Individuals differ in their preference for alcohol and propensity to develop alcoholism, where the behavioral profile, such as the bold-shy axis, plays an important role for such a difference. However, literature is limited and conflicting on the causes and consequences of this relationship. Translational studies using animal models, such as zebrafish, can help identify behavioral traits that predispose individuals to drink alcohol compulsively. Here, the preference for alcohol was investigated in two distinct traits in zebrafish: shy and bold. For this purpose, fish were separated into shy and bold traits and then a conditioned place preference paradigm was used, a strategy that allows the rewarding effects from alcohol to be assessed by the ability to enhance the animal’s preference for an environment that initially was not preferred. It was found that bold zebrafish actively searched for the environment that was paired to alcohol after one acute exposure, whereas, shy fish changed their place preference even without alcohol administration, showing that the conditioned place preference protocol, given the short amount time to assess place preference, is not ample enough for shy fish to choose. Our results show that behavioral profiles must be considered in further studies since differences between shy and bold individuals on preference behavior can strongly interfere in the assessment of drug preference, mainly when using the conditioned place preference paradigm.

Nile tilapia farmers must deal with production challenges, such as increased aggressiveness and high stress levels, which potentially diminishes fish welfare. Tryptophan supplementation is a strategy to cope with such problems. However, data is scarce on how tryptophan affects the aggressiveness of this species and other aspects need to be understood on how it influences stress in fish. In this study, we investigate how a 1× (0.32%), 4×(1.28%) and 8× (2.56%) supplemented tryptophan diet affects aggressiveness and stress in Nile tilapia. Aggressiveness in fish was assessed after short-term exposure (7 days) to a tryptophan supplemented diet while stress in fish was assessed after long-term exposure (60 days). The 4x and 8x diets reduced aggressiveness in fish, while the 8x diet reduced aggressiveness more effectively than the 4x diet. Also, long-term exposure to the 8x diet reduced stress in fish, before and after they were exposed to an acute stress. In conclusion, this study showed that a tryptophan supplemented diet can diminish aggressiveness and stress in Nile tilapia, thus demonstrating a potential to improve fish welfare.

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Cannabidiol (CBD) is a substance derived from Cannabis sativa, widely studied in medicine for controlling neural diseases in humans. Besides the positive effects on humans, it also presents anxiolytic proprieties and decreases aggressiveness and stress in mammals. Therefore, CBD has the potential to increase welfare in reared animals, as it seems to reduce negative states commonly experienced in artificial environments. Here, we tested the effect of different CBD doses (0, 1, 10 and 20 mg/kg) on aggressiveness, stress and reproductive development of the Nile tilapia (Oreochromis niloticus) a fish reared worldwide for farming and research purposes. CBD mixed with fish food was offered to isolated fish for 5 weeks. The 10 mg/kg dose decreased fish’s aggressiveness over time, whereas 20 mg/kg attenuated non-social stress. Both doses decreased the baseline cortisol level of fish and increased the gonadosomatic index. However, CBD 1 and 10 mg/kg doses decreased the spermatozoa number. No CBD dose affected feeding ingestion and growth variables, showing that it is not harmful to meat production amount. Despite the effect on spermatozoa, CBD supplementation exhibits high potential to benefit animals’ lives in artificial environments. Therefore, we showed for the first time that CBD could be used as a tool to increase non-mammal welfare, presenting a great potential to be explored in other husbandry and captivity species.

Cannabidiol (CBD) is a substance derived from Cannabis sativa, widely studied in medicine for controlling neural diseases in humans. Besides the positive effects on humans, it also presents anxiolytic proprieties and decreases aggressiveness and stress in mammals. Therefore, CBD has the potential to increase welfare in reared animals, as it seems to reduce negative states commonly experienced in artificial environments. Here, we tested the effect of different CBD doses (0,1,10, and 20 mg/kg) on aggressiveness, stress, and reproductive development of the Nile tilapia (Oreochromis niloticus) a worldwide fish reared for farming and research purposes. CBD mixed with fish food was offered to isolated fish for 5 weeks. The 10 mg/kg dose decreased fish’s aggressiveness over time, whereas 20 mg/kg attenuated non-social stress. Both doses decreased the baseline cortisol level of fish and increased the gonadosomatic index. However, CBD 1 and 10 mg/kg doses decreased the spermatozoa number. All CBD doses did not affect feeding ingestion and growth variables, showing that it is not harmful to meat production amount. Despite the effect on spermatozoa, CBD supplementation exhibits high potential to benefit animals’ lives on an integrative-based welfare approach. Therefore, we showed for the first time that CBD could be used as a tool to increase non-mammal welfare, presenting a great potential to be explored in other husbandry and captivity species.