Inbreeding: manage it to maximize profit
While certainly not a new concept, inbreeding has become a hot topic in recent years. Producer concern
is on the rise over whether genomics is creating too much inbreeding in the dairy cattle population. The
worry is that there will soon be limited options to which a herd can be bred to avoid negative effects of
inbreeding.
While mating an animal to her father or brother is certainly not desirable, we need to ask what the real
goal is in terms of inbreeding. Should we aim for zero percent inbreeding or rather manage it to
maximize profit?
The linear effect of inbreeding depression
As animals become more related to each other, inbreeding depression or sub-par productive
performance can occur. While inbreeding depression is not ideal, it should still be weighed against the
potential added value from genetic gain.
A common misconception is there is a magic level of inbreeding that we should never go beyond for any
given mating. In reality, numerous studies over time have shown the effects of inbreeding depression to
be linear.
For every 1% increase in inbreeding for a mating, you will realize $22-241 less profit over the life of the
resulting offspring. The same cost, or loss, is predicted when going from 9% to 10% inbreeding as is
expected between 1% and 2%.
Genetic progress
It’s well-documented that inbreeding has been on the rise since the mainstream adoption of AI. Despite
this increase, dairy cattle have made significant strides in production traits like milk, fat, and protein. It’s
safe to say that producers would not trade today’s high producing cows for the less inbred, but also
lower producing, cows of the 1960’s.
The chart below shows the average US inbreeding and milk production trends since 19602.
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Real-world examples
Let’s look into the records of a random cross-section of 10 upper Midwest dairies averaging 1,500 cows,
who implement a mating program on their farm. This analysis shows how cows with superior genetics
are more productive than cows with inferior genetics, despite the more highly productive group also
being more inbred.
In this analysis, cows born between 2005 and 2010, with at least one lactation on record were included.
Each individual herd was first analyzed separately, and cows were split into quartiles based on their
individual level of inbreeding.
Here, you can see the difference in genetics, 1st lactation milk production, and NM$ between the top
25% most inbred from each herd and top 25% least inbred animals from each herd. The most highly
inbred quartile of cows was also the most genetically superior group of cows in each of these ten herds.
Despite the elevated inbreeding in the most highly inbred quartile of each herd, the genetics more than
make up for that when their actual performance is measured. Their NM$ levels, pounds of milk and milk
deviations were all favorable for the more highly inbred, but also more genetically superior group.
This is not to say that selecting a mating resulting in a 25% inbreeding level is the best option, but rather
that when managed properly as part of a program, excellent genetics can more than make up for
predicted inbreeding depression.
What many producers also don’t realize is that current proof values of a bull already account for the
level of predicted future inbreeding. Adjustments are made in favor of a bull that is considered an
outcross sire, and a bull that is more closely related to the average population will see a negative impact
on his PTA’s because of these adjustments.
Manage inbreeding to maximize profit
To manage inbreeding, we look to an example to see how managing, rather than avoiding inbreeding is
the best route.
The example below shows three options to use for a mating in your herd. Rabo and CR both offer high
Net Merit levels. However, their 8% and 6.5% inbreeding levels would be above the suggested 6.25%
industry standard, which would eliminate them as potential mating sires in many breeding programs.
Porter is the third option, and the outcross mating with him would only cause 1% inbreeding.
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Above-average inbreeding levels would result from this female’s mating with Rabo or CR. Yet both of
these choices would still produce a much more profitable mating over the life of the resulting offspring
than a mating to Porter, even after the adjustment for inbreeding depression is accounted for.
So while 6.25% is often considered the industry norm inbreeding limit, there are often cases when a
mating beyond that level of inbreeding still produces the best potential for future profit.
Within your herd, a two-part approach to record management and mating can help maximize your
future profit potential.
1. Maintain accurate animal identification
Inbreeding cannot be managed if it cannot be measured. It’s impossible to know what the
predicted inbreeding level will be if you do not keep accurate records on your animals. A mating
you thought would be a minimal 1% or 2% could easily become 12% or more if an animal is
misidentified, or if correct records are not kept.
2. Make the right mating program work for you
With accurate identification in place, a mating program can offer a solution to manage
inbreeding. And while a mating program can manage inbreeding, the first step is actually to
select which bulls best fit your genetic plan (see Sire selection vs mating article by Zwald). If you
select the best bulls available to meet your goals, and keep only those bulls in your tank, then
you automatically avoid poor mating decisions – provided that you manage inbreeding to
appropriate levels.
After you’ve selected the best bulls for your genetic plan, the more traditional mating method
suggests a 1st, 2nd, and 3rd choice sire from that group of bulls. Each of the three choices would
ensure a mating below your set maximum inbreeding level.
However, a simpler mating method is a pen mate, which takes the opposite approach of a
traditional mating program. Instead of trying to find the perfect mating for a cow or heifer, a
pen mate lists the bulls in your tank that should not be used on any given female to avoid a
mating that exceeds your set inbreeding maximum.
A pen mate also increases efficiency and accuracy for technicians on big breeding days. A
technician can forego the stress of loading five AI guns with five different bulls, making sure
each cow is bred to the correct bull, and that each insemination is then recorded accurately.
Instead, the technician can head to the pen to breed with five AI guns all loaded with one bull
that appropriately manages inbreeding for all five cows. The pen mate aids in accurate recordkeeping, and also provides peace of mind that inbreeding is properly managed.
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Takeaways on inbreeding
With all of this in mind, it’s important to ask yourself if your goal is to eliminate inbreeding in your herd,
or to maximize profit potential.
1. The average inbreeding of animals is on the rise, but so are genetic values and average
production levels.
2. Instead of aiming for zero percent, or even sticking to the industry average 6.25% inbreeding
maximum, the goal should be to manage inbreeding levels within your herd so you can
capitalize on genetic progress and maximize potential future profits.
3. Accurate identification and records are key to managing inbreeding in your herd.
4. Proper sire selection to fit your genetic plan will ensure no mating is a bad one, but a simple pen
mate program can give you added peace of mind that inbreeding levels are kept below your
desired maximum.
Sources:
1. Smith LA, Cassell BG, Pearson RE. Effects of Inbreeding on Lifetime Performance of Dairy Cows.
Advances in Dairy Technology. Volume 11. (1999) 13.
2. CDCB. Trend in Milk BV for Holstein or Red & White, calculated August 2014. Web. 1 Oct 2014.
https://www.cdcb.us/eval/summary/trend.cfm
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