Milking frequency (2x vs 3x)

Definition

Milking frequency is how many times a day cows are milked: 2x (about every 12 hours), 3x (about every 8 hours), or more. In automatic (robotic) milking systems, frequency is voluntary and varies by cow, often averaging between about 2.5 and 3 visits a day.

Milking more often removes milk before the udder fills and before local feedback inhibitors build up, so the udder secretes more. Effects:

Milk response: 3x usually gives more milk than 2x for the same cows; the response is larger when cows start 3x early in lactation.
Components: test % usually falls slightly, but component pounds rise.
Early-lactation frequent milking: milking 4–6x for the first few weeks after calving, then returning to 2x or 3x, has been shown to carry over into higher milk later in the lactation.
Costs: more labor, parlor hours, utilities and equipment wear per cow, and less time for cows to eat and rest if the parlor is overloaded or walk distances are long.
Mixed systems: herds often milk high and fresh pens 3x and late-lactation pens 2x. Moving a cow from 3x to 2x causes a step drop in milk.

Some herds use activity or rumination monitors to track cow time budgets when changing frequency, because long times away from the pen offset the gain.

How to pull it in DC305

DC305 has no single standard item for milking frequency. Herds record it as:

Pen convention (certain pens are 3x), so frequency is pulled by pen.
A user-defined item, or an event when a cow changes frequency.
A herd setup setting used for production standardization.

SUM MILK BY PEN FOR LACT>0          compare 3x and 2x pens at similar DIM
PLOT MILK FOR LACT>0                look for step drops at a frequency change (PLOT graphs against DIM)

The item, event or pen convention varies by herd; check the herd’s private dc305-vocab mapping. Compare like-for-like DIM and parity groups (see Lactation curve).

Typical range

Herd context: US Holsteins, freestall or dry-lot, parlor milking.

3x vs 2x response: best treated as a roughly fixed gain rather than a percentage. Erdman & Varner 1995 (19 literature reports) found 3x yield was 3.5 kg/day (about 7.7 lb) higher than 2x (95% CI 3.1–3.9 kg/day), with 92 g/day more fat, regardless of the 2x yield level, and similar in first-lactation and older cows. In DHI herd summaries for 1998–2000, 3x herds had a 15–16% higher rolling herd average and 13–15% higher ECM than 2x herds, with lower fat and protein tests (Smith et al. 2002); that is a herd comparison, not a controlled response.
Early-lactation 4–6x for about the first 21 days: in Dahl et al. 2004, multiparous cows milked 6x for the first 21 days and then 3x produced more milk, fat and protein than 3x controls from test day 2 through test day 6, with lower SCC early in lactation (a small field study: 9 vs 17 cows).

Parlor capacity: 3x needs each full milking to finish in roughly 7–8 hours with time left for washing; a common goal is cows away from the pen no more than about 1 hour per milking.

Common mistakes

Comparing herds or pens without stating frequency. A 3x pen and a 2x pen at the same DIM are not like-for-like.
Crediting 3x for gains caused by other changes. A switch to 3x often comes with new cows, rations or facilities; compare against a baseline.
Ignoring time budgets. Long walks or holding-pen waits on 3x cut rest and feeding time and can erase the response.
Reading a 3x-to-2x drop as a persistency problem. It is a step change from the frequency switch.
Ignoring labor cost. Judge the switch on milk value minus extra labor and parlor cost per cwt, not milk alone.
Treating robotic visits like fixed milkings. Robot frequency differs by cow and stage of lactation; report the average and its spread.