Friday, 13 December 2019 07:55

Mastitis can milk you dry

Written by  Amanda Kilby, MSD animal health veterinarian

Most clinical mastitis occurs over calving, so if you’ve had a good spring, you probably feel like you’re in the clear. 

But, if left unchecked, clinical and subclinical mastitis occurring between the end of calving and dry-off can reduce milk production and increase both the cost of dry-off and mastitis-related culls. To minimise the impact of mastitis beyond calving, follow these 5 best-practices. 

1. Keep the teat spray flowing

Effective teat spraying is the single biggest step you can take to prevent mastitis1,2. Teat spray all cows, all season. Ensure that you are mixing your commercial teat spray with high-quality water and a clean measuring container, every 2-3 days, following the manufacturer’s recommendations. Apply 20 mL for hand-spraying, or 30 mL for automatic spraying, just after the cups come off3. Periodically check that teats are being completely covered by wrapping paper towels around 10 different teats after spraying, to see that each paper towel is uniformly moist when you remove it. 

2. Minimise overmilking

Overmilking means pressure is being applied to teats without a corresponding amount of milk flowing from the teat end; this can occur at cups on or at cups off. Overmilking damages teat ends and increases the likelihood of bacteria being sucked into open teats while the cups are on. Both consequences of overmilking increase mastitis risk4. If overmilking is a problem in your herd, you may notice many rough teat ends. Keep an eye on this as the season progresses to see if you need to take a closer look at overmilking. 

To minimise overmilking at cups-on, handle cattle in a stress-free manner, following the same routine at each milking. Avoid using alarms, dogs, or backing gates and keep milking calm and quiet to facilitate efficient milk let-down. 

At cups off, you should be able to hand-strip 50-65 mL of milk from each quarter4. If you can strip more than this, milk-out is incomplete. If you can strip less, the cow has been overmilked. If overmilking is occurring at cups off, you can remove cups sooner. This will increase milking speed and help with cow-flow through the shed without affecting milk yield. 

3. Address problem cows

Mastitis spreads from infected cows to uninfected cows in the shed via contaminated cups and milkers’ hands. If you know some cows are infected you can do something with these cows to protect the rest of the herd. Options include: drying the problem cows off early with dry cow antibiotics, culling them, three-quartering them, or putting them in their own herd and milking them last5. Working with your vet to take some milk cultures from these animals will help you decide which option is best and identify the source of the problem. 

4. Change liners on time, every time

Synthetic rubber liners should be changed every 2,500 cow-milkings6. Use one of several online liner-change calculators to set your next date for liner change. Worn-out liners become less effective and develop cracks which act as repositories for mastitis-causing bacteria, increasing the spread of mastitis during milking.

When it’s time for your next liner change, keep in mind that different liners are appropriate for different cows. Liner slips and squawks in the shed, swollen or bruised-looking teats at cups-off, incomplete or uneven milk-out, and cows kicking the cups off are all signs of a mismatch between cows and cups.7 Work with a milk plant expert to check that you have the right liners and shed settings for your cows. 

5. Keep good records and ask for help

Monitor your bulk milk cell count, record your clinical mastitis cases all season, and if you herd test or carry-out a whole-herd RMT, check your percentage of high cell count cows (>150,000 cells/mL, or RMT positive). If your bulk milk cell count creeps well over 150,000, if you have more than 1% clinical mastitis per month after the calving period, or if you have more than 15% of cows with high cell counts at any given time, ask your vet or a milk quality expert for some help getting ahead of mastitis8. 

For more information about mastitis, speak with your vet, consult DairyNZ SmartSAMM resources, or visit www.TopFarmers.co.nz. 

• Amanda Kilby is MSD animal health veterinarian 

More like this

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Dr Sean Daly, vet and technical adviser at MSD Animal Health, explains best-practice guidelines for treating cows with clinical mastitis.

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Mastitis is the most common disease of dairy cattle and is a significant cause of losses on the dairy farm, explains Dr Sean Daly, vet and technical adviser at MSD Animal Health.

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