Now showing items 1-12 of 12

    • Conference paper

      Amino acid and fatty acid profiles in aquaculture nutrition studies 

      LV Benitez - In SS De Silva (Ed.), Fish Nutrition Research in Asia: Proceedings of the Third Asian Fish Nutrition Network Meeting, 6-10 June 1988, Bangkok, Thailand, 1989 - Asian Fisheries Society
      The amino acid profile is an important parameter in the evaluation of protein quality and in requirement studies. Amino acid profiles are usually determined in 2 steps: hydrolysis of the protein to constituent amino acids followed by quantitative analysis of the amino acids in the hydrolysate. The 10 amino acids known to be essential in most animals have been found to be essential in all fish so far studied. The reference amino acid profiles used in the amino acid requirement studies of various fish species include that of whole chicken, egg, fish egg and fish muscle. The amino acid profile of fish muscle provides a useful first approximation of the amino acid requirement of the young, growing fish in which the greatest proportion of weight gain is in the form of muscle.
    • Article

      The effect of dietary protein-energy levels on growth and metabolism of milkfish (Chanos chanos Forsskal) 

      RM Coloso, LV Benitez & LB Tiro - Comparative Biochemistry and Physiology - Part A: Physiology, 1988 - Elsevier
      1. Groups of milkfish juveniles (mean weight, 2.8 g) were fed diets containing white fishmeal and gelatin with varying protein-energy to total metabolizable energy (PE:TME) ratios.
      2. Amino acids were incorporated in the diets to stimulate the pattern of milkfish protein. The control diet contained fishmeal as sole protein source and was not supplemented with amino acids
      3. Among the amino acid supplemented diets, best growth was observed at PE:TME ratio of 44.4%. However, the control diet gave better growth rate than any of the amino acid supplemented diets
      4. Specific activities of pyruvate kinase (PK) and glutamate dehydrogenase (GDH) increased significantly with increase in dietary protein-energy level.
    • Conference paper

      Heterogeneity in Philippine milkfish populations 

      JM Macaranas, MJR Pante & LV Benitez - In R Hirano & I Hanyu (Eds.), The Second Asian Fisheries Forum. Proceedings of the Second Asian Fisheries Forum, 17-22 April 1989, Tokyo, Japan, 1990 - Asian Fisheries Society
      Twelve milkfish (Chanos chanos ) populations from 6 coastal areas in the Philippines, collected at the fry stage and reared until fingerling size, were analysed for electrophoretic variation at 28 presumptive loci. Seven loci were polymorphic at the 0.99 level (5 at the 0.95 level) while 21 were monomorphic. Significant departures from the expected Hardy-Weinberg genotype distributions were observed only at the Pgm locus in samples 843 and 862. G-tests for heterogeneity revealed significant differences in genotype distributions at the Est-1, Gpi-1, Gpi-2, Mp-2 and Pgm loci within each year of sampling, within one location at different sampling years, and within two geographical areas east and west of the Philippines.
    • Article

      Lactate dehydrogenase isozyme patterns during the development of milkfish, (Chanos chanos (Forskal)) 

      PD Requintina, LM Engle & LV Benitez - Kalikasan, The Philippine Journal of Biology, 1981 - University of the Philippines at Los Baños
      Polyacrylamide disc gel electrophoresis was done to determine the lactate dehydrogenase (LDH) isozyme patterns for fry (5-3 mg), fingerling (6-12 g), pond-size (150-250 g) and adult (6-9 kg) milkfish. The patterns were tissue specific; the different tissues examined, viz., eye, liver, heart, and skeletal muscle had different expressions of LDH isozymes. The resolved patterns appeared to be products of LDH gene loci A, B, and C. Subunits A and B were present in all tissues. A4 and B4 were predominant in skeletal and heart muscle, respectively; the two associated non-randomly in vivo and formed only the heteropolymers A3B and AB3. A liver band, L4, was most conspicuous in the fingerling, pond-size, and adult; it was assumed to be coded by locus C. A negatively charged band, X4, was detected in fully developed ovary and in fry homogenized as whole individuals, but it could not be resolved in tissues of fingerling.

      Six-mo old stunts and 3-mo old fingerlings had similar LDH patterns for all tissues examined. The patterns for 11-mo old stunts and fingerlings also were similar but the one for the eye of the former was the same pattern resolved for the eye of adults.

      There was no change in the LDH isozyme patterns of milk fish stunted for 6 mo under different salinity levels (0-5, 15-20, 32-35 ppt).
    • Article

      Lipid and fatty acid composition of milkfish (Chanos chanos Forsskal) grown in freshwater and seawater 

      IG Borlongan & LV Benitez - Aquaculture, 1992 - Elsevier
      The lipid and fatty acid compositions of the various organs of milkfish fed with an invariant diet and reared in seawater (SW) and freshwater (FW) were determined using column chromatography and gas chromatography. Phospholipid content of the gills, kidney, liver, intestines and depot fat was higher in SW than in FW while the organs from fish in FW had higher contents of neutral lipid. Fatty acid patterns of total lipids in the liver, intestines and depot fat of milkfish reared in FW and SW were similar. There were marked differences in fatty acid patterns of gills and kidney. The proportions of saturated to unsaturated fatty acids in gills and kidney were lower in SW than in FW. Likewise, the ratio of n-3 to n-6 fatty acids and total polyunsaturated fatty acids (PUFAs) of gills and kidney were higher in SW than in FW. The fatty acid patterns of the phospholipid fractions showed that SW-reared milkfish have higher total PUFAs, especially of the n-3 fatty acids, than the FW-reared milkfish not only in gills and kidney but in all organs examined. The differences in lipid and fatty acid composition reflect a physiological response to the salinity in which milkfish were reared.
    • Conference paper

      Lipid composition of milkfish grown in ponds by traditional aquaculture 

      LV Benitez & IR Gorriceta - In CY Cho, CB Cowey & T Watanabe (Eds.), Finfish Nutrition in Asia : Methodological Approaches to Research and Development, 1985 - International Development Research Centre
      Milkfish is one of the most important food fish in the Southeast Asia. It is widely cultured in Indonesia, the Philippines, and Taiwan(Chen 1976). In the Philippines, about 90% of the total aquaculture production comes from milkfish culture (BFAR 1976). Traditional aquaculture techniques are still favoured by many Philippine fish farmers. Tese techniques rely on cultivation of natural food bases. As suitable areas for aquaculture become a limiting factor, an increase in productivity could be brought about the use of artificial diets. Fundamental studies on nutrient requirements and metabolism are desirable to formulate artificial diets for aquaculture. Most fish are known to effeciently digest and metabolize lipids. However, there is no informationon lipid metabolism, composition, and requirement of milkfish. This study, therefore, compares the lipid composition of milkfish grown on two different natural food bases by traditional aquaculture.
    • Conference paper

      Milkfish nutrition 

      LV Benitez - In JV Juario, RP Ferraris & LV Benitez (Eds.), Advances in milkfish biology and culture: Proceedings of the Second International Milkfish Aquaculture Conference, 4-8 October 1983, Iloilo City, Philippines, 1984 - Published by Island Pub. House in association with the Aquaculture Dept., Southeast Asian Fisheries Development Center and the International Development Research Centre
      This paper reviews major contributions in the field of milkfish (Chanos chanos ) nutrition since the First International Milkfish Aquaculture Conference in 1976. Substantial progress has been made toward understanding the digestion, foods, and feeding behavior of milkfish, which in its natural habitat apparently feeds on planktonic microorganisms and is most frequently designated as a microphagons planktivore. Vision seems to be the most important sensory mechanism for feeding in fry as well as in juvenilles and larger milkfish. There is very scant information on nutrient requirements and other important aspects of milkfish nutrition. A preliminary study on protein requirement showed that a dietary level of 40% protein was required by fry. Other studies showed that fry responded positively and were easily trained to accept artificial diets. The "deep water method" of growing milkfish practised in Taiwan demonstrated that, with the use of formulated diets, productivity in milkfish aquaculture could be increased three-fold over traditional culture methods, which rely on natural food bases.
    • Conference paper

      Milkfish nutrition: a review 

      LV Benitez - In RD Fortes, LC Darvin & DL de Guzman (Eds.), Fish and crustacean feeds and nutrition : Proceedings of the seminar-workshop on fish and crustacean feeds and nutrition held on 25-26 February 1985 at UPV, Iloilo City, 1989 - Philippine Council for Aquatic and Marine Research and Development
      This paper reviews recent work on milkfish nutrition. Substantial progress had been made towards understanding the digestive physiology of milkfish. Major enzaymes envolved in the digestions of carbohydrates, protein and lipids had been detected in the pyloric caece, intestines and pancreas of milkfish. The most active carbohydrates were involved in the hydrolysis of α - glocosidic bonds. Intestinal amylase activity consistently reached the peak at about noon when milkfish gut was full. This confirms that milkfish is s daytime feeder. No cellulase activity was detected in any region orf the digertive treat although the fish relies heavily algae and other plant source for food.

      Trypsin, chymotrypsin and general proteases were also detected in milkfish digestive tract. A powerful milkfish trypsin inhabitor was detected in the filementous algae, Chaetomorpha brachygona which is predominant species in lumot. Lipass in the pancreas and intestines had two pH optima, suggesting a physiologic versatility for lipid digestion in milkfish.

      There is a limit information on the nutrient requirement of milkfish. Most studies showed that milkfish fry has a dietary requirement of 40% protein, and 7-10 lipid. Studies on the protein-energy requirement of fingerlings suggested that 30-40% protein, 10% fat and 25% carbohydrates are required. Subsequent studies showed an optimum protein energy to total metabolizable energy ratio of 44.4%. Amino acid test diets for milkfish had been formulated to contain white fish meal, gelatin and approprate amino acid mix.
    • Article

      Quantitative lysine requirement of milkfish (Chanos chanos) juveniles 

      IG Borlongan & LV Benitez - Aquaculture, 1990 - Elsevier
      A feeding experiment was conducted to determine the quantitative dietary requirement of milkfish juveniles for lysine. Milkfish (Chanoschanos Forsskal) of mean weight 5.92±0.14 g were fed diets containing 7.0, 11.0, 15.0, 19.0, 23.0 and 27.0 g lysine/kg dry diet for 12 weeks. The amino acid test diets contained white fish meal and zein supplemented with crystalline amino acids to provide an amino acid profile similar to milkfish proteins except for lysine. Each of the six diets was fed to four replicate groups of 25 fish in a completely randomized design and at a feeding rate of 5% of the fish body weight per day. On the basis of the growth response, lysinerequirement of juvenile milkfish was found to be 20 g/kg diet. This value corresponds to 4.0% when expressed as a percentage of the dietary protein. Survival (94–97%) was consistently high in all treatments. Except for loss of appetite resulting in low food intake and depressed growth, no nutritional deficiency signs were observed in fish given the lysine-deficient diets.
    • Article

      Requirement for tryptophan by milkfish (Chanos chanos Forsskal) juveniles 

      RM Coloso, LB Tiro & LV Benitez - Fish Physiology and Biochemistry, 1992 - Springer Verlag
      Groups of milkfish juveniles (mean initial weight 7.7 g) were fed semipurified diets containing 0.9, 1.4, 2.1, 3.1, 4.1 and 6.1 g tryptophan/kg dry diet for 12 weeks. The mean crude protein content of the diets (containing white fishmeal, gelatin and free amino acid mixture to simulate the pattern of hydrolysed milkfish protein) was 49%. On the basis of the growth response, the tryptophan requirement of milkfish juveniles was estimated to be 3.1 g/kg diet. Fish fed low levels of tryptophan exhibited low weight gains and poor feed conversion ratios. Survival (92–100%) was consistently high in all treatments. Fish fed diets containing tryptophan levels greater than 3.1 g/kg had slightly lower survival rates. The activity of hepatic tryptophan pyrrolase showed no significant differences with increasing dietary tryptophan levels. No nutritional deficiency signs were observed other than the depression in growth rates in fish given the tryptophan deficient diets.
    • Article

      Studies on the carbohydrases in the digestive tract of the milkfish Chanos chanos 

      YN Chiu & LV Benitez - Marine Biology, 1981 - Springer Verlag
      Crude extracts from various regions of the digestive tract of pond grown milkfish were tested forttheir ability to catalyze the hydrolysis of various carbohydrates. The most active carbohydrases were those involved in the hydrolysis of agr-glucosidic bonds. Maltose, trehalose, dextrin, starch and glycogen were rapidly hydrolyzed in the presence of crude extracts from the intestines and the pyloric caeca. High amylase activity was observed in extracts from the intestines, pancreas, pyloric caeca and liver. The intestinal amylase had optimum activity at pH 6.2 and at a temperature of about 50°C. It was active at a chloride concentration of 10 to 40 ppt. The amylase activity in the intestines consistently peaked daily at about noon when the milkfish gut was full. In contrast, enzyme activity was significantly lower at 0030 hrs when the gut was empty. These results are consistent with earlier observations that the milkfish is a daytime feeder and suggest further that intestinal amylase secretion is in phase with the feeding activity of the milkfish. Although the fishes used in this study fed mostly on the naturally occurring algae in the ponds, no cellulase activity was detected in any region of the digestive tract. Less active carbohydrases that were detected include a beta-glucosidase and beta-galactosidase, both of which were of limited substrate specificity.
    • Article

      Studies on the digestive proteases of the milkfish Chanos chanos 

      LV Benitez & LB Tiro Jr. - Marine Biology, 1982 - Springer
      The protease activity of crude extracts from various organs of the digestive tract of two groups of milkfish was determined. One group (Sample A) derived their food from ponds that had predominantly unicellular algae while the other group (Sample B) were reared on ponds dominated by the filamentous green algae Chaetomorpha brachygona . In general, crude extracts from Sample A fish had a higher protease activity than Sample B fish. In both samples, high protease activity was observed in crude extracts from the pyloric caeca, intestines and pancreas. Chymotryptic activity was observed in crude extracts of pancreas, intestines and pyloric caeca of both fish samples. Tryptic activity was, however, observed only in fish grown on unicellular algae. Experimental evidence suggests that a powerful trypsin inhibitor in Chaetomorpha brachygona may account for the absence of tryptic activity in all crude extracts of Sample B fish. The presence of this inhibitor may also explain the widely observed poor growth rate of milkfish reared on this natural food.