Among the long-chain fatty acids (FA), the omega-3 (n-3) FA have the most potent immunomodulatory activities. In the present large-scale study, we tested the effects of supplementation of α-linolenic acid (ALA) from flaxseed commenced at the dry period on milk yield, health and fertility of dairy cows. Cows in a large commercial dairy farm were randomly divided into two groups 21 days before expected calving. During the dry period, cows in the treatment group were fed a diet that contained, on a DM basis, 40 g/kg of an extruded flaxseed supplement (EFLX; n = 276); their postpartum diet contained 50 g/kg of the same supplement. The cows were group-fed, and based on average cow's intake, the EFLX cows consumed 80 and 220 g ALA/day per cow prepartum and postpartum, respectively. The control cows received a diet with a different composition but a similar content of nutrients (CTL; n = 240). A veterinarian routinely examined the cows 7 to 10 days after calving, treated them according to the farm's routine practice, and determined their body condition score at that visit and at peak lactation. Milk yield was 4.5% greater (1.8 kg/day; P < 0.0001), and fat (P < 0.0001) and protein (P = 0.002) contents were lower in the EFLX vs. CTL group. The proportion of n-3 FA in milk was 3.9 times higher in EFLX than in CTL cows (P < 0.0001), and the omega-6 (n-6):n-3 ratio in the milk fat decreased from 13.0 in the CTL cows to 4.1 in the EFLX cows (P < 0.0001). The unsaturated FA content in milk fat was 20.1% greater in EFLX than in CTL cows (P < 0.0001). Ketosis incidence was lower in the EFLX vs. CTL group, 23.5 and 31.2%, respectively (P = 0.05), and ketosis was less severe in the former (P = 0.03). The mortality rates in EFLX and CTL cows were 0.7 and 4.6%, respectively (P = 0.005). No differences were observed in conception rates at first or second insemination, but days from first service to conception and calving to conception were 17 (P = 0.07) and 18 days (P = 0.09) less in the EFLX cows, respectively. In conclusion, supplementation of EFLX to dairy cows from the dry period increased milk yield, decreased incidence of ketosis and severe metritis, reduced mortality, and tended to enhance fertility performance. Overall, ALA supplementation improved milk quality and was beneficial to the cow's health and fertility.

在长链脂肪酸（FA）中，omega-3（n-3）FA具有最有效的免疫调节活性。在当前的大规模研究中，我们测试了在干旱时期从亚麻籽中补充α-亚麻酸（ALA）对奶牛的产奶量，健康和生育能力的影响。在预期产犊前21天，将大型商业奶牛场中的母牛随机分为两组。在干燥期，治疗组的母牛饲喂的日粮中含有以干物质为基础的40 g / kg挤出亚麻籽补品（EFLX; n = 276）；他们的产后饮食中含有50克/千克的相同补充剂。母牛是集体喂养的，根据母牛的平均摄入量，EFLX母牛在产前和产后每天分别消耗80和220 g ALA。对照母牛的饮食结构不同，但营养成分相似（CTL；n  = 240）。兽医对产犊后的7至10天进行例行检查，并按照农场的常规做法对其进行处理，并在每次探视和泌乳高峰期确定其身体状况得分。牛奶产量提高4.5％（1.8公斤/天; P <0.0001），脂肪（P <0.0001）和蛋白质（P = 0.002）EFLX与CTL组相比含量较低。牛奶中n-3 FA的比例在EFLX中比CTL牛高3.9倍（P <0.0001），牛奶中omega-6（n-6）：n-3的比例从CTL中的13.0降低EFLX奶牛中的奶牛达到4.1（P <0.0001）。EFLX中乳脂中的不饱和脂肪酸含量比CTL牛高20.1％（P <0.0001）。与CTL组相比，EFLX组的酮症发生率较低，分别为23.5％和31.2％（P  = 0.05），而在前者中酮症的严重程度较轻（P  = 0.03）。EFLX和CTL奶牛的死亡率分别为0.7和4.6％（P = 0.005）。第一次或第二次授精的受胎率没有差异，但是 在EFLX奶牛中，从第一次服务到受孕和产犊到受孕的天数分别减少了17天（P  = 0.07）和18天（P = 0.09）。总之，在干旱时期向奶牛补充EFLX可以增加产奶量，减少酮症和严重子宫炎的发生率，降低死亡率，并倾向于提高生育能力。总体而言，ALA补充剂改善了牛奶质量，并有益于母牛的健康和生育能力。