RESUMO

This study evaluated the effects of phytase supplementation on growth performance and apparent digestibility of Nile tilapia (Oreochromis niloticus) in a commercial fish farm setting. Nile tilapia (6300 male, 57.48 ± 1.04 g) were randomly stocked into 42 floating cages. The experimental design was completely randomized, comprising six treatments and seven replications. Fish were fed five phosphorus deficient plant-based diets with graded levels of phytase supplementation (0, 500, 1000, 1500, 2000 UF kg-1) and an additional diet containing phosphorus supplementation to meet the requirement of this fish species (positive control). After 97 days of feeding, growth performance data were collected and 900 fish (500 ± 10 g) were relocated to 6 floating cages for the digestibility assessment. Quadratic polynomial regression analysis indicated 1537.5 and 1593.2 UF kg-1 as the optimum dietary levels for daily weight gain and feed conversion rate, respectively. Including 2000 UF kg-1 resulted in the higher dry matter, crude protein, energy, and ash apparent digestibility coefficient values. Therefore, phytase supplementation from 1500 to 2000 UF kg-1 is recommended to enhance growth performance and nutrient bioavailability of Nile tilapia reared according to industry practices.

RESUMO

The effects of dietary digestible protein (DP) levels (22, 26, 29, 32, and 34%) and different stressors (cold-induced stress, CIS; heat/dissolved oxygen-induced stress, HDOIS; transport-induced stress, TIS; and size-sorting-induced stress, SSIS) on hemato-biochemical parameters were evaluated. Four hundred and forty Nile tilapia fingerlings were distributed into 40-250 L aquaria and fed experimental diets for 110 days, and fed each of the five experimental diets, that were randomly distributed to eight replicates per treatment. Then, different groups of fish were subjected to one type of stress. Groups of 40 fish were used on CIS (17 °C), HDOIS (32 °C), and TIS (4 h), and a group of 140 fish on SSIS (15 min air exposure and 60 s handling). There was no effect on hemato-biochemical profile when DP levels were compared, neither before nor after stress; however, there was a significant stress effect. Digestible protein did not mitigate stress response under SSIS and CIS; lymphopenia and neutrophilia were the main cell-mediated immune response; dietary 22 and 26% DP impaired oxygenation on SSIS and TIS; fish under HDOIS and SSIS demanded more energy using triglycerides as an energy source; the diet formulated to contain 22% DP was not adequate to keep homeostasis under temperature stress. Cluster analysis showed that, for DP levels below the requirement for growth, SSIS and CIS were considered the most stressful conditions. At 34% DP level, HDOIS response was comparable to that of non-stressing conditions.(AU)

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In fish, fasting leads to loss of muscle mass. This condition triggers oxidative stress, and therefore, antioxidants can be an alternative to muscle recovery. We investigated the effects of antioxidant ascorbic acid (AA) on the morphology, antioxidant enzyme activity, and gene expression in the skeletal muscle of pacu (Piaractus mesopotamicus) following fasting, using in vitro and in vivo strategies. Isolated muscle cells of the pacu were subjected to 72 h of nutrient restriction, followed by 24 h of incubation with nutrients or nutrients and AA (200 µM). Fish were fasted for 15 days, followed by 6 h and 15 and 30 days of refeeding with 100, 200, and 400 mg/kg of AA supplementation. AA addition increased cell diameter and the expression of anabolic and cell proliferation genes in vitro. In vivo, 400 mg/kg of AA increased anabolic and proliferative genes expression at 6 h of refeeding, the fiber diameter and the expression of genes related to cell proliferation at 15 days, and the expression of catabolic and oxidative metabolism genes at 30 days. Catalase activity remained low in the higher supplementation group. In conclusion, AA directly affected the isolated muscle cells, and the higher AA supplementation positively influenced muscle growth after fasting.

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RESUMO

We evaluated the economic responses of Nile tilapia in the final stage (450 to 800 g) fed diets containing five levels of digestible protein (DP): 20, 23, 26, 29 and 32% and two digestible energy levels (DE): 3,000 and 3,300 kcal kg-1 based on the sale of whole animals or fillet. This experiment was carried out into 50 m3 net cages in an aquaculture area located in Paranapanema River, Palmital - São Paulo State, Brazil, from November 21st, 2010 to January 21st. Economic performance indicators were: gross revenue, partial production cost, net revenue, leveling point, balance point, benefit cost ratio and cost of feed kg-1 gain. Twenty-nine percent of DP and 3,000 kcal DE kg-1 diet provided better economic performance for sale of whole fish, meaning higher net revenue (R$ 23.09 net cage-1) and benefit cost ratio (1.08), besides the lowest balance point (R$ 3.91 kg-1). Thirty-two percent of DP and 3,000 kcal DE kg-1 diet provided the lowest cost of feed kg-1 (R$ 2.53), leveling point (17.35 kg net cage-1) and balance point (R$ 13.63 kg-1), besides the highest benefit cost ratio (1.54) when the fish were sold in fillet form. Diets with 29% and diet with 32% digestible protein, both of them with 3,000 kcal of digestible energy kg-1 diet provides better economic responses in Nile tilapia reared in net cages (450 to 800 g), to be sold, respectively, whole or fillets form.

Avaliaram-se as respostas econômicas da produção de tilápia-do-nilo na fase de terminação (450 a 800 g), alimentadas com dietas contendo cinco níveis de proteína digestível (PD): 20, 23, 26, 29 e 32% e dois de energia digestível (ED): 3.000 e 3.300 kcal kg-1 de dieta, com base na venda de animais inteiros ou filés. A pesquisa foi conduzida em 50 tanques-rede (1 m3), em área aquícola localizada no rio Paranapanema, Palmital-SP, Brasil, de 21 de novembro de 2010 à 21 de janeiro de 2011. Os indicadores de desempenho econômico calculados foram: receita bruta, custo de produção parcial, receita líquida, ponto de nivelamento, ponto de equilíbrio, relação benefício custo e custo da ração kg-1. A dieta contendo 29% de PD e 3.000 kcal de ED kg-1 proporcionou melhor desempenho econômico para venda de peixes inteiros, ou seja, maior receita líquida (R$ 23,09 tanque-rede-1) e relação benefício custo (1,08), além do menor ponto de equilíbrio (R$ 3,91 kg-1). A dieta com 32% de PD e 3.000 kcal de ED kg-1 possibilitou para a venda de filés o menor custo da ração kg-1 (R$ 2,53), menor ponto de nivelamento (17,35 kg tanque-rede-1) e de equilíbrio (R$ 13,63 kg-1), além da mais alta relação benefício custo (1,54). A dieta contendo 29% e a dieta contendo 32% de proteína digestível, ambas com 3.000 kcal de energia digestível kg-1 proporcionam melhores respostas econômicas de tilápias-do-nilo recriadas em tanques-rede (450 a 800 g), ao serem vendidas, respectivamente, inteiras e na forma de filés.

Assuntos

RESUMO

We evaluated the economic responses of Nile tilapia in the final stage (450 to 800 g) fed diets containing five levels of digestible protein (DP): 20, 23, 26, 29 and 32% and two digestible energy levels (DE): 3,000 and 3,300 kcal kg-1 based on the sale of whole animals or fillet. This experiment was carried out into 50 m3 net cages in an aquaculture area located in Paranapanema River, Palmital - São Paulo State, Brazil, from November 21st, 2010 to January 21st. Economic performance indicators were: gross revenue, partial production cost, net revenue, leveling point, balance point, benefit cost ratio and cost of feed kg-1 gain. Twenty-nine percent of DP and 3,000 kcal DE kg-1 diet provided better economic performance for sale of whole fish, meaning higher net revenue (R$ 23.09 net cage-1) and benefit cost ratio (1.08), besides the lowest balance point (R$ 3.91 kg-1). Thirty-two percent of DP and 3,000 kcal DE kg-1 diet provided the lowest cost of feed kg-1 (R$ 2.53), leveling point (17.35 kg net cage-1) and balance point (R$ 13.63 kg-1), besides the highest benefit cost ratio (1.54) when the fish were sold in fillet form. Diets with 29% and diet with 32% digestible protein, both of them with 3,000 kcal of digestible energy kg-1 diet provides better economic responses in Nile tilapia reared in net cages (450 to 800 g), to be sold, respectively, whole or fillets form.(AU)

Avaliaram-se as respostas econômicas da produção de tilápia-do-nilo na fase de terminação (450 a 800 g), alimentadas com dietas contendo cinco níveis de proteína digestível (PD): 20, 23, 26, 29 e 32% e dois de energia digestível (ED): 3.000 e 3.300 kcal kg-1 de dieta, com base na venda de animais inteiros ou filés. A pesquisa foi conduzida em 50 tanques-rede (1 m3), em área aquícola localizada no rio Paranapanema, Palmital-SP, Brasil, de 21 de novembro de 2010 à 21 de janeiro de 2011. Os indicadores de desempenho econômico calculados foram: receita bruta, custo de produção parcial, receita líquida, ponto de nivelamento, ponto de equilíbrio, relação benefício custo e custo da ração kg-1. A dieta contendo 29% de PD e 3.000 kcal de ED kg-1 proporcionou melhor desempenho econômico para venda de peixes inteiros, ou seja, maior receita líquida (R$ 23,09 tanque-rede-1) e relação benefício custo (1,08), além do menor ponto de equilíbrio (R$ 3,91 kg-1). A dieta com 32% de PD e 3.000 kcal de ED kg-1 possibilitou para a venda de filés o menor custo da ração kg-1 (R$ 2,53), menor ponto de nivelamento (17,35 kg tanque-rede-1) e de equilíbrio (R$ 13,63 kg-1), além da mais alta relação benefício custo (1,54). A dieta contendo 29% e a dieta contendo 32% de proteína digestível, ambas com 3.000 kcal de energia digestível kg-1 proporcionam melhores respostas econômicas de tilápias-do-nilo recriadas em tanques-rede (450 a 800 g), ao serem vendidas, respectivamente, inteiras e na forma de filés.(AU)

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RESUMO

Rhipicephalus sanguineus are bloodsucking ectoparasites, whose main host is the domestic dog, thus being present in urban areas and closely located to people. Eventually, this tick species parasitize humans and can become a potential vector of infectious diseases. Methods to control this type of pest have been the focus of many research groups worldwide. The use of natural products is increasingly considered nowadays, due to the low toxicity levels to the host and low waste generation to the environment. This study tested the effect of ricinoleic acid esters from castor oil (as an potential acaricide) on the reproductive system of R. sanguineus females, more specifically on the vitellogenesis process. For this, two groups were established: the control group (CG) and the treatment group (TG) with five rabbits in each (New Zealand White), used as hosts. NaCl and ester were added to rabbits' food and offered to the hosts. After full engorgement, the females were collected and had their ovaries extracted. The ticks ovaries were submitted to histochemical techniques so the effects of esters could be observed over polysaccharides, proteins and lipids yolk. Changes in the deposition of yolk components were observed. This caused modifications on elements of polysaccharide origin and on glycoprotein compounds, interfering in the final yolk synthesis and compromising the development of the future embryo.

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