The unique rumen of dairy cows allows them to digest fibrous forages and feedstuffs. Surprisingly, to date few attempts have been made to develop national methods to gain an understanding on the make-up of a dairy cow's diet, despite the importance of milk production. Consumer interest is growing in purchasing milk based on the composition of the cows' diet and the time they spend grazing. The goal of this research was to develop such a methodology using the national farm survey of Ireland as a data source. The analysis was completed for a 3-yr period from 2013 to 2015 on a nationally representative sample of 275 to 318 dairy farms. Trained auditors carried out economic surveys on farms 3 to 4 times per annum. The auditors collected important additional information necessary to estimate the diet of cows including the length of the grazing season, monthly concentrate feeding, type of forage(s) conserved, and milk production. Annual cow intakes were calculated to meet net energy requirements for production, maintenance, activity, pregnancy, growth, and live weight change using survey data and published literature. Our analysis showed that the average annual cow feed intake on a fresh matter basis ranged from 22.7 t in 2013 to 24.8 t in 2015 and from 4.8 to 5 t on a dry matter basis for the same period. Forage, particularly pasture, was the largest component of the Irish cow diet, typically accounting for 96% of the diet on a fresh matter basis and 82% of dry matter intake over the 3 yr. Within the cows' forage diet, grazed pasture was the dominant component and on average contributed 74 to 77% to the average annual cow fresh matter diet over the period. The proportion of pasture in the annual cow diet as fed was also identified as a good indicator of the time cows spend grazing (e.g., coefficient of determination = 0.85). Monthly, forage was typically the main component of the cow diet, but the average contribution of concentrate was substantial for the early spring months of January and February (30 to 35% of dry matter intake). Grazed pasture was the dominant source of forage from March to October and usually contributed 95 to 97% of the diet as fed in the summer period. Overall, the national farm survey from 2013 to 2015 shows that Irish dairy farms are very reliant on forage, particularly pasture, regardless of whether it is reported on a dry matter basis or as fed. There is potential to replicate this methodology in any regions or nations where representative farm surveys are conducted.

奶牛独特的瘤胃使他们能够消化纤维状的饲料和饲料。出乎意料的是，尽管牛奶生产很重要，但迄今为止，几乎没有人尝试开发出全国性的方法来了解奶牛饮食的组成。消费者对购买牛奶的兴趣正根据奶牛的饮食组成和他们放牧的时间而增加。这项研究的目的是使用爱尔兰全国农场调查作为数据源来开发这种方法。该分析在2013年至2015年的3年时间内完成，对全国有代表性的275至318个奶牛场进行了分析。训练有素的审核员每年对农场进行3至4次经济调查。审核员收集了估算奶牛饮食所必需的重要其他信息，包括放牧季节的长短，每月精饲料的投喂量，保存的草料类型和产奶量。使用调查数据和已发表的文献计算出牛的年摄入量，以满足生产，维持，活动，妊娠，生长和活体重变化的净能量需求。我们的分析表明，同期新鲜牛平均年摄食量从2013年的22.7吨到2015年的24.8吨，以干物质计从4.8吨到5吨不等。牧草，特别是牧草，是爱尔兰奶牛日粮中最大的组成部分，在过去三年中，通常以新鲜物质为基础占日粮的96％，以干物质为食占82％。在奶牛的饲料饮食中，放牧的牧草是主要的组成部分，在此期间，平均每年对牛新鲜物质饮食的贡献为74％至77％。饲喂的年牛饲料中牧场的比例也被确定为母牛放牧时间的良好指标（例如，确定系数= 0.85）。每月饲草通常是母牛饮食的主要组成部分，但在一月和二月的初春月份，精料的平均贡献是巨大的（占干物质摄入量的30％至35％）。从三月到十月，放牧的牧草是牧草的主要来源，通常占夏季饲喂日粮的95％到97％。总体而言，2013年至2015年的全国农场调查显示，爱尔兰的奶牛场非常依赖牧草，尤其是牧场，不论是以干物质为基础还是以饲料为基础进行报告。有可能在进行代表性农场调查的任何地区或国家都采用这种方法。