Use of Non-fish Meal Diets for Yellowtail: Second Trial

Transcription

1 SUISANZOSHOKU 48(1), 7379 (2000) Use of Nonfish Meal Diets for Yellowtail: Second Trial Hideo AOKI*1,2, Kanako WATANABE*3, Shuichi SATOH*3, Yoichi YAMAGATA*1, and Takeshi WATANABE*3 (Accepted November 1, 1999) Abstract: Feeding experiments with young and juvenile yellowtail, Seriola quinqueradiata, were performed to examine the use of nonfish meal diets formulated with soy protein concentrate, defatted soybean meal, corn gluten meal, meat meal, and poultry feather meal in combination. The fish weighing about 210 g (Expt.I) or 8 g (Expt.II) on average were fed the experimental diets for 113 or 41 days, respectively. The experimental nonfish meal diets showed good palatability to the young fish, but poor to the juvenile fish. In Expt.I, the normal growth and feed performances were obtained in young fish fed the nonfish meal diets for the first about 8 weeks of feeding, but thereafter growth was gradually retarded and high mortality was observed without regard to the dietary treatments at the end of feeding. A similar pattern was also obtained in Expt.II, although supplemental effect of amino acids was observed to some extent in juvenile fish. Moreover, the anatomical examination at the end of feeding revealed that both young and juvenile fish on the nonfish meal diets had green liver status, which was not found in the fish fed the control fish meal diet. This observation together with hemochemical assessments demonstrated that feeding nonfish meal diets resulted in physiological conditions inferior to the control for both sizes of fish. Thus, these results confirmed that the nonfish meal diets could not sustain normal growth and health conditions of yellowtail due to induction of green liver. Key words: Yellowtail; Nonfish meal diets; Alternative protein source; Green liver The first trial to culture juvenile (13 g on average) and young (130 g on average) yellowtail with extruded dry pellets (EP) formulated with out fish meal has shown that the experimental nonfish meal diets were of poor palatability to juvenile fish, but were actively accepted by young yellowtail. The diets sustained normal growth of the young fish for the first 46 days of feeding, but thereafter resulted in stagnant growth, poor feed gain ratio, and high mortality irrespective of the dietary treatments1). Moreover, at the end of the experiments, both juvenile and young fish fed the nonfish meal diets revealed the green liver symptom and poor blood characteristics, indicative of the abnormal physiological status. These nonfish meal diets were formulated to include soy protein concentrate (SPC), defatted soybean meal (SBM), corn gluten meal (CGM), meat meal (MM) as alternate protein sources, and crystalline amino acid mixture was supplemented in the diets to match the amino acid profile with that of the control fish meal diet. Therefore, the reduced growth performances observed in fish fed the nonfish meal diets might partly be due to the poor utilization efficiency of supplemental amino acids, and partly be linked with the appearance of green liver, although its mechanism remains unknown. Thus, the present study was conducted to confirm the results obtained in the first trial whether the appearance of green liver in yellow *1Owase Branch, Fisheries Research Institute of Mie, Owase, Mie , Japan. Present address: Fisheries Research Institute of Mie, Hamajima, Mie , *2 Japan. Department of Aquatic Biosciences, Tokyo University of Fisheries, Konan, Minato, *3 Tokyo , Japan.

2 74 H. Aoki, K. Watanabe, S. Satoh, Y. Yamagata, and T. Watanabe tail is always closely linked with feeding nonfish meal diets, and to investigate supplemental effect of crystalline amino acids on feed perform ances of nonfish meal diets. Experimental Diets Materials and Methods The composition of the experimental nonfish meal diets and their proximate values analyzed by the same methods described previously2) are shown in Table 1. All the diets were formulated to have around 45% crude protein (CP) and 20% crude lipid (CL) those hitherto used in yellowtail experiments. A commercial yellowtail dry diet containing 65% fish meal (CP : 68%) as a main protein source was used as a control diet (diet 1) and was produced by Sakamoto Fish Feed Co. Ltd. using large size twin screw extruder. The fish meal component was entirely eliminated from the experimental nonfish meal diets and replaced by a combination of alternate protein sources including SPC (Protao, a product of Aarhus Olie; CP : 70%), SBM (CP : 46%), CGM (CP : 65%), MM (CP : 82%), and poultry feather meal (PFM) (CP : 82%). All the diets except the control diet were incorporated with 10% krill meal to enhance palatability to juveniles, although its noninclusion diet not impair palata bility to young yellowtail1). The wheat flour or starch (only the control diet) as a carbohydrate source and binder was included at 8 or 5%, re spectively. The vitamin and mineral mixtures were added to match the requirements of yellowtail. The supplemental feed oil level was 13% for the control and 17% for the test diets to elevate the dietary energy levels. Moreover, diets 36 contained 2.7% amino acid mixtures (1.5% Llysine, 0.5% DLmethionme, 0.5% L threonine, and 0.2 Ltryptophan) to match the amino acid profile with that of the control diet. The experimental diets were prepared as dry Table 1. Composition of the experimental nonfish meal diets for yellowtail * Lysine 1.5, methionine 0.5, threonine 0.5, and tryptophan 0.2.

3

4 76 H. Aoki, K. Watanabe, S. Satoh, Y. Yamagata, and T. Watanabe Expt.I: The experimental nonfish meal diets showed good palatability to the fish. The best final body weight and growth rate (GR) were obtained from fish on the control fish meal diet. There was no large difference in average body weight between fish on the nonfish meal diets Table 3. Growth and feed gain ratio of young yellowtail fed the nonfish meal diets in net cages and the control diet until the 59th day (Oct. 6, 39 days feeding) from the start of feeding (being g for the nonfish meal diet groups and 450 g for the control). But, thereafter the feed ing activity of nonfish meal diet groups became gradually poor, and GR of these diet groups dropped dramatically at the end of the experi ment without regard to dietary components. The final body weight of fish fed the control diet was 692 g, and was much higher than that of the fish on the nonfish meal diets ( g). Thus the nonfish meal diets used in this study could not sustain normal growth of yellowtail for more than 2 months. The same tendency was also *1g feed/g weight gain.*1 g/100 g body weight. Table 4. Growth and feed gain ratio of juvenile yellowtail fed the nonfish meal diets in polycarbonate tanks

5 Nonfish Meal Diets for Yellowtail 77 obtained for feed gain ratio (FGR), showing that this value of nonfish meal diet groups worsened with growth retarded. Both GR and FGR were not different among the nonfish meal diet groups. On comparing the performance para meters between fish on diets 2 and 3, namely the diets with or without crystalline EAA, there seemed to be no supplemental effect on im provement of the feed quality. High mortalities (2649%) were observed for fish of the nonfish meal diet groups during the final feeding period of Nov. 128, while no mor tality in the control group. Dissection of dead fish revealed that most of fish had green liver status as observed in the former trial1), indicat ing the poor health condition for fish on the non fish meal diets irrespective nents. The anatomical assessment of the dietary compo conducted ab out every 2 weeks from the start of feeding showed that green liver symptom peculiarly appeared in fish on the nonfish meal diet after the end of October6). Thereafter, the occurr ence rate of this symptom increased, and almost all the fish on the nonfish meal diets suffered at the end of the experiment. Contrary, there were few green liver fish in the control groups. The histological examination conducted at the Labora tory of Fish Physiology, Tokyo University of Fisheries revealed that this symptom was caused by occlusion of bile duct due to parasitic mucosporozoa, as same in the first trial1). Expt.II: Feeding activity in fish fed the non fish meal diets was generally poor for all the diet treatments during the whole feeding period, un like young fish in Expt.I, suggesting the differ ence in palatability to test diets between fish sizes. Growth and feed performances showed almost the same tendency as those obtained in Expt.I. The final average body weight and FGR were 124 g and 0.95 for the control and 4373 g and for the test groups, respectively. The best protein efficiency ratio (PER) value was also observed for the control diet. Mortality was generally low, ranged between 15 fish (n= 30) for all the treatments. But the anatomical examination at the final of feeding showed that all of fish on the nonfish meal diets had green liver status due to the same reason mentioned earlier.on the other hand, when comparing the performance parameters between fish on diets 2 and 3, GR, FGR, and PER of fish fed diet 2 (without EAA) were inferior to fish on diet 3 (with EAA), unlike in the case of Expt.I. This result indicates the effectiveness of EAA supple mentation to the nonfish meal diets to improve the feed utilization to some extent. Therefore, more detailed study must be carried out to in vestigate the availability of supplemental amino acids to diets with alternate ingredients. In the first trial on the use of nonfish meal diets to yellowtail1), normal growth and feed performances were obtained until one and a half months after the initiation of the feeding (net pen experiment), but thereafter growth gradually retarded and subsequently high mortality was observed. Moreover, the anatomical examination at the end of the experiment revealed that almost all the fish fed the nonfish meal diets were suffering from green liver, while few fish on the control fish meal diet. These results agreed well with those obtained in the present study. Therefore, although the cause of the re duction of growth and feed performances was unknown, the results from the present and for mer studies suggested that there was some nut ritional inadequacies in the nonfish meal diets to yellowtail, regardless of the dietary components. The inferior feed performances and high mortal ity observed in fish fed the nonfish meal diets might partly be due to poor utilization efficiency of supplemental lated to the appearance amino acids and partly be re of green liver symptom. The reason for green liver appearance induced by feeding the nonfish meal diets was still un known. Therefore, further studies are needed to clarify the mechanism of this phenomenon velop a nonfish meal diet. Proximate Composition to de The results of proximate analysis of the dorsal muscle, liver (Expt.I), of fish are presented and whole body (Expt.II) in Table 5. In Expt.I, the protein content of the dorsal muscle did not dif fer largely among the treatments, but this value of the liver in fish on the nonfish meal diets slightly higher than that in fish on the control

6 78 H. Aoki, K. Watanabe, S. Satoh, Y. Yamagata, and T. Watanabe Table 5. Proximate composition (%) of dorsal muscle, liver, and whole body from yellowtail fed the nonfish meal diets diet. The lipid content of muscle in fish on the nonfish meal diets ranged from 2.0 to 3.7%, and was remarkably trol diet (8.2%). lower than that on the con A similar trend was shown in the liver lipid too, 21.2% for the control and % for the nonfish meal diet groups. The moisture content was inversely lower in both muscle and liver of fish fed the control diet re flected by higher lipid content. In Expt.II, the patterns of proximate composition were similar to Expt.I. The lipid content in the whole body was the highest in fish on the control diet. The lower lipid levels were reflected by lower growth of fish of the nonfish meal diet groups. The results of proximate analysis from this study showed the same tendency as those obtained in the previous experiment1). *1 No data for the diet 2 group due to the failure of sample preparation.*2 Figures in parentheses are values on dry matter basis. Hemochemical Characteristics The results of hemochemical assessments of fish in Expts.I and II are presented in Table 6. In Expt.I, the hematocrit (Ht) value of fish fed Table 6. Results of hemochemical examination in yellowtail fed the experimental nonfish meal diets

7 Nonfish Meal Diets for Yellowtail 79 the nonfish meal diets was significantly lower than that on the control diet, 40.7% for the con trol and % for the test groups, showing an anemic state in fish of the latter groups. Also, fish fed the nonfish meal diets had greatly lower blood lipid metabolism indexes, namely phospho lipid (PL), total cholesterol (TCHO), free cholesterol (FCHO), and cholesterolester ratio. This indicates that an abnormal liver function in the fish of the test groups, compared to the con trol group. The total protein (TP) and creatinine (CRE) levels of test groups were also lower than those of the control, suggesting the poor nutrient condition. On the contrary, alkaline phosphatase (ALP) activity and glucose (GLU) content were higher in fish fed the nonfish meal diets. The results in Expt.II showed almost the same trend as those obtained in Expt.I. Fish of the nonfish meal diet groups were in an anemic state and had significantly lower lipid metabo lites, regardless of dietary treatments. From these results, the physiological condition of fish fed the nonfish meal diets was evaluated as being quite inferior to those on the control fish meal diet. In conclusion, the feed performances together with hemochemical examination have shown that the nonfish meal diets could not produce normal growth and health condition and cause green liver symptom for yellowtail, irrespective of the ingredient composition, as already observed in the previous trial1). Additional works are neces sary to clear the nutritional defect of the nonfish meal diets, especially from the viewpoint of availability of the supplemental amino acids. References 1) Watanabe, T., H. Aoki, K. Shimamoto, M. Hadzuma, M. Maita, Y. Yamagata, V. Kiron, and S. Satoh (1998): A trial to culture yellowtail with nonfishmeal diets. Fisheries Sci., 64(4), ) Watanabe, T, and J. Pongmaneerat (1991): Quality evaluation of some animal protein sources for rainbow trout Oncorhynchus mykiss. Nippon Suisan Gakkaishi, 57(3), ) Watanabe. T., H. Sakamoto, M. Abiru, and J. Yamashita (1991): Development of a new type of dry pellet for yellowtail. Nippon Suisan Gakkaishi, 57(5), ) Watanabe, T., V. Viyakarn, H. Kimura, K. Ogawa, N. Okamoto, and N. Iso (1992): Utilization of soybean meal as a protein source in a newly developed softdry pellet for yellowtail. Nippon Suisan Gakkaishi, 58(9), ) Viyakarn, V., T. Watanabe, H. Aoki, H. Tsuda, H. Sakamoto, N. Okamoto, N. Iso, S. Satoh, and T. Takeuchi (1992): Use of soybean meal as a substitute for fish meal in a newly developed softdry pellet for yellowtail. Nippon Suisan Gakkaishi, 58(10), ) Maita, M., H. Aoki, Y. Yamagata, K. Watanabe, S. Satoh, and T. Watanabe (1997): Green liver observed in yellowtail fed nonfish meal diet. Nippon Suisan Gakkaishi, 63(3),