Conception rate
Definition
Section titled “Definition”Conception rate (CR) is the share of inseminations that result in a pregnancy, counting only inseminations whose outcome is known. It is a per-service measure: a cow bred three times adds three services.
It tells you how often a breeding works. It does not tell you how quickly cows get pregnant. That is pregnancy rate, which also depends on how many eligible cows get bred.
A service’s outcome is known once it has been checked pregnant or open, or once the cow was re-bred, which implies she was open. Services still waiting for a check have no outcome and are left out. So are services whose outcome can’t be known: the cow was sold or died before a check, or an abortion was recorded with no confirmed pregnancy.
Formula
Section titled “Formula”Plain text:
CR (%) = pregnant services / (pregnant services + open services) × 100LaTeX:
\mathrm{CR} = \frac{N_{\text{preg}}}{N_{\text{preg}} + N_{\text{open}}} \times 100Services with outcome “other” (unknown, sold, died) and services still waiting for a check are in neither the numerator nor the denominator.
How to pull it in DC305
Section titled “How to pull it in DC305”BREDSUM is DairyComp’s built-in breeding summary. It gives conception rate by
row, with counts of pregnant, open, other and total services.
BREDSUM FOR LACT>0 cows onlyBREDSUM FOR LACT=0 heifers onlyCommon stratifications (switch letters vary by DC305 version; check them with the command help on your install):
[!VERIFY] Switch letters below are from memory and must be checked against the DC305 version in use:
\Bby month of breeding,\Cby service number,\Eby service sire,\Tby technician,\Lby lactation group,\Dby DIM at breeding.
- By service number: CR for 1st, 2nd and 3rd+ services. First-service CR is the cleanest herd-level signal.
- By month of breeding: shows heat-stress seasonality. The last one to two months are incomplete because their pregnancy checks haven’t happened yet.
- By technician and by sire: only meaningful at roughly 30+ services per row.
DC305 counts a breeding as pending until it is old enough to have been checked. Make sure the pending window matches the herd’s actual pregnancy-check timing (see BREDSUM).
Typical range
Section titled “Typical range”Herd context: US Holsteins, freestall or dry-lot housing, mix of timed AI and detected heats, first pregnancy check by ultrasound or palpation at about 28–40 days after breeding.
| Group | Typical | Good |
|---|---|---|
| Lactating cows, all services | 30–40% | > 40% |
| Lactating cows, 1st service | 30–40% | > 45% |
| Nulliparous heifers | 50–60% | > 60% |
[!VERIFY] The figures above are general US benchmarks for Holsteins and need checking against current sources (e.g. Ferguson & Skidmore 2013; DCRC benchmarks).
- Heat stress (Southwest, Southeast US): summer CR in lactating cows often falls to about 15–25% without strong cooling, then recovers 1–2 months after temperatures drop.
[!VERIFY] Summer heat-stress CR range for Southwest dry-lot and freestall herds.
- Check timing: herds that check early (about 28–32 days) report a higher CR than herds that check at 40+ days, because some pregnancies are lost between those two points. Always state the check day when comparing herds.
- Jerseys usually run a few points higher than Holsteins in the same system.
[!VERIFY] Jersey vs Holstein CR difference.
Common mistakes
Section titled “Common mistakes”- Counting pending services as open. This drags CR down for the most recent months. Recent rows always look bad until their checks are done.
- Putting “other” outcomes in the denominator. Cows sold or dead before a check are not failures.
- Mixing heifers and cows. Heifer CR is 15–25 points higher, so a shift in the heifer/cow mix moves the blended number.
- Small samples. At 35% CR, a technician or sire row with 15 services has a 95% confidence interval of roughly ±24 points. Don’t rank on it.
- Double breedings. Two inseminations a few days apart for one heat can be counted as two services, the first one “open”. Know how the herd records these.
- Comparing timed-AI and detected-heat CR as if they were the same population. Timed AI includes cows that wouldn’t have shown heat, so its CR is often lower. That doesn’t mean the program is worse; compare pregnancy rate instead.
- Treating CR as the reproduction KPI. A herd can have 45% CR and a poor pregnancy rate if few eligible cows get bred.