Dietary l-lysine requirement of juvenile Chinese sucker, Myxocyprinus asiaticus

Authors

  • Yucong Lin,

    1. Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Ministry of Education, College of Fishery, Huazhong Agricultural University, Wuhan, China
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  • Yuan Gong,

    1. Nutrition Laboratory, College of Fishery, Huazhong Agricultural University, Wuhan, China
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  • Yongchao Yuan,

    Corresponding author
    1. Nutrition Laboratory, College of Fishery, Huazhong Agricultural University, Wuhan, China
    • Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Ministry of Education, College of Fishery, Huazhong Agricultural University, Wuhan, China
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  • Shiyuan Gong,

    Corresponding author
    1. Nutrition Laboratory, College of Fishery, Huazhong Agricultural University, Wuhan, China
    • Key Laboratory of Agricultural Animal Genetics, Breeding and Reproduction, Ministry of Education, College of Fishery, Huazhong Agricultural University, Wuhan, China
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  • Denghang Yu,

    1. Nutrition Laboratory, College of Fishery, Huazhong Agricultural University, Wuhan, China
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  • Qiang Li,

    1. Nutrition Laboratory, College of Fishery, Huazhong Agricultural University, Wuhan, China
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  • Zhi Luo

    1. Nutrition Laboratory, College of Fishery, Huazhong Agricultural University, Wuhan, China
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Correspondence: Y Yuan and S Gong, College of Fisheries, Huazhong Agricultural University, Wuhan 430070, China. E-mails: yuanyc2007@yahoo.com.cn; gsy@mail.hzau.edu.cn

Abstract

An 8-week feeding trial was conducted to quantify the dietary l-lysine requirement of juvenile Chinese sucker with an initial weight of 1.81 ± 0.04 g reared in indoor flow-through and aerated tanks. Six isonitrogenous and isoenergetic practical diets were formulated to contain graded levels of lysine (1.23%, 1.80%, 2.39%, 2.98%, 3.56% and 4.18% dry matter) at 0.6% increments from dietary ingredients and crystalline l-lysine. Each diet was randomly assigned to triplicate groups of 30 fish each and was fed to apparent satiation by hand three times a day (09:00, 13:00 and 17:00 hours) for 8 weeks. There were significant differences in growth performance and feed utilization among the treatments. Weight gain (WG), specific growth rate and protein efficiency ratio (PER) significantly increased with increasing lysine levels up to 2.39% of diet (< 0.05) and remained nearly the same thereafter (> 0.05). Feed efficiency was the poorest for fish fed the lowest lysine diet (< 0.05) and showed no significant differences when dietary lysine level increased from 2.39% to 4.18%. The N retention (% N intake) significantly increased with dietary lysine level but did not attain a plateau (< 0.05). Survival could not be related to dietary treatments. Whole body protein increased (< 0.05) and whole body lipid decreased (< 0.05) with increasing dietary lysine level. The condition factor and hepatosomatic index were significantly affected by dietary lysine levels, however, viscersomatic index, whole body moisture and ash did not differ significantly among dietary treatments. Broken-line analysis on the basis of WG and PER showed that dietary lysine requirements of juvenile Chinese sucker were 2.43% and 2.40% dry diet (5.52% and 5.45% dietary protein) respectively. Based on the ideal protein approach and the A/E ratios determined from muscle amino acid profile an estimation of the EAA requirements of Chinese sucker juveniles were calculated.

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