Breeding for Health Traits

Interrelationships are the key!

You’ve probably heard the excuses why Health and Management traits shouldn’t be a key focus within your breeding program - low heritabilities, low reliabilities and perhaps most significantly the belief that the numbers can’t be right if they promote a more moderate framed cow with less stature that isn’t as refined. Proponents of Health and Management traits are less likely to be concerned about this apparent conflict with “big cow” breeding goals from the past accepting that we should instead be basing our breeding decisions on what works best for the cow. And while it’s true that reliabilities for Health and Management traits can be a challenge early in a sire’s marketing career there’s one additional fact that helps offset this concern: many of the traits like Productive Life, Daughter Pregnancy Rate, Somatic Cell Score and Calving Ease influence each other. Bulls that fare well on one trait often fare well on many of these traits. That’s why using an index that includes all of these traits helps overcome any reliability concerns that might exist.

Why a Health Index Makes Sense

In August Alta introduced the US industry’s first Health index to aid producers in the selection for improved health and longevity in future generations. The logic was simple: one number is easier to focus on than individual indexes for all the traits that go into creating it. As a further step, the best rated Alta sires are now being marketed under the Healthplus brand. To demonstrate how interrelated the health traits are here are some facts about the current listing of Healthplus sires:

• 20 out of 20 bulls rated above +1.00 UDC
• 15 out of 20 bulls rated above +1.00 FLC
• 16 out of 20 bulls rated above +1.0 PL
• 13 out of 20 bulls rated above +2.0 PL
• 13 out of 20 bulls rated below 3.00 SCS
• 18 out of 20 bulls rated 9 or lower for CE
• 20 out of 20 bulls rated 8 or lower for DCE
• 18 out of 20 bulls rated average or higher for DPR

It all starts with Calving Ease...

Do you remember the argument that we used to use to justify breeding bigger cows? We used to say that in part it was to reduce the incidence level of difficult calvings. In fact, we also used to say that relying on Calving Ease sires would worsen the problem in subsequent generations – smaller calves become smaller cows that have more difficulty delivering a calf themselves. It turns out this argument is completely false! Most Calving Ease sires are also a source of improved Daughter Calving Ease. Using the Jersey cow as an extreme example, perhaps this fact shouldn’t surprise us. After all, calving difficulty is barely an issue in the Jersey breed and the Jersey heifer typically joins the milking string at a younger age than the Holstein.

So why start with Calving Ease? Think about it - when a cow calves easily, more often than not she will also come back into heat sooner and she is more likely to get pregnant sooner. So in fact this logic helps explain why there would be a positive relationship between Calving Ease proofs and Daughter Pregnancy Rates.

Somatic Cell Score too!

As part of an overall milk quality management strategy, breeding for lower Somatic Cell Scores (SCS) makes sense. The potential penalties as well as the quality bonus opportunities should provide lots of incentive to do so, but there’s one other reason that you might not think about right off the bat. Cows with elevated SCS or clinical mastitis can experience hormonal imbalances that exert a negative influence on heat expression and pregnancy rate. Not surprisingly, many bulls with the worst SCS ratings also fare poorly on Daughter Pregnancy Rates.

A University of Idaho study demonstrates the point. Based on nearly 1000 cows, data shows that cows afflicted with Mastitis after 105 days in milk have significantly poorer reproductive performance. Days to First Service were similar across groups and Days Open was capped at 220 days.

Pregnant cows are key...

There’s little doubt about how important pregnancy rates are to cow longevity. On almost all dairies the number one reason cows leave is because they fail to get pregnant. And it’s always the same; the cows you’d like to be able to keep - the high performers - are most likely to experience reproductive problems. Cows that are extreme for dairyness or angularity – the ones most likely to be the highest producers are also more likely to be the reproductively challenged. It all adds up. When cows are too thin, Mother Nature tells them they are in no condition to support a pregnancy and hence they either demonstrate poor or no estrus activity, produce poor quality eggs that are less likely to produce a pregnancy and when or if they become pregnant are more likely to experience early embryonic death. Whether it’s a difficult calving, a bout of mastitis or a poor body condition score that is the root cause, the negative effect on pregnancies is real. That’s why breeding for improvement in these traits also makes sense: it will also provide a positive impact on Daughter Pregnancy Rates. In reverse, breeding for DPR will also result in less difficult calvings, lower Somatic Cell Scores and cows that are less extreme for dairyness.

They all relate to Productive Life

When Productive Life proofs were first introduced many were quick to dismiss their importance since our industry’s Type specialists were often predicted to be mediocre at best in this area. That’s not to say that Type isn’t important to longevity, but instead that our definition of desirable Type is out of step with what the cow herself tells us works for her. We’ve bred for bigger, more angular, open dairy cows with the capability of achieving high production yields. Along the way we’ve created the scenario for increased calving problems, more susceptibility to Mastitis and a decrease in reproductive performance. No wonder improved Type hasn’t delivered longer lasting cows.

What’s the take home message?

Through the many years of improving our Holstein cow, it was right to focus on improving udder, feet and leg characteristics as well as some other Type traits. It has likely helped improve longevity significantly. But now that our confinement housing systems and our management approach de-emphasizes the individual cow, favoring the cow that can fend for herself with minimal special care, we should re-evaluate our beliefs as well. Is bigger better? Is extreme dairyness desirable? Are cows that score well under our classification systems actually lasting longer in our herds?

Proof information on management traits like Productive Life, Somatic Cell Score, Daughter Pregnancy Rate and Calving Ease, when combined into one index like Healthplus, are more likely to deliver upon our longevity objectives than selecting solely for Type – especially Type that rewards sires delivering bigger, taller, or more extreme dairy cows. Since health traits are often interrelated, there’s good reason to include them in your breeding program.

Related Topics:

-> The Type that Last

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Posted Oct 27th

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