ABSTRACT The use of carp pituitary extract (CPE) in fish reproduction may have drawbacks, whereas analogues of mammalian (aGnRHm) or salmon (aGnRHs) gonadotropins containing dopamine inhibitor (DI) may offer greater advantages. The objective of this study was to evaluate the effect of different hormone inducers on the reproduction of Prochilodus brevis males. A total of 44 specimens of P. brevis were divided into six groups, namely, CPE 4.0 mg; saline solution 1.0 mL; aGnRHm + DI 0.3 mg and 0.5 mg; and aGnRHs + DI 0.25 mL and 0.35 mL kg-1 of live weight. The number of ejaculates, seminal volume, curvilinear velocity (VCL), straight-line velocity (VSL), average path velocity (VAP), sperm morphology and concentration, and membrane and DNA integrity were determined. Sample normality was examined using the Shapiro-Wilk test, and homogeneity using the Levene test. Analysis of variance (ANOVA) was conducted, followed by Tukey's test to compare means, with statistical significance set at p < 0.05. Notably, all fish induced with CPE 4.0 and aGnRHm + DI demonstrated ejaculation, yielding a greater seminal volume. Sperm concentration under aGnRHs + DI 0.35 exceeded that with aGnRHm + DI 0.3 and CPE 4.0. Regarding velocity, aGnRHm + DI 0.3 outperformed aGnRHs + DI 0.35 in VCL, while aGnRHm + DI 0.3 and 0.5 and aGnRHs + DI 0.25 led to higher VSL than aGnRHs 0.35. Additionally, VAP was elevated under aGnRHm + DI 0.3 and CPE, in contrast to aGnRHs + DI 0.35. Improved sperm morphology was observed with aGnRHm + DI 0.5 and aGnRHs + DI 0.25 compared to aGnRHm + DI 0.3. The remaining parameters did not differ significantly.

ABSTRACT. The present work aimed at assessing the possibility of compensating the notorious deficiencies of bioflocs in lipids by supplementing the tilapia commercial diet with soybean oil. In the positive control, there was no feeding restriction nor dietary supplementation with soybean oil. In the experimental treatments, the commercial diet was restricted by 25% over the positive control level. In the negative control tanks, there was feeding restriction and the artificial diet had no oil supplementation. In the experimental tanks, soybean oil was mixed daily with the commercial diet at the levels of 0.6%, 1.2 and 2.4%. Additionally, there were fed-restricted tanks that received a daily supplementation of 1.2% soybean oil mixed with dry molasses, and not with the commercial diet. In general, only the restriction of the commercial diet affected the water quality. The supplementation of the artificial diet with soybean oil up to 2.4% has not improved the proximate composition of bioflocs, nor the fish growth performance. It was concluded that the strategy of supplementing the Nile tilapia juveniles’ commercial diet with increasing levels of soybean meal, in BFT tanks submitted to 25%-feeding restriction, was not capable of avoiding the fish growth performance deterioration.

Abstract To assist the reproductive management of tambaqui (Colossoma macropomum) males in laboratory and commercial fish farming, a linear regression model was obtained from concentration curves using the spectrophotometric method. Twenty-two tambaqui males with an average age of three years old were selected and divided into two groups containing 11 animals each. Both groups alternately received a single dose of carp pituitary extract (CPE; 2.0 mg/kg body weight, intracoelomic). Sperm was collected 14 h after hormonal treatment and diluted (1:4000; sperm:formaldehyde saline). The concentration was estimated by counting spermatozoa in a Neubauer chamber and by using a spectrophotometer (λ=540 nm). Individual sperm concentration ranged from 11.40 to 71.13 × 109 sperm/mL. The degree of transmittance ranged from 62.1% to 95.0%. There was a significant correlation (r2 = 0.966; p < 0.0001) between sperm concentration analyzed in a Neubauer chamber and transmittance at 540 nm. Analysis by spectrophotometry and the prediction provided by the equation Y=100.293 - 0.509X proved to be an efficient and fast method for estimating sperm concentration in tambaqui and can be used in routine procedures in artificial fish reproduction laboratories.

Resumo Visando auxiliar o manejo reprodutivo de machos de tambaqui (Colossoma macropomum) em piscicultura de laboratório e comercial, obteve-se um modelo de regressão linear a partir de curvas de concentração por método espectrofotométrico. Foram selecionados 22 machos de tambaqui com idade média de três anos. Eles foram divididos em dois grupos contendo 11 animais cada. Ambos os grupos receberam alternadamente uma única dose de extrato de hipófise de carpa (EHC; 2,0 mg/kg de peso corporal, intracelomático). O esperma foi coletado 14 horas após o tratamento hormonal e diluído (1:4000; esperma: solução salina formaldeído). A concentração foi estimada por contagem de espermatozoides em câmara de Neubauer e por espectrofotômetro (λ=540 nm). A concentração espermática individual variou de 11,40 a 71,13 × 109 espermatozoides/mL. O grau de transmitância variou de 62,1 a 95,0%. Houve correlação significativa (r2 = 0,966; p < 0,0001) entre a concentração espermática analisada em câmara de Neubauer e a transmitância em 540 nm. A análise por espectrofotometria e a predição pela equação Y=100,293 - 0,509X mostrou ser um método eficiente e rápido para estimar a concentração espermática de tambaqui, podendo ser utilizado em procedimentos de rotina em laboratórios de reprodução artificial de peixes.

Resumo O presente estudo teve por objetivo determinar os efeitos da suplementação da ração balanceada de juvenis de tilápia do Nilo (peso médio inicial = 2,76 ± 0,06 g), submetidos à restrição na oferta de alimento artificial em tanques BFT de cultivo (18 juvenis/tanque 100 L), com DL-metionina, sobre a qualidade da água, composição dos bioflocos e desempenho zootécnico. Os tratamentos experimentais foram constituídos por dois grupos controle (1 - sem restrição alimentar, sem suplementação com metionina; 2 - com restrição alimentar de 25%, sem suplementação com metionina) e quatro tratamentos experimentais (3 - restrição alimentar de 25%, suplementação da ração com 0,5% de DL-metionina, misturada à ração; 4 - restrição alimentar de 25%, suplementação da ração com 1,0% de DL-metionina, misturada à ração; 5 - restrição alimentar de 25%, suplementação da ração com 2,0% de DL-metionina, misturada à ração; 6 - restrição alimentar de 25%, suplementação do melaço em 1,0% de DL-metionina, misturada ao melaço). A suplementação da ração balanceada com DL-metionina não afetou a qualidade da água de cultivo de juvenis de tilápia do Nilo, em tanques BFT, nem a composição centesimal do bioflocos. Após 8 semanas, o ganho em peso corporal dos peixes mantidos nos tanques com restrição alimentar e suplementação da ração com 1% ou 2% de DL-metionina não diferiu (P>0,05) do observado nos tanques sem restrição alimentar. Concluiu-se que é possível restringir as taxas de arraçoamento de juvenis de tilápia do Nilo, mantidos em tanques BFT de cultivo, em 25%, sem prejuízo zootécnico, desde que se faça a suplementação da dieta com, pelo menos, 1% de DL-metionina.

Abstract The present study aimed at determining the effects of dietary DL-methionine supplementation on the water quality, bioflocs composition and Nile tilapia juvenile’s (initial body weight = 2.76 ± 0.06 g) growth performance in BFT rearing tanks (18 fish/100-L tank). Fish were or not subjected to artificial feed restriction. The experimental treatments consisted of two control groups: 1 - no feed restriction, no methionine supplementation; 2 - feed restriction at 25%, no methionine supplementation. There were also four treated groups: 1 - feed restriction at 25%, dietary DL-methionine supplementation at 0.5%; 2 - feed restriction at 25%, dietary DL-methionine supplementation at 1.0%; 3 - feed restriction at 25%, dietary DL-methionine supplementation at 2.0%; 4 - feed restriction at 25%, DL-methionine supplementation of molasses at 1.0. Supplementation of the commercial diet with DL-methionine has not affected either the water quality of the BFT Nile tilapia rearing tanks or the proximate composition of the bioflocs. After 8 weeks, weight gain of fish reared in tanks with feed restriction and dietary DL-methionine supplementation at 1% or 2% has not differed (P>0.05) from the tanks without feed restriction. In conclusion, it is possible to restrict the daily feed allowances of Nile tilapia juveniles reared in BFT tanks at 25%, with no growth performance impairment, if a minimal dietary DL-methionine supplementation of 1.0% is given.