BACKGROUND Milk fat is important in terms of economic value and in its potential to provide information concerning cow diet and health. Under current milk payment schemes in Ireland farmer income is directly linked to milk fat production. METHODS A descriptive analysis of milk fat depression (MFD) as calculated from test day milk recording data across all milk recording herds from 2004 to 2014 was undertaken. A dataset of 17 million test day records was used to calculate the prevalence of MFD in Irish milk recorded herds and to create a graphical description of the major descriptive epidemiological trends in milk fat depression in time and space in Ireland. The bulk tank equivalent (BTE) for test day milk fat was calculated for each herd and for cohorts of cows within herds using the formula; BTE milk fat = sum test day fat kg/sum test day milk kg. Milk fat depression was defined as BTE <3.3% milk fat and BTE > 3.2% milk protein. RESULTS The annual prevalence of MFD decreased significantly over time in a linear manner until 2014. Across all years the highest prevalence of MFD occurred in April or May. The highest prevalence occurred most commonly in May, with 9.1% of herds experiencing MFD in 2014. The highest prevalence of MFD in autumn calved cohorts occurred at 181-210 days in milk whereas it occurred at days 61-90 in milk in spring calving cohorts. The stage of lactation for the most common occurrence of MFD in both the spring and autumn cohorts corresponded with the month of May. There were some notable spatial patterns regarding variations in prevalence of MFD across the country. Cohorts of cows with the highest genetic values for milk yield had the highest prevalence of MFD whereas cohorts of cows with the highest breeding values for milk fat percent had the lowest prevalence of MFD. CONCLUSIONS A subpopulation of Irish herds experienced the condition of MFD. Descriptive analysis suggested spatial, temporal and animal level associations. This condition warrants further investigation.

中文翻译：

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记录在案的牛群中，散装罐中等效乳脂降低的流行，时间和空间趋势。

背景技术就经济价值及其提供有关母牛饮食和健康的信息的潜力而言，乳脂很重要。根据爱尔兰现行的牛奶付款计划，农民的收入与牛奶脂肪的生产直接相关。方法采用描述性分析方法，对2004年至2014年间所有奶牛记录日的测试日奶牛记录数据计算得出的牛奶脂肪抑制（MFD）。测试日记录为1,700万的数据集用于计算爱尔兰牛奶记录牛群中MFD的患病率，并以图形方式描述爱尔兰牛奶和脂肪时空分布的主要描述性流行病学趋势。使用以下公式，计算了每头牛群和牛群内牛群的测试日乳脂当量（BTE）。BTE牛奶脂肪=总测试日脂肪公斤/总测试日牛奶公斤。乳脂降低定义为BTE <3.3％乳脂和BTE> 3.2％乳蛋白。结果直到2014年，MFD的年度流行率均随时间呈线性下降。在所有年份中，MFD的最高流行发生在4月或5月。最高发病率发生在五月，2014年有9.1％的牧羊群发生MFD。秋季产犊队列中MFD的最高发病率发生在奶牛181-210天，而春季产犊队列中61-90天发生MFD。 。春季和秋季队列中最常见的MFD发生的泌乳阶段与5月相对应。在全国各地，MFD流行率存在一些明显的空间格局。牛奶产量遗传价值最高的奶牛群体的MFD患病率最高，而牛奶脂肪百分比育种价值最高的奶牛群体的MFD患病率最低。结论一群爱尔兰人经历了MFD的病情。描述性分析提示了空间，时间和动物水平的关联。这种情况值得进一步调查。