Heat detection rate (insemination rate)
Definition
Section titled “Definition”Heat detection rate (HDR) is the share of cows eligible to be bred during a 21-day period that receive at least one insemination in it. Eligibility is the same as for pregnancy rate: past the VWP, not pregnant, not do-not-breed.
On herds that use timed AI, the name is misleading: many inseminations follow a synchronization protocol, not a detected heat. Insemination rate or service rate is the more accurate name. DC305’s 21-day table reports it as the “bred” percentage.
HDR measures how many eligible cows get bred. Conception rate measures how many of those breedings work. Together they make up pregnancy rate.
Formula
Section titled “Formula”Plain text:
HDR (%) = eligible cows inseminated at least once in the period / cows eligible in the period × 100LaTeX:
\mathrm{HDR}_{21} = \frac{N_{\text{eligible cows bred in period}}}{N_{\text{eligible in period}}} \times 100Count cows, not inseminations: a cow bred twice in one period counts once.
How to pull it in DC305
Section titled “How to pull it in DC305”BREDSUM \P FOR LACT>0The breeding-eligible, bred and percentage columns of the 21-day table are HDR by period. The summary row pools completed periods.
[!VERIFY] Column names for the breeding side of the
BREDSUM \Ptable on the DC305 version in use.
To split detected heats from timed AI, you need the herd’s breeding remark or
protocol codes on BRED events, and these vary by herd. Look up the herd’s
codes in its private dc305-vocab mapping before filtering. Typical approach:
EVENTS\2 FOR ... list BRED events with remarks in a date range[!VERIFY] The cleanest DC305 command to tabulate BRED events by remark (heat vs. timed AI) for a period.
Another check: the inter-service interval distribution
(BREDSUM intervals or an EVENTS list). A large share of 18–24-day intervals
means heats are being caught. Many 3–17-day or 25–35-day intervals point to
detection or recording errors, or missed heats.
[!VERIFY] DC305 command for the inter-service interval histogram.
Typical range
Section titled “Typical range”Herd context: US Holsteins, lactating cows, freestall or dry-lot, VWP 50–60 days.
| Program | Typical HDR |
|---|---|
| Visual detection only | 35–50% |
| Activity monitors / tail chalk + some timed AI | 55–65% |
| Heavy timed AI (e.g. Ovsynch-based 1st service + resynch) | 65–75%+ |
[!VERIFY] HDR bands by program type. Check them against current sources.
- Heat stress reduces how strongly cows show estrus, so herds that rely on detection see summer HDR fall more than timed-AI herds do.
Common mistakes
Section titled “Common mistakes”- Counting inseminations instead of cows. Double breedings and re-breeds inside one period inflate HDR.
- Calling it “heat detection” on a timed-AI herd. A high rate there reflects protocol compliance, not detection skill.
- Ignoring false positives. Breeding cows that aren’t in heat raises HDR but lowers CR. Look at both together, and at inter-service intervals.
- A wrong VWP or DNB status, as with pregnancy rate. This puts the wrong cows in the denominator.
- Looking at HDR alone. 75% HDR with 25% CR is an 18–19% PR. A different herd with 55% HDR and 40% CR reaches 22%.