Ana Lúcia Salaro

Condicionamento alimentar de alevinos de trairão (Hoplias cf. lacerdae)

An evaluation of training strategies in fingerlings of trairao was carried out. The experimental design included six 20 L tanks with artificial aeration, controlled temperature variation (27±0.5oC), and continuously darkened (0L:24D), except during daily management. Fingerlings with 2.9±0.2 cm long were kept at a 4 specimens/L and they were allotted to the following treatments: the first was direct offering of artificial diet and the second involved training strategies by means of the replacement of semi humid food for dry food. At the end of the experiment, average survival rates were 27.5 and 96.66% for the first and second treatments, respectively, demonstrating that feeding conditioning is an efficient management in production and survival of Hoplias cf. lacerdae fingerlings.

Diferentes densidades de estocagem na produção de alevinos de trairão (Hoplias cf. lacerdae)

Alevinos de trairao (Hoplias cf. lacerdae), com peso e comprimento total medios de 12,52 g e 10,5 cm, respectivamente, previamente condicionados ao aceite de dietas artificiais, foram distribuidos em seis tanques de alvenaria (5m²) nas densidades de: 1 e 4 alevinos/m². Os peixes dos diferentes tratamentos foram alimentados ad libitum nos horarios de 8 e 14 h com racao comercial extrusada contendo 42% de proteina bruta. A cada trinta dias realizou-se a troca do volume total de agua de todos os tanques. Ao final do experimento (120 dias) foi avaliado o desempenho produtivo dos peixes, por meio da taxa de sobrevivencia, conversao alimentar, ganhos em comprimento e em peso diario. Foram observadas taxas medias de sobrevivencia de 86,7 e 96,7% para as densidades de 1 e 4 peixes/m², respectivamente. A conversao alimentar foi de 1,6 e 1,2; o ganho em peso diario e em comprimento de 0,70 e 0,38 g e 8,01 e 7,27 cm, respectivamente. Estes valores nao diferiram entre si. Com os resultados obtidos pode-se concluir que as densidades de estocagem de 1 e 4 peixes/m² podem ser utilizadas no cultivo de alevinos de trairao sem que haja comprometimento no seu desempenho produtivo.

Desenvolvimento de alevinos de trairão alimentados com dietas artificiais em tanques de cultivo

This experiment was done at Hydrobiology and Pisciculture Section of the Dept of Animal Biology of the University Federal de Vicosa. Fingerlings of Hoplias lacerdae previously trained to accept artificial feed were selected for length and stocked in three tanks with 5000 liters each, until a biomass total of 36.72 g was reached. After 30 days the fishes were selected again for length and distribute into the same tanks, with density of 5 fishes/m², and left again for an additional 30 days. Every day at 8 a.m. and 2 p.m. the fishes were fed with comercial feed (42% CP). At the end of each 30-day period the following parameters were determined: survival rate, biomass gain, standard length and feed: gain ratio. The average rates of survival were 99.23 and 89.33%, feeding ratio were 1.3:1.0 and 1.05:1.0 and biomass gain were 92.19 and 133.08 g. It was frequently observed that the standard length was heterogenoeus in both periods and in all tanks, suggesting the need of period re-evaluations of size when dialing with carnivorous fishes. These data show that Hoplias lacerdae has great potential to be cultivated with artificial feed, after been previously trained to accept comercial food.

Diferentes densidades de estocagem na produção de alevinos de trairão

Alevinos de trairao (Hoplias cf. lacerdae), com peso e comprimento total medios de 12,52 g e 10,5 cm, respectivamente, previamente condicionados ao aceite de dietas artificiais, foram distribuidos em seis tanques de alvenaria (5m²) nas densidades de: 1 e 4 alevinos/m². Os peixes dos diferentes tratamentos foram alimentados ad libitum nos horarios de 8 e 14 h com racao comercial extrusada contendo 42% de proteina bruta. A cada trinta dias realizou-se a troca do volume total de agua de todos os tanques. Ao final do experimento (120 dias) foi avaliado o desempenho produtivo dos peixes, por meio da taxa de sobrevivencia, conversao alimentar, ganhos em comprimento e em peso diario. Foram observadas taxas medias de sobrevivencia de 86,7 e 96,7% para as densidades de 1 e 4 peixes/m², respectivamente. A conversao alimentar foi de 1,6 e 1,2; o ganho em peso diario e em comprimento de 0,70 e 0,38 g e 8,01 e 7,27 cm, respectivamente. Estes valores nao diferiram entre si. Com os resultados obtidos pode-se concluir que as densidades de estocagem de 1 e 4 peixes/m² podem ser utilizadas no cultivo de alevinos de trairao sem que haja comprometimento no seu desempenho produtivo.

Desempenho e espermatogênese de alevinos de tilápia alimentados com farelo ou farinha de semente de algodão

RESUMO - Este trabalho avaliou o efeito do farelo e da farinha de semente de algodao no ganho depeso e na atividade testicular de alevinos de tilapia-do-nilo ( Oreochromis niloticus ). Cento e cinquen-ta alevinos com peso medio inicial de 1,26 g foram mantidos em aquarios de 45 L, com renovacaocontinua d’agua, e alimentados por 120 dias com dietas isoproteicas (28% PB) e isocaloricas(4.030 kcal EB/kg de racao) contendo 0%, 2%, 4% e 6% de semente de algodao descorticada e moida,e 24% de farelo de algodao. Foi observado que os niveis avaliados interferem na atividade testicular,diminuindo a espermatogenese, embora nao tenham comprometido de forma significativa o ganho depeso dos alevinos.Termos para indexacao: ganho de peso, atividade testicular, gossipol, fator antinutricional, sistemareprodutor, Oreochromis niloticus.PERFORMANCE AND SPERMATOGENESIS OF NILE TILAPIA FINGERLINGSFED WITH COTTONSEED MEAL OR COTTONSEED FLOURABSTRACT - This experiment evaluated the effect of cottonseed meal or cottonseed flour on growthand testis activity of Nile tilapia fingerlings (Oreochromis niloticus). One hundred and fiftyfingerlings with mean initial weight of 1.26 g were maintained in 45 L aquaria with continuous watersupply. Fish were fed in isoproteic (28% CP) and isoenergetic (4,030 kcal CE/kg of ration) dietsduring 120 days. The experimental diets comprised a control diet, without cottonseed flour or meal,and diets containing 2%, 4% and 6% of cottonseed flour and 24% cottonseed meal. The results indi-cated that the use of seed flour or meal should be limited since at the tested levels they interferred withtestis activity although they had not adversely affected the weight gain of fingerlings.Index terms: weight gain, testis activity, gossypol, antinutritional factor, reproductive system,Oreochromis niloticus.

Efeito da inclusão do farelo e da farinha de semente de algodão em rações para reprodutores de tilápia do Nilo (Oreochromis niloticus)

This experiment was conducted to evaluate the effect of cottonseed meal and cotton seed flour on the reproductive behavior and on the testis activity of Nile tilapia broodstock. Twenty-five fishes were fed diets containing 0, 2, 4 and 6% ground cottonseed flour and 24% cottonseed meal (CSM). The reproductive behavior of the fishes was daily observed and the nest construction, courtship and spawning were evaluated. At 90 days, the males gonads were microscopically evaluated. The control group (soybean meal) showed higher number of spawning. The fishes fed diets with cottonseed flour or cottonseed meal, despite of had not presented the same number of spawning, showed nest construction and courtship. The histology analysis of the testis indicated that the addition of 24% of cottonseed meal or 2% or higher of cottonseed flour affected the testis activity. The gossypol present in the cottonseed flour or cottonseed meal had a negative effect on the gonads of these animals.

A complete enzymatic capacity for long-chain polyunsaturated fatty acid biosynthesis is present in the Amazonian teleost tambaqui, Colossoma macropomum

In vertebrates, the essential fatty acids (FA) that satisfy the dietary requirements for a given species depend upon its desaturation and elongation capabilities to convert the C18 polyunsaturated fatty acids (PUFA), namely linoleic acid (LA, 18:2n-6) and α-linolenic acid (ALA, 18:3n-3), into the biologically active long-chain (C20-24) polyunsaturated fatty acids (LC-PUFA), including arachidonic acid (ARA, 20:4n-6), eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3). Recent studies have established that tambaqui (Colossoma macropomum), an important aquaculture-produced species in Brazil, is a herbivorous fish that can fulfil its essential FA requirements with dietary provision C18 PUFA LA and ALA, although the molecular mechanisms underpinning such ability remained unclear. The present study aimed at cloning and functionally characterizing genes encoding key desaturase and elongase enzymes, namely fads2, elovl5 and elovl2, involved in the LC-PUFA biosynthetic pathways in tambaqui. First, a fads2-like desaturase was isolated from tambaqui. When expressed in yeast, the tambaqui Fads2 showed Δ6, Δ5 and Δ8 desaturase capacities within the same enzyme, enabling all desaturation reactions required for ARA, EPA and DHA biosynthesis. Moreover, tambaqui possesses two elongases that are bona fide orthologs of elovl5 and elovl2. Their functional characterization confirmed that they can operate towards a variety of PUFA substrates with chain lengths ranging from 18 to 22 carbons. Overall our results provide compelling evidence that demonstrates that all the desaturase and elongase activities required to convert LA and ALA into ARA, EPA and DHA are present in tambaqui within the three genes studied herein, i.e. fads2, elovl5 and elovl2.