Efeito da estimulação táctil de longo prazo sobre o bem-estar da tilápia-do-nilo

Na piscicultura, estressores como alta densidade de estocagem e elevadas interações agressivas entre os indivíduos podem aumentar o estresse e diminuir o bem-estar de peixes. No entanto, pesquisas direcionadas à redução desses efeitos ainda são escassas. Alguns estudos mostram que a estimulação táctil, semelhante à massagem corporal, tem efeitos positivos na diminuição do estresse e aumento do bem-estar, principalmente em mamíferos. Em peixes, a estimulação táctil de curto prazo (10 dias ou menos) reduz o estresse em um peixe de recife de coral e diminui a agressividade em indivíduos isolados de tilápia-do-nilo. Alguns estudos sugerem que a massagem a longo prazo tenha efeito cumulativo em mamíferos, porém, efeitos prolongados precisam ser investigados em outros vertebrados para testar se esse procedimento seria adequado para melhorar o bem-estar. Assim, testamos o efeito da estimulação táctil de longo prazo no bem-estar de grupos de tilápia-do-nilo, terceira espécie mais produzida na piscicultura mundial. Essa espécie é um ciclídeo e, portanto, apresenta comportamento territorial e de hierarquia de dominância, os quais são definidos por meio de interações agressivas. Foi defendida a tese de que a estimulação táctil de longo prazo traz efeitos positivos aos parâmetros ligados ao bem-estar e a produtividade em espécies agressivas. Assim, foram realizados dois estudos para testar o efeito da estimulação táctil sobre a interação social agressiva e o estresse e também, sobre o estresse e os parâmetros produtivos em diferentes densidades de estocagem. Em ambos os estudos, um aparato formado por uma moldura retangular de PVC, com hastes plásticas posicionadas na vertical e contendo cerdas de silicone nas laterais, foi introduzido do centro do aquário. Os peixes passavam por entre as cerdas, recebendo estimulação táctil corporal. Um aparato semelhante, mas sem as cerdas de silicone, funcionou como controle. No primeiro estudo, foi testado o efeito da estimulação táctil de longo prazo sobre a agressividade, o estresse e os parâmetros produtivos em grupos de tilápia-do-nilo. Quatro machos adultos foram agrupados e mantidos por 21 dias sem acesso (7 réplicas controle) ou com acesso (10 réplicas) à estimulação táctil. A cada 3 dias foram quantificadas as interações agressivas e número de atravessamentos dos animais pelo aparato. Os animais foram medidos e pesados nos dias 1, 7 e 21 e o sangue foi coletado nos dias 7 e 21. Foi observado diminuição do estresse e menor número de interações agressivas no tratamento com estimulação táctil a partir do dia 10. Essa diminuição foi mais acentuada a longo prazo (dias 19 e 21). Além disso, o nível de testosterona (T) aumentou ao longo do tempo nos animais mais dominantes do tratamento com estimulação táctil e não houve diferença no nível de 11-cetotestosterona (11-KT). Foi observado, também, maior taxa de crescimento, eficiência alimentar, sobrevivência e fator de condição dos animais no tratamento com estimulação táctil. Tanto a diminuição da agressividade, quanto o aumento no crescimento foram mais evidenciados no peixe alfa. No segundo estudo, foi testado se a estimulação táctil de longo prazo reduz os efeitos negativos da alta densidade de estocagem. Foram realizados 4 tratamentos, com 10 réplicas cada: 1) Sem estimulação táctil e alta densidade (1 peixe / 0,014 m3); 2) Sem estimulação táctil e baixa densidade (1 peixe / 0,028 m3); 3) Com estimulação táctil e alta densidade (1 peixe / 0,014 m3); 4) Com estimulação táctil e baixa densidade (1 peixe / 0,028 m3). Dez animais foram agrupados e mantidos, também, por 21 dias. Os animais passaram por biometrias nos dias 1, 10 e 21 e por coleta de sangue no dia 21. Não houve diminuição no nível de cortisol, mas a taxa de crescimento, ganho de peso, ganho de comprimento e eficiência alimentar foram maiores no tratamento com estimulação táctil, mesmo quando em alta densidade. Essas variáveis foram ainda maiores no tratamento com baixa densidade e estimulação táctil. Além disso, o fator de condição aumentou no final dos 21 dias somente no tratamento com estimulação e baixa densidade. Com isso, podemos concluir que a estimulação táctil de longo prazo apresenta efeitos positivos sobre a agressividade e os parâmetros de desempenho produtivo na tilápia-do-nilo. Desse modo, pode ser usada como ferramenta para melhorar a produção e aumentar o bem-estar dos peixes.

In fish farming, stressors such as high stocking density and high aggressive interactions between individuals can increase stress and decrease fish welfare. However, research that aim reducing these effects are still scarce. Some studies show that tactile stimulation, similar to body massage, has positive effects in reducing stress and increasing welfare, especially in mammals. In fish, short-term tactile stimulation (10 days or less) reduces stress in a coral reef fish and decreases aggression in isolated individuals of Nile tilapia. Some studies suggest that long-term massage has a cumulative effect in mammals, however, prolonged effects need to be investigated in other vertebrates to test whether this procedure would be adequate to improve welfare. Thus, we tested the effect of long-term tactile stimulation on the welfare of groups of Nile tilapia, the third most raised species in fish farming worldwide. This species is a cichlid and, therefore, exhibits territorial and hierarchical dominance behavior, which is defined through aggressive interactions. The thesis defended was that long-term tactile stimulation has positive effects on parameters related to welfare and productivity in aggressive species. Hence, two studies were carried out to test the effect of tactile stimulation on aggressive social interaction and stress and also on stress and productive parameters at different stocking densities. In both studies, an apparatus formed by a rectangular PVC frame, with plastic rods positioned vertically and containing silicone bristles on the sides, was introduced in the center of the aquarium. The fish passed through the bristles, receiving tactile stimulation on its body. A similar apparatus, but without the silicone bristles, worked as a control. In the first study, the effect of long-term tactile stimulation on aggression, stress and parameters of productive performance in groups of Nile tilapia was tested. Four adult males were grouped and maintained for 21 days without access (7 replicates - control) or with access (10 replicates) to tactile stimulation. Every 3 days, aggressive interactions and the number of animals that crossed the apparatus were quantified. The animals were measured and weighed on days 1, 7 and 21 and blood was collected on days 7 and 21. A decrease in stress levels and fewer aggressive interactions were observed in the treatment with tactile stimulation from the 10th day on. This decrease was more accentuated in the long-term treatment (days 19 and 21). In addition, the testosterone (T) level increased over time in the most dominant animals on the tactile stimulation treatment and there was no difference in the level of 11-ketotestosterone (11-KT). It was also observed a higher growth rate, feed efficiency, survival and condition factor of the animals in the treatment with tactile stimulation. Both the decrease in aggressiveness and the increase in growth were more evident in alpha fish. In the second study, it was tested whether long-term tactile stimulation reduces the negative effects of high stocking density. Four treatments were carried out, with 10 replicates each: 1) Without tactile stimulation and high density (1 fish / 0.014 m3); 2) Without tactile stimulation and low density (1 fish / 0.028 m3); 3) With tactile stimulation and high density (1 fish / 0.014 m3); 4) With tactile stimulation and low density (1 fish / 0.028 m3). Ten animals were grouped and kept, too, for 21 days. The animals underwent biometrics on days 1, 10 and 21 and blood collection took place on day 21. There was no decrease in the level of cortisol, but the growth rate, weight gain, length gain and feeding efficiency were higher in the treatment with tactile stimulation, even when in high density. These variables were even greater in the treatment with low density and tactile stimulation. In addition, the condition factor increased at the end of the 21 days, but only in the treatment with stimulation and low density. By this means, we can conclude that the long-term tactile stimulation has positive effects on the aggressiveness and in the parameters of productive performance of Nile tilapia. Therefore, it can be used as a tool to improve production and increase fish welfare.

The effect of increased light intensity on the aggressive behavior of the Nile tilapia, Oreochromis niloticus (Teleostei: Cichlidae)

Animals show behavioral and physiological changes that emerge in response to environmental perturbations (i.e., emergency life-history stages). In this study, we investigate the effects of light intensity on aggressive encounters and social stability in groups of adult male Nile tilapia, Oreochromis niloticus (Linnaeus, 1758). The study compared the behavior observed under low (280.75 ± 50.60 lx) and high (1394.14 ± 520.32 lx) light intensities, with 12 replicates for each treatment. Adult fish were isolated in 36-L aquaria for 96 hours, and three males were grouped for 11 days in 140-L aquaria. Agonistic behavior was video-recorded (10 min/day) on the 3rd, 5th, 7th, and 9th day to quantify aggressive interactions and social stability. There was an effect of light intensity and day of observation on the total number of agonistic behaviors performed by the fish group. Besides, increased frequency of aggressive interactions (the sum of the four sessions) by the alpha, beta and gamma fish occurred at the higher light intensity. The dominance ranks of the fish remained unchanged across the observation sessions under both the low and high light intensities. We concluded that enhanced light intensity has a cumulative effect that increases the aggressiveness of the Nile tilapia but that this effect is not sufficiently strong to destabilize the social hierarchy.

The effect of increased light intensity on the aggressive behavior of the Nile tilapia, Oreochromis niloticus (Teleostei: Cichlidae)

Animals show behavioral and physiological changes that emerge in response to environmental perturbations (i.e., emergency life-history stages). In this study, we investigate the effects of light intensity on aggressive encounters and social stability in groups of adult male Nile tilapia, Oreochromis niloticus (Linnaeus, 1758). The study compared the behavior observed under low (280.75 ± 50.60 lx) and high (1394.14 ± 520.32 lx) light intensities, with 12 replicates for each treatment. Adult fish were isolated in 36-L aquaria for 96 hours, and three males were grouped for 11 days in 140-L aquaria. Agonistic behavior was video-recorded (10 min/day) on the 3rd, 5th, 7th, and 9th day to quantify aggressive interactions and social stability. There was an effect of light intensity and day of observation on the total number of agonistic behaviors performed by the fish group. Besides, increased frequency of aggressive interactions (the sum of the four sessions) by the alpha, beta and gamma fish occurred at the higher light intensity. The dominance ranks of the fish remained unchanged across the observation sessions under both the low and high light intensities. We concluded that enhanced light intensity has a cumulative effect that increases the aggressiveness of the Nile tilapia but that this effect is not sufficiently strong to destabilize the social hierarchy.

The effect of increased light intensity on the aggressive behavior of the Nile tilapia, Oreochromis niloticus (Teleostei: Cichlidae)

Animals show behavioral and physiological changes that emerge in response to environmental perturbations (i.e., emergency life-history stages). In this study, we investigate the effects of light intensity on aggressive encounters and social stability in groups of adult male Nile tilapia, Oreochromis niloticus (Linnaeus, 1758). The study compared the behavior observed under low (280.75 ± 50.60 lx) and high (1394.14 ± 520.32 lx) light intensities, with 12 replicates for each treatment. Adult fish were isolated in 36-L aquaria for 96 hours, and three males were grouped for 11 days in 140-L aquaria. Agonistic behavior was video-recorded (10 min/day) on the 3rd, 5th, 7th, and 9th day to quantify aggressive interactions and social stability. There was an effect of light intensity and day of observation on the total number of agonistic behaviors performed by the fish group. Besides, increased frequency of aggressive interactions (the sum of the four sessions) by the alpha, beta and gamma fish occurred at the higher light intensity. The dominance ranks of the fish remained unchanged across the observation sessions under both the low and high light intensities. We concluded that enhanced light intensity has a cumulative effect that increases the aggressiveness of the Nile tilapia but that this effect is not sufficiently strong to destabilize the social hierarchy.(AU)

Preference of lactating dairy cows for strawyard or cubicle housing systems at two space allowances / Preferência de vacas leiteiras em lactação por sistemas de confinamentos com ou sem baias em duas disponibilidades de espaço

Two preference tests were conducted with 16 lactating dairy cows in which they were allowed to choose between strawyard and cubicle housing systems. The two tests each of 14 days duration examined preferences at high and low space allowances. All cows had previous experience of both systems, but in the week prior to the preference tests, half the animals were housed in a strawyard and half in a cubicle system. This prior treatment was found to have no significant influence on subsequent choice of housing system. Continuous video recordings showed that the mean proportion of time over 14 days spent in the strawyard and cubicle areas was 66:34 at high space allowance and 68:32 at low space allowance respectively. In the second week of test at both space allowances, the total lying time proportion in the strawyard and cubicles was 91:09 indicating a strong preference to lie in the strawyard area, even when the area was restricted at the low space allowance. Social rank and dominance values were determined prior to the tests, and were found to correlate more strongly with age than with liveweight. They did not significantly influence the choice of housing system at either space allowance. The occurrence of minority preferences for the cubicle system suggests that using preference as an indicator of welfare, may lead to the development of systems which will not provide the best welf

Dois testes de preferência foram conduzidos em 16 vacas leiteiras em lactação as quais tiveram que escolher entre confinamento com baias (com divisórias na área de repouso) ou sem baias (sem divisórias na área de repouso). Os dois testes, cada um com 14 dias de duração examinaram preferência dos animais em diferentes disponibilidades de espaço. Todas as vacas tinham experiência prévia nos dois tipos de confinamentos, mas, na semana anterior aos testes de preferência, metade dos animais foram mantidos no confinamento sem baias e a outra metade no confinamento com baias. Não foi observada influência desse tratamento prévio na escolha do tipo de confinamento pelos animais. O registro continuo, através de vídeo mostrou que, depois de 14 dias, a proporção mêdia de tempo despendido nas áreas dos confinamento sem e com baias foi respectivamente de 66:34 quando havia maior disponibilidade de espaço e de 68:32 quando havia menor disponibilidade de espaço. Na segunda semana dos dois testes verificou-se que, em ambas disponibilidade de espaço a proporção total de tempo em repouso no confinamento sem e com baias foi de 91:09, indicando uma forte preferência dos animais para se deitarem na área do confinamento sem baias, mesmo quando o espaço disponível para os mesmos foi restringido. Ordem social e valor de dominância foram determinados antes dos testes e verificou-se que correlacionavam m