, and feed coefficient significantly decreased by11.6%-23.3%(p<0.05). At the time, the water quality of NH3-N, NO2-N, and COD between eachtreatment had no significant difference (p>0.05).2. Both the P50feed and L8feed significantly increased skin carotene by15.4%and37.86%(p<0.05), and low lipid feed could increase melanin by22.1%(p<0.05).Lutein level in skin is very low. Feed with P50, L8and APP interaction (6#) notablelyincreased the skin carotene level by43.2%-88.3%(p<0.05). Besides, the experimentfound that the trial fish’s skin carotene and melanin content increased or decreased bythe same way under different treatment. Therefore, it is unable to raise the skincarotene and reduce the melanin at the same time for the sake of regulating the fishskin color. That presented a law of the unity of opposite.3. Both P50and L10feed increased the lipidase and Na+,K+-ATase acticity. Thelipidase acticity increased by23.5%and51.3%, and the Na+,K+-ATase acticityincreased by40.8%and13.0%(p<0.05). P50feed also increased AKP acticity by67.8%(p<0.05). L10APP interactional feed increased trypsin by12.1-45.4%(p<0.05).In short, P50, L10interacted with APP feed improved trial fish’s digestive andabsorptive ability.4. P50feed increased GOT and GPT activity in hepatopancreas by25.8%and18.1%(p<0.05). L10feed increased GPT avtivity by20.5%(p<0.05). P50APP feedsifnificantly increased LDH activity by13.6%-32.1%(p<0.05, p<0.01) and GOTactivity35.8%-56.2%(p<0.05). The trial fish exhibited stronger metabolic activityfeeding with P50L10APP interactional feed (p<0.05). LDH activity significantlyincreased by34.3%-48.6%; GOT activity increased by21.0%-73.3%; GPT activityincreased35.8%-56.2%. L10feed could rise serum SOD activity. P50diet could raiseLZM activity and reduce MDA level in serum. Both L8APP and L10VPPinteractional feed reduced MDA level. P46L10APP feed could rise SOD activity by20.8%-35.3%(p<0.05). P46L10APP interactional feed could rise17β-E2and VTGlevel in serum. However, this phenomenon could not explain the effects of differentialdiets on trial fish’s sexual development, and it need further study. 5. The survival rate and feed intake between different light color treatment had nosignificant difference (p>0.05). The weight gain rate of D-L light group increased28.6%than dark group (p<0.05), and39.2%than red light group (p<0.01), but had nosignificant difference with blue light group (p>0.05). The weight gain rate of bluelight group increased31.2%than red light group (p<0.05). The feed coefficientbetween each treatment had no significant difference (p>0.05). The carotene level ofD-L group was significantly higher than blue and dark group by45.7%and68.5%(p<0.05). While the carotene level of red group has the increasing trend. Besides, theexperiment found that the trial fish’s skin carotene and melanin content increased ordecreased by the same way under different treatment. The17β-E2and VTG level offish in dark were significantly higher than other’s, increased by45.5%-94.2%and34.6%-50.1%separately (p<0.05, p<0.01). Its high level of sexual development maydepress its body growth, but provide a reference for culturing parent fish.6. The pepsin activity in gastrointestinal tract of fish under D-L light increased by48.0%-88.5%(p<0.05). On the other side, trypsin in blue group was significantlyhigher than red and D-L group by34.3%and21.8%(p<0.05), and its high proteindigestive ability conresponding to its high weight gain rate. Red and D-L light couldincrease trial fish’s Na+,K+-ATase acticity. GOT activity of dark group significantlyincreased by26.8%-75.5%than others (p<0.05). Besides, D-L group had betterimmunity, its SOD and LZM activity significantly higher than others did (p<0.01),and MDA level lower than dark and red group (p<0.05, p<0.01).In conclusion, the results indicated that: main nutrient element and source did affectgrowth performance, skin pigment content, and metabolism of Plectropomusleopardus. Animal protein pigment is better than vegetal, and the proposed idealcombination is P50, L8with APP for growth, skin color, digestion and absorption.P50L10APP interactional feed could raise fish’s metabolic enzyme activity, butprotein and lipid level should regulate for improving fish’s immunity and skin color.Besides, fish under D-L light had shown better growth, skin color and immunityperformance. However, experiment found that blue light could improve fish’s proteindigestive ability and then incease growth. Red light could raise carotene level, and it is helpful for regulating. While it is beneficial to sexual development when fish livingin dark environment.At last, the researches have obtained the parameters of feed nutrients and sourceand light color of fast-growing and bright-colored Plectropomus leopardus juvenile inindustrial culture, determined the preferred solution, and figured out the specificphysiological mechanism preliminary. Therefore, the paper provided reference forproducing specific feed for the fish and its light regulation in industrial culture, andfilled the gaps in this field. In addition, they had improved the technologies andbenefits of culturing the fish in recirculating system, and promoted its healthy andsustainable development. |
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