Stillbirth rate

Definition

A stillbirth is a calf born dead or that dies within a short period after birth, usually 24 hours in herd records and 48 hours in many studies and in US genetic evaluations (CDCB scores 1 = live calf, 2 = born dead, 3 = born alive but died within 48 hours, and combines 2 and 3). Most stillborn calves at term were alive when calving started and died from a difficult or slow delivery. Herds often record these as DOA (dead on arrival).

Abortions (pregnancy loss well before term, commonly before about 260 days of gestation) are not stillbirths and are counted separately.

The rate can be computed per calving (did the calving produce at least one dead calf) or per calf. Per-calving is standard for herd monitoring and genetic evaluation; per-calf is used for calf-loss accounting. With twins the two differ, so state which one is used.

Only calvings with a known outcome go in the denominator. Calvings where the calf status was not recorded are excluded, and the share excluded should be reported.

Formula

Plain text:

Stillbirth rate, per calving (%) = calvings with ≥1 calf dead at birth or within 24-48 h / calvings with known calf outcome × 100

Stillbirth rate, per calf (%) = calves dead at birth or within 24-48 h / calves with known outcome × 100

LaTeX:

\mathrm{SB}_{\text{calving}} = \frac{N_{\text{calvings with dead calf}}}{N_{\text{calvings, known outcome}}} \times 100

Report first-calf heifers and cows separately, and single and twin calvings separately.

How to pull it in DC305

Calf outcome is usually recorded on the FRESH event, as calf codes in the remark (sex and alive/dead for each calf) or in calf items filled in at calving. The codes differ by herd (e.g. one letter for sex and one for status), and some herds enter a dead calf as a separate event. Check the herd’s private dc305-vocab mapping before parsing.

EVENTS FRESH ID LACT FDAT FOR LACT=1    first-calf heifer FRESH events, with remark (calf codes)
EVENTS FRESH ID LACT FDAT FOR LACT>1    cows
EVENTS\3                                calf table
EVENTS\B FRESH ID LACT FDAT FOR LACT>0  including dams that have since left the herd

Name the event after EVENTS to select it, or use \I to be prompted (as in EVENTS\2SI); \S prompts for the date window. EVENTS covers live animals only by default, so dams sold or dead since calving need \B.

Parse the remark into calves per calving and status per calf; count calvings with no parseable status as “unknown”.
Deaths in the first 24–48 hours that are entered later as calf deaths need to be matched back to the calving.
Cross-tab with calving ease and twin status.

Typical range

Herd context: US Holsteins, freestall or dry-lot, single-calf and twin calvings combined unless stated.

Group	Typical	Goal
First-calf heifers	8–13%	< 8%
Cows (2nd+ lactation)	4–7%	< 5%
All calvings	6–9%	< 6%
Twin calvings (≥1 dead)	25–40%	—

For reference, US Holstein stillbirths rose from 9.5% to 13.2% in first-calf heifers and from 5.0% to 6.6% in cows between 1985 and 1996 (Meyer et al. 2001; 666,341 births). In Minnesota DHIA data, one or both calves were dead in 25.5% of twin calvings in cows and 38.0% in heifers, vs 5.0% and 10.4% for single births (Silva del Río et al. 2007).

Stillbirth rises steeply with calving difficulty: dystocia is the largest single risk factor (see calving ease). Male calves, twins, heavy calves, short or long gestations and over-conditioned dams also raise risk (Mee 2008).

Common mistakes

Counting calvings with unknown outcome as live. Unrecorded calves are more likely to be dead ones nobody wrote down. Exclude them and report the share unknown.
Mixing per-calving and per-calf rates, especially in herds with many twins.
Including abortions or premature calvings well before term.
Inconsistent time window. Dead at birth only vs within 48 hours can differ by a couple of points.
Blending heifers and cows. Heifer stillbirth is roughly double; a change in heifer share moves the herd rate.
Small monthly numbers. Use rolling quarters or years.