A recent USDA Cattle Inventory Report identified that Pennsylvania was down 5,000 head of milk cows at the start of 2014 compared to 2013 (NASS, 2013). Dairy replacement heifers 500+ pounds for Pennsylvania were up 5,000 head, suggesting there are ample replacements for Pennsylvania dairies in 2014. Considering cull prices should remain steady due to lower beef inventories currently in the U.S., greater culling decisions could be made on dairy operations this year. To assist with those tough decisions, there are a few test-day metrics that can help sort out the top and bottom of the average cull list.
Economic vs. Biological Culls
In order to make the most of culls, cows need to leave the herd based on low production or dairy purposes. Fetrow et al. suggested in a 2006 culling nomenclature review that these low production or dairy purpose culls be considered “economic” culls, instead of the more popular “voluntary” culls. Other culls, those typically labeled “involuntary,” should be considered “biological” culls. For herds to have success with culling strategies, accurate data is crucial to determining why animals have left the herd. If all culls fall into the biological cull category, the producer’s decision to cull is nearly made for them. Cows in the economic cull category allow for greater producer control over which animals stay or leave.
Potential Production Metrics
Making economic culls on current test day production alone may not be enough under current market changes. Variables like lactation to date (LTD) milk and projected 305-d mature equivalent (ME) milk can aid in ranking cows based on overall lactation performance. Potential metrics like Dairy Comp 305 current relative value (RELV) or PCDart Money Corrected Milk™ (MCM) can also enhance the ranking of cows on overall performance. RELV is based on ME305 and is an average of the herd ME. So cows less than 100 are lower than herd average, and those above 100 are higher than herd average. MCM™ is a relatively new metric to PCDart. The variable is a measure of cow productivity based on market values (either component or fluid market) and other milk check values for a specific herd. This allows the calculated value to be based on market value of milk, not just the energy of milk.
A Ten Cow Example
To best demonstrate how different metrics can be used to sort out potential culls based on production, ten cows from a sample farm were selected. Cows were selected based on their reproductive diagnosis of open or do not breed, or based on DIM > 250 and days until due > 100. Cows with current production greater than the herd average (in this case, 80 lbs on the most recent test) were excluded. The resulting ten cows are listed in Tables 1 and 2. Table 1 depicts the current test day production values for the 10 cows, while Table 2 presents some of their current lactation and ME 305D measurements. Just looking at individual values may not clearly show which cow should be culled.