This study was carried out to evaluate the impact of including Acacia mearnsii tannin extract (TA) as a feed additive on nutrition and productive performance of dairy cows grazing a high‐quality temperate pasture and receiving supplementation with a concentrate feedstuff. Fourteen multiparous Holstein cows were assigned to either of the following treatments: concentrate without or with 20 g TA/kg dry matter (DM). Concentrate intake accounted for 32% of the total DM intake. Tannin addition increased the herbage DM intake by 22% (p  < .05). There was no effect of TA inclusion on milk yield, milk composition, milk nitrogen (N) excretion, milk and plasma urea‐N concentration, urinary excretion of total N, urea‐N, and purine derivatives. However, TA inclusion increased the N intake and retention, total N excretion in manure, fecal N to urine N ratio, and decreased the dietary N efficiency for milk production and the percentage of ingested N excreted in urine (p  < .05). In conclusion, supplementing dairy cows grazing a high‐quality temperate pasture with a concentrate containing 20 g TA/kg DM showed the potential of decreasing the proportion of ingested N excreted in urine without affecting the productive performance.

中文翻译：

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使用金合欢单宁提取物作为饲料添加剂对温带牧场放牧奶牛营养变量和生产性能的影响。

本研究旨在评估将金合欢单宁提取物 (TA) 作为饲料添加剂对在优质温带牧场放牧并补充浓缩饲料的奶牛的营养和生产性能的影响。将 14 头经产荷斯坦奶牛分配到以下任一处理：不含或含 20 g TA/kg 干物质 (DM) 的浓缩物。浓缩物摄入量占干物质摄入总量的32%。添加单宁使牧草 DM 摄入量增加了 22% ( p < .05)。添加 TA 对牛奶产量、牛奶成分、牛奶氮 (N) 排泄、牛奶和血浆尿素-N 浓度、总 N、尿素-N 和嘌呤衍生物的尿排泄没有影响。然而，添加 TA 会增加 N 摄入量和保留量、粪便中的总 N 排泄量、粪便 N 与尿液 N 的比率，并降低日粮 N 的产奶效率和尿液中排泄的摄入 N 百分比 (p < .05 )  。总之，给在优质温带牧场放牧的奶牛补充含有 20 g TA/kg DM 的浓缩物显示出降低尿液中摄入的 N 比例而不影响生产性能的潜力。