日粮添加LA和DHA对乳脂脂肪酸含量及比值的影响

Effects of Dietary LA and DHA Supplementation on the Fatty Acid Profiles of Milk Fat in Lactating Holstein Cows

本试验选用带有永久性瘤胃、十二指肠和回肠瘘管的泌乳荷斯坦奶牛4头,采用4×4拉丁方试验设计,研究日粮添加亚油酸(LA)和二十二碳六烯酸(DHA)对乳常规组成、消化道各段食糜pH以及乳脂脂肪酸构成的影响。试验结果表明:添加LA和DHA不影响乳蛋白和乳糖含量(P>0.05),而添加DHA有显著降低乳脂含量的趋势(P>0.05);日粮共同添加LA与DHA能提高十二指肠前消化道的pH,但差异不显著(P>0.05),而单独添加DHA显著降低了回肠的pH(P<0.05);日粮单独添加DHA增加乳脂中C23:0脂肪酸的含量,但并不降低乳脂中总饱和脂肪酸量。与对照组相比,LA与DHA共同添加使乳脂中总多不饱和脂肪酸增加了100%(P<0.05)。LA与DHA共同添加使乳脂中饱和脂肪酸/不饱和脂肪酸由3.18降低至1.24(P<0.05)。添加DHA使乳脂中总单不饱和脂肪酸/多不饱和脂肪酸由5.94降低至3.00(P<0.05)。上述研究结果表明,日粮添加LA和DHA可改变乳脂中脂肪酸的组成和比例,有利于人体健康,但DHA使产奶量有一定程度的降低。

The objective of this study was to evaluate milk fatty acid profiles and milk composition of lactating cows when LA and DHA were supplemented in diets. Four dairy cows with ruminal, ileac and duodenal fistulas were randomly assigned to control （CK, without additional oil supplementation）, basal diet with 2.7% LA （LA）, 2.7% LA plus 0.5% DHA （LA ＋ DHA）, or 0.5% DHA （DHA） in a 4×4 latin square with 12-week durational periods. The results showed that compared with CK, milk yield and milk fat content decreased when DHA was supplemented, but there were no significant differences among four treatments （P〉0.05）. The pH in duodenal digesta numerically increased with LA and DHA combinational addition （P〉0.05）. The pH of ileac digesta decreased significantly （P〈0.05） only when DHA was supplemented compared with CK. C23：0 content of milk fat in DHA treatment increased, while total saturated fatty acid concentration did not change in contrast with CK. Compared with CK, total polyunsaturated fatty acid was improved by 100% in milk fat from combinational addition of LA and DHA （P〈0.05）. In addition, saturated fatty acids to unsaturated fatty acids ratio in milk fat decreased （P〈0.05） from 3.18 in CK to 1.24 in LA ＋ DHA treatment, while monounsaturated to polyunsaturated fatty acid ratio decreased （P〈0.05） from 5.94 in CK to 3.00 in DHA treatment. In conclusion, our study indicated that fatty acid profiles were changed, and milk quality was improved by dietary LA and DHA supplementation. However, DHA addition in diets had slight negative effect on milk yield.