We’ve all heard the statement, “Genetics don’t matter without first creating a pregnancy.” This insightful truth has shifted our global breeding strategy to a stronger focus on fertility.
When improved fertility is one of your ultimate goals, you can use genetics as one part of the equation to help get you there – both now and into the future.
1. Get more pregnancies now
If you’re looking for a fertility advantage on inseminations today, sire fertility rankings are where you’ll want to focus. Sire Conception Rate (SCR), calculated by the Council on Dairy Cattle Breeding (CDCB), ranks sires on their ability to get cows pregnant.
These evaluations are based on real pregnancy check results and take into account the age, lactation number, service number and stage of lactation of the cow being serviced to most accurately identify sires with high, low or average fertility.
When looking at these evaluations, a bull with a SCR of 1.0 means services to this sire will provide an average of 1 percent higher conception rates than a bull with an SCR of 0.0. Individual bull studs may also offer their own version of a fertility ranking specific to their bulls. This valuable information can also be helpful in selecting semen with the greatest potential to result in a confirmed pregnancy.
2. Create more fertile cows for the future
While sire fertility selection can get you more pregnancies now, it takes genetic selection for female fertility to ensure your herd’s reproduction continues to improve into the future.
Daughter Pregnancy Rate (DPR), Heifer Conception Rate (HCR) and Cow Conception Rate (CCR) all provide a genetic basis for creating more fertile females. Emphasizing one, or any combination, of these traits within your customized genetic plan means you are breeding a next generation of cows with a greater ability to conceive.
Daughter Pregnancy Rate is defined as the number of nonpregnant cows that become pregnant within each 21-day period. When a sire has a DPR of 1.0, it means his daughters are 1 percent more likely than the average herdmate to become pregnant in a given 21-day window. And each added point of DPR equates to four fewer days open.
When referring to HCR and CCR, these traits are defined respectively as a virgin heifer or lactating cow’s ability to conceive. For each of these traits, when a sire has a value of 1.0, it means his daughters are 1 percent more likely to conceive than daughters of a sire with an HCR or CCR of 0.0.
While DPR is a slightly different calculation than HCR or CCR, all three are a way to measure the fertility of the female herself.
Why select for fertility traits if heritability is low?
Heritability is the proportion of the total amount of variation in a trait between groups due to genetics.
In the simplest terms, think about two cows in two different herds. How much of the difference in their pregnancy rates is due to genetics, and how much is due to management? It turns out that in terms of DPR, about 4 percent is due to genetics, and the remaining 96 percent is due to management and environment. Therefore, DPR has a heritability of 0.04.
In spite of low heritability, it would be wrong to conclude that selection for DPR within a genetic plan won’t directly impact your herd’s fertility results.
As an example, think of a herd with a 22 percent pregnancy rate. If this dairy owner selects a group of sires with a favorable DPR average of +3.0 to create more fertile cows for the future, then we expect daughters of those sires to have a 25 percent pregnancy rate, or 3 percent higher than the average of the entire herd.
Even though heritability for DPR is low, selection for this trait makes a difference in real herds. Take this real life example from a 1,500-cow dairy with very good reproductive performance (Table 1). We’ve separated out first-lactation cows into quartiles based only on their sires’ DPR.
It’s clear to see that the high DPR sires, do indeed, create daughters that become pregnant more quickly than the daughters of low DPR sires. These results can be commonly seen in well-managed herds with accurate sire identification.
Improve your fertility results – now and into the future
If you’re looking to improve fertility and reproduction in your herd, don’t miss out on the impact genetics can play in taking you to the next level. Despite the low heritability of fertility traits, these two steps will help improve your herd’s reproductive results now and into the future:
- Improve conception rates now by using sires with high-fertility SCR or comparable fertility rankings to boost your herd’s current conception rates.
- Improve fertility for the future of your herd by including DPR and/or HCR and CCR in your customized genetic plan to create a next generation of more fertile females.