吉富罗非鱼对饲料中苏氨酸的需要量

Dietary threonine requirement of GIFT Oreochromis niloticus

选用初始体质量为(67.08±0.22)g的吉富罗非鱼(GIFT Oreochromis niloticus)360尾,随机分成6组,每组3个重复,分别在水泥池(2.5 m×1.4 m×1.5 m)中饲喂苏氨酸水平为0.49%、0.88%、1.27%、1.67%、2.06%和2.46%(占饲料的质量分数)的6组等氮半精制饲料(蛋白质质量分数为32.13%),经60 d生长实验确定吉富罗非鱼的苏氨酸需要量。结果显示,随着饲料苏氨酸水平增加,各饲料处理组成活率(96.67%～98.83%)无显著差异。吉富罗非鱼的增重率、特定生长率和蛋白质效率显著升高,均在1.67%组达到最大值;饲料系数显著降低,在1.67%组达到最小值;随着饲料苏氨酸水平进一步提高,上述指标不再发生显著变化。随饲料苏氨酸水平增加,吉富罗非鱼的肥满度无明显变化,肝体指数和脏体指数呈明显的先降后升趋势。饲料苏氨酸适宜水平(0.49%～1.67%)能使吉富罗非鱼肌肉水分含量显著降低,蛋白质含量显著增加,对脂肪和灰分含量无显著影响。饲料中苏氨酸水平为1.67%时,吉富罗非鱼肌肉苏氨酸含量和氨基酸总量均为最大值,显著高于其它各组。以增重率、特定生长率、饲料系数和蛋白质评价指标经二次回归分析得出,吉富罗非鱼饲料中苏氨酸适宜需要量以占饲料的质量分数计为1.62%～1.72%(饲料蛋白质质量分数32.13%)或以占饲料蛋白质的质量分数为5.04%～5.35%。

This experiment was conducted to determine the dietary threonine requirement for GIFT Oreochromis niloticus by formulating six isonitrogenous diets （ 32.13% protein ） containing threonine with increasing levels of 0.49%, 0.88%, 1.27%, 1.67%, 2.06%and 2.46%, respectively.Casein-gelatin-zein meal and crystalline amino acid mixture were used as dietary protein source.The dietary amino acid pattern , except for threonine , was applied to the amino acid pattern of the muscle of GIFT Oreochromis niloticus.Each experimental diet was fed to triplicate groups of 20 GIFT O.niloticus with initial body weight （67.08 ±0.22） g in cement pool （2.5 m ×1.4 m ×1.5 m） for 60 days.The result showed that with the increase of dietary threonine levels , the survival rates of feed test groups had no significant difference.The weight gain＆amp;nbsp;ratios （WGR）, specific growth rates （SGR） and protein efficiency ratios （PER） increased significantly, and reached their peaks in 1.67%group; whereas the feed conversion ratios （ FCR） decreased significantly , and reached its troughs in the same group.As the dietary threonine levels increased further , the above indicators showed no significant difference.The hepatosomatic index （ HIS） and viscerosomatic index （ VSI） of GIFT Oreochromis niloticus first decreased with increasing dietary threonine levels but then increased , but the condition factor （ CF） were no significant differences.Appropriate thre-onine level （0.49%-1.67%） could make GIFT Oreochromis niloticus muscle moisture content decreased significantly , increased protein , and had no significant effect on fat and ash content.As the threonine level reached 1.67%, the muscle threonine content and total amino acids were maximum , higher than other groups.The second-order polynomial regression analysis of WGRs , SGRs, FCRs and PERs.Optimal requirement of dietary threonine for GIFT Oreochromis niloticus was 1.62%-1.72%（of diet with 32.13%protein） or 5.04%-5.35%of diet protein）.