饲料蛋白质水平与投喂频率对大黄鱼生长、体组成及蛋白质代谢的影响

【关键词】:大黄鱼;;蛋白质;;投喂频率;;生长;;营养
【摘要】:以初始体重为(13.64±0.18)g的大黄鱼(Pseudosciaena crocea R.)幼鱼为实验对象,采用3×2双因子实验,研究饲料蛋白质水平(40%、45%、50%)和投喂频率(2次/d、1次/d)及其交互作用对其生长、体组成和蛋白质代谢的影响。养殖实验在海水浮式网箱中进行,养殖周期为8周。结果表明:饲料蛋白质水平和投喂频率对大黄鱼幼鱼的增重率(WGR)、特定生长率(SGR)和饲料转化率(FCR)均影响显著(P<0.05)。在40%和45%蛋白质组,1次/d投喂的大黄鱼幼鱼的WGR和SGR均显著低于2次/d投喂组,而FCR则相反。在2次/d投喂时,45%蛋白质组的大黄鱼幼鱼SGR显著高于40%蛋白质组,但与50%蛋白质组差异不显著(P>0.05)。而在1次/d投喂时,50%蛋白质组的大黄鱼幼鱼SGR显著高于40%和45%蛋白质组。在两种投喂频率下,随着饲料蛋白质水平提高,鱼体水分含量均有升高趋势,蛋白质含量显著升高而脂肪含量显著下降(P<0.05)。饲料的蛋白质水平和投喂频率分别对大黄鱼幼鱼的肝脏指数(HSI)、内脏指数(VSI)和血清中的谷丙转氨酶(ALT)及谷草转氨酶(AST)均影响不显著(P>0.05)。投喂频率对肝脏的ALT和AST的影响不显著(P>0.05)。在同一投喂频率下,肝脏ALT和AST均随着饲料蛋白质水平的增加而显著提高(P<0.05)。饲料中的蛋白质水平和投喂频率对大黄鱼幼鱼的生长和FCR的影响存在显著的交互作用(P<0.05),而对血清和肝脏中的ALT和AST、HSI、VSI、肥满度(CF)以及体组成的影响均无交互作用。
An 8-week 3×2 two-factorial experiment was conducted to examine effects of dietary protein level(40%,45% and 50%) and feeding regimen(twice daily and once daily) on the growth,body composition and protein metabolism of juvenile large yellow croakers [initial average weight of(13.64±0.18) g] cultured in floating net cages.Three isolipidic(crude lipid 12%) practical diets were formulated to provide three dietary protein levels of 40%,45% and 50%.Feeding frequencies were twice daily(05:00 and 17:00) and once daily(05:00).Three cages(replicates) were randomly allotted to one treatment with combination of dietary protein level and feeding frequency in a complete randomized design.Each cage was stocked with 50 juvenile large yellow croakers.Fish were carefully fed to apparent satiation by the same person during the feeding trial.The temperature ranged from 26.5 to 30.5°C,salinity from 29‰ to 33‰,and the dissolved oxygen was approximately 7 mg/L during the experiment period.At the termination of the feeding experiment,the total number and mean body weight of the fish in each cage were measured.Five fish were randomly sampled from each cage for individual proximate composition analysis.Activities of alanine aminotransferase(ALT) and aspartate aminotransferase(AST) in serum and liver were determined.The results showed that survival rates,ranging from 90.00% to 94.00%,were not significantly affected by feeding frequency or dietary protein level(P >0.05).Compared with fish fed twice daily,fish fed once daily had significantly lower final weight and specific growth rate(SGR),but significantly higher feed conversion ratio(FCR) at 40% and 45% dietary protein level(P<0.05).The specific growth rate of fish fed the diet with 45% protein was significantly higher than that fed 40% dietary protein(P<0.05),but had no significant difference with that in group with 50% dietary protein when the feeding regimen was two times daily(P>0.05).However,for the regimen of once daily,SGR of fish fed the 50% protein diet was significantly higher than those with 40% and 45% dietary protein(P<0.05).Regardless of feeding frequency,higher dietary protein level lead to higher whole body moisture,body protein contents,and significantly lower body lipid contents.Dietary protein level and feeding frequency both had no significant effect on Hepatosomatic index(HSI),Viscerosomatic index(VSI),activities of ALT and AST of serum(P>0.05).Higher activity of liver ALT and AST were observed in higher dietary protein level at each feeding frequency.Feeding frequency had no significant effect on liver ALT and AST(P>0.05).Regardless of feeding frequency,higher dietary protein level lead to higher liver ALT and AST.Significant interactions between dietary protein level and feeding frequency were found on the growth and FCR of juvenile large yellow croakers(P<0.05),but not on the HSI,VSI,condition factor(CF),body composition and the activity of ALT and AST in serum and liver(P>0.05).This research indicated that 45% of dietary protein level should be used for juvenile large yellow croakers fed two times daily.However,when the feeding regimen was once daily,dietary protein level should be increased to 50% in order to obtain the maximum growth rate.