You’re not alone if your herd suffers from lower conception rates, undesirable pregnancy rates, longer days open and increased culling for fertility. That’s been the story of
However, much has changed since 1985, and you don’t have to accept poor fertility. You have the tools to make a difference on your dairy. The key is to dive into your herd’s genetic pool and take control. And while a number of factors affect cow fertility, “genetics are what producers can control, and what they must control,” says Bennet Cassell, extension dairy-genetics specialist at Virginia Tech.
There’s a payoff to your bottom-line. Danish research indicates that when you select for total genetic merit, which includes production traits, body conformation and the functional traits of female fertility, calving ease and health resistance, you earn $10 per cow per year (in U.S. dollars) over selection for milk yield only.
Here is why you should use the following genetic tools to improve your herd’s fertility. They should be used as tie-breakers when choosing between bulls that you’ve picked off of selection indices, such as Net Merit or Cheese Merit.
1. Select against skinny cows.
Inadequate body condition has been identified as a fertility-sapping culprit by several recent studies of the relationship between genetic merit, nutritional status and reproductive performance. And the antagonistic relationship is fairly high. “You don’t want skinny cows,” says Kent Weigel, extension dairy-genetics specialist at the
Although “dairy character” or “dairy form” has been a highly desirable characteristic in the past, you should place it lower on your priority list.
Here’s why. Research in 2005 at the
A couple of years ago, Holstein Association USA introduced a negative economic weight for dairy form into the Type Production Index, or TPI, to help reduce the negative impact of cow angularity in your herd. This trait is not included in the indices of Net Merit, Cheese Merit or Fluid Merit.
Genetically, you want to avoid bulls with daughters in the extreme dairy-form category to improve fertility, recommends Weigel.
2. Use productive life.
This genetic evaluation has been available since 1994 and has been incorporated into the major selection indices.
Productive life helps you step away from building cows that intuitively look like they should last and create those that do last.
Productive life is a measure of dairy-cow survival. In addition to favoring cows that resist culling for physical problems, it also favors those that breed back quickly and maintain a regular calving interval. This makes it an indirect measure of fertility.
The genetic differences between bulls are significant, notes Weigel. “The best bull versus the worst bull may be a full lactation’s difference.” And it’s common to find bulls that offer three or four months of additional productive life.
For example, if a cow milks 50 pounds a day, she would generate 4,500 pounds or 45 more hundredweights in those three months. If your income-over-feed cost is $6, she would generate an additional $270 ($6 X 45 = $270).
Some European countries, particularly in
3. Factor in daughter pregnancy rate.
The next opportunity to improve fertility is daughter pregnancy rate, or DPR. This is a fairly new tool, introduced in 2003. It is included in all major selection indices used in the
Give DPR serious consideration as you rank bulls for use. Again, the differences between sires can be dramatic, according to Weigel. Currently, daughters of the highest and lowest sires differ by approximately 29 days open per lactation, or more than one heat period.
There’s a moderately strong tendency for bulls with high predicted transmitting ability (
4. Put it all together.
Using these tools should result in an improved level of fertility. You can reasonably expect to gain a couple of months of productive life and a point of daughter pregnancy rate per generation, says Weigel.
Remember that fertility never was 100 percent — not even in the wild, says Cassell. However, you can positively influence fertility on your dairy. “Use selection pressure for all health traits, including fertility, he recommends. “Selection pressure has been successful for milk production, so there’s no reason it can’t work for fertility.”
For the first time, genetic indices have theoretical selection responses headed in the right direction for all traits, says George Shook,
So, instead of functional traits holding little economic value in genetic analyses — because production traits have traditionally been considered most desirable — health and fertility now hold significant economic weight in bull indexes. To learn about the economic values assigned to various traits, including fertility, go to: http://aipl.arsusda.gov/reference/nmcalc.htm
Things should continue to improve as more and more producers use the genetic tools available for fertility.
Productive life and daughter pregnancy rate go hand-in-hand. The decline in DPR started to stabilize about the same time that productive life was included in sire evaluations.