不同胎次中国荷斯坦牛鲜乳脂肪酸组成研究

对5个胎次共98头中国荷斯坦牛鲜奶乳成分及脂肪酸含量进行了测定分析。结果表明，乳脂率、乳蛋白率及体细胞数在胎次间存在显著（P＜0．05）或极显著（P＜0．01）差异；短、中链脂肪酸（C4∶0～C16∶0）中，除C6∶0在第一胎与其他4胎间含量差异显著（P＜0．05）、C12∶0在第2、5胎间含量差异显著（P＜0．05）外，其他脂肪酸含量在胎次间差异不显著（P＞0．05）；长链脂肪酸中，硬脂酸（C18：0）在第1胎含量最高。第3胎含量最低，1、3胎间差异极显著（P＜0．01）；油酸（C18∶1）和亚油酸（C18∶2）含量在胎次间变化规律相似，均表现为第1胎最低，第3胎最高，且两胎间存在极显著（P＜0．01）和显著差异（P＜0．05）。

Effects of parities on milk fatty acid composition of Chinese Holstein

Milk composition and fatty acids content in fresh milk of 98 Chinese Holstein cows with five parities were determined.The results showed that there were a significant(P<0.05 or P<0.01) differences in milk fat percentage,protein percentage and Somatic cell count(SCC) among different parities.Of the short-and medium-chain fatty acids(C4:0 to C16:0),milk C6:0 content of first calving cows were significantly(P<0.05) more than other parities,milk from second calving cows contained significantly(P<0.05) more C12:0 than that from fifth calving cows,but other fatty acids contents were similar(P>0.05) among different parities.Of the long-chain fatty acids,the first calving cows had the highest level of milk Stearic(C18:0),but the third calving cows were at the lowest levels and there was a significant(P<0.01) difference between the first and the third calving;milk Oleic(C18:1) and Linoleic(C18:2) contents demonstrated a similar pattern of changes among parities with the lowest at first calving and the highest at third calving,and the significant(P<0.01 or P<0.05) differences in milk Oleic and Linoleic contents were noticed between the first and the third calving cows.