Mastitis

Mastitis is inflammation of the mammary gland and is caused by bacteria entering the udder via the teat canal.

Clinical mastitis

Clinical mastitis occurs when this udder inflammation produces visible produces visible changes in the affected quarter or milk. Best practice management of a cow with clinical mastitis is crucial for  her welfare, ongoing milk production and reproductive performance, and will limit the costs associated with this disease.

Each case of clinical mastitis costs $350-400, and  includes the cost of treatments, additional animal husbandry time, reduced milk yield, and discarded milk ,This figure also accounts for the increased risks for cow death or culling and/or antibiotic residues of the bulk vat. This estimate is based on average production, so this cost could be significantly more in higher input and/or higher producing herds.

Managing cows with clinical mastitis also impacts dairy staff. Mastitis interrupts the smooth running of milking, creates additional work, can be frustrating when treatment is not successful, and stressful when there are many cases. Accurate diagnosis of the causative bacteria is essential when there is a herd mastitis problem.

Bulk milk cell counts

Most milk companies pay a premium for milk with a bulk milk cell count (BMCC) below 250,000 cells/ml. Previous Dairy Australia analyses estimate that a farmer milking 300 cows who lowered their BMCC from 250,000 to 100,000, would add $39,000 per year to their bottom line.

Mastitis is a multi-factorial disease, meaning there are many factors that contribute to a high BMCC and/or an increased number of sub-clinical or clinical mastitis cases.In the short term, the best way farmers can address high BMCCs is to carry out a herd test on all cows in the herd, gathering both production and individual cell count information.

Informed decisions can then be made based on this herd testing data, such as:

• Identification of cows to collect samples from for diagnostics.
• Identification of which cows are contributing the most to the BMCC (and can then be kept out of the vat).
• Identification of which cows to dry off.

DataGene - an industry owned organisation specialising in genetic and herd improvement – offers useful resources for farmers carrying out herd testing. The HerdPlatform provides a snapshot of herd level metrics, helping to identify herd health issues and providing alerts on individual cows.

Drying off

After each lactation, dairy cows require a dry (i.e. non-milking) period that allows the udder tissue to rest, repair and rejuvenate. Many of the mammary epithelial cells that produce milk are removed and replaced again before the next calving. A minimum of six weeks – preferably eight weeks – is recommended between drying off and calving.

The dry period is a critical period to treat existing mastitis infections, and it is vital to also prevent new infections during this time. 

When hygiene and other management at drying off is not well done, the process of drying off can lead to an increase in mastitis in both the dry period and the next lactation. The Milk Quality checklist helps dairy farmers consider some important things that will ensure the drying off period is as successful as possible. It can be used either before a meeting with a Countdown advisor or to guide discussion with the farm’s veterinarian.

Selective dry cow therapy

More farmers are starting to implement part-herd (selective) antibiotic dry cow therapy. This change in management is not without its risks and should be done in close consultation with a Countdown-trained advisor. Farms that are well-placed to implement this part-herd antibiotic dry cow treatment already have:

• A low BMCC year-round.
• Regular herd testing.
• Accurate clinical mastitis records.
• Low calving time mastitis (less than 5 per cent of cows with clinical mastitis in the first 14 days after calving).
• Good transitions into both the dry cow period and calving time.
• No history of cows getting mastitis after drying off.
• A good working relationship with a mastitis advisor
• Proactive staff training around the drying off process.
• No history of Streptococcus agalactiae (Strep ag) mastitis.

Most farms moving to part-herd antibiotic therapy use whole-herd (blanket) administration of internal teat sealants, which are used to prevention new infections during the dry period. However, this decision should be made in consultation with a Countdown-trained advisor.

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