Mastitis

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

Clinical mastitis

Mastitis reduces milk yield and reproductive performance, costs money to treat and negatively impacts animal welfare. It also potentially degrades milk quality at the vat level. Together, these factors can erode farm profits.

It is estimated that poor udder health costs Australian dairy farmers more than $150 million each year.

Clinical mastitis is where inflammation of the udder produces visible symptoms in the affected quarter or milk. Preventing and optimising the management of a cow with clinical mastitis is crucial for the animal’s welfare, her ongoing milk production and to limit the costs associated with this disease.

Each case of clinical mastitis costs around $350, which includes the cost of treatment drugs, additional animal husbandry time, reduced milk yield, discarded milk in addition to the increased risk of cow death, culling and antibiotic residues. This estimate is based on an average producing herd, so this cost could be significantly more in higher input and/or higher producing herds.

Managing cows with clinical mastitis also has human impacts. Managing many cases is stressful. Mastitis interrupts the smooth running of milking, creates additional work and can be frustrating when treatment is not successful.

Mycoplasma bovis and other Mycoplasma species are specific bacteria that cause clinical mastitis (among some other syndromes) that have been present in the Australian dairy cow population for many years. Accurate diagnosis of this particular mastitis causing pathogen is essential where it is suspected.

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 analysis estimates that a farmer milking 300 cows who could lower their BMCC from 250,000 to 100,000, would add $39,000 per year to their bottom line.

High BMCCs can be a source of great concern for farmers wanting to optimise their returns from milk produced and lower mastitis cases in their herd. Mastitis is a multi-factorial disease, meaning there are many factors that contribute to a high BMCC or an increased number of sub-clinical or clinical mastitis cases.

The best way farmers can address high BMCCs in the short term is to carry out a herd test on all cows in the herd, gathering both production and individual cell count information. Herd testing is a valuable and important on-farm management tool which enables farmers and advisors to record herd data and make more informed management decisions.

Some examples of decisions which can be made based on herd testing data include identifying:

• Which cows to dry off using individual milk production data.
• Animals suited for dry-cow therapy, using individual cow cell counts.
• Actions to improve BMCC, using the Mastitis Focus Report.

DataGene – an industry owned organisation specialising in genetic and herd improvement – offers a beneficial resource for farmers carrying out herd testing.

The Herd Test Dashboard provides a snapshot of herd level activities with overviews of several key metrics, both within herd health and herd composition. It also helps to identify herd health issues and provides alerts on individual cows.

Drying off

After each lactation, dairy cows require a dry period which is long enough to allow 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, and prevent new, mastitis infections. Research has suggested approximately half of clinical mastitis cases occurring in the first 100 days of lactation from environmental bacteria can be attributed to the dry period.

Dry cow treatment is used to:

• Treat existing sub-clinical infections that have persisted during lactation.
• Reduce the number of new infections which may occur during the dry period.

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 Dry Cow Consult 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 veterinarian.

Selective dry cow therapy

More farmers are starting to implement part-herd 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 part-herd (selective) dry cow antibiotic already have:

• A low BMCC year-round.
• Herd testing.
• Good/complete 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 dry cow period and calving time management.
• No history of cows getting mastitis after drying off or in the dry period.
• A good working relationship with a mastitis adviser and are proactive with staff training on dry cow treatment.
• 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. However, this decision should be made in consultation with a Countdown-trained advisor.