Study On Astaxanthin And Protease In Feed Of Rainbow Trout (Oncorhynchus Mykiss)

Exp.1Effects of dietary astaxanthin on pigmentation of muscle and tissueantioxidation of rainbow trout (Oncorhynchus mykiss)The present study was conducted to assess the effects of supplemented astaxanthin(100mg/kg) from DSM, BASF, XHU, Wisdom-A, and Wisdom-B on pigmentation ofmuscle and antioxidation of muscle, serum and liver in rainbow trout with an initial weightof52.1g. After60days feeding, results showed that there were no significant differences inweight gain (WG), feed conversion ratio (FCR) and muscle proximate composition ofrainbow trout among groups (P＞0.05); The SalmoFan score, redness, astaxanthin contentof muscle in rainbow trout fed diets supplemented with astaxanthins, were higher thanthose of control group (P＜0.05). Rainbow trout fed with Wisdom-B astaxanthin additionhad the highest SalmoFan score (28.50) and redness (21.82) among group. At0h,12h,24h,48h,72h after thawing, flesh malondialdehyde (MDA) content of the five astaxanthingroups were lower than those of control group (P＜0.05); Liver total anti-oxidant capacity(T-AOC) of the five astaxanthin groups was significant higher, but serum catalase (CAT)lower than that of control group (P＜0.05). Results above showed that the addition of100mg/kg DSM-Ax, BASF-Ax, XHU-Ax, Wisdom-A-Ax or Wisdom-B-Ax in feed couldimprove the muscle redness and liver T-AOC, reduce serum CAT, SOD and flesh MDA,and extend the shelf life of flesh.Exp.2The study of deposition and degradation of astaxanthin in rainbow trout(Oncorhynchus mykiss)To study the deposition and degradation of astaxanthin in the body of rainbow trout,coloured and un-coloured rainbow trouts with average initial weight of101.9g wereselected. Un-coloured rainbow trout was fed with diet containing100mg/kg astaxanthin tostudy the deposition of astaxanthin in body, which was named as deposition group.Coloured rainbow trout was fed with basal diet without astaxanthin (feeding degradation group), or deprived of diet during the whole feeding period (starving degradation group) tostudy the degradation of astaxanthin in body. The fourth group was designed as positivecontrol with coloured rainbow trout continued being fed diet with100mg/kg astaxanthin.The feeding trial had four groups with triplicates, and last for four weeks. Samples werecollected once a week, which were measured with astaxanthin content of flesh, liver andwhole fish, serum carotenoids, flesh chromatism(L*, a*, b*), and flesh Salmo Fan score.Results showed that astaxanthin contents of flesh, liver and whole fish, flesh a*value,Salmo Fan score of rainbow trout in deposition group increased with feeding timeprolonging (P<0.05), which kept stable in the3rd week, and there were no significantdifference in those indexes between3rd week and4th week(P＞0.05). Axtaxanthinretention rate of whole fish was highest in the first week, and reduced gradually in thefollowing three weeks. Astaxanthin content of tissue, flesh a*and Salmo Fan score ofrainbow trouts in both starving and feeding degradation groups decreased with feedingtime prolonging(P<0.05). The decreasing speed of those indexes in starving degradationgroup was faster than those in feeding degradation group. In both groups, the decreasingtrend of tissue astaxanthin content, flesh a*value and Salmo Fan score slowed down in the3rd week. In positive control group, axtaxanthin contents of whole fish and flesh, SalmoFan score of coloured rainbow trout kept stable, but liver astaxanthin content increasedduring feeding period. Results above showed that an addition of100mg/kg astaxanthin indiet could make the flesh of rainbow trout present ideal red colour after three weeksfeeding, but the retention rate of astaxanthin decreased with feeding time prolonging. Forrainbow trout fed diet without astaxanthin or deprived of diet, flesh astaxanthin and a*value significantly decreased during feeding period, and starving make astaxanthin reducemore quickly than feeding diet without axtaxanthin. The degradation speed of astaxanthinin body of rainbow trout tended to slow down with time prolonging.Exp.3Effects of supplemental protease on growth and intestinal tissue structure ofrainbow trout (Oncorhynchus mykiss)The present study was conducted to investigate the effects of protease on growth,muscle proximate composition, intestinal and gastric protease activities, and goregut tissuestructure of rainbow trout. There was35%fish meal in high fish meal diet, there was28%fish meal in low fish meal diet, and protease diet was supplemented175mg/kg protease onthe basis of low fish meal diet. Rainbow trout with an initial weight of52.1g was fed with this three diets lasting for60days. The results showed that weight gain of rainbow trout inhigh fish meal diet, low fish meal diet and protease diet were98.45%,88.48%and96.82%,and feed conversion ratio were1.36,1.52and1.41, respectively. Weight gain of rainbowtrout in low fish meal diet was lowest, and feed conversion ratio was highest. After addingprotease to low fish meal diet, weight gain of rainbow trout was increased by9.42%, andfeed conversion ratio was decreased by7.80%(P＞0.05), there was no Significantdifference with rainbow trout in high fish meal diet (P＞0.05). There was no Significantdifferences on muscle proximate composition among rainbow trout with the three diet(P＞0.05). Intestine and gastric protease activities, foregut rugae height and area of rainbowtrout in protease diet increased more significantly than rainbow trout in low fish meal diet(P＜0.05), and with almost the same level to high fish meal diet. Research above showedthat an addition of protease on basis of low fish meal diet could enhance intestine andgastric protease activities, and improve the tissue structure of intestine and the growthperformance of rainbow trout.