Ketosis and displaced abomasum rate

Definition

Ketosis is a metabolic disorder of early lactation in which fat mobilization outruns the liver’s capacity to process it, and ketone bodies, mainly beta-hydroxybutyrate (BHB), build up in blood.

Clinical ketosis: a cow with signs (off feed, drop in milk, sometimes nervous signs) and a positive ketone test, diagnosed and treated.
Subclinical ketosis (SCK), also called hyperketonemia: blood BHB ≥ 1.2 mmol/L without clinical signs (McArt et al. 2012 used 1.2–2.9 mmol/L). Duffield et al. 2009 found serum BHB ≥ 1.2 mmol/L in week 1 raised the odds of later DA and metritis, and proposed 1.4 mmol/L as the hyperketonemia cutoff, so some studies use ≥ 1.4 mmol/L. Most cases occur in the first two weeks of lactation.

Displaced abomasum (DA): the abomasum fills with gas and moves out of place, usually to the left (LDA); right displacements (RDA, with risk of volvulus) are less common. Most DAs occur in the first month after calving and are strongly associated with ketosis and low intake around calving. A DA is usually a clinical diagnosis followed by surgery, roll-and-toggle or culling.

Testing schemes for SCK

Test every fresh cow two or more times between about 3 and 16 DIM (e.g. twice a week) with a handheld blood BHB meter. This measures cumulative incidence.
Herd screening: test a sample of cows (often 12 or more) at 5–15 DIM on one day. This measures prevalence, which is lower than cumulative incidence because each test catches only the cows positive that day.
Urine or milk tests: urine acetoacetate strips and milk BHB strips or DHI milk BHB are cheaper but less accurate than blood BHB; state the test.

McArt et al. 2012 tested every cow 6 times from 3 to 16 DIM; first positive tests peaked at 5 DIM.

Formula

Plain text:

Ketosis incidence (%) = cows with ≥1 ketosis case (clinical, or BHB ≥ 1.2 mmol/L) within N DIM / cows calving in the cohort × 100

SCK prevalence (%) = cows testing BHB ≥ 1.2 mmol/L on test day / cows tested × 100

DA incidence (%) = cows with ≥1 DA within N DIM / cows calving in the cohort × 100

LaTeX:

\mathrm{Ketosis}_{N} = \frac{N_{\text{cows with ketosis}\,\leq N\,\mathrm{DIM}}}{N_{\text{calvings}}} \times 100
\qquad
\mathrm{DA}_{N} = \frac{N_{\text{cows with DA}\,\leq N\,\mathrm{DIM}}}{N_{\text{calvings}}} \times 100

N is usually 30 DIM for ketosis and 30 or 60 DIM for DA. Each cow counts once per lactation.

How to pull it in DC305

There is no standard ketosis or DA item. Herds record them as events, often named KETOSIS, KETO, DA, LDA or RDA, sometimes with the BHB value or treatment in the remark, and sometimes only inside a general ILLNESS or SICK event with a remark code. Check the herd’s private dc305-vocab mapping.

EVENTS\B ID LACT FDAT DIM FOR FDAT>-90 FDAT<-30   events for a completed 30-DIM cohort, including cows that left
COUNT\B FOR FDAT>-90 FDAT<-30                     cohort size, including cows that left
EVENTS\UDR                                        transition events table, with sold/died

EVENTS and COUNT cover live animals only by default; \B adds cows that were sold or died. Select specific events by naming them (EVENTS KETOSIS ...) or with \I (prompt for which events, as in EVENTS\2SI).

Count each cow once: first ketosis event and first DA event in the window.
If BHB values are recorded only in remarks, export and parse them outside DC305; record the test type and threshold.
If the herd records no ketosis or DA events at all, the rate cannot be computed. Report it as “not recorded”, not as zero.

Typical range

Herd context: US Holsteins, freestall or dry-lot, cohorts followed to 30 or 60 DIM.

Measure	Typical	Goal
Subclinical ketosis, cumulative incidence (every cow tested, 3–16 DIM)	25–45%	< 25%
Subclinical ketosis, prevalence (one-day screen, 5–15 DIM)	10–25%	< 10–15%
Clinical ketosis, recorded, ≤ 30 DIM	2–10%	< 5%
Displaced abomasum, ≤ 60 DIM	2–5%	< 2–3%

In 4 freestall herds in New York and Wisconsin, 43.2% of cows had at least one positive test from 3 to 16 DIM, and prevalence peaked at 28.9% at 5 DIM (McArt et al. 2012).

Cows with SCK in early lactation have higher odds of DA, metritis and early culling and lower early milk (Duffield et al. 2009; McArt et al. 2012).

Recorded incidence is a floor. Many herds don’t record ketosis or DAs consistently: cows get treated from a fresh-pen protocol without an event, DAs that are culled are coded as a sale for “illness”, and subclinical cases are never seen without testing. Read a low recorded rate as “at least this many”.

Common mistakes

Mixing incidence and prevalence. A one-day screen at 20% positive and an every-cow program at 40% positive can describe the same herd.
Mixing thresholds and tests. BHB ≥ 1.2 vs ≥ 1.4 mmol/L, blood vs milk vs urine: always state which.
Treating zero events as zero disease. No recorded events usually means no recording.
Missing DAs that were culled without surgery. Look at sale reasons and DIM at sale in early lactation too.
Counting cows twice. A cow treated for ketosis on three days is one case.
Reporting incomplete cohorts. Cows that calved in the last 30 days have not completed the risk window.