Source: https://repository.seafdec.org.ph/browse?type=author&authority=09d9767a-20a2-483f-9fef-a749d8b5e2d3
Timestamp: 2019-04-23 06:30:51+00:00

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Browsing by Author "Lavilla-Pitogo, Celia R."
A survey of aflatoxin B1 (AFLB1) levels in commonly used commercial shrimp finisher feeds in the Philippines showed a various range of values from not detected to 120 μg kg−1 using high-performance thin-layer chromatography. Six experimental diets were prepared to contain various levels of AFLB1 based on survey results to determine the effects of such contamination in pre-adult shrimp Penaeus monodon (17.5 ± 0.6 g). Results showed that shrimps fed diets containing AFLB1 greater than or equal to 73.8 μg kg−1 gave comparatively poor growth rate and higher susceptibility to shell diseases. No AFLB1 residues were detected in sampled whole shrimp tissues after 62 days of exposure to AFLB1 containing diets indicating a low potential for transmission of the toxin from edible shrimp tissues to consumers. Histopathological alterations in the hepatopancreas of shrimp chronically exposed to AFLB, were observed in all samples. The degree of alterations correlated with the level of AFLB1. Based on growth performance, pre-adult shrimps can tolerate AFLB1 levels of up to 52.3 μg kg−1 in the feeds although histopathological changes were already evident in the tissues of shrimps given diets with 26.5 μg kg−1 AFLB1.
A condition of the tetrasporophyte stage Gracilaria spp., characterized by white to pinkish discoloration and gradual disintegration of the thallus, has been observed in tank-held stocks. Microscopic observation revealed no fungal or protozoan parasites. Appropriate dilutions of homogenates plated on nutrient agar and bromthymol blue teepol agar showed the presence of bacteria, all of which were agar-digesting, at the rate of 1.42 × 107 cells per g of affected thalli. Colonies on bromthymol blue teepol agar were round and yellow, while those on nutrient agar appeared creamy and round with entire edges, and were rapid agar digesters. The bacteria were Gram negative, fermentative and motile rods. Based on biochemical characteristics, the isolates were classified as belonging to the genus Vibrio. Microscopic observations of thalli cross-sections showed erosion of the pericarp, thus revealing the cortical and the medullary cells. Scanning electron microscopy revealed rod-shaped bacteria, including dividing cells, in affected tissues. Antibiotic sensitivity tests indicated that the bacteria were sensitive to Polymyxin B, nalidixic acid, nitrofurazone and oxytetracycline.
Shrimp monoculture systems have been beset with devastating losses due to infectious diseases and environmental deterioration. On a global scale, efforts to make shrimp culture a sustainable industry are warranted because of the high value and demand of shrimp. A Code of Practice for Sustainable Shrimp Farming prepared by the Global Aquaculture Alliance has been adopted by various shrimp producing countries addressing issues like mangroves, site evaluation, design and construction, feeds and feed use, shrimp health management, therapeutic agents and other chemicals, general pond operations, effluents and solid wastes, and community and employee relations.
Shrimp hatcheries have benefited from technological advances in practically every aspect of rearing including implements to control water quality, eliminate pathogens, and improved nutrition through innovative artificial feeds and supplements. These technologies have made postlarval production very successful, although in many cases, high survival cannot exactly be equated with good quality. Thus a closer look at hatcheries is essential to ensure that rearing protocols match the conditions to which postlarvae will be exposed to upon stocking in ponds. Compiled information on the estimated number of hatcheries and forms in major shrimp growing areas in Asia show a relatively smaller number of small independent hatcheries compared to farms, which demonstrates that effective disease control programmes need to emanate from hatcheries. Presently, three programmes for the hatchery need serious attention. These are (a) the continued implementation of fry analysis procedures, not only as a marketing tool, but so as to exclude pathogenic organisms from ponds, (b) adherence to agreed-upon codes of practice and conformity with accepted guidelines on live transfers to minimise disease spread, and (c) development of a reliable source of domesticated broodstock and incorporating specific pathogen free (SPF) and specific pathogen resistant (SPR) stocks in these programmes to minimise or eliminate dependence on wild broodstock.
One of the main constraints is the lack of cost-effective and efficient methods to prevent and correct environmental deterioration, and to maintain biosecurity. In addition to providing primary health care, disease control strategies should be a combination of pathogen exclusion and environmental management: the former for primary pathogens such as viruses and the latter for secondary pathogens like bacteria, whose pathogenicity is heightened by environmental degradation and lowered resistance of shrimps. Shrimp forming should start employing systems to manage and lessen waste and the outflow of organic pollutants that could contribute to self-pollution or deterioration of the quality of receiving waters. These include improved feeds and conversion ratios to make feed utilisation more economical and efficient, implementation of recirculating or zero discharge technology, improving the efficiency of aeration systems, improvement of pond siting, understanding of the pond ecosystem and the role of microbes in the environment. In addition to implementing disease control measures and ensuring product quality in various industry sectors, approaches need to be welded together for a holistic approach to health management.
Four practical diets were formulated to contain 0.05%, of the following antioxidants: butylated hydroxytoluene (BHT), butylated hydroxy anisole (BHA), propyl gallate (PG) or ethoxyquin (ETHQ). A fifth diet, with no added antioxidant, served as a control. The diets were fed to Penaeus monodon juveniles to determine the effects of antioxidants on feed quality and growth of the animals. The results showed no significant difference (P> 0.05) between the control and the feeds containing antioxidants in 2-thiobarbituric acid values after 0, 30, 60, and 90 days storage, respectively. There was a significant difference by the 120th day of storage, but no signs of physical deterioration were observed in any of the diets. The highest weight gains (704% and 742%) were obtained with shrimps fed diets with BHT and BHA, respectively, as antioxidants. Hepatopancreatic lesion formation was evident with shrimps fed diets containing antioxidants but not with shrimps fed a diet without antioxidant. Shrimps fed with BHT-added feed showed fewest lesions in the hepatopancreas. Although all shrimp samples given feed containing PG and ETHQ showed lesions, these were patchy in nature and did not affect the growth rates of the animals.
The aim of the present study was to use three PCR-based techniques for the analysis of genetic variability among Vibrio parahaemolyticus strains isolated from the Philippines. Seventeen strains of V. parahaemolyticus isolated from shrimps and from the environments where these shrimps are being cultivated were analyzed by RAPD, ERIC and REP-PCR. Antimicrobial susceptibility of these strains to selected compounds was investigated using broth microdilution method. Results of this work and analysis of similarity among strains using Dice coefficient and unweighted average pair group method have demonstrated genetic variability within the V. parahaemolyticus strains. The RAPD, ERIC and REP-PCR were found to be suitable typing methods for V. parahaemolyticus. They have good discriminative ability and can be used as rapid means of comparing these strains for epidemiological investigation. However, the REP-PCR analysis yielded a relatively small number of products suggesting that the REP sequences may not be widely distributed in the V. parahaemolyticus genome. Results of antimicrobial susceptibility revealed that resistance among the strains was rare. In conclusion, RAPD, ERIC and REP-PCR techniques are useful methods for molecular typing of V. parahaemolyticus strains. To our knowledge this is the first study of this kind carried out on V. parahaemolyticus strains isolated from the Philippines.
Vibrio sp., was consistently isolated from grouper, Epinephelus suillus, with bacterial infection. Fingerlings, which were challenged with the bacterium by injection, were highly susceptible. Immersion challenge resulted in 100% mortality within 48 hrs in fish subjected to combination of injury and exposure to the bacterium. Mortality in uninjured fish was observed in the long bath subgroup, but not in the short bath subgroup. These results are correlated with the present practices in the grouper fingerling industry in the Philippines.
Shrimp harvests from intensive aquaculture have recently declined in areas which have been productive for many years. Because the most convenient, although not necessarily factual, explanation for these crop failures has been the occurrence of infectious diseases, there is a need to consider shrimp health from a holistic point of view. The classical method used for the study of shrimp disease dealt mainly with identification of the causative organism and the search for methods of prevention and control through chemotherapy. The adverse affects resulting from the use of chemicals in aquaculture have led to a clamor for alternative approaches to disease management. For effective shrimp health maintenance and surveillance, the following components need consideration: development of rapid and sensitive methods for pathogen detection; establishment of shrimp tissue cultures for virology; immunological studies, toxicological studies and drug efficacy evaluation. The epidemiological approach to disease management should augment the classic approach to shrimp pathology, and this calls for multidisciplinary cooperation.
With attractive prawn export prices and the availability of hatchery fry and commercial feeds, Philippine aquaculture has experienced a shift from milkfish to prawn Penaeus monodon and an intensification from traditional and extensive prawn culture to higher stocking densities. This paper features the results of a survey of intensive prawn farms (n = 21) in Western Visayas and Northern Mindanao conducted in 1990. Average farm size, production, feeding and water management are described. To solve the self-pollution characteristic of intensive ponds, the farms utilized some 40 chemical and biological products; at least another 35 were available in the market at the time of the study. These include therapeutants and disinfectants, soil conditioners, bacteria-enzyme preparations, algicides and piscicides, plankton growth promoters, and feed additives. The possible ecological effects of effluents drained into adjacent marine waters are discussed; some recommendations are given.

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