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- Gräns, Albin, 1979, et al.
(författare)
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Stunning fish with CO2 or electricity: contradictory results on behavioural and physiological stress responses
- 2016
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Ingår i: Animal. - 1751-7311 .- 1751-732X. ; 10:2, s. 294-301
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Tidskriftsartikel (refereegranskat)abstract
- Studies that address fi sh welfare before slaughter have concluded that many of the traditional systems used to stun fi sh including CO 2 narcosis are unacceptable as they cause avoidable stress before death. One system recommended as a better alternative is electrical stunning, however, the welfare aspects of this method are not yet fully understood. To assess welfare in aquaculture both behavioural and physiological measurements have been used, but few studies have examined the relationship between these variables. In an on-site study aversive behaviours and several physiological stress indicators, including plasma levels of cortisol and ions as well as blood physiological variables, were compared in Arctic char ( Salvelinus alpinus ) stunned with CO 2 or electricity. Exposure to water saturated with CO 2 triggered aversive struggling and escape responses for several minutes before immobilization, whereas in fi sh exposed to an electric current immobilization was close to instant. On average, it took 5 min for the fi sh to recover from electrical stunning, whereas fi sh stunned with CO 2 did not recover. Despite this, the electrically stunned fi sh had more than double the plasma levels of cortisol compared with fi sh stunned with CO 2 . This result is surprising considering that the behavioural reactions were much more pronounced following CO 2 exposure. These contradictory results are discussed with regard to animal welfare and stress physiological responses. The present results emphasise the importance of using an integrative and interdisciplinary approach and to include both behavioural and physiological stress indicators in order to make accurate welfare assessments of fish in aquaculture.
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| 3. |
- Lundh, Torbjörn, et al.
(författare)
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Dietary protein requirements of tire track eel (Mastacembelus favus Hora, 1923) fingerling
- 2022
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Ingår i: Livestock Research For Rural Development. - 0121-3784. ; 34
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Tidskriftsartikel (refereegranskat)abstract
- Tire track eel Mastacembus favus is an important candidate species for commercial aquaculture in Vietnam, therefore, a ninety day-feeding experiment was carried out to determine appropriate protein levels for efficiently rearing tire track eel fingerlings to complete the procedure of raising this species by using commercial feed. The fish were fed one of seven diets formulated with different levels of protein (24%, 29%, 34%, 39%, 44%, 49% and 54%) at the same energy and fat levels. Triplicate groups of 50 tire track eel fingerlings (initial weight ranged 2.67 - 2.7 g) were randomly assigned to 21 identical conical 500-L tanks equipped with an aeration system and substrates for shelter. Feed intake (FI), protein intake (PI), daily weight gain (DWG), specific growth rate (SGR), feed conversion ratio (FCR), feed conversion efficiency (FCE), protein efficiency (PE), survival rate (SR), net protein utilisation (NPU) and body indices were determined at the end of the experiment. The highest growth rate of fish fed different levels of protein was obtained in group fish fed 44% protein. DWG of this group (0.093 g/day) was higher than those of the groups (24%, 29%, 34% and 54%, p < 0.05), but there was not different from the remaining groups (39% and 49%, p > 0.05). SGR of fish in group fed the 44% protein (1.59%/day) was similar to those of the groups (39% - 54%) but was higher than the remaining groups (24% - 34%). The optimal protein requirement of tire track eel was determined based on the quadratic regression method of Zeitoun et al (1976) with the equation y = - 0.0014 x2 + 0.1265 x - 1.5351 (R 2 = 0.8355). From this equation, the value x-max = 45.2 is the protein content for the fish to achieve maximum growth. After ninety-day treatment period, SR of tire track eel were relatively high ranging from 76.7% to 84.7% as well as body indices was no difference between treatment groups (p > 0.05). FCR was lowest in the 44% protein treatment group (1.43). This study revealed that 44% protein content stimulated the best growth and the lowest FCR as well as the value of 45.2% protein in the feed allowed the fish grow optimally.
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