草鱼肠系膜脂肪沉积量的测定与分析

为了精确且批量测定草鱼肠系膜脂肪（肠脂）沉积量，避免传统人工刮取称量方法耗时费力、量化粗糙等问题，本研究利用脂溶性染料油红O可特异性着色脂肪的特性，探索开发出一种便捷定量草鱼肠脂含量的新方法。测试发现，麻醉解剖200尾平均体质量约80 g的草鱼，取出整个内脏团简单处理并塞入PIT个体识别标记后，样品集中进行多聚甲醛固定、无水乙醇脱水、油红O染液定染，可在维持样品组织完整的基础上，实现肠脂组织的特异性、均一化批量染色处理。各染色样品再分别通过无水乙醇溶剂完全萃取，萃取液吸光度测定，并依据绘制的标准曲线（y = 0.0276x + 0.0403, R2 = 0.9997），即可精确获得个体肠脂沉积的相对含量，是以萃取出的油红O质量来表示。对比发现，样品肠脂组织染色-萃取量化结果与传统刮取称量数据保持了较高的相关性（n = 20，r = 0.80）。进一步的统计分析显示，对于同塘养殖体质量变异系数8.93%的草鱼群体（n = 200），萃取测定的肠脂沉积量变异系数达到24.49%，预示该性状具有丰富变异特征及遗传改良潜力。相关与聚类分析显示，肠脂沉积量与内脏质量相关性最高（r = 0.60），并且聚为一类，符合二者同属脏器关联指标的预期。多元线性回归分析显示，利用简单易测的形态指标只能解释肠脂沉积量的少量变异（R2 = 0.20），表明基于表型性状的拟合回归方程进行间接预测的效果不佳，直接测定是该性状精准量化的有效途径。本研究为草鱼体脂性状改良提供了一种性状精确测定方法。

Determination and analysis of the amount of mesenteric fat deposition in grass carp (Ctenopharyngodon idella)

Mesenteric fat weight (MFW) is a representative index used to reflect body lipid level in Ctenopharyngodon idella. However, the traditional measurements by artificial scrape and weighing is time-consuming, labor intensive and high operating errors, especially when many samples are to be handled. To avoid such limitations, this study developed a rapid and sensitive method for the quantitation of mesenteric fat utilizing the lysochrome dye oil red O. The initial operation procedures included: fish anesthetization, sample collection of visceral mass, PIT-tag implantation, sample fixation, sample dehydration, oil red O staining. After the above steps, mesenteric fat could be specifically stained by oil red O dye, and all the samples were stained uniformly. After sample extraction and absorbance measurement of extraction liquid, the weight of oil red O extracted from the stained sample could be accurately obtained according to the standard curve of oil red O (y = 0.0276x + 0.0403, R2 = 0.9997). The oil red O weights were used as MFWs in this study, and had good consistency with the fat weights quantified by the conventional scraping method (r = 0.80). Furthermore, data analysis showed that the coefficient of variation for MFW (24.49%) was greater than for body weight (8.93%) in the cultured population of C. idella (n = 200), indicating a significant potential for its genetic improvement. Correlation and cluster analysis showed that MFW was positively correlated with all the observed traits, of which visceral weight (VW) had the highest correlation coefficient of 0.60 (P ? 0.01), and was clustered into one group. The results were as expected that both MFW and VW belonged to viscera-related indexes. Multiple linear regression analysis showed that morphological indexes could explain only a small amount of variation for MFW (R2 = 0.20), indicating that the regression prediction was unsatisfactory, and direct measurement remained an effective approach. This study provided an accurate quantitative method for genetic improvement of body lipid traits in C. idella.