Calf scours metrics

Definition

Calf scours (neonatal calf diarrhea) is loose or watery feces, often with dehydration and acidosis. It is the most common disease and the leading cause of death in preweaned US dairy calves. Most cases start in the first 3 weeks of life. Common causes by typical age:

Cause	Typical age of onset
E. coli (K99/F5, enterotoxigenic)	first 4 days (most susceptible)
Rotavirus, coronavirus	1–2 weeks
Cryptosporidium parvum	about 5–21 days
Salmonella	any age; commonly calves < 3 weeks
Coccidia (Eimeria)	usually > 3 weeks

The E. coli, rotavirus, coronavirus and Salmonella ages are from Cho & Yoon 2014. In NAHMS Dairy 2014, digestive cases peaked at about 2 weeks of age and calves that died of digestive disease averaged 18.3 days old (Urie et al. 2018).

Nutritional scours (milk changes, overfeeding, cold or poorly mixed milk) also occurs and is usually milder.

Case and episode definition

Case: a calf that meets the herd’s scours definition. This is either a fecal score (for example, 2–3 on a 0–3 scale: loose to watery) or a scours treatment (electrolytes, antimicrobial, or both). State which.
Episode: treatment days for one calf that are close together form one episode. Choose a gap: a scours treatment more than N days after the last one starts a new episode. Many protocols use 5–7 days. Some use a longer gap for scours, because one bout can run 1–2 weeks with on-and-off treatment.

Core metrics

Scours incidence (morbidity): calves with ≥ 1 scours episode by a set age (usually 21 or 30 days), divided by calves born alive in the cohort.
Age at first case: onset in the first days of life points to colostrum, calving-pen hygiene or E. coli. Onset at 1–3 weeks points to viral or Cryptosporidium pressure.
Antimicrobial treatment rate: the share of cases given antimicrobials. Most uncomplicated scours needs fluids and electrolytes, not antimicrobials; antimicrobials are generally reserved for calves with systemic illness (fever, depression, off feed, blood in feces).
Treatment success / relapse: the share of first episodes with no new scours episode or death within N days.
Scours mortality and case fatality: scours deaths ÷ calves at risk, and scours deaths ÷ scours cases.

Formula

Plain text:

Scours incidence (%) = calves with ≥ 1 scours episode by age X / calves born alive × 100

Scours mortality (%) = calves dying of scours by age X / calves born alive × 100

Case fatality (%) = scours cases that die within N days / scours cases × 100

LaTeX:

\text{Incidence}_{\text{scours}} = \frac{N_{\geq 1\ \text{episode},\,<X}}{B_{\text{alive}}} \times 100
\qquad
\text{CFR} = \frac{D_{\text{scours},\,\le N}}{N_{\text{cases}}} \times 100

Use the same cohort and denominator rules as calf morbidity vs mortality.

How to pull it in DC305

Scours treatments are herd-defined events (for example a SCOUR, SCRS or DIARR event, sometimes with the drug or “electrolytes” in the remark). The death cause may be in the died event’s remark. Check the herd’s private dc305-vocab mapping for names.

EVENTS\B ID BDAT FOR LACT=0 BDAT>-90              calf events, including calves that died or were sold
COUNT\B FOR LACT=0 BDAT>-90 BDAT<-30              birth cohort, including calves that left
EVENTS\D DIED ID BDAT FOR LACT=0 BDAT>-90         calf deaths, with the cause in the remark
LIST\D ID BDAT DIEDT FOR LACT=0 BDAT>-90         age at death = DIEDT − BDAT

Select one event type by naming it after EVENTS (e.g. the herd’s scours event), or with \I (prompt for which events, as in EVENTS\2SI). EVENTS and COUNT cover live animals only by default; \B adds calves that died or were sold and \D gives those alone.

List scours events for a birth cohort, count distinct IDs, and divide by calves born alive. Compute age at first episode as event date minus BDAT. Episode merging is easier outside DC305 on an export.

Many calf operations record electrolyte-only treatments on paper or in a calf app, not in DC305. If only antimicrobial treatments are entered, incidence will be understated; say so.

Typical range

Herd context: US Holstein heifer calves, hutches or group pens, on freestall or dry-lot dairies and calf ranches.

Measure	Typical	Goal
Scours incidence, preweaning	15–25%	< 25% (DCHA); strong herds < 15%
Share of preweaning deaths due to scours	about 30–40%	—
Scours mortality, preweaning	1–3%	< 2%

Reference points:

NAHMS Dairy 2014 (Urie et al. 2018; 2,545 heifer calves): digestive signs in 18.9% of preweaned heifers (17.2% as the primary sign); digestive disease was the recorded cause of 32.0% of deaths, plus 7.0% concurrent digestive and respiratory; 1.6% of all calves died of digestive disease; digestive case fatality 8.5%. A quarter of deaths had an unknown cause, so the true share is likely higher.
The older “about half of deaths” figure comes from NAHMS Dairy 2007, as cited by Cho & Yoon 2014.
The DCHA goal (as listed by Cornell AHDC) is scours morbidity < 25% at 24 h–60 d, counting diarrhea that needs intervention for more than 24 hours.

Incidence depends on the case definition. Fecal-score incidence (any loose feces) can be well over 50%; treatment-based incidence is lower.

Common mistakes

Counting treatment days as cases. Merge them into episodes with a fixed gap.
Recording only antimicrobial treatments, so calves on electrolytes alone don’t appear.
Inferring cause of death from the last treatment. A calf treated for scours may die of pneumonia or septicemia.
Sampling scouring calves for passive transfer. Dehydration gives falsely high serum total protein. See passive transfer.
Reporting incidence for cohorts too young to have passed the risk window (calves under 3 weeks old).
Treating every scours case with antimicrobials. It isn’t indicated for most cases and inflates treatment counts.