Dry cow strategies
What's going on in the udder?
How to dry off
Dry cow mastitis
Setting up for next year
Avoiding inhibitory substance grades
Procedure for Dry Cow Therapy and PAR supply
We have a fairly standard procedure for the selection and dispensing of the dry cow therapy most appropriate for you. As we have said in previous years, recent legislation has brought tighter regulation into this area-we are obliged legally to demonstrate that we are suitably informed about the mastitis issues on your farm before prescribing dry cow therapy. This has created the ‘dry cow consult’ which we try and do at the same time as the PAR consult in the clinic. The PAR consult selects and quantifies prescription animal remedies you are likely to need for the coming year.
The consults provide a good opportunity for us to discuss with you animal health requirements particularly around mastitis, for this reason we send out a ‘dry cow consult ‘ form for you to fill in before you come in so we have all the information we need on the day. This will be sent out separately.
Please fill it in and then ring to make an appointment for a dry cow and PAR consult. This normally takes about 40 minutes.
Please note we will be operating a no return policy on dry cow this year.
Dry cow treatment has two main aims. Firstly – to cure existing (usually subclinical) infections. Secondly – to reduce the number of new infections that may occur during the dry period. Dry cow treatment may also reduce the number of clinical cases and the BTSCC the following lactation.
Your choice of dry cow product will depend on what you want to achieve from your investment. But roughly speaking, the objective of dry cow treatment changes from prevention to cure of subclinical infections with increasing BTSCC. Longer acting products are generally going to give us higher cure rates than shorter acting products as the pathogens (often S. aureus) will be exposed to the antibiotic for a longer period of time. Short acting products are good for prevention, as they protect the cow over the initial dry period while a teat plug (the cows natural defense) is being formed. Longer acting products generally have longer with-holding periods, and this needs to be considered carefully in reference to your herds drying off and calving start dates.
For prevention at dry off and around the peri-calving period, teat seal – an non antibiotic intra-mammary preparation is very effective (reduces peri-calving mastitis by 50%). Teat seal can be applied to cows treated with a dry cow antibiotic, or to cows that are given no treatment. It can also be given to heifers, and is just as effective in preventing heifer mastitis at calving time. Because teat seal contains no antibiotic, it must be administered under very hygienic conditions. This is a very effective mastitis preventer, and if your herd suffers from a high incidence of spring mastitis you should seriously consider using this proven product.
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At Drying Off
The highest incidence of high level IS grades occurs around drying off, most often due to cows recently treated with DCT. What can you do to reduce this risk?
· Udder involution begins once milk production falls below 7L a day. The changes occurring in the udder alter the distribution of the antibiotic and can mean there is a longer period for which residues can be detected in the milk. If the herd average is below 5L/cow/day at drying off there will be individual cows that are virtually dry and therefore have a prolonged period of antibiotic activity.
· If part of the herd is dried off early, ensure they are well marked and kept away from the milking herd.
· It is best to dry off immediately after milking rather than during milking as there is a risk that antibiotic can be transferred from milker’s hands to teats and then into the vat.
· Clearly mark all cows before they are treated.
· Have a consistent order for administering DCT eg BL-BR-FL-FR to reduce the risk that any cow or teat will be treated twice. A double dose of DCT considerably alters how much antibiotic will be left in the udder at the end of the dry period.
· Do not put dry cow therapy into quarters which are already dry. The antibiotic is broken down much more slowly in these quarters resulting in a very long period of antibiotic residue detectable in the milk.
· Ensure all staff members are familiar with how the treated cows are marked and what to do should a treated cow re-enter the herd.
· Call the dairy company immediately if you suspect the vat has been contaminated.
Dry Cow products have 3 withholding period components
1. A period following treatment (28-49 days) – the treatment to calving interval
2. 8 milkings after calving
3. A meat withholding period
There are two main reasons why DCT related IS grades occur in early lactation.
1. Not following the withholding period on the label
a. This is generally due to cows calving prior to the minimum treatment to calving interval. If a cow calves within this time, withhold her milk from supply and contact a vet at the RSC for specific advice relating the DCT product you used.
b. If you only milk your colostrum cows once a day, you must still withhold milk for 8 milkings, not just 4 days.
c. Make sure colostrums cows are either milked separately or marked well so their milk doesn’t enter the vat. Don’t just rely on knowing the cows.
2. Low milk volume at first pick up.
a. If you only have a few cows in supply at the first pick up there will be less dilution of the milk from any individual cows with higher than expected milk residues.
b. The first milking into the vat must be properly agitated – depending on your vat size this may require as much as 800L in a large vat. If there is insufficient volume in the tank to reach the agitator, milk at the bottom of the tank freezes whilst warmer milk at the top doesn’t trigger the cooler to turn off. This changes the concentration of antibiotic in the milk. Fonterra recommends that you should aim to supply at least 1000L at your first collection of the season.
Provided the cow has calved outside of the treatment to calving interval, milk from the first 8 milkings of cows treated with DCT can be fed to bobby calves.
If a cow calves within the treatment to calving interval, please contact one of the vets at the RSC for advice on when the calves can be sent to slaughter. Colostrum from these cows CAN NOT be fed to bobby calves.
If a calf drinks contaminated milk it must be fed residue free milk for at least 7 days before going to slaughter.