Dietary calcium/phosphorus ratio requirement of GIFT tilapia fingerling，Oreochromis niloticus | 吉富罗非鱼饲料钙磷比研究

Chinese. 探讨饲料钙磷比(质量比)对吉富罗非鱼生长、饲料利用、磷表观消化率、体成分、骨组织无机物含量、血清生化指标的影响，确定吉富罗非鱼饲料中适宜的钙磷比。以磷酸二氢钾为磷源、氯化钙为钙源，分别配制等磷（总磷为9～10 g/kg）、等氮、等能、钙磷比理论值分别为2∶1，1.5∶1，1∶1，1∶1.5，1∶2和1∶3（实测值分别为1.8∶1，1.3∶1，1∶1.1，1∶1.5，1∶2.5和1∶2.9）的6组纯化饲料，用之饲养吉富罗非鱼（初始体质量为(46.03±2.14) g/尾）8周，每组设3个重复，测定其体质量增加率、饲料系数、磷表观消化率、体成分、骨组织无机物含量、血清生化指标等。用折线模型分别对供试罗非鱼的特定生长率、全鱼磷含量、脊椎骨磷含量和血清磷含量与饲料钙磷比水平进行相关分析，确定饲料中钙磷比的适宜水平。钙磷比为1∶1.1～1∶2.9的试验组鱼体质量增加率和特定生长率均显著高于钙磷比1.8∶1组(P＜0.05)；钙磷比1∶2.5组的饲料系数显著低于1.8∶1组(P＜0.05)，但与其他各组间无显著差异(P＞0.05)；钙磷比1∶2.5组的磷表观消化率显著高于1.8∶1组、1.3∶1组和1∶2.9组(P＜0.05)，但与1∶1.1组和1∶1.5组无显著差异(P＞0.05)；饲料钙磷比对吉富罗非鱼的脏体比、肝体比、肥满度及成活率均无显著影响(P＞0.05)。随着饲料钙磷比的下降（钙水平的降低），全鱼和脊椎骨的钙、磷含量均呈先升高后降低的趋势(P＜0.05)，肌肉的粗脂肪含量呈升高趋势(P＜0.05)，而全鱼和脊椎骨的粗灰分含量及Ca/P值均无显著变化(P＞0.05)。血清磷含量随饲料钙磷比的下降呈升高的趋势(P＜0.05)，饲料钙磷比对血清钙含量无显著影响(P＞0.05)；血清碱性磷酸酶活力和甲状旁腺激素含量均随饲料钙磷比的下降呈先升高后降低的趋势(P＜0.05)，血清总胆固醇和甘油三酯的含量随饲料钙磷比的下降均呈先降低后升高的趋势(P＜0.05)。吉富罗非鱼要获得最大的特定生长率、全鱼磷含量、脊椎骨磷含量和血清磷含量，其饲料中最适钙磷比分别应为1∶1.5，1∶1.1，1∶1.1和1∶2.4，据此建议在饲料总磷水平为9～10 g/kg时，吉富罗非鱼饲料中钙磷比的适宜水平为1∶1.1～1∶1.5。

English. This experiment was conducted to evaluate the effects dietary calcium/phosphorus ratios (mass ratio) on the growth performance, feed utilization efficiency, the apparent digestibility of phosphorus, body composition, inorganic matter content in bone and serum biochemical indexes of GIFT tilapia fingering, to determine the optimal dietary calcium/phosphorus ratio of feed. GIFT tilapia（Oreochromis niloticus）(Initial weight （46.03±2.14） g) were satiably fed on six experimental isonitrogenous and isoenergetic purfied diets with increasing contents of total phosphate（9-10 g/kg）and calcium/phosphorus ratios（1.8∶1, 1.3∶1, 1∶1.1, 1∶1.5, 1∶2.5 and 1∶2.9）for 8 weeks respectively. Potassium dihydrogen phosphate was the source of phosphate and calcium chloride was the source of calcium. Each treatment was triplicate. The results showed that fish fed the diet with high level of calcium/phosphorus ratio (diet 1) has significantly lower weight gain rate（WGR）and specific growth rate（SGR）than those of fish fed the test diets with diet 3, diet 4, diet 5, diet 6 (P＜0.05), and there were no significant differences among treatments of diet 3, diet 4, diet 5, diet 6(P＞0.05); the feed conversion ratio（FCR）of fish fed the test diets with diet 5 was significantly lower than that fed diets 1 (P＜0.05), while the survival rate(SR), fat factor(FR), viscerosomatic index (VSI), hepatosomatic index (HIS) of fish didn’t show significant differences among various dietary treatments (P＞0.05). The body composition analysis showed that dietary calcium/phosphorus ratios had no significant effect on crude protein and crude ash contents in the whole body, as well as vertebrae crude ash content (P＞0.05). The whole body and vertebrae caclcium, phosphorus concentration were significantly affected by dietary calcium/ phosphorus ratios (P＜0.05), as well as the muscle crude lipid and crude ash contents (P＜0.05), while Ca/P ratios in whole body and vertebrae exhibited no significant differences among various dietary treatments (P＞0.05). The blood chemistry analysis showed that dietary calcium/ phosphorus ratios had distinct effects on serum phosphorus concentration, enzyme activities of alkaline phosphatase (ALP) and parathyroid hormone (PTH) level, as well as contents of triacyglycerol (TG) and total cholesterol (T-CHO) (P＜0.05), but serum calcium content was not clearly influenced by dietary calcium/phosphorus ratios (P＞0.05). Broken-line analysis based on SGR indicated that the optimum calcium/phosphorus ratios requirement for the optimal growth of GIFT tilapia was 1∶1.5. Based on the phosphorus concentration either in the whole body, vertebrae or serum, the dietary calcium/phosphorus ratios requirements were 1∶1.1, 1∶1.1 and 1∶24, respectively. It can be concluded that the calcium/phosphorus requirement for GIFT Tilapia fingerling was 1∶1.1-1∶1.5.