Dry period and close-up

Definition

The dry period is the time from dry-off (the last milking of a lactation) to the next calving. The udder involutes and regenerates secretory tissue during it, so a cow with no dry period, or a very short one, gives less milk in the next lactation.

Most herds split it into two feeding groups:

Far-off dry: from dry-off to about 3 weeks before the expected calving. A lower-energy, higher-fiber diet that holds body condition steady.
Close-up (pre-fresh): the last ~21 days before calving. A diet that prepares the rumen and calcium metabolism for lactation, often a negative DCAD diet.

Some herds use a one-group dry period, a single diet from dry-off to calving. The close-up metrics below still apply to the pen move before calving, if there is one.

Three related measures:

Dry period length: days from dry-off to the calving that follows. It can only be measured after the cow calves.
Days carrying calf at dry-off: how far into the pregnancy the cow was dried. With a planned dry period, this sets the dry-off date.
Days in close-up: days from the move into the close-up pen to calving. Too few days on the close-up diet is linked with more fresh-cow disease.

Formula

Plain text:

dry period length (days) = calving date − dry-off date
days carrying calf at dry-off = dry-off date − conception date
planned dry-off date = expected calving date − planned dry period length
days in close-up = calving date − close-up pen entry date

LaTeX:

L_{\text{dry}} = D_{\text{calve}} - D_{\text{dry}}
\qquad
\mathrm{DCC}_{\text{dry}} = D_{\text{dry}} - D_{\text{conc}}
\qquad
D_{\text{dry, planned}} = D_{\text{due}} - L_{\text{planned}}
\qquad
L_{\text{close-up}} = D_{\text{calve}} - D_{\text{close-up}}

With a gestation of about 280 days, a 60-day dry period means drying off at about 220 days carrying calf; a 45-day dry period, at about 235. US Holstein cows average 279.4 days of gestation (heifers 277.8; Norman et al. 2009).

How to pull it in DC305

Items used (see item codes):

DDAT: dry date, set by the DRY event (which also sets RC to 6).
DCC: days carrying calf; DUE: expected calving date.
FDAT: fresh date of the current lactation.

Cows coming up for dry-off and cows in the dry groups:

LIST ID PEN LACT DCC DUE FOR RC=5 DCC>210          pregnant milking cows nearing dry-off
LIST ID PEN DDAT DUE DCC FOR RC=6                  dry cows, with due dates
LIST ID PEN DUE DCC FOR RC=6 DCC>255               cows that should be in close-up

RC 5 is pregnant and RC 6 is dry (see RC codes).

Dry period length and days in close-up are completed measures. After a cow calves, her current DDAT belongs to the old lactation or is reset, so rebuild both from events:

EVENTS DRY FRESH ID LACT FOR EDAY>-120        dry-off and calving events, last 120 days
EVENTS MOVE FRESH ID FOR EDAY>-60             pen moves and calvings, for close-up days

Pair each FRESH with the cow’s previous DRY (dry period length) and with the last MOVE into a close-up pen before it (days in close-up). Which pens are close-up pens, and whether the herd records pen moves as MOVE events at all, varies by herd; check the herd’s private dc305-vocab mapping.

EVENTS\2SI gives a list of cows and their events, prompting for the date range and which events. Add \B to keep cows that have since left the herd.

Report each measure as a distribution (share of calvings in each band), split by first-calf heifers vs cows. Heifers have no dry period; for them, only days in close-up applies.

Typical range

Herd context: US Holsteins, freestall or dry-lot, two-group (far-off and close-up) dry cow program.

Measure	Common target	Watch
Planned dry period length	45–60 days	—
Actual dry period, share of cows < 40 days	as low as possible	> 10–15%
Actual dry period, share of cows > 70 days	as low as possible	> 10%
Days in close-up, target	about 14–24 days	—
Share of calvings with < 10 days in close-up	< 10–15%	> 20%

Short dry periods (about 30–40 days) cost little or no milk in multiparous cows in several studies, but more in first-to-second-lactation cows. Dry periods under about 30 days, or none, reduce next-lactation milk noticeably.
Long dry periods (over about 70 days) usually come from cows that calved early (wrong conception date, twins, abortions recorded late) or from cows dried off for low yield. They raise the risk of over-conditioning.

Common mistakes

Measuring planned instead of actual dry days. The plan says 60; early calvers, twins and wrong conception dates spread the real distribution wide. Measure from events after calving.
Wrong conception date. If CDAT is from the wrong breeding (e.g. a rebreed after a missed pregnancy loss), DUE and the dry-off date are wrong too. Short dry periods often trace back to this.
Counting first-calf heifers in dry period averages. They have no dry period. Keep them out of dry period length but in days in close-up.
Averaging days in close-up. A mean of 21 days can hide many cows with under a week. Report the share below 10 days.
No record of the close-up move. If pen moves aren’t recorded as events, days in close-up can’t be measured; it has to come from pen move sheets.
Forgetting cows that leave before calving. Dry cows sold or dead before calving drop out of calving-based measures. Track them as dry-period losses.