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Dry Period in Dairy Cattle


Dry
Period

Cows walking to the barn.

Dry Period and Subsequent Lactation

*** The mammary gland of the dairy cow requires a nonlactating (dry) period prior to an impending parturition to optimize milk production in the subsequent lactation.


This period is called the dry period, and it includes the time between halting of milk removal (milk stasis) and the subsequent calving. Generally, 45 to 50 days is recommended. If less than 40 days, then milk yield in the next lactation will be decreased. [see Swanson 1965; Coppock et al. 1974; Dias and Allaire, 1982.]

The normal procedure to dry off a cow is to withdraw all grain and reduce the water supply several days before the start of the dry period. This drastically reduces the milk production during that time. Then milking is halted about 45 to 50 days before expected date of parturition. Infusion of the udder with antibiotics can help prevent infections that may occur in early involution. After milking is stopped intramammary pressure increases, milk products accumulate in the gland, and further milk secretion is inhibited. Sometimes if the udder becomes extremely congested, it may need to be re-milked. However, this practice stimulates further milk synthesis because intramammary pressure is reduced and pituitary hormones (oxytocin and prolactin) are released. Perhaps more importantly re-milking removes the leukocytes from the udder at a time when many are needed to prevent infection. It usually is unnecessary to re-milk if production is reduced below about 50 lbs per day before milking is stopped.

In studies with identical twins, milked 2X/day the twin with no dry period gave only 62-75% as much milk as the twin with 60 day dry period.

If you milk 1/2 of the udder throughout the dry period while the other 1/2 is dry, then the milked side gives less milk in the subsequent lactation. (DNA concentrations are the same in both halves)

Cows with a dry period of 10-40 days produce 450-680 kg less milk than those with 40 or more days dry.

Conclusions :

  • There is an optimum length of dry period.
  • A dry period shorter than 40 days will decrease subsequent production (also long dry periods over 70 or 80 days will result in lowered production in the next lactation).
  • Changes occur in the mammary gland during the dry period which influence mammary cell proliferation and mammary function in the subsequent lactation.


A dry period may not be required for goats (see Fowler et al. 1991). The requirement for a dry period between lactations may be peculiar to the dairy cow. Consider that most species are not concurrently pregnant and lactating (they exhibit some level of lactational anestrus or other inhibitory effect of lactation on reproductive function). Therefore, they only start reproductive cycling after weaning (the end of lactation), so there indeed will be a nonlactating period prior to the next parturition.


Summary of Changes in Composition of Mammary Secretions During the Dry Period

Milk component

Active
Involution

Steady State
Involution

Redevelopment and
Colostrogenesis

Lactose

decreasing

low

increasing (late)

Milk Proteins

decreasing

low

increasing

Milk Fat

decreasing

low

increasing

Udder fluid volume

decreasing

low

increasing

Concentrations of:

Milk components

decreasing

low

increasing

Leukocytes

increasing

high

low

Lactoferrin

increasing

high

low

Immunoglobulins

increasing

high

increasing


 
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