Submitted by (edna.saturno@ufrpe.br) on 2017-02-22T16:32:41Z No. of bitstreams: 1 Victor Andrade da Silva.pdf: 390078 bytes, checksum: c2381631004f76239866e7fbd989d9a9 (MD5) / Made available in DSpace on 2017-02-22T16:32:41Z (GMT). No. of bitstreams: 1 Victor Andrade da Silva.pdf: 390078 bytes, checksum: c2381631004f76239866e7fbd989d9a9 (MD5) Previous issue date: 2013-02-27 / Stocking density is recognized as a critical factor in aquaculture, since high densities represent a potential source of chronic stress. This study investigated the effects of a chronic stressor, such as high stocking densities, on growth, physiological responses, and flesh quality of juvenile cobia (Rachycentron canadum) tested for a period of 42 days. The trial was conducted in a recirculating aquaculture system equipped with tanks of 70 L tanks. Cobia of 46.32 ± 0.22 g (mean ± SEM) were randomly distributed into three stocking densities (3.30 ± 0.02; 6.67 ± 0.03; 13.15 ± 0.16 g L-1), and three replicates. Treatment groups were nominally assigned as low density (LD; 5 fish/tank), medium density (MD; 10 fish/tank), and high density (HD; 20 fish/tank), respectively. Plasma concentrations of cortisol, osmolality and lactate were not affected by density levels, and values were according with those reported as basal for juvenile cobia. However, growth rate were influenced by density levels, in which weight gain and specific growth rate were significantly higher in the LD group. Drip loss did not differ among density groups. However, stocking density influenced the onset and development of rigor mortis. Our findings indicated that rearing juvenile cobia at the high densities negatively affected growth rate and flesh quality. Results suggest that juvenile cobia reared at the high densities were able to counteract stress. However, energy from the diet and/or body reserves was diverted from growth as a response to the elevated metabolic demand caused by stress. In this regard, juvenile cobia should be maintained at a final biomass up to approximately 15 kg m-3 to ensure a maximal growth rate and an improved final product quality. To our knowledge, this is the first report assessing the influence of a chronic stressor on both physiological responses and flesh quality parameters in cobia. This may provide information to the advancement of cobia aquaculture, leading to improvements in fish welfare, final product quality and increased productivity. / A densidade de estocagem é amplamente reconhecida como um fator crítico em aquicultura, uma vez que altas densidades representam uma potencial fonte de estresse crônico. Este estudo avaliou a resposta fisiológica, desempenho zootécnico e qualidade de filé de juvenis de beijupirá (Rachycentron canadum) submetidos a um estressor crônico, como altas densidades, visando à definição de condições de criação que levem à melhoria do bem estar animal e ao incremento da produtividade e qualidade do produto final. Os peixes foram testados por um período de 42 dias, em que juvenis de 46,32 ± 0,22 g (média ± erro padrão) foram aleatoriamente distribuídos em três densidades (3,30 ± 0,02; 6,67 ± 0,03; 13,15 ± 0,16 g L-1), e em três repetições. Os tratamentos foram designados como baixa densidade (LD; 5 peixe/tanque), densidade média (MD; 10 peixe/tanque), e alta densidade (HD; 20 peixes/tanque), respectivamente. As concentrações de cortisol e lactato e a osmolalidade do plasma sanguíneo não foram afetadas pela densidade de estocagem, e seus valores estavam de acordo com as faixas basais previamente relatados para juvenis de beijupirá. No entanto, o ganho de peso e a taxa de crescimento específico foram significativamente maiores no grupo LD. A densidade de estocagem também influenciou o início e o desenvolvimento do rigor mortis. Juvenis de beijupirá criados na alta densidade apresentaram menor taxa de crescimento e qualidade de filé. Os resultados sugerem que juvenis de beijupirá criados nas altas densidades foram capazes de contrapor o estresse ao nível de composição do plasma. Contudo, energia da dieta e/ou reservas do corpo podem ter sido desviadas do crescimento como resposta à alta demanda metabólica causada pelo estresse. Dessa forma, o presente estudo sugere que juvenis de beijupirá devem ser mantidos em uma biomassa final de até 15 kg m-3, aproximadamente para garantir máximo crescimento e melhor qualidade do produto final. Aparentemente, este estudo é o primeiro a abordar a influencia de um estresse crônico na resposta fisiológica e qualidade de filé de juvenis de beijupirá. Os resultados podem fornecer informações para avanços na criação dessa espécie, conduzindo a melhorias no bem estar animal, na qualidade do produto final e no aumento da produtividade

Comparison of pig?s stunning (by electricity or CO2) at slaughterhouse and monitoring the occurrence of quality variance PSE during 48 hours post mortem was main goal of this work. Basic indicators such as pH1, drip loss of water and meat colour (lightness) were determined to assess PSE. In addition to these indicators have been also evaluated values of pH24 and pH48. The result of those indicators is that during stunning by CO2 gas value of pH1 was higher by 0,3 degree (P < 0,001), value of pH24 was higher by 0,243 (P < 0,001) and average drip loss of water was lower by 2,16 % (P < 0,001). Changes in other evaluated indicators were statistically non-significant. Occurrence of quality variance which tends to PSE (PSEi) and PSE was evaluated at slaughterhouse which is using electricity for stunning as higher by 7,843 % at PSEi and 1,961 % at PSE based on value of pH1. As higher was evaluated also drip loss of water by 23,810 % at PSEi respectively 4,762% at PSE. Difference between occurring of PSEi and PSE based on meat colour was not observed. The highest correlation dependence was found between pH1 and drip loss of water (r = 0,586, R2 = 34,315 %).