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AgridianDairy KB

Do-not-breed (DNB) decisions

Definition

Section titled “Definition”

A do-not-breed (DNB) decision marks a cow so she will not be inseminated again. She stays in the herd, usually milking, until a planned exit: sale for beef, sale as a dairy cow, or (if already pregnant) drying off and calving without being rebred afterwards.

DNB is the point where a cow moves from the breeding program to the cull list. It is a management decision, normally based on her expected value compared with a replacement (see cull index): open late in lactation, repeated failed services, low production, chronic mastitis or lameness, or age.

DNB matters for reproduction metrics because a DNB cow is no longer eligible to be bred. From the DNB date she should leave the denominators of pregnancy rate and heat detection rate. The timing of the mark therefore changes those metrics:

  • Marked late (decision made but not recorded): the cow keeps counting as eligible every 21-day period, is not bred and doesn’t get pregnant. This lowers heat detection and pregnancy rate.
  • Marked aggressively early: hard-to-breed cows leave the denominator before they fail, which flatters pregnancy rate. The herd still loses those cows; the cost moves to the cull rate.

So DNB should be recorded on the day the decision is made, and DNB activity reported alongside pregnancy rate.

Formula

Section titled “Formula”

Plain text:

DIM at DNB = DNB event date − fresh date (current lactation)
DNB to exit (days) = sold or died date (SELDT or DIEDT) − DNB event date
% of lactating cows DNB = cows with RC = DNB / lactating cows × 100

LaTeX:

\mathrm{DIM}_{\mathrm{DNB}} = D_{\mathrm{DNB}} - D_{\text{fresh}}
\qquad
\Delta_{\text{exit}} = D_{\text{exit}} - D_{\mathrm{DNB}}
\qquad
\%_{\mathrm{DNB}} = \frac{N_{\mathrm{RC}=1}}{N_{\text{lactating}}} \times 100

How to pull it in DC305

Section titled “How to pull it in DC305”

The DNB event sets RC to 1 (see RC codes and events). The event name, and any remark codes giving the reason, vary by herd; check the herd’s private dc305-vocab mapping.

COUNT FOR RC=1 LACT>0                          current DNB cows
LIST ID PEN LACT DIM DCC TBRD MILK FOR RC=1    DNB cows, with pregnancy status and milk
SUM BY LACT FOR RC=1                           DNB cows by lactation
EVENTS DNB ID LACT FOR EDAY>-365               DNB decisions in the last year, live cows
EVENTS\B DNB ID LACT FOR EDAY>-365             the same, including cows that have since left
  • DIM at DNB: compute from the event date and the fresh date of that lactation. DIM in an EVENTS list may show today’s DIM, not DIM on the event date (see events).
  • Pregnant DNB cows: RC shows 1, not 5, so DCC is the way to find DNB cows that are pregnant.
  • DNB to exit: pair the DNB event with the later SOLD or DIED event, including cows that have left the herd. EVENTS lists live animals only by default; \B adds sold and dead animals and \D gives those alone.
  • BREDSUM’s 21-day pregnancy risk table (BREDSUM\E) drops a cow from eligibility once she is DNB. Check how the installed version handles the 21-day period in which the DNB is recorded.

Typical range

Section titled “Typical range”

Herd context: US Holsteins, freestall or dry-lot, herd with a 50–80 day voluntary waiting period.

Measure Typical
DNB cows, % of lactating herd at any time about 3–10%
Median DIM at DNB about 200–300 DIM
DNB cows that are open most
Median days from DNB to exit about 30–120 days
  • Herds with high milk prices, cheap feed and few heifers mark cows DNB later and hold them longer; herds with surplus heifers mark DNB earlier.
  • A DNB cow held for months produces milk while open; that can be the right call if her daily margin is positive and the slot isn’t needed.

Common mistakes

Section titled “Common mistakes”
  • Deciding but not recording. The cow stays in the breeding denominators until the event is entered. Enter DNB the day it is decided.
  • Back-dating DNB. Entering it with an earlier date rewrites past pregnancy rate periods.
  • Using DNB to improve pregnancy rate. Early, aggressive DNB raises pregnancy rate without more pregnancies. Report DNB counts and DIM at DNB next to pregnancy rate.
  • Counting DNB cows as open. In open-cow counts, report DNB separately (see RC codes).
  • Breeding a DNB cow anyway. A later BRED event can reset RC and put the cow back in the program without a decision. Check for services after DNB.
  • No exit plan. DNB cows that sit for months use slots and feed. Track DNB to exit.
  • Using one reason code for everything. Without the reason (open, low milk, mastitis, lameness), DNB data can’t explain why cows leave.
Section titled “Related”