After every lactation, dairy cows require time to undergo a natural process of udder tissue rejuvenation — this is usually referred to as the ‘dry’ period, and typically lasts six to eight weeks.
This has health benefits for the cow, and production benefits for the farmer in the subsequent lactation.
Efforts should be made in the weeks preceding drying-off to decrease milk production and encourage teat plug formation.
Cows producing less than 5 litres/day can significantly increase bulk milk cell counts (even when they do not have mastitis) as cells concentrate in the reduced milk volume, and milk composition and quality can be adversely affected.
Thus, cows are ready to dry-off once production falls to 5 litres/day or below. For high producing herds, the figure may sit closer to 7 or even 12 litres/day.
For cows producing greater than 12 litres/day, management changes such as a reducing plane of nutrition, and in some cases ceasing concentrate or supplementary feeding can accelerate the reduction, but it is still important to ensure a cow’s increased late-gestational energy requirements are met.
Complete feed deprivation or water restriction are serious breaches of welfare compliance and should never be attempted.
Drying-off can also be accelerated by alterations to routine or disrupting social structures within the herd.
Current industry recommendations encourage an abrupt dry-off once production is lowered — skipping milkings isn’t advised.
Dry cow treatment with intra-mammary antibiotics and/or internal teat sealants may be administered immediately after the last milking.
Intra-mammary treatments at this time must be infused in an extremely hygienic manner into a sanitised teat to avoid introducing new infections at the time of dry-off.
All four quarters should be treated (unless the cow was a three-teater during lactation).
Teat spray or dip should be applied afterwards, and cows then placed in a clean area for two hours where they cannot lie on bare or contaminated ground.
Recording all treatments appropriately and marking cows for easy recognition should also form part of your dry-off routine.
Dry cow antibiotic treatment may be used either selectively or as a blanket therapy for all dry cows.
The two main goals of dry cow antibiotic treatment are to treat existing or persistent subclinical infections without discarding milk, and minimise potential new infections occurring during the dry period.
Research indicates up to 50 per cent of clinical cases of mastitis in the first 100 days of lactation are environmental pathogens acquired during the dry period.
Dry cow antibiotic treatments are designed to remain in the udder at high concentrations for extended periods of time, providing both treatment and protection if used correctly.
Dry cow antibiotic treatment will not protect against some of the environmental bacteria species that may be introduced during drying-off if hygiene is poor.
Choice of dry cow antibiotic will vary depending on duration of coverage required, types of bacteria present and previous responses to treatment.
No antibiotic product offers 100 per cent efficacy, and the decision is best made in consultation with your milk quality advisers.
For Selective Dry Cow Treatment, antibiotics are typically used only in cows where peak individual cell counts were greater than 250,000 cells/ml in the current lactation, and in any cow that had a clinical case of mastitis.
Farms could consider a Selective Dry Cow Treatment program if they have: good clinical mastitis records, a low annual average BMCC, regular herd testing, low rates of calving-time mastitis, good dry cow management with no cases of mastitis after drying-off and no history of mastitis caused by Streptococcus agalactiae.
The risk of acquiring a new infection in the dry period is also reduced considerably by using an internal teat sealant at the time of dry-off and most farms using selective treatment programs will still administer a sealant to the whole herd.
When implemented correctly, Selective Dry Cow Treatment programs can offer significant cost savings and greatly reduce the amount of antibiotic used on your farm.
Staff training, planned treatment protocols and having a well-established relationship with your milk quality advisory team will all help maximise the success of your next dry-off.
For further information, visit: bit.ly/3dFMnnj
Dairy Australia’s Countdown Milk Quality program also has some fantastic resources that can assist farmers to make informed decisions about their dry cow strategy.
The author has no affiliations (financial or otherwise) with any manufacturers of intra-mammary products.
Lucy Collins is completing her Dairy Residency with The University of Melbourne. She works as an on-farm veterinarian in Kyabram with Apiam Animal Health, and alongside her partner on his family’s 650-cow dairy farm in Dixie. She is a 2021 Nuffield Scholar supported by Gardiner Dairy Foundation.