Preliminary Studies on the Formulation and Presentation of ...

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Table 1. Ingredients and proximate composition of seabass weaning diet Ingredients % Fish meal 40 Squid meal 10 Soybean meal 10 Groundnut oil cake F~sh oil Vegetable oil Lecith~n Wheat flour Wheat bran Yeast Aminoacid mix' Vitamin mix' Mineral mix' Total Prox~mate composition Mo~sture 7.30 Crude protein 37.06 Crude tibre 8.31 Ether extract 8.91 Total ash 7.10 NFE 31.32 1. Amino acid mlx Lysine. Methionine, Glutamic acid in the ratio of 1: I:l 2 Vitamin mix (mgtkg) : Thiamine 20.0, Riboflavin 25.0, Pyridox~ne 20.0, Pantothen~c acid 50.0. Niacin 150.0. Folic acid 10.0. Cyanocobalamine 0.02. lnosltol 2C0.0. Choline chloride 500.0, Biotin 1.0. Ascorbic acid 2(M).O. Vitamin A4.0 (6000 i.u), Vitamin E 50.0 and Vitamin K 10.0. 3. M~nenl mix (glkg): Calcium 5.0. Phosphorus 7.0. Magnesium 0.5, Sodium 2.0. Potassium 2.0. Sulphur 4.0. Chloride 3.0, Iron 0.1, Copper 2.0. Manganese 0.025, Cobalt 0.01, Zinc 0.1 and Iodine 0.2 Growth experiment After successfully evolving the process of weaning seabass to formulated diet, three diets were formulated to study the acceptability of feed and their growth performance. Ingredients used and proximate composition of test diets are presented in Table 2. The diets were prepared as dry pellets as described earlier and were crumbled to 0.5 mm granules. In this experiment juveniles of hatchery reared seabass with an average weight of 1.60+0.48 g were used. As in the first experiment, 20 fishes in triplicate were taken in 100 1 tanks filled with seawater. Each group of fish was weaned to the respective test diet by the same method of gradually incorporating the fish meat in the first 10 days. The feeding trial with test feeds was commenced after this period. Duration of the trial was 30 days. The control group was fed with fish meat (approximately 10% of body weight on dry weight basis). Test group of fish were offered feed approximately at 10% of their body weight divided in three rations. Weight gain, specific growth rate (SGR) and feed conversion ratio (FCR) were determined at the end of the experiment. Proximate composition of test diets was analysed by following the methods of AOAC (1990). Table2. Ingredients and proximate composition of test diets for seabass Ingredients Diet-2 Diet-3 Diet-4 (%) (%) (%I Fish meal 20.0 30.0 40.0 Squilla nzeal 5.0 5.0 5.0 Soybean meal 17.0 12.0 12.0 Groundnut oil cake 15.0 10.0 10.0 Fish oil 4.0 4.0 4.0 Sun flower oil 3.0 3.0 3.0 Lecithin 1 .O 1 .O 1 .O Wheat flour 20.0 20.0 15.0 Wheat bran 10.5 11.7 6.7 Aminoacid mix* 1.5 0.3 0.3 Vitamin mix* I .O 1 .O I .O Mineral mix* 2.0 2.0 2.0 Proximate composition Moisture 8.11 . 8.23 8.35 Crude protein 34.94 35.76 39.63 Crude fibre 3.26 2.93 2.91 Ether extracl 9.5 1 9.08 9.62 Total ash 12.43 14.59 18.63 NFE 31.75 29.41 21.86 * The composition are same as in weaning diet as given in Table I Water temperature and salinity during the experiment were in the range of 27-29°C and 25-28 %o, respectively. Dissolved oxygen and pH in the rearing tanks were 7.2-8.0 mgA and 7.8-8.1, respectively. Data obtained in the experiments were subjected to one way ANOVA on the SAS package for the IBM-PC (SAS Institute Inc., 1988). Results Weaning trial The method of preparation of diet adapted in this study resulted in the desired physical properties. Formulation of diet and subsequent vacuum drying resulted in puffy texture in the dry diet. The diet pellets floated 2-3 minutes and started sinking slowly. Feeding the weaning diet directly resulted in poor acceptability by fish both in the dry as well as moist form. Gradually mortality had set in after one week in both the treatments. However, the fish fed with a mixture of diet and lish meat started accepting the diet right from the beginning. The fish offered dry and moist diet directly emaciated due to starving and the survival of fish was reduced to 20% in the case of dry diet and 40% in the case of moist diet (Fig. 1) in the smaller group (0.5 g). In larger group (5.0 g), the respective survival levels were 30% and 50%. In both the cases the moist diet appears to score over the dry diet. On the other hand the survival levels recorded with mixed diet after 15 days of rearing were 80% in smaller and 90% in larger size
groups. In the case of mixed diet, within 10 days the fish could be fed with 100% diet. totally replacing the fish meat in Group I fish. In case of Larger group (Group 11) the total rtplacemenr of fish meat with diet could be achieved in 7 days. Once the fish was weaned to formulated diet it accepted the diet in dry as well as moist forms. Even the feed kept at the bottom of the tank was consumed. Observations had shown that moist diet was more readily consumed compared to the dry diet. Dry del Moistd~et D~el+F~shma' Weaning methods Fig 1. Survival (%) of seabass fingerlings fed with weaning diets in three different ways at the end of 15 days Growth The results of 30-days feeding trial with three growth diets are presented In Table 3. The growth of fish improved with the increased fishmeal level in the diet. Diet having 39.63% crude protein gave significantly (P < 0.05) higher growth (46%) and better FCR of 2.75. The FCR did not show any significant difference between the treatments (P > 0.05). Table 3. Weight gain, SGR, FCR and survival levels of seabass fingerlings fed on test diets for 30 days Average Diet-2 Diet-3 Diet-4 Control In~tial ave. live 1.57a.31 1.634.42 1.624.38 1.604.43 Wt.(g) Ftnal average 2.07-cO.41 2.244.49 2.37k0.42 - live wt.(g) Wetght gain (%) 32~k1.9198+21 46k2.27' FCR 2.90d.09" 2.904. 1097550.1 I" - SGR (5%) 0.91d.O 1 1.05&0.02 1.26kO.02 Surv~val (%) 66 68 66 lOO(on 10th davl 'Menns bennng the dtfferent superscript in the sane row d~ffer s~gntficantly (P c 0.05) The survival levels were in the range of 6648% in the different treatments. However, total mortality of fish occurred within ten days in the case of control d ~ (fish e ~ meat). A striking observation made during feed trial was that in the case of control diet, the dead fish mas consumed by the live ones (cannibalism), whrle in case of formulated diets this tendency was not noticed. Discussion Seabass seems to be conservative ir, its feeding habit. It is tough to change from one type of dret to another type. Unless the diet is acceptable to the fish. it prefers to starve rather than to eat whatevcr comes its way In the present study, by allowing short time fermentation of feed through yeast and subsequent vacuum drying. puify texture could be imparted in to the pellets, especially in dry pellets. This had resulted pellets floating for 2-3 mlnutes and then sinking slowly after absorb~ng sufficient water. Th~s was resorted mainly to simulate the slow-s~nking pellet as moving prey. Although seabass prefers to feel on moving prey, the sinking pellets in dry or moist form d~d not attracl the fish adequately to feed on At times, even IF it takes diet pellets into its mouth, it lmmedlately spits out The attractability and texture of teed seems to bc inore important factors. Since fishmeal was presenl In the weaning test diet in the present study, it had fishy flavour and the moist diet was soft in texture. St111 the diet was not acceptable to seabass when fed alone. Out of the different ways of weaning tried, incorporation of the diet in the fish meat and gradually replacing the later finally succeeded in adopting the compounded diet by the fish wh~ch took 7-15 days. Once the fish adapted to the formulated d~et it accepted dry as well as moist fo~m of the diets directly. References in this line on seabass are scarce. Investigations cmied out on seabass (Cuzon and Fuchus, 1988; Sakaras er al., 1988; Tucker et al., 1988, Cuzon et nl., 1989: Mackinnon, 1989; Wong and Chou, 1989: Perez et al., 1993; Boonyaratpalin, 1991; Catacuttan and Coloso, 1995,1997) did not bring out any of the aspects associated with weaning of seabass to formulated diets. The present study suggested that Asian seabass could be weaned to formulated feeds by incorporating fish meat with formulated diets within a per~od of 7-15 days. Once adopted the fish easily accepts formulated diet. The results also indicated that weaning may be faster as the size of the fish increases. In growth trial conducted with formulated feeds on fingerlings, the method evolved for weaning the fish to formulated diet was successfully adopted All the three diets formulated and tested were accepted by the fish and supported the growth. Since the pellets are made to sink slowly, the fish readily swallowed the diet, once they were adopted to eat. Fish consumed even the diet settled at the bottom of tank. The results suggest that adaptation of fish to
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