title: Feeding rates affect growth, intestinal digestive and absorptive capabilities and endocrine functions of juvenile blunt snout bream Megalobrama amblycephala.
abstract: This study aimed to investigate the optimal feeding rate for juvenile blunt snout bream (average initial weight 23.74 ± 0.09 g) based on the results on growth performance, intestinal digestive and absorptive capabilities and endocrine functions. A total of 840 fish were randomly distributed into 24 cages and fed a commercial feed at six feeding rates ranging from 2.0 to 7.0% body weight (BW)/day. The results indicated that weight gain rate increased significantly (P < 0.05) as feeding rates increased from 2.0 to 5.0% BW/day, but decreased with the further increasing feeding rates (P > 0.05). Protein efficiency ratio and nitrogen and energy retention all showed a similar trend. However, feed conversion ratio increased significantly (P < 0.05) with increasing feeding rates. Feeding rates have little effects (P > 0.05) on whole-body moisture, ash and protein contents, but significantly (P < 0.05) affect both lipid and energy contents with the highest values both observed in fish fed 4.0% BW/day. In addition, moderate ration sizes (2.0-4.0% BW/day) resulted in the enhanced activities of intestinal enzymes, including lipase, protease, Na(+), K(+)-ATPase, alkaline phosphatase and creatine kinase. Furthermore, the mRNA levels of growth hormone, insulin-like growth factors-I, growth hormone receptor and neuropeptide all increased significantly (P < 0.05) as feeding rates increased from 2.0 to 5.0% and 6.0% BW/day, but decreased significantly (P < 0.05) with the further increase in feeding rates, whereas both leptin and cholecystokinin expressions showed an opposite trend. Based on the broken-line regression analysis of SGR against feeding rates, the optimal feeding rate for juvenile blunt snout bream was estimated to be 4.57% BW/day.
authors.affiliation: Key Laboratory of Aquatic Nutrition and Feed Science of Jiangsu Province, College of Animal Science and Technology, Nanjing Agricultural University, No.1 Weigang Road, Nanjing, 210095, Jiangsu Province, People's Republic of China.|Wuxi Fisheries College, Nanjing Agricultural University, No. 69 Xuejiali, Nanquan, Binhu District, Wuxi, 214182, People's Republic of China.
authors.forename: Chao
authors.initials: C
authors.lastname: Xu
authors.affiliation: Key Laboratory of Aquatic Nutrition and Feed Science of Jiangsu Province, College of Animal Science and Technology, Nanjing Agricultural University, No.1 Weigang Road, Nanjing, 210095, Jiangsu Province, People's Republic of China.
authors.forename: Xiang-Fei
authors.initials: XF
authors.lastname: Li
authors.affiliation: Key Laboratory of Aquatic Nutrition and Feed Science of Jiangsu Province, College of Animal Science and Technology, Nanjing Agricultural University, No.1 Weigang Road, Nanjing, 210095, Jiangsu Province, People's Republic of China.
authors.forename: Hong-Yan
authors.initials: HY
authors.lastname: Tian
authors.affiliation: Key Laboratory of Aquatic Nutrition and Feed Science of Jiangsu Province, College of Animal Science and Technology, Nanjing Agricultural University, No.1 Weigang Road, Nanjing, 210095, Jiangsu Province, People's Republic of China.
authors.forename: Guang-Zhen
authors.initials: GZ
authors.lastname: Jiang
authors.affiliation: Key Laboratory of Aquatic Nutrition and Feed Science of Jiangsu Province, College of Animal Science and Technology, Nanjing Agricultural University, No.1 Weigang Road, Nanjing, 210095, Jiangsu Province, People's Republic of China. wbliu@njau.edu.cn.
authors.forename: Wen-Bin
authors.initials: WB
authors.lastname: Liu
mesh_terms: D000818:Animals; D002766:Cholecystokinin; D003530:Cyprinidae / Q000502:physiology*; D004063:Digestion / Q000502:physiology*; D004703:Endocrine System / Q000502:physiology*; D007422:Intestines / Q000502:physiology; D008049:Lipase
chemical_list: D002766:Cholecystokinin; D008049:Lipase
keywords: Blunt snout bream; Gene expression; Growth; Intestinal enzyme activities; Ration size