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摘要
The present experiment was conducted to determine the dietary vitamin A (VA) requirement of juvenile Wuchang bream by formulating six isonitrogenous and isoenergetic purified experimental diets containing 0, 1934, 3885, 7924, 15,935 and 47,917 IU VA (as retinol acetate) kg(-1) diet, respectively. Each experimental diet was fed to triplicate groups of 25 juveniles each with initial average weights of 2.40 +/- 0.01 g in the circular tank for 90 days. Weight gain, protein efficiency ratio, plasma complement 3, plasma complement 4, white blood cell, red blood cell and hemoglobin content significantly increased with increasing dietary VA level, reached a peak with 1934 or 3885 IU kg(-1) VA, and then decreased. Feed conversion ratio (FCR) was lower in the group fed 3885 IU kg(-1) dietary VA than those fed the 0, 15,939 and 47,917 IU kg(-1) VA diets. Hepatosomatic index and plasma alanine aminotransferase activity were higher in fish fed the 0 IU VA kg(-1) diet than those fed with dietary VA. Similar trend was obtained for aspartate aminotransferase activity and the highest activity was found in the group of 47,917 IU kg(-1) VA. The cumulative mortality after Aeromonas hydrophila challenge of the group fed the 3885, 7924 and 15,935 IU kg(-1) VA diets was significantly lower than those fed 0 IU kg(-1) dietary VA. The overall results of the present study indicate that the dietary VA requirement of juvenile Wuchang bream on the bases of the broken-line regression analysis of FCR was estimated to be 3914 IU kg(-1) of diet. @@@ Statement of relevance: The requirements and immune responses of vitamin A in aquatic animals have been studied in many fish. Dietary deficiency symptoms of vitamin A include skeletal deformity, eye lesions, hemorrhages of fins and eyes, and reduced immunity and growth. Therefore, it is important to know the vitamin A requirement of targeted species and incorporate into diets to prevent deficiency symptoms. Wuchang bream (M. amblycephala) is a principal species in Chinese freshwater polyculture systems with production in China of approximately 0.72 million tons in 2012. However, the growth and immune responses associated with vitamin A in Wuchang bream have not been studied. Therefore, the aim of this study was to quantify the dietary vitamin A requirement of Wuchang bream using growth and immunity parameters. @@@ The present experiment was conducted to determine the dietary vitamin A (VA) requirement of juvenile Wuchang bream by formulating six isonitrogenous and isoenergetic purified experimental diets containing 0, 1934, 3885, 7924, 15,935 and 47,917 IU VA (as retinol acetate) kg(-1) diet, respectively. Each experimental diet was fed to triplicate groups of 25 juveniles each with initial average weights of 2.40 +/- 0.01 g in the circular tank for 90 days. Weight gain, protein efficiency ratio, plasma complement 3, plasma complement 4, white blood cell, red blood cell and hemoglobin content significantly increased with increasing dietary VA level, reached a peak with 1934 or 3885 IU kg(-1) VA, and then decreased. Feed conversion ratio (FCR) was lower in the group fed 3885 IU kg(-1) dietary VA than those fed the 0, 15,939 and 47,917 IU kg(-1) VA diets. Hepatosomatic index and plasma alanine aminotransferase activity were higher in fish fed the 0 IU VA kg(-1) diet than those fed with dietary VA. Similar trend was obtained for aspartate aminotransferase activity and the highest activity was found in the group of 47,917 IU kg(-1) VA. The cumulative mortality after A. hydrophila challenge of the group fed 3885, 7924 and 15,935 IU kg(-1) VA diets was significantly lower than those fed 0 IU kg(-1) dietary VA. @@@ In a word, an excess or deficiency of VA reduced WBC, RBC, HBG, C3 and C4 contents, increased blood AST and ALT activities and enhanced morality after A. hydrophila infection. Taken together, our results suggest that the optimum requirement of dietary VA for juvenile Wuchang bream is 3914 IU kg(-1) of diet based on the broken-line regression analysis of FCR versus different dietary VA levels, respectively.
- 出版日期2016-1-1
- 单位南京农业大学; 中国水产科学研究院淡水渔业研究中心
