DairyCo

Dry Periods - Resting cows

The dry period

The dry period is an important resting period for the dairy cow, where fresh udder tissue is formed in readiness for the lactation, and it provides an important opportunity to rid the udder of many potential pathogens that can cause mastitis. Some pathogens such as E. coli will not prevail from one lactation to the next; in many instances, quarters badly affected by an infection can recover to become productive again in the next lactation.

As the cow dries up, changes begin to occur in the mammary secretions that are able to kill bacteria (known as lactoferrin and alpha-lactoglobulin), in addition to increases in antibody levels, which are able to kill existing infections. In some cases, particularly with Staphylococcus aureus and Streptococcus uberis infections, much better clinical cure results are achieved when antibiotic treatment occurs at drying-off rather than during lactation.

However, management of the cow during the dry period must not be neglected as new infections of E. coli and  Streptococcus uberis in particular can occur during this period and not become apparent as clinical mastitis until later in the lactation. Therefore hygiene during the dry period and pre-calving is especially important in controlling new mastitis infections. Clean bedding or field conditions are paramount. Good nutritional management will help to maintain health and immunity levels; dry cow management of housing, grazing, and nutrition should be at least as good as the management of the milking herd.

Long-term antibiotic dry cow therapy has an important role - it has been part of the Five Point Plan since the 1960s - and teat sealants can be used to further limit bacterial entry into the teat canal, particularly as the natural keratin 'plug' that forms under normal circumstances to seal the teat ends between milkings and during the dry period often fails to be adequately produced in the modern dairy cow.

Dry cow antibiotic treatment aims to prevent new udder infections in the early dry period and can eliminate sub-clinical infections persisting from the previous lactation. Generally, the choice of product should be based on vet advice as well as any prior knowledge of the antibiotic sensitivity patterns for known mastitis agents in the herd. All quarters should be treated, not just those having shown symptoms of mastitis.

It may be necessary with cows with long dry periods, for example, to administer further dry cow antibiotics during the dry period, but care must be taken over withdrawal periods.

Drying cows off

There are several guidelines to follow when administering dry cow antibiotics to prevent mastitis bacteria from being accidentally introduced into the teat:

• Cows should be dried-off abruptly when they are producing less than 15 litres.
• Cows must be removed from the milking herd so that they do not experience the milk let-down stimuli.
• Clean disposable gloves should be worn and kept clean.
• Clean towels must be used for wiping and drying.

Before administration of the antibiotic:

• Teats should be washed and must be thoroughly dried.
• Teats should be dipped in an effective germicidal teat pre-dip and the appropriate contact time allowed before wiping off.
• The teats should be swabbed with surgical spirit, starting with the furthest away and working towards the closest teat.
• The dry cow antibiotic should be infused into the nearest teat first, then into those furthest away to prevent contamination of clean teat ends. The process can be repeated with the teat sealant, if used.

Teats should be dipped in an effective germicidal teat post-dip after treatment, and cows should be penned-up for 30 minutes after treatment to allow teat sphincters to close before they are allowed to lie down, and should be housed away from the milking parlour and herd so they do not experience the let-down stimuli.