Feed Peas in diets for shrimp tilapia and milkfish - Northern Pulse ...

Materials and MethodsExperimental dietsThe feed ingredients used in this study were obtained from commercial suppliers through the SEAFDECpilot feed mill plant. Feed pea of US origin was supplied through a local distributor in Manila, Philippines.Prior to use, all dry feed ingredients were ground and sieved through a 60µm mesh screen sieve.Proximate analyses for each feed ingredient were conducted and the resulting data were used in dietformulation (Table 1). Six isonitrogenous diets were formulated to contain 40% protein (Table 2). Proteinfrom feed pea replaced 0, 20, 40, 60, 80, and 100% of the protein from defatted soybean meal in the diets.These values were equivalent to 0, 5, 10, 15, 20, 25%, respectively, of the total protein in the diet.Replacement of protein was based on the essential amino acid requirements of tiger shrimp (Kanazawaand Teshima, 1981; NRC, 1993; FDS Manual, 1994; Millamena et al., 1996-1999). A negative control withno protein sources was added to the treatments. Protein content of 40% in the shrimp diet has beenreported to be optimal for juvenile Penaeus monodon (Alava and Lim 1983; Bautista, 1986; Shiau et al.1991). The diet containing no feed pea meal served as the control diet. Other animal protein sources, suchas fish meal, shrimp meal, shrimp head meal, and squid meal, were included in the dietary formulations atthe same levels. The levels of wheat flour and rice bran were adjusted to maintain similar dietary proteincontents. Diets were prepared according to standard diet preparation in the laboratory as described in FDSManual, 1994. To prevent lipid oxidation during storage, all diets were packed in sealed plastic containersand stored inside a cold room at –20ºC until used in the feeding trials.Proximate analyses were conducted of the various diets prepared following the methods of Association ofOfficial Analytical Chemists (AOAC 1990). The amino acid composition of both soybean meal and feed peameal and experimental diets was determined using the method of Simpson et al., 1976.Feeding trialsGood quality and disease-free post-larval Penaeus monodon were sourced from a private hatchery inTigbauan, Iloilo, Philippines. They were placed in 2-tonne fiberglass tanks and fed with Artemia sp andcontrol diet for a week before they were transferred to experimental tanks. Twelve shrimp post-larvae withan average weight of 0.02 ± 0.01g were randomly assigned in 35, 60 L oval tanks equipped with a flowthroughseawater system. Prior to start of the feeding trial, shrimps were acclimatized to experimental diets.The shrimp were fed the formulated diets at a daily feeding rate of 20-25% of total body weight for 90 daysin 5 replicate samples. Shrimp were fed three times daily at 0800, 1300, and 1700h. The wet weights ofthe shrimp were recorded every 15-d interval for 90 days and the amount of feed given was adjusted everysampling day. All experimental tanks were cleaned before every feeding. Water temperature, salinity,dissolved oxygen, and pH were measured daily in all tanks. Total values for ammonia-nitrogen and nitritenitrogenwere measured once a week. Shrimp were collected at the beginning of the feeding trial forproximate analyses. At the conclusion of the feeding trial, all shrimp samples from each tank were pooled,freeze-dried and ground for proximate analyses of whole body composition following the standard methodsof AOAC (1990).Biological analysisDiet performance was evaluated by calculation of percent weight gain=final weight-initial weight/initialweight x 100; specific growth rate=100 (ln ave. final wt-ln ave. initial wt)/no. of culture days; feed conversionratio (FCR)= total dry feed intake (g)/wet weight gain (g); percent survival =final number of shrimp/initialnumber of shrimp x 100.In vivo digestibility experimentApparent digestibility coefficients for dry matter (ADMD) and crude protein (APD) of feed peas as ingredientand feed-peas based diets were measured using 1% Cr 2 O 3 as external indicator. The method by Cho. etal. (1982) was adapted in a ratio of 70:30 (reference diet to test ingredient) in each test diet. The controldiet used for growth experiment was used as reference diet. Composition of the diet is shown in Table 3.In the digestibility experiment for the test ingredient and feed pea-based diets, 10 shrimp with mean bodyweight of 14.53± 0.57g and 8 shrimp with mean body weight of 13.56±0.56g were stocked in 250 L conicalfiberglass tanks for the test ingredient and feed pea-based diets, respectively. The shrimp were acclimatedto experimental diets and laboratory conditions for 7 days before the experiment. All shrimp were fed at 8-10% of the total body weight 3x daily. A flow-through filtered seawater system with continuous aeration andflow rate of 600-700 ml/min was provided for each tank. Water temperature and salinity were maintained at24-48ºC and at 30-34 ppt, respectively. Culture period was 80 days. Fecal collection was done manually.The feces were allowed to float into a plastic scoop and then pipetted and gently transferred into acollecting vial. Care was taken to prevent the breaking-up of fecal strands to facilitate collection and toavoid leaching of nutrients. Thereafter, fecal samples were carefully rinsed with distilled water andimmediately stored in a freezer to retard bacterial decomposition. At the end of fecal collection, samples4