This study investigated the effects of substituting ear corn silage (ECS) for commercial formula feed on milk production and milk fatty acid profiles in grazing dairy farms during the summer season. A field survey was conducted on five grazing dairy farms in every summer month of 2017, 2018, and 2019. Three of the five farms substituted fresh ECS for the commercial formula feed at a ratio of 2:1 from July of each year (ECS farms). Other farms maintained the same feeding management as before (non‐ECS farms). An interview survey was conducted on each farm to calculate feed intake and milk yield per cow. Feed and milk samples were collected in each survey. Milk compositions and milk fatty acid profiles were determined. The substitution of ECS for the commercial formula feed did not affect milk yield or milk composition, but ECS farms maintained low levels of milk urea compared with non‐ECS farms (p < .01). The ECS substitution also influenced some of the milk fatty acid proportions; C16:0 and C16:1 increased, and trans‐11 C18:1, cis‐9,trans‐11 C18:2, and the sum of polyunsaturated fatty acids decreased, while these fatty acid proportions were maintained in non‐ECS farms throughout the summer season (p < .05).

中文翻译：

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穗玉米青贮饲料补充对放牧奶牛场牛奶产量和牛奶脂肪酸谱的影响。

本研究调查了用穗玉米青贮饲料 (ECS) 替代商业配方饲料对夏季放牧奶牛场牛奶产量和牛奶脂肪酸组成的影响。在 2017 年、2018 年和 2019 年的每个夏季月份对五个放牧奶牛场进行了实地调查。五个奶牛场中的三个从每年 7 月开始以 2:1 的比例用新鲜 ECS 代替商品配方饲料（ECS 农场). 其他农场保持与以前相同的饲养管理（非 ECS 农场）。对每个农场进行了访谈调查，以计算每头奶牛的采食量和产奶量。每次调查都收集了饲料和牛奶样本。确定了乳成分和乳脂肪酸谱。用 ECS 替代商业配方饲料不会影响牛奶产量或牛奶成分，p  < .01）。ECS 替代品也影响了一些乳脂肪酸比例；C16:0 和 C16:1 增加，反式‐11 C18:1、顺式‐9、反式‐11 C18:2 和多不饱和脂肪酸总量减少，而这些脂肪酸比例在整个非 ECS 农场中保持不变夏季 ( p  < .05)。