ABSTRACT The objective with this study was to evaluate the liver histology and hematological parameters of female Rhamdia quelen fed diets supplemented with different oils: 5% marine fish oil, 5% refined palm oil, 5% soybean oil, and a combination of the three. The lipid vacuolization (steatosis) in the liver was analyzed according to a score of vacuolization when: 0 = absence, 1 = reduced, 2 = intermediate, and 3 = intense. At the end of the experiment, females (n = 10) were selected from each treatment (two per cage), and the blood was collected for erythrocyte and biochemical analysis. Lower vacuolization indices in the liver were observed at the beginning of the experiment. However, with time, the presence of vacuoles was more evident but presented similar morphology among all treatments. The blood parameters were also not influenced by the different diets, except for glucose levels, which was higher in the treatment with the mixture of oils. The absence of differences regarding liver morphology (steatosis) and hematological parameters indicates that the replacement of fish oil by vegetable oils could be performed without damage to the health of R. quelen females.

ABSTRACT The effects of a diet supplemented with 5% marine fish oil, 5% refined palm oil, 5% soybean oil, and a combination of the three on reproductive parameters of females Rhamdia quelen was investigated. Spawning was artificially induced to evaluate rates of fertilization, hatching and larvae normality. Fatty acid profiles of the diets, ovaries and oocytes were determined. A higher spawning rate (%) was observed for diets containing fish oil (78.65 ± 3.60) and palm oil (77.15 ± 3.97), followed by oil mix (65.46 ± 4.57). The diet containing soybean oil was associated with significantly lower fertilization (60.14 ± 5.66; P < 0.05) than the palm and fish oil diets. Lower fertilization may be explained by a high level of n-6 fatty acids in the diet, which possibly accelerate the oocyte maturation. Satisfactory fecundity (P > 0.05) were observed for all tested diets, whit 289.77 ± 23.90 (palm oil) until 323.31 ± 38.45 oocytes g-1 body weight (fish oil). The treatments were not shown to influence oocyte size, larval size or rate of larva deformity. Oocyte fatty acid composition was like that of gonads. Docosahexaenoic (DHA; C22:6 n-3) fatty acid was preferentially deposited in ovaries and oocytes. Ratios of n3/n6, DHA/EPA, EPA/ARA, did not affect the reproductive performance of females. Therefore, regarding female reproductive performance, the vegetable lipid sources tested are suitable for being used in R. quelen diet, and palm oil, in particular, is considered an excellent alternative to fish oil.

Resumo: O objetivo deste trabalho foi avaliar o uso de glicerol bruto como fonte de energia em substituição ao milho, em dietas para tilápia-do-nilo (Oreochromis niloticus) em fase de engorda. Duzentas tilápias-do-nilo (190±4,5 g) foram distribuídas em 20 tanques, em delineamento inteiramente casualizado. Os tratamentos consistiram de 0, 60, 120, 180 e 240 g kg-1 de glicerol bruto, em substituição ao milho na dieta, para manter a energia digestível constante. Foram avaliados o desempenho produtivo dos peixes e a composição química dos filés. Também foram realizadas análises histológicas do hepatopâncreas, do intestino e da gordura visceral. O glicerol bruto não teve efeito sobre os parâmetros de desempenho; no entanto, causou redução quadrática da gordura visceral. Houve aumento da umidade e redução do extrato etéreo dos filés. Verificou-se efeito linear dos níveis de glicose no sangue dos peixes alimentados com a dieta sem glicerol, com pico aos 90 min. Não houve diferenças quanto às medidas referentes à altura das vilosidades intestinais e à área dos hepatócitos. O glicerol bruto pode ser utilizado em substituição ao milho, em dietas para tilápias-do-nilo na fase de engorda, pois não afeta negativamente o metabolismo, o desempenho produtivo ou a sobrevivência dos peixes.

Abstract: The objective of this work was to evaluate the use of crude glycerol as an energy source to replace corn, in diets for Nile tilapia (Oreochromis niloticus) in the fattening stage. Two hundred Nile tilapia (190±4.5 g) were distributed in 20 tanks, in a completely randomized design. The treatments consisted of crude glycerol at 0, 60, 120, 180, and 240 g kg-1, to replace the dietary levels of corn, in order to maintain a constant digestible energy. Fish productive performance and the chemical composition of the fillet were evaluated. Histological analyses of the hepatopancreas, intestine, and visceral fat were also carried out. Crude glycerol had no effect on the performance parameters; however, it caused a quadratic reduction of visceral fat. There was an increase in the moisture and a decrease in the ether extract of the fillet. A linear effect on the blood glucose levels was verified in fish fed the diet without glycerol, and the peak occurred at 90 min. There were no differences for measurements of intestinal villi height and hepatocyte area. Crude glycerol can replace corn in diets for Nile tilapia in the fattening stage, without adversely affecting fish metabolism, productive performance, or survival.

ABSTRACT By using informetric tools, we evaluated the contribution and impact of the open source computer-assisted sperm analysis (CASA) software on sperm studies, especially pertaining to fish. The article was cited 125 times between 2007 and 2014 in four publication types (articles, doctoral dissertations, master’s theses, and books). Among articles, the number of citations increased at rate of three citations per year and the calculated h-index was 17. Of the studies that cited Wilson-Leedy and Ingermann (2007), fish were the main group of organisms studied (61 articles); of these, 34 articles used the open source CASA, covering 23 marine or freshwater species. Studies conducted in 12 countries were published in 21 journals. Four ways of knowledge sharing were identified: by direct partnership with the system developers; by knowledge multipliers, who worked directly with the system developers; by groups that adopted the system by their own initiative; and through expansion of cooperation networks with autodidacts. In regard to specific analytical procedures, motility, curvilinear velocity, average path velocity, and straight-line velocity were the main CASA parameters used to describe sperm movements. As expected, the usage of this tool has been increasing over the years, being a reliable and versatile alternative to more costly similar platforms. However, the potential of the CASA system has not been completely explored and it is our assessment that some results produced by CASA are poorly understood or even misunderstood.

ABSTRACT This experiment was conducted in outdoor tanks to evaluate the effect of inclusion of ractopamine at increasing levels (0, 4, 8, 12, and 16 mg kg−1) as additive in Nile tilapia (Oreochromis niloticus) diet in the final grow-out period (750-920 g) during 31 days. Therefore, 400 fish were housed into 20 experimental tanks, in a completely randomized design with five treatments and four replications. Growth performance, body yield, and chemical composition of fish muscle and organs were evaluated. Fish fed diets containing up to 16 mg kg−1 of ractopamine for 31 days did not improve growth or performance parameters. However, lipid percentage of abdominal muscle was different in fish fed ractopamine, reaching the lowest level of 199.3 g kg−1 of ether extract at 8 mg kg−1 treatment. Other body chemical composition parameters did not differ between animals treated or not treated. Feeding ractopamine up to 31 days has limited effect on body composition in Nile tilapia (~900 g), without any changes in growth parameters. This is a lower metabolic response in this species when compared with mammals and other terrestrial animals.

RESUMO O DNA barcoding é uma ferramenta molecular precisa para a identificação de espécies e resoluções taxonômicas. Até recentemente, Rhamdia voulezi e Rhamdia branneri eram consideradas sinônimas de Rhamdia quelen, contudo caracteres morfológicos e citogenéticos têm apontado à validade de ambas. Devido à escassez de informações sobre a taxonomia molecular de R. voulezi e R. branneri, o objetivo do presente estudo foi testar a validade das mesmas através do método de DNA barcoding tradicional e GMYC (General Mixed Yule Coalescent), por meio da análise do gene COI em 19 espécimes do rio Iguaçu. Em ambos os métodos, três MOTUs (Unidades Taxonômicas Operacionais Moleculares) foram identificadas com base no ótimo threshold (OT = 0,77). A média inter-MOTU (NJ, K2P) entre R. branneri e R. voulezi foi 1,4%, com valores de 0% intra-MOTUs em ambas espécies. As duas espécies identificadas como R. voulezi e R. branneri apresentaram correspondência com a identificação taxonômica e morfológica dos respectivos vouchers. No que se refere a R. quelen, os resultados intra-MOTU foram superiores ao OT (2,7%), evidenciando a possibilidade de existirem diferentes MOTUs denominadas como R. quelen. Sugerimos que estudos moleculares e taxonômicos sejam empregados em R. quelen, para evitar a contaminação de espécies selvagens por hibridizações.

ABSTRACT DNA barcoding is a widely utilized molecular-based identification of species and taxonomic resolutions. Until recently, Rhamdia voulezi and Rhamdia branneri were considered species synonyms of Rhamdia quelen; however, morphological and cytogenetic analyses have suggested the validity of distinct species. Due to the absence of molecular taxonomy of R. voulezi and R. branneri, the objective of this study was to test its validity through traditional DNA barcoding and the GMYC (General Mixed Yule Coalescent) COI-based analyses in 19 specimens from the Iguaçu River Basin. In both methodologies, three MOTUs (Molecular Operational Taxonomic Units) were identified based on the estimated optimum threshold (OT = 0.77). The average inter-MOTU distance (NJ, K2P) between R. branneri and R. voulezi was 1.4%, and 0% intra-MOTU distance in both species. The two species identified as R. branneri and R. voulezi showed correspondence with taxonomic and morphological identifications. With regard to R. quelen, the average intra-MOTU distance was greater than OT (2.7%), indicating that this species can be formed by different MOTUs. We suggest that molecular and taxonomic studies should be employed concurrently in R. quelen, to prevent contamination of wild species by hybridizations.

RESUMO: O objetivo deste trabalho foi avaliar o efeito da utilização do óleo essencial de alho (Allium sativum) sobre as taxas de fertilização dos ovos e eclosão e normalidade de larvas de jundiá cinza, Rhamdia quelen, incubados artificialmente. O experimento foi realizado utilizando delineamento experimental inteiramente casualizado com quatro tratamentos e cinco repetições. Os tratamentos consistiram na introdução de óleo essencial de alho nas incubadoras, utilizando um sistema fechado de recirculação de água, com concentrações de 0; 1; 3 e 5mg L-1 de óleo essencial de alho. As taxas de fertilização dos ovos e eclosão das larvas foram determinadas, respectivamente as 10 e 24h após o início da hidratação dos ovos. Utilizou-se do padrão morfológico de larvas para determinar a taxa de normalidade, com o auxílio de um microscópio estereoscópio. A concentração de 5mg L-1 promoveu melhores taxas de fertilização de ovos e eclosão de larvas. As concentrações de óleo essencial de alho apresentaram efeito linear sobre as taxas de fertilização dos ovos e eclosão das larvas. O óleo de alho não influenciou na normalidade das larvas (P>0,05). Recomenda-se utilizar 5mg L-1 de óleo essencial de alho para promover melhores taxas de fertilização de ovos e eclosão de larvas de jundiá cinza incubados artificialmente.

ABSTRACT: The objective of this study was to evaluate the effects of garlic (Allium sativum) essential oil on the rates of eggs fertilization and hatching and on the normal development of larvae of artificially incubated silver catfish (Rhamdia quelen). The experiment was carried out using a completely randomized experimental design with four treatments and five replicates. The treatments consisted of introducing garlic essential oil into the incubators, which used a closed system of water recirculation, at concentrations of 0, 1, 3, and 5mg L-1. Rates of eggs fertilization and larval hatching were determined at 10 and 24h after the beginning of eggs hydration. Morphology of larvae was assessed with the aid of a stereo microscope to determine the rate of normal development. The concentration of 5mg L-1 promoted better rates of eggs fertilization and larval hatching. Concentrations of garlic essential oil had a linear effect on eggs fertilization rates and larval hatching. Garlic oil did not influence the morphology of the larvae (P>0.05). It is recommended to use 5mg L-1 of garlic essential oil to promote better rates of eggs fertilization and larval hatching of artificially incubated silver catfish.

Resumo O Steindachneridion parahybae é um bagre ameaçado de extinção no Brasil e estratégias aplicadas para a otimização de gametas são necessárias. O objetivo deste estudo foi avaliar doses inseminantes e volume de água sobre os valores das taxas de fertilização, eclosão e larvas normais em S. parahybae. Utilizando-se um delineamento experimental casualizado em esquema fatorial (4×4), com quatro doses inseminantes: 1,0×104; 1,0×105; 1,0×106; 1,0×107 espermatozóides ovócito-1 e quatro volumes de água: 1; 35; 65 e 95mL de água g-1 de ovócitos. As combinações de doses e volumes foram realizadas em triplicatas (n=48). Cada incubadora (1,5L de volume útil) contendo 1g de ovócitos foi considerada como uma unidade experimental. Interações significativas entre doses inseminantes e volumes de água para os valores das taxas de fertilização e efeito quadrático das doses e do volume para os valores das taxas de eclosão foram verificadas. As dosagens e os volumes aplicados não influenciaram no percentual de larvas normais (87,70±5,06). Recomenda-se a aplicação de 5,5×106 espermatozoides ovócito-1 e a utilização de 1mL de água.g-1 de ovócitos no procedimento de fertilização artificial in vitro. Estes resultados permitiram desenvolver novas estratégias biotecnológicas aplicadas na conservação do S. parahybae.

Abstract The Steindachneridion parahybae is an endangered catfish from Brazil and strategies applied for gametes optimization are necessary. The aim of this study was to assess inseminating doses and water volume upon the fertilization, hatching rates and percentage of normal larvae in S. parahybae . Was used a randomized design in factorial scheme (4×4) with four inseminating doses: 1.0×104, 1.0×105, 1.0×106, 1.0×107spermatozoa oocyte-1 and four volumes of water: 1, 35, 65 and 95mL of water g-1 of oocytes. The combination of doses and volumes were performed in triplicates (n=48). Each incubator (1.5L of useful volume) with 1g of oocytes was considered as an experimental unit. Significant interaction between inseminating doses and volumes of water to the values of the fertilization rates and quadratic effect of doses and volume for the values of hatching rates were observed. The doses and volumes did not influence the percentage of normal larvae (87.70±5.06%). It is recommended the use of 5.5×106 spermatozoa oocyte-1 and 1mL of water g-1 of oocytes during in vitro fertilization procedure. These results allowed us to develop new biotechnological strategies applied to the conservation of S. parahybae .

This study aimed to evaluate gut colonization by probiotic bacteria, and their influence on the bacterial microflora, hematological profile, growth rate and proximate composition, and water quality parameters in the cultivation of Nile tilapia juveniles of the Genetically Improved Farmed Tilapia (GIFT) strain. 1800 fry were randomly distributed into four experimental groups (T1= basal diet (BD) without probiotic addition; T2 = BD + 0.5% Bacillus cereus var. toyoi (BC); T3 = BD + 0.5% B. subtilis C-3102 (BS); T4 = BD + 0.25% BC + 0.25% BS) with five replicates. Cages (0.175 m³ capacity) containing 90 tilapia fry (0.34 ± 0.06 g) were used as culture units and individually installed in 8.4 m³ ponds. Except for hemoglobin, hematocrit, glucose, and neutrophil levels, no differences in hematological profile were observed among the groups after 127 days of culture (P > 0.05). The probiotic bacteria either added individually or in combination, successfully colonized the intestines of the fish, without negatively influencing the intestinal bacterial microflora, growth rate, proximate composition, or water quality parameters (P > 0.05). Thus, dietary probiotic supplementation of juvenile Nile tilapia alters the hematological profile, especially hemoglobin, hematocrit, glucose, and neutrophil levels.

Este estudio tuvo como objetivo evaluar la colonización por bacterias probióticas del intestino y su influencia en la microflora bacteriana, perfil hematológico, tasa de crecimiento, composición proximal, y los parámetros de calidad del agua en el cultivo de juveniles de tilapia del Nilo de la cepa Genetically Improved Farmed Tilapia (GIFT). 1.800 alevines fueron distribuidos aleatoriamente en cuatro grupos experimentales (T1 = dieta basal (BD) sin adición de probióticos; T2 = BD + 0,5% B. cereus var. toyoi (BC); T3 = BD + 0,5% B. subtilis C-3102 (BS); T4 = BD + 0,25% BC + 0,25% BS) con cinco repeticiones. Se utilizaron jaulas (0,175 m³ de capacidad) con 90 alevines de tilapia (0,34 ± 0,06 g) como unidades de cultivo e instaladas de forma individual en estanques de 8,4 m³. No se observaron diferencias en el perfil hematológico entre los grupos después de 127 días de cultivo (P > 0,05), excepto para la hemoglobina, hematocrito, glucosa y niveles de neutrófilos. Las bacterias probióticas, suministradas individualmente o en combinación, colonizaron los intestinos de los peces, sin influir negativamente en la microflora intestinal bacteriana, tasa de crecimiento, tasa de composición corporal o los parámetros de calidad del agua (P > 0,05). Por lo tanto, la suplementación con probióticos en la dieta de juveniles de tilapia del Nilo altera el perfil hematológico, especialmente hemoglobina, hematocrito, glucosa y niveles de neutrófilos.

This study evaluated the effect of feed supplementation (at doses of 0, 50, 100, 150, and 200 mg/kg) with SALUTO®, a microencapsulated blend of essential oils including carvacrol, cinnamaldehyde, 1,8-cineol, and pepper oleoresin, in Nile tilapia (Oreochromis niloticus) broodstock on reproductive and growth parameters during the initial phase of rearing. The growth parameters, somatic indexes and gonadal and hepatic parameters were analyzed. Quantitative parameters of growth, ovary fat and crude protein were not affected by supplementation of the additive. However, an increase in crude protein in the female liver was observed in correlation with increased essential oil levels. The female hepatosomatic index was also correlated with supplementation of essential oils. Feeding Nile tilapia broodstock diets containing an essential oil compound (SALUTO®) affects only the females, promoting an increase in liver protein inclusion and hepatosomatic index without impairing performance.

O aumento na produção mundial de biodiesel está gerando um excesso de glicerol, sem destinação definida. Uma alternativa para superar este problema é seu uso como fonte de energia na alimentação animal. No Brasil, o pacu (Piaractus mesopotamicus) é uma das espécies de peixes nativas mais cultivadas, enquanto que o jundiá (Rhamdia quelen) é apropriado para a produção na região subtropical. Considerando a falta de conhecimento sobre a utilização do glicerol bruto em rações para espécies de peixes Neotropicais, determinaram-se os coeficientes de digestibilidade aparente (CDAs) para a energia do glicerol bruto em P. mesopotamicus e R. quelen. A digestibilidade e o conteúdo de energia digestível do glicerol bruto podem ser considerados excelentes, mesmo quando comparados à energia de ingredientes comuns, como o milho e o trigo, apresentando para energia CDA de 0,97 e 0,89, e 15,2 e 13,95MJ kg-1 de energia digestível para o pacu e o jundiá, respectivamente. Por fim, o glicerol bruto é um ingrediente energético com bom potencial para dietas de peixes nativos do Brasil.

The increase in global biodiesel production is originating a glycerol surplus, which has no defined destination. An alternative to overcome this problem is its use as energy source in animal feeding. In Brazil, Pacu (Piaractus mesopotamicus) is one of the most farmed native fish species, whereas Silver catfish (Rhamdia quelen) is suitable for production in subtropical region. Considering little knowledge about crude glycerol utilization in feeds for Neotropical fish species, it was evaluated the apparent digestibility coefficients (ADCs) for energy of crude glycerol for P. mesopotamicus and R. quelen. The digestibility and digestible energy content of crude glycerol can be considered excellent even when compared to energy of common ingredients such as maize and wheat, presenting 0.97 and 0.89 of energy ADCs, and 15.2 and 13.95MJ kg-1 of digestible energy for Pacu and Silver catfish, respectively. In conclusion, crude glycerol is an energetic ingredient with good potential in Brazilian native fish diets.

A utilização de óleos essenciais e extratos herbais como aditivos para alimentação dos peixes têm demonstrado grande potencial, necessitando ainda que ensaios a campo sejam realizados para se determinar a utilização definitiva destes compostos. Com o objetivo de avaliar o desempenho zootécnico de alevinos de tilápia do Nilo Oreochromis niloticus alimentados com ração contendo diferentes níveis de óleos essenciais, realizou-se um experimento em delineamento inteiramente casualizado com 5 tratamentos e 4 repetições: 0.000; 0,005; 0,010; 0,015 e 0,020% de um aditivo comercial microencapsulado à base de óleos essenciais adicionados na ração. Tanques-rede com volume de 1m³ foram utilizados como unidades experimentais com uma densidade de estocagem de 50 alevinos.m-3. Ao final de 69 dias de cultivo não se verificou uma relação entre os diferentes níveis de óleos essenciais e os parâmetros de sobrevivência (%), ganho em peso (g), taxa de crescimento (g/dia) e conversão alimentar aparente (CAA). Por outro lado verificou-se uma relação quadrática para o conteúdo de proteína corporal, com ponto de máximo estimado em 0,0097% de inclusão. Sendo assim, conclui-se que os níveis do aditivo utilizados no presente estudo não forneceram evidências do efeito positivo dos óleos essenciais sobre o desempenho de alevinos de tilápia do Nilo, principalmente como promotor de crescimento.

The use of herbal extracts and essential oils as additives for fish feed have shown great potential, still requiring that the field trials are performed to determine the final use of these compounds. Aiming to evaluate the growth performance of Nile tilapia fingerlings Oreochromis niloticus fed with different levels essential oils, an experiment was conducted in a completely randomized design with 5 treatments and 4 replicates: 0,000, 0,005, 0,010, 0,015 and 0,020% of a commercial blend microencapsulate based on essential oils in the diet. Net tanks with volume of 1m³ were used as experimental units with a stocking density of 50 fingerling m³. At the end of 69 days of culture there was no relation between levels of essential oils and the parameters of survival (%), weight gain (g), growth rate (g/day) and feed conversion. On the other hand there was a quadratic relationship of body protein content for different levels of the commercial blend microencapsulate in the diet with the maximum point estimated at 0,0097% inclusion. Therefore, it is concluded that the levels of essential oils used in this study did not provide evidence of the positive effect on the performance of Nile tilapia fingerlings, mainly as a growth promoter.

This study was carried out to evaluate the influence of different levels of digestible energy and digestible protein in diets of Nile tilapia (Oreochromis niloticus) broodstock on offspring growth during sex reversal stage. A total of 2,700 post-larvae (8.2±0.001 mg) derived from breeders fed nine diets with distinct levels of digestible protein (28, 34 and 40% DP) and digestible energy (2,800; 3,400; and 4,000 kcal DE.kg-1) were stored in twenty-seven 70 L tanks. After 30 days of growth, their average final weight (AFW, g), average weight gain (AWG, g), final standard length (SL, cm), condition factor (CF), specific growth rate (SGR, %/day), stock uniformity (UNI, %), survival (SUR, %) and sex reversal rate (SRR, %) were measured. Although female nutrition is thought to influence the performance or quality of progeny during early life stages, no influence of diets supplied to broodstock was detected on any parameter. Nonetheless, the offspring presented commercially satisfactory growth rates. Thus, diets containing 28% of digestible protein and 2,800 kcal of digestible energy.kg of diet-1 can be used to feed Nile tilapia broodstock without jeopardizing offspring performance during the sex reversal phase.

The objective of this study was to evaluate the effects of water volume and water temperature on the sperm motility duration and the number of spermatozoa, and the water volume on the fertilization rates of oocytes of Rhinelepis aspera. Experiments were carried out to evaluate the effect of semen dilutions (1.74×10-5, 1.74×10-4, 1.74×10-3, 1.74×10-2, 1.74×10-1 and 1.00 mL of sperm.mL-1 of water) and water temperature (5, 10, 15, 20, 25, 30, 35, 40, 45, and 50 ºC) on spermatozoa motility duration. In addition, the effects of insemination dose (7×10³, 7×10(4), 7×10(5), 7×10(6) and 7×10(7) spermatozoa.oocyte-1) and water volume (1.0, 30.0, 60.0, 90.0 and 120.0 mL water.2.0 mL-1 oocytes) on the artificial fertilization rates of oocytes were evaluated. The longest sperm motility duration were observed for the semen dilution of 1.74×10-5 mL semen.mL-1 water and in water at 5 ºC. The highest fertilization rates were obtained for insemination doses between 7.00×10³ and 1.23×10(7) spermatozoa. oocyte-1 and water volume of 28.11 mL water.2.0 mL-1 oocytes.

A reversão sexual é uma das fases mais importantes para a criação comercial da tilápia do Nilo em função dos problemas advindos com a reprodução precoce dessa espécie em tanques de cultivo. Objetivou-se determinar o efeito da frequência de arraçoamento sobre o crescimento e a percentagem sexual da tilápia do Nilo (Oreochromis niloticus) durante a fase de reversão sexual. Quinhentas pós-larvas de tilápia do Nilo foram utilizadas e estocadas em vinte e cinco aquários plásticos (36L) em um delineamento experimental totalmente casualizado com cinco tratamentos e cinco repetições. Os tratamentos foram: uma alimentação (10h), duas alimentações (09h e 17h), três alimentações (09h; 13h e 17h), quatro alimentações (07h; 10h; 13h e 17h) e cinco alimentações (07h; 09h; 11h; 15h e 17h). A frequência de arraçoamento influencia a percentagem de machos, na qual os tratamentos com quatro e cinco arraçoamento proporcionam valores semelhantes entre si, porém superiores (P<0,01) aos demais tratamentos. Recomendam-se pelo menos quatro alimentações diárias para proporcionar lotes de alevinos de tilápia do Nilo com índice de reversão sexual adequado para a criação.

The sex reversal is one of the most important stages for the commercial breeding of Nile tilapia in relation to the problems arising from early breeding of this species in cultivation tanks. The objective was to determine the effect of feeding frequency on growth and sex ratio of Nile tilapia (Oreochromis niloticus) during the sex reversal phase. Five hundred Nile tilapia fry were used and stocked in twenty-five plastic aquaria (36L) in a completely randomized design with five treatments and five replicates. The treatments were: one feeding (10h), two feeding (09h and 17h), three feeding (09h; 13h and 17h), four feeding (07h; 10h; 13h and 17h), and five feeding (07h; 09h; 11h; 15h and 17h). The feeding frequency affected sex ratio of male fingerlings, where the treatments with four and five feedings provided similar values, but higher (P<0.01) than other treatments. It is recommended feeding frequency at least four times a day to provide lots with suitable index of sex reversal for cultivation.