Abstract The majority of tilapia farming is used for the production of fillets, resulting in the generation of waste that can be used to increase food stocks by producing minced fish. The aim of this study was to characterize and evaluate the viability of boiling and mechanical techniques for obtaining minced fish in relation to performance, physical-chemical and microbiological parameters and to reduce the waste generated in the process of filleting Nile tilapia. Based on performance outcomes, the mechanical technique proved to be 12% more efficient than the boiling one. The cost of the boiling technique was higher due to performance and operating costs. In both techniques microbiological alterations were not observed. Centesimal analysis results showed a difference in humidity between the techniques, which was expected due to loss of water during the boiling process, which possibly also affected protein levels. Over all, the use of a deboning machine allied lower operating cost, better performance, quality and practicality. The debone machine technique it's feasible considering the large volume of waste generated daily on fish farms, which requires a speedy and effective disposal. Further, makes possible obtaining a nutritional raw material of high added-value and contributing to the reduction of environmental impacts.

O conhecimento de como os animais depositam componentes químicos como água, proteína, gordura e cinzas na carcaça é importante para a formulação de uma dieta equilibrada, permitindo o máximo desempenho com baixo impacto ambiental. Logo, o trabalho foi conduzido, com o objetivo de avaliar a influência de diferentes linhagens de tilápia sobre a deposição de componentes químicos na carcaça. Os componentes corporais analisados foram água, proteína, gordura e cinzas. Para a determinação das curvas de deposição química corporal em função da idade foram ajustados os modelos exponencial, Brody, logístico, Gompertz e vonBertalanffy. Houve ajuste apenas do modelo exponencial para a água, tendo as linhagens UFLA e Comerciais as que depositaram numa velocidade mais rápida (P<0,05) em relação às demais linhagens. Quanto à proteína, a linhagem Vermelha foi a que teve menor peso à maturidade, estimado (49,37g) e foi mais precoce quanto à deposição máxima em relação as outras linhagens (Chitralada, UFLA e Comercial), no qual obtiveram peso a maturidade estimada em 231,5g e deposição máxima aos 337 dias de idade. Não houve diferença (P>0,05) dos parâmetros do modelo logístico entre as linhagens Vermelha,UFLA e Comercial para extrato etéreo, sendo a deposição máxima (0,23 g) aos 310 dias de idade. Em relação à deposição de cinzas, a linhagem Comercial teve maior deposição máxima (0,10 g) e, aos 337 dias de idade, sendo mais tardia em relação as outras linhagens que obtiveram deposição máxima de 0,033 g, aos 254 dias de idade. Portanto, conclui-se que as linhagens genéticas avaliadas diferem quanto às curvas de deposição química de água, proteína, extrato etéreo e cinzas.

The knowledge of how animals deposited chemical components as water, protein, fat and ash in the carcass is importance for the formulation of a balanced diet, allowing maximum performance with a low environmental impact. So, the study was carried out to evaluate the influence of different tilapia strains (Chitralada, Commercial, Red and Universidade Federal de Lavras [UFLA]) on the deposition of bodily chemical components in the carcass. The bodily components analyzed were water, protein, fat and ash. For the determination of the bodily chemical deposition curves by age, the exponential, Brody, logistic, Gompertz and von Bertalanffy models were adjusted. The Commercial and UFLA strains deposited water at a faster speed (P<0.05) compared with the remaining strains. As for protein, the Red strain had a lower estimated maturity weight (49.37 g), and was more precocious (202 days) with regard to maximum deposition in comparison to the other strains (Chitralada, UFLA and Commercial) in which there was an estimated maturity weight of 231.5 g and maximum depositionfor 337 days. There were no differences (P>0.05) for the logistic model parameter between Red, UFLA and Commercial strains for fat, which presented a maximum fat deposition (0.23 g) at 310 days of age. Regarding ash deposition, the Commercial strain presented a higher maximum deposition (0.10 g) at 337 days, occurring later than the other strains that presented maximum deposition (0.033g) at 254 days of age. Thus, it was concluded that the genetic strains evaluated differ in chemical deposition curves of water, protein, fat and ash.

Para o desenvolvimento de uma tecnologia de cultivo é necessária a determinação da densidade de estocagem ideal. Objetivou-se determinar a melhor densidade de estocagem para juvenis de Brycon orthotaenia, cultivados em tanques-rede, durante a fase de recria. A pesquisa foi conduzida na Fazenda Experimental da Epamig, em Felixlândia, Estado de Minas Gerais, na represa de Três Marias. Foram utilizados 9.000 alevinos, distribuídos em 12 berçários com 2 m³ em tanques-rede, seguindo o delineamento inteiramente casualizado, com três repetições e quatro diferentes densidades de estocagem (150, 300, 450, 600 peixes m-3). Amostras aleatórias de cada tanque-rede foram coletadas para as avaliações, no início do experimento e aos 60 dias de cultivo. Foram estimados os parâmetros produtivos, índice de crescimento específico e uniformidade. Obteve-se uma relação linear positiva (p < 0,05) para biomassa final (r² = 0,88), ganho de peso da biomassa (r² = 0,87), produtividade (r² = 0,86), conversão alimentar aparente (r² = 0,96) e para viabilidade econômica (r² = 0,96). Para sobrevivência (r² = 0,98), a relação linear foi negativa (p < 0,05). Não houve diferença significativa entre os tratamentos (p > 0,05) para os parâmetros de crescimento, uniformidade e peso final. Conclui-se que a densidade de 300 peixes m-3 é a mais indicada, pois, proporciona maior receita líquida, sobrevivência e boa conversão alimentar.

Developing a rearing technology requires the determination of the optimum stocking density. This study aimed to determine the best stocking density for Brycon orthotaenia juveniles grown in net cages, during the rearing phase. The research was conducted at the Experimental Farm of EPAMIG, in Felixlândia, Minas Gerais State, in the Três Marias Reservoir. 9,000 fingerlings were distributed into 12 net cages, 2 m³ each, according to a completely randomized design with three replications and four different stocking densities (150, 300, 450, 600 fish m-3). Random samples were taken from each net cage, at the onset of the experiment and at 60 rearing days, to assess production parameters, specific growth rate and uniformity. We verified a positive linear relationship (p < 0.05) for final biomass (r² = 0.88), weight gain (r² = 0.87), productivity (r² = 0.86), apparent feed conversion (r² = 0.96) and economic viability (r² = 0.96). For survival (r² = 0.98), the relationship was negative (p < 0.05). There were no significant differences between treatments (p > 0.05) for growth parameters, uniformity and final weight. It can be concluded that the density of 300 fish m-3 is the most suitable, because it provides higher net revenue, survival, and a good feed conversion.

The objective of this study was to evaluate the morphometric growth and weight gain of strains of tilapia (Thai, Red, UFLA and Commercial) by nonlinear models. Initially, 500 male fingerlings of each strain, at 85 (Red and UFLA) and 86 (Thai and Commercial) days of age, were stocked separately in raceways with 56 m³. Twenty fish of each strain were randomly sampled, weighed and measured monthly. Five nonlinear models (Brody, von Bertalanffy, Gompertz, logistic and exponential) were tested, choosing one that best fit to the data. The variables studied were: weight, standard length (SL), head length (HL), height 1 (H1), height 2 (H2), height 3 (H3), first distance (D1), second distance (D2), first width (W1), second width (W2) and third width (W3). The exponential model had the best fit to weight and morphometric data, with the exception of W2, in which the best fitted model was von Bertalanffy. The convergence of the exponential model to data indicates that the cultivation period studied was not enough for the strains to reach maturity weight. The UFLA strain presented the lowest value for parameter "a" (initial weight estimate), 8.71 g, and the highest for parameter k (specific growth rate), 0.0127, when compared with other evaluated strains. However, the highest k of UFLA was not enough to overcome the final weight observed for the Commercial strain (603.1 g), which was higher than all other strains. Regarding the morphometric measurements, the UFLA strain also had the highest k for the variables SL, HL, HH, H1, H2, H3 and D2, and similar k to Commercial and Thai strains for the variables D1 and W3 respectively. The strains differ as to weight gain and morphometric growth.

With the purpose of evaluating the changes and the degree of heterosis on performance and carcass traits of fish from the diallel crossing between Pacu and Tambaqui, four genetic groups were generated through hormonal induction: pacu, tambaqui, tambacu and paqui. For 196 days, 400 juveniles of each genetic group were stocked in a pond divided into four parts of equal size, one for each group. At the end of this period, when the fish weighed on average 1024 g (±115.52 g), 20 specimens of each genetic group were sampled, weighed, measured: head length; standard length; body height; and width; and also processed resulting in following body yield: viscera; carcass; head; fillet; rib; residue and skin yields. There was positive heterosis for body weight, viscera and skin yield and head measures and negative heterosis for carcass and filet yield and body width, indicating that the hybrids have better performance on weight gain, but are inferior in relation to the carcass conformation.