短期添加高水平亚麻籽对奶牛生产性能、牛奶脂肪酸组成和瘤胃发酵的影响

本试验旨在研究短期添加高水平亚麻籽对奶牛生产性能、牛奶脂肪酸组成和瘤胃发酵的影响。选取健康、体重相近的荷斯坦牛奶牛30头，随机分为3组，每组10头。分别饲喂牧场基础饲粮（CK组）、添加3 000 g/d （13.01% DM）完整亚麻籽饲粮（WF组）和添加3 000 g/d （13.01% DM）粉碎亚麻籽饲粮（GF组）。试验周期为7周，第1周为环境适应期，第2~6周为饲粮适应期，第7周为试验期，记录试验期日采食量和产奶量，于试验最后1天采集奶样和瘤胃液样品，利用气相色谱-质谱联用（GC-MS）测定乳和瘤胃液中脂肪酸组成。结果表明：①与CK组相比，添加3 000 g/d亚麻籽对奶牛干物质采食量和产奶量均无显著影响（P>0.05），GF组乳脂率和乳蛋白率较CK组有降低的趋势（0.05<P<0.1）。②WF和GF组乳中α-亚麻酸（ALA）和ω-3多不饱和脂肪酸（ω-3 PUFA）的产量较CK组均显著提高（P<0.05），且GF组ALA和ω-3 PUFA的产量显著高于WF组（P<0.05）。③WF组瘤胃pH显著低于CK和GF组（P<0.05），氨态氮（NH₃-N）浓度显著高于CK和GF组（P<0.05）。综上所述，饲粮中短期添加高水平完整亚麻籽和粉碎亚麻籽均不影响奶牛干物质采食量和产奶量，但提高了乳中ALA含量，GF组提高效果较WF组更明显。添加高水平粉碎亚麻籽有降低乳蛋白率和乳脂率的趋势，高水平完整亚麻籽影响了奶牛瘤胃内环境。在实际生产中，应控制亚麻籽的添加量及其饲喂形式，在提高乳中ALA含量的同时，减少亚麻籽对瘤胃发酵的影响。

Effects of Short-term Addition of High-level Flaxseeds on Dairy Performance,Fatty Acid Profiles of Milk and Rumen Fermentation

The purpose of this experiment was to study the effects of short-term addition of high-level flaxseed on production performance, fatty acid profiles of milk and rumen fermentation. Thirty healthy mid-lactation Holstein dairy cows with similar body weight were selected and divided into 3 groups randomly, and fed basal pasture diet (CK group), 3 000 g/d (13.01% of DM) whole flaxseed diet (WF group), and 3 000 g/d (13.01% of DM) ground flaxseed diet (GF group) respectively. The experiment lasted for 7 weeks, first week was aim to adapt the feeding environmental, 2 to 6 weeks was the feed adaptation period, and the 7th week was the test period. Daily feed intake and milk production were recorded during the test period. Milk samples and rumen fluid samples were collected on the last day of the test, and the fatty acid composition of the milk and rumen fluid was determined by GC-MS. The results showed that:①Compared with CK group, the addition of 3 000 g/d flaxseed had no significant effect on dry matter intake and milk production for dairy cows (P>0.05). The milk fat rate and milk protein rate of GF group had a lower tendency than that of CK group (0.05<P<0.1). ②The 3 000 g/d flaxseed addition increased the production of alpha-linolenic acid (ALA) and ω-3 PUFA of milk compared with CK group (P<0.05), and the production of ALA and ω-3 PUFA in GF group were significantly higher than that in WF group (P<0.05). ③The rumen pH of WF group was significantly lower than that of CK and GF groups (P<0.05), and the NH₃-N concentration of WF group was significantly higher than that of CK and GF groups (P<0.05). The acetic to propionic acid ratio in GF group was significantly lower than that in CK group (P<0.05). In summary, short-term addition of high level whole flaxseed and ground flaxseed in the diet did not affect the dry matter intake and milk production of dairy cows, but the ALA content in milk was increased, and the improvement effect of GF group was more obvious than that of WF group. However, the addition of high-level ground flaxseed had a tendency to reduce the milk protein rate and milk fat rate, and the high-level whole flaxseed affects the internal environment of the rumen of dairy cows. Therefore, the amount of flaxseed added and its feeding form should be controlled to increase the ALA content in milk while reducing the impact of flaxseed on rumen fermentation.