ONCORHYNCHUS-MYKISS - TESTING THE ANTIOXI DIZING EFFECT OF NEOX IN DRY PELLETS FOR THE MARKET RAINBOW-TROUT ONCORHYNCHUS-MYKISS

In the course of four-month storage of dry pellets for the market rain bow trout (Oncorhynchus mykiss) antioxidizing effectiveness was repeat edly evaluated in a mix preparation Neox (a coumpound on BHT basis) in loose form which was to replace liquid Kurasan used until now (quinol ine derivative, the synonyms of identical foreign substances are Ethox yquin, Santoquin, Santoflex, Niflex). Neox did not have the expected a ntioxidizing effectiveness at three tested rates (100, 200 and 300 mg/ kg feed) and at one treatment as Neox forte (100 mg/kg), similarly lik e butylhydroxytoluol (BHT) was not efficient enough in previous experi ments (Rehulka, Jirasek, 1987). It is to note that in our experiments fatty acid oxidation did not comply with the concepts derived from exp erience of the experiments in the cited papers. Chemical blockage of o xidation lacked equilibrium and was characterized by conspicious culmi nation of peroxides after 60-day storage of the mix (Fig. 1). Signific antly better results of oxidation suppression were gained when the dry pellets were enriched with 0.5 to 1 % rapessed lecithin particularly in combination with Kurasan (200 mg/kg), which conclusively demonstrat ed its antioxidizing qualities with respect to the BHT-based compounds (Fig. 2). The average peroxide value of the mix with this antioxidizi ng protection was 15.3 meq/kg with the peak 24.4 meq/g in comparison w ith dry pellets containing Neox (300 mg/kg) or Neox forte (100 mg/kg), in which the average peroxide values were 25.7 and 28.1, respectively , with the respective peaks 45.2 and 35.7 meq/kg. But this favorable r esult was obtained in experiment B only when the dry pellets had the h igher percentage of fat (7.29 %) unlike the results achieved in experi ment C with the fat content of 3.50 % in the dry pellets (Fig. 3). Thi s fact documents more effective utilization of natural antioxidative q ualities of lecithin in combination with Kurasan against its combinati on with Neox. In keeping with the findings reported by the Sabalina (1 976), who investigated the variation in acid value of fat and peroxide value in granules enriched with phosphatids (sunflower oil), we demon strated the marked effect of lecithin on abatement of the hydrolytic d ecomposition of fat. This effect was observed not only in the dry pell ets with Neox (Fig. 4), but also with Kurasan (Fig. 5).