军曹鱼幼鱼对吡哆醇的需要量

Dietary pyridoxine requirement for juvenile cobia(Rachycentron canadum)

以初始体重(3.23±0.06)g的军曹鱼为研究对象,以酪蛋白(不含维生素)、明胶、鱼肉浓缩蛋白为蛋白源,在基础饲料中分别添加0、2、4、8、16和32mgPN/kg,配制出6种实验饲料,使饲料中吡哆醇的水平分别达到0.22、1.89、3.87、7.54、14.75和29.88mgPN/kg,研究军曹鱼对吡哆醇的需要量。养殖实验在室内流水系统中(250L)进行,每个处理设3个重复,每个重复放养军曹鱼25尾。养殖实验过程中,海水盐度为30～34,水温28～32℃,溶氧>7mg/L,养殖实验持续9周。实验结果显示,在0.22～3.87mgPN/kg水平范围内,随着饲料中吡哆醇含量的升高,实验鱼特定生长率显著升高,当饲料吡哆醇水平达到或高于3.87mg/kg时,各饲料组实验鱼的特定生长率(2.68～2.71%/d)无显著差异,而都显著高于0.22和1.89mg/kg饲料组的特定生长率(1.17～2.06%/d)P<0.05)。军曹鱼肝脏吡哆醇含量、吡哆醛含量、谷丙转氨酶活力、谷草转氨酶活力均与特定生长率有相似的变化趋势,即在3.87mg/kg饲料组接近或者达到最大值,在达到或超过3.87mg/kg时达到或近似达到一平台。根据实验结果,以军曹鱼幼鱼特定生长率和谷丙转氨酶活力、谷草转氨酶活力分别拟合折线模型,得到军曹鱼幼鱼对饲料中吡哆醇的需要量为3.09～3.26mg/kg饲料。

Vitamin B6 or pyridoxine in the form of pyridoxal phosphate participates as a prosthetic group of enzymes in a large number of metabolic reactions, particularly those associated with the metabolism of proteins and amino acids. With the success of artificial propagation and larval production, the culture of cobia becomes widely distributed in southern coastal provinces of China （especially in Guangdong and Hainan Provinces） as well as Southeast Asia. However, currently the growth of cobia heavily depends on trash fish and the development of formulated feeds for cobia is still in its infancy. The objective of this study is to detect the optimal requirement of pyridoxine in diet of juvenile cobia Rachycentron. canadum. Basal diet was formulated using vitamin-free casein, gelatin and fish protein concentrate as the protein source. The graded levels of PN （0,2,4,8,16 and 32 mg/kg diet） were added to the basal diets to formulate six experimental diets containing 0. 22 ,1. 89 , 3. 87 , 7. 54, 14.75 and 29. 88 mg PN/kg diet, analyzed by HPLC, respectively. Each diet was fed to three replicate groups of cobia in 300 L tanks for 9 weeks, and each tank was stocked with 25 fish [ initial weight （3.23 ±0.06） g]. The water salinity was from 30 to 34, temperature fluctuated from 28 to 32 ℃ and dissolved oxygen was above 7 mg/L. The results showed that specific growth rate（SGR） have an increasing trend with the increase of dietary pyridoxine（ from 0.22 to 3.87 mg/kg ）, but no significant differences were observed among diets containing 3.87 mg/kg PN or above. The contents of PN and AST in liver of fish fed diets with 3.87 mg/kg were significantly higher than the treatments with the contents of PN lower than 3.87 mg/kg, however, there were no significant differences among diets containing 3.87 - 29.88 mg/kg PN. The contents of PLP and the activities of ALT of the diet containing 7.54 mg/kg PN were significantly higher than the diets containing PN 〈 7.54 mg/kg, however, no significant differences were discovered among diets containing PN 〉 7.54 mg/kg. The dietary pyridoxine requirement was estimated to be 3.09 - 3.26 mg/kg by the broken-line model based on the SGR, and the activities of ALT in fish liver.