The dry period is a crucial time in a cow's lactation cycle and is also an opportune time to implement strategic culling and management decisions.
The dry period is not only a good time for cows to put on weight and reach body condition score (BCS) targets before calving, but it is also during this period that the udder prepares for next year's lactation. In this time many of the cells that produce milk are removed and replaced before the next calving - this process of tissue repair and rejuvenation takes six to eight weeks. Another change which occurs at the start of the dry period is the closure of the teat canal by the formation of a keratin plug. This is the udder's natural defense mechanism against new infections during the dry period.
How does this affect the choice of treatment at dry-off?
While intramammary antibiotic treatment at drying off will clear most existing infections and prevent new infections during the first few weeks, treatment alone will not prevent new infections developing later on in the dry period due to the limited coverage of antibiotics. It is also worth noting that not all cows form a functional keratin plug (up to 20% of quarters by six weeks after dry-off). This is where internal teat sealants (ITS) are used. ITS mimic the natural keratin plug to prevent bacteria from entering the teat canal and protect uninfected quarters during the dry period and at calving. When used in conjunction with dry cow therapy (DCT) it helps extend the protection provided by the intramammary antibiotics.
What are the options?
The different approaches to drying off include whole herd DCT, partial herd DCT, and combination therapy (DCT with ITS). Choosing the right option can differ between farms. The decision making takes into consideration a number of factors such as the spectrum of activity, likely cure rates, knowledge of the specific bacteria responsible for clinical mastitis, the period of protection provided by different products, and the expected duration of the dry period. Partial herd DCT requires adequate information from herd tests and/or rapid mastitis testing in order to select which cows to give which treatment. It also requires excellent cow identification and record keeping to ensure with-holding periods at the start of the next lactation are adhered to.
Lastly, it is timely to mention the current global concerns, being highlighted in the media, around the use of antibiotics in animals and the possible implications of antimicrobial resistance in human medicine. See next months newsletter to find out more but, in the meantime, utilise drying off as the perfect opportunity to review the role that farmers and vets play in ensuring the responsible use of antibiotics on farms.
Call the clinic and book in for your Milk Quality Consult and ensure you make the most of the dry period this season.