Dairy Herd Improvement (DHI) testing was developed and continues to provide convenient standardized monthly assessments of milk production and milk components (fat, protein, and somatic cell count (SCC)) for individual dairy cows within a herd. By conducting monthly DHI testing, producers can monitor changes in milk production and components over time, and detect deviations needing to be addressed by management. Remember we cannot manage what we do not measure! DHI reports can identify which cows have just been tested with a SCC of 200,000 cells/mL or greater, as well as cows that have been chronically infected, as shown with multiple tests with a high SCC. When a herd is enrolled in DHI testing, various DHI reports are available. This article will cover one of these reports available from Dairy Records Management Systems (www.DRMS.org) to help producers manage and detect high SCC dairy cows.

Test Day Bulk Tank SCC Report- (DHI 421)

The DHI 421 Test Day Bulk Tank report is similar to a DHI-lab hot-sheet. The DHI-lab hot-sheet lists for each cow tested the milk production, milk components, SCC (score and actual), days in milk, lactation number and the bulk tank SCC if this high SCC cow was removed for the current test date. Cows are listed in order from those contributing the most to the least somatic cells to the bulk tank for the milking tested.

Unlike the Hot sheet, the DHI 421 (Figure 1) also calculates the total milk income, using the milk price reported with no additional quality premiums, for the test day excluding selected high SCC cows. The DHI 421 report identifies the cow, lists her current milk production, current 

SCC and previous test day 

SCC. It also includes the Value Adjusted by SCC which is calculated using the cow’s individual milk production and adjusts the value of the milk based on the SCC. Like the Hot-sheet, this report also provides the percent of SCC contributed to the tank by each cow for the milking tested.

The DHI 421 report and DHI-lab Hot-sheet highlight high SCC cows by ranking them by their contribution of SCC to the bulk tank. Remember when assessing a cow’s contribution of SCC to a shipment of milk, her SCC shedding can fluctuate from milking to milking. The first cow on the list will be the largest contributor of SCC in the bulk tank for the milking sampled. Information from this report helps identify specific cows with high SCC and help make decisions necessary to meet targets for SCC in milk shipped. If a producer is interested in what the bulk tank SCC and income values would be with a certain cow removed, they can use the information listed in the “Without This Cow” column.

What makes these reports useful is the “Without This and Higher Cows” column (highlighted in black). The “Without This and Higher Cows” column displays what the SCC 

average and milk income would be if the cow of interest and all cows with a higher percent of SCC in the tank are removed. The example in Figure 1 indicates that if Pink and Sissy were not included in the bulk tank, the bulk tank SCC would be 169,000 cells and the milk income would be $800.93, not accounting for any potential bonuses. This reduction in income needs to be replaced by protection of your milk market or SCC bonuses.  This report allows producers to target high SCC cows which should be cultured and then a decision made regarding if they should be treated (if clinical), dried off early, or culled.

Take Home Message:

DHI testing provides standardized, accurate milk production and milk component information for every cow for each test date. Producers using DHI testing and DHI reports can track trends in order to improve their milk quality by identifying high SCC cows. Accurately identifying high SCC cows provides a producer with reliable information in order to target cows to culture, and then make an educated decision for the future these cows. Remember we cannot manage what we do not measure!

To sign up for DHI testing or the reports discussed in this article contact www.mydhia.org or www.drms.org.

Authors:  Michele Jones and Donna Amaral-Phillips, Ph.D.

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