Abstract
BackgroundMilk 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.MethodsA 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.ResultsThe 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.ConclusionsA subpopulation of Irish herds experienced the condition of MFD. Descriptive analysis suggested spatial, temporal and animal level associations. This condition warrants further investigation.
Highlights
Milk fat is important in terms of economic value and in its potential to provide information concerning cow diet and health
For dairy processors, who buy the milk from the farmer and set milk price, higher levels of milk fat are desirable for its economic value, for value added dairy products
Milk fat depression (MFD) or low milk fat syndrome is defined as reduced milk fat yield in the presence of normal or expected milk yield or yield of other milk components such as milk protein [5, 6]
Summary
Milk fat is important in terms of economic value and in its potential to provide information concerning cow diet and health. Milk fat depression (MFD) or low milk fat syndrome is defined as reduced milk fat yield in the presence of normal or expected milk yield or yield of other milk components such as milk protein [5, 6]. Other definitions used include milk fat percentage below 3.2% for Holstein herds [4], or a decrease in herd milk fat percentage of more than 0.4% for a period of ten days or more [5] In addition to these herd level definitions within herd targets have been proposed. It has been suggested that no more than 10% of any group of cows, especially after 70 days in milk, should have a milk fat test of below 2.5% [4]
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