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The genetic guide to healthier cows

Chrissy Meyer for Progressive Dairyman Published on 24 February 2016

There’s a great deal of industry buzz around programs and technology that promise to create healthier cows for your herd, but don’t forget about the tool you already have available.

Now is the perfect time to revisit the impact selection for productive life within your genetic plan can have on the overall health and longevity of your cows.



The productive life (PL) number that appears for any given sire on your proof sheet is defined as the number of months longer (or shorter) that his daughters will be productive in your herd as compared to herdmates.

If a bull is 7.0 for PL, his daughters within a given herd are predicted to live seven months longer than the average cow in that herd. If a bull is -2.0 for PL, his daughters are predicted to live about two months less than the average cow in that given herd.

PL is often associated with old cows. However, if you think about which cows live longest in your herd, it would be those that have no troubles calving, fewer incidences of mastitis, no respiratory issues, fewer hoof problems and so on.

‘Four-event’ cows

In reality, genetic selection for PL doesn’t just mean more old cows; it predicts which cows are toughest, healthiest and easiest to manage. We call those the “four-event” cows. If you look at a cow card on your herd management software program, a four-event cow has only four events listed throughout her lactation: fresh, bred, confirmed pregnant and dry.

If those four events are the only major things a cow experiences throughout her lactation, chances are she’s trouble-free, making you money, and will stick around for several lactations.


Any time an event takes place, such as milk fever, a displaced abomasum, retained placenta, mastitis, pneumonia or any other disruption to the normal progression of a cow’s lactation, milk is lost. In addition to lost milk production, vet and treatment costs add to the dollars lost.

The proof is in the numbers

Selection for PL propels you toward the goal of a herd full of four-event cows. Since the actual measure of PL is not calculated until after a cow leaves the herd, we can use other ways to see if higher-PL bulls actually create healthier and more trouble-free cows.

Table 1 breaks down the events within a real 2,400-cow Holstein herd on all first-lactation animals with known, identified sires.

Breakdown of the events within a real 2,400-cow Holstein herd

Click here or on the image above to view it at full size in a new window. (PDF, 1.9 MB)

Based only on the animal’s parent average or PL, this shows the extreme difference in health events between cows with a high-PL pedigree versus those with a low-PL pedigree.


These are real numbers, recorded on this farm’s herd management software program. Keep in mind, management is consistent throughout the herd, and no preferential treatment is provided for any given cows.

As the table clearly illustrates, far fewer of the high-PL cows had issues after calving and throughout their lactation. Fewer cows from the high-PL group were coded as “do not breeds” and, therefore, fewer of the high-PL cows died or were sold.

This means more cows from within that high-PL group claimed the title of trouble-free, four-event cows.

On your dairy, how much does a displaced abomasum decrease a cow’s profitability over her lactation? How much of your milk check is sacrificed with every case of mastitis?

How many dollars are lost for every lame cow or case of pneumonia? If you put a dollar value to the lost production and treatment cost associated with each extra health event experienced by the group of low-PL cows, it adds up significantly.

Want healthier cows? Let PL get you there

While environment, cow comfort and overall management practices all play an integral role in the health of any given herd, genetic selection can also aid your quest for a herd of healthy, trouble-free cows. To do that, keep these points in mind.

  1. Genetic selection for PL will help you create longer-living cows.

  2. PL remains the standard for breeding tougher, healthier cows with fewer issues throughout their lactations.

  3. Include selection for PL as part of your customized genetic plan in order to build your herd of profitable, four-event cows.  PD

Chrissy Meyer is a marketing editor with Alta Genetics. Email Chrissy Meyer