Características morfométricas, rendimento e composição do filé de tilápia do Nilo... Recebido para publicação 13/07/05 Aprovado em 28/11/05 ARTIGOS / ARTICLES ZOOTECNIA Características morfométricas, rendimento e composição do filé de tilápia do Nilo, Oreochromis niloticus, da linhagem tailandesa, local e do cruzamento de ambas Morphometrics, fillet yield and fillet composition in Nile tilapia,

Isolamento de Streptococcus spp de tilápias do nilo (Oreochromis niloticus) e qualidade da água de tanques... 35Semina: Ciências Agrárias, Londrina, v. 24, n. 1, p. 35-42, jan./jun. 2003 Isolamento de Streptococcus spp de tilápias do nilo (Oreochromis AbstractThis study evaluated 12 intensive breed of Nile tilapia (Oreochromis niloticus) in four properties localized in the north of Parana State, Brazil. In the period of 13 months, 71 fishes were collected and analyzed of hapas nets that presenting morbidity and mortality of tilapias. Parallel, to evaluate the quality of the water of these hapas nets, there was measured the temperature, dissolved oxygen, pH, alkalinity, nitrite and ammonia. Of the 71 fishes, were collected 220 biological samples. 17 (23.94%) fishes were positive for Streptococcus spp. Of the 53 biological samples from 17 fishes, in 24 (45.28%) were isolated streptococci. Londrina, v. 24, n. 1, p. 35-42, jan./jun. 2003 36The main clinical signs and macroscopic lesions in the fishes with isolation of Streptococcus spp. were hepatomegaly and splenomegaly, skin lesion and base of the fins and exoftalmia with cornea opacity. The higher incidence of infections caused by streptococci happened in the months with higher temperatures, mainly in the transition period winter for spring. The values of dissolved oxygen, pH, alkalinity, nitrite and ammonia of the water were normal.

Two hundred and forty 45-day-old fingerlings of Nile tilapia (Oreochromis niloticus), sexually reverted with an initial average weight of 1.25 ± 0.14 g, distributed in a totally casualized delineation, during 330 days. The effect of the substitution of 10%, 20% and 30% of the ration by distillery yeast (Saccharomiyces cerevisae) in balanced experimental rations on the development in the breeding of tilapias did not show a harmful effect up to the maximum tested level of 30%, showing that the choice of the yeast in the ration for these fishes depends on the availability and occasional cost. The yeast provides fish with good resistance to unfavorable environmental conditions, which could be verified since there were no statistical differences among the treatments with different levels of yeast and the witness. The long growth rate in terms of length and weight can be attributed to the little available space for each specimen, not obeying the limit of populational density, as well as reduction of food ingestion, which coincide with the winter season, above of the absence of natural feeding.Key words: yeast, Oreochromis niloticus, ration, tilapia. RESUMOCrescimento das tilápias do Nilo Oreochromis niloticus alimentadas com diferentes níveis de levedura alcooleiraForam utilizados 240 alevinos de tilápia do Nilo (Oreochromis niloticus), com 45 dias, sexualmente revertidos com peso médio inicial de 1,25 ± 0,14 g, distribuídos em um delineamento inteiramente casualizado, durante 330 dias. O desempenho da substituição de 10%, 20% e 30% da ração por levedura de destilaria (Saccharomyces cerevisiae) em rações experimentais balanceadas sobre o desenvolvimento na criação de tilápia do Nilo não mostrou efeito prejudicial até o nível máximo testado de 30%, indicando que a escolha do nível de levedura na ração para estes peixes depende de sua disponibilidade e custo ocasional. A levedura proporcionou aos peixes boa resistência às condições ambientais desfavoráveis, o que foi constatado pela não diferença estatística entre os tratamentos com diferentes níveis de levedura e o controle. O baixo índice de crescimento em comprimento e peso pode ser atribuído ao pouco espaço disponível por exemplar, não obedecendo o limite de densidade populacional, e uma diminuição da ingestão de alimentos coincidindo com o período de inverno, além da ausência de alimentação natural.Palavras-chave: levedura, Oreochromis niloticus, ração, tilápias.Rev. Brasil. Biol., 60(1): 113-121 114 MEDRI, V., PEREIRA, G. V. and LEONHARDT, J. H.

ABSTRACT. Tissue growth in most fishes occurs by muscular hyperplasia and hypertrophy, which are influenced by different regulatory factors, such as myostatin. The current study evaluated the influence of cultivation in hapas and earthen ponds on the diameter of white muscle fibers and on the myostatin (MSTN-1) gene in GIFT and Supreme varieties of tilapia. Fish of both varieties were reared for 204 days and then divided into four developmental stages. White muscle samples, corresponding to 100 fibers per slide, were collected from the middle region of fish of each variety and cultivation system, and were measured and divided into two classes representing hyperplasia and hypertrophy. Samples were subjected to real-time PCR to analyze gene expression. Hyperplasia decreased during the developing stages, coupled with increased hypertrophy. There was a higher rate of hypertrophy in fish raised in earthen ponds when compared to those raised in hapas, during juvenile and developing phases, and greater hypertrophic growth was observed in GIFT specimens when compared to Supreme specimens in earthen ponds. Since increased MSTN-1 gene expression was observed in GIFT specimens during the developing phase in pond cultivations, and in Supreme tilapia in hapas, MSTN-1 expression is related to greater hypertrophy. These results demonstrate the capacity for increased muscle growth in earthen pond cultivation in which the GIFT variety developed best. How the environment affects the growth of different tilapia varieties may be employed to optimize culture management and genetic improvement programs. Further investigations should aim to describe mechanisms affecting muscle growth and development.

ResumoOs ácidos algínicos são extraídos de algas marinhas e quando utilizados na dieta dos peixes podem induzir respostas imunomoduladoras e imunoestimulantes. AbstractThe alginic acid is extracted from seaweed and when used in fish ration may induce immunomodulatory and immunostimulants responses. This study aimed to evaluate the effect of alginic acid incorporated in the ration on performance and handling of juvenile Nile tilapia, Oreochromis niloticus. The first phase of the experiment occurred in two excavated ponds earth. 57,000 juveniles were used for Nile tilapia, local strains with the average weight of 14 grams. The juvenile Nile tilapia received the experimental diet treated with ergosan at a dose of 1% of the diet. The survival rate of fish and feed conversion in the experimental Nile tilapia was higher than the control Nile tilapia. In the second stage 54,126 juveniles with average weight 40.63 grams, were used. These fish were transferred to 16 fish cages. There were no significant differences in mortality rate between treatments. The highest mortality occurred between the third and seventh days after the handling. The data confirm that the transfer of juvenile Nile tilapia in the ponds to fish cages is a strong stressor.