Journal
COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY B-BIOCHEMISTRY & MOLECULAR BIOLOGY
Volume 233, Issue -, Pages 4-10Publisher
ELSEVIER SCIENCE INC
DOI: 10.1016/j.cbpb.2019.03.007
Keywords
Illumination time; Growth; Heterogeneity; Antioxidant enzymes; Blunt snout bream
Categories
Funding
- National Technology System for Conventional Freshwater Fish Industries of China [CARS-46-20]
- Nutrient Requirements Evaluation and Formulated Feed Development for Aquatic Species Mainly Cultured in China [201003020]
- Key Laboratory of Aquatic Nutrition and Feed Science of Jiangsu Province
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Juvenile blunt snout bream Megalobrama amblycephala were reared under three photoperiods, 8 L: 16D, 12 L: 12D and 16 L: 8D (L: light; D: dark) for over 8 weeks. The results showed that growth performance was significantly enhanced by long photoperiod. Contrary to feed conversion ratio, final length, final weight, weight gain and feed intake increased significantly as illumination time increased from 8 h daily to 16 h daily. Low size heterogeneity and whole-body lipid content in fish exposed to long photoperiod were also observed. Both relative mRNA expression level of GH and IGF-I increased as illumination time increased from 8 h to 16 h daily. The lowest value of plasma cortisol was observed at the middle the photophase while the highest value was observed at the transition between the day and night span. Hepatic MDA content significantly increased as illumination time increased from 8 h daily to 16 h daily. The activities of hepatic catalase and glutathione peroxidase were lowest in fish exposed to 16 L: 8D photoperiod and significantly lower than that in fish exposed to 8 L: 16D. These results indicate that photoperiod manipulation may not only improve growth performance but also reduce size heterogeneity. However, prolonged photoperiod could cause chronic stress since plasma cortisol level was higher in the long photoperiod group, leading to an increasing oxidative stress.
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