中国荷斯坦牛乳中体细胞评分与脂肪酸含量和组成的相关分析

 【目的】探索中国荷斯坦牛乳中体细胞评分（SCS）与脂肪酸含量和组成的相关性。【方法】采集121头无临床乳房炎、胎次为2—3胎、泌乳期在100—300 d的中国荷斯坦牛早、中、晚共3次的混合奶样，用气相色谱法测定乳中脂肪酸含量，并用多因素方差分析法分析季节、胎次、泌乳阶段、乳中体细胞评分对乳脂率和脂肪酸含量的影响，同时对乳脂率和脂肪酸含量与乳中体细胞评分进行了相关和回归分析。【结果】乳中共检出21种脂肪酸，季节对脂肪酸含量和组成有显著影响（P＜0.05），泌乳阶段对脂肪酸含量和组成影响较小；除十四碳一烯酸（C14：1）、棕榈油酸（C16：1）、十七酸（C17：0）、硬脂酸（C18：0）、亚油酸（C18：2n6c）、二十酸（C20：0）、二十碳三烯酸（C20：3）、花生四烯酸（C20：4）和多不饱和脂肪酸（PUFA）等8种脂肪酸外，SCS显著影响乳脂率和其它脂肪酸绝对含量（P＜0.05）。乳脂率、脂肪酸总含量、饱和脂肪酸（SFA）、单不饱和脂肪酸（MUFA）及短、中和长链等19类脂肪酸的绝对含量随着乳SCS的逐渐增加而降低。除4种相对含量较低的脂肪酸（十一酸（C11：0）、二十酸（C20：0）、二十碳三烯酸（C20：3）和二十二碳六烯酸（DHA，C22：6）外，SCS对乳中其它脂肪酸及饱和SFA、MUFA、多不饱和脂肪酸（PUFA）及短、中和长链等23类脂肪酸的相对含量均无显著影响。相关分析表明，SCS与SFA、MUFA及短、中和长链脂肪酸绝对含量均呈显著负相关（P＜0.05），与PUFA和长链脂肪酸的相对含量呈显著正相关（P＜0.05），与SFA、中、短链脂肪酸的相对含量呈显著负相关（P＜0.05）。回归分析表明，SCS与脂肪酸总量、SFA、MUFA及短、中和长链脂肪酸绝对含量的最佳回归方程均为对数函数，拟合度均在0.9以上；与SFA相对含量的最佳回归方程为指数函数，拟合度达到0.9以上，而与其它各种类脂肪酸相对含量的回归方程拟合度均低于0.9。【结论】该结果为通过SCS来预测和评估乳脂肪酸含量和组成提供了科学依据。

Correlation Between the SCS and the Amount and Composition of Fatty Acids in Milk of Chinese Holstein

【Objective】 The objective of this study was to investigate the correlation between the SCC and the amount and composition of fatty acids in milk of Chinese Holstein 【Method】 Mixed milk samples were collected in the morning, noon and at night from 121 Chinese Holstein cows that free of clinical mastitis, and the parity was two or three, day in milk was from 100 to 300. The amounts of fatty acid of milk were determined by gas chromatography. The effects of SCS on fat percentage and fatty acid composition of milk were analyzed by one-way ANOVA. The SPSS software was used to analyze SCS and milk fatty acids composition of correlation and regression. 【Result】 Twenty-one fatty acids which are from C4 to C22 can be found out. Season had significant effects on the quantity and composition of fatty acids (P＜0.05), and the milking stage had minor effects on the quantity and composition of fatty acids. The effects of SCS on fat percentage and the amount of fatty acids were significant at 0.05 except eight fatty acids (C14：1, C16：1, C17：0, C18：0, C18：2n6c, C20：0, C20：3, C20：4 and PUFA). With the increasing of SCS in milk, fat percentage, the amount of total fatty acid, SFA, MUFA, short chain FA, medium chain FA and long chain FA were decreasing. The SCS showed no significant effects on the relative amount of twenty-three FA including SFA, MUFA, PUFA, short chain FA, medium chain FA and long chain FA except four low content of FA (C11：0, C20：0, C20：3 and DHA). SCS a showed significant negative relationship with the amounts of SFA, MUFA, short chain FA, medium chain FA and long chain FA (P＜0.05), and a significant positive relationship with the relative amount of PUFA and long chain FA. SCS showed a significant negative relationship with the relative amount of SFA, short chain FA and medium chain FA (P＜0.05). Logarithm equations were optimum for the amount of total FA, SFA, MUFA, short chain FA, medium chain FA and long chain FA depending on SCS, and the fitness of the equations were above 0.9. Exponent equations were optimum for the relative amount of SFA depending on SCS, and the fitness of the equations were also above 0.9. The fitness of other equations with the relative amount of FA depending on SCS were below 0.9. 【Conclusion】These results have provided a useful foundation for the prediction and evaluation of FA through SCS.