Thursday, March 28, 2024

Drying Miss Daisy

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The dry period is a chance for farmers to take a breather before calving gets under way, and is a crucial time for mastitis treatment and prevention.
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“The process isn’t essential,” Dr Richard Laven, associate professor in production animal health at Massey University, says.

“There are some nice reports coming out at the moment that in high-producing herds, not drying cows off at all and carrying on milking during the ‘dry period’ doesn’t cause any problems for the cow. Their peak milk tends to be lower and they have fewer problems, so that might be something we see more of in the future. The only disadvantage for that is around mastitis control.”

When to dry off

Making the decision to dry-off can be tricky, and this year, there are many factors to consider. Following the standard DairyNZ recommendations of drying cows as soon as their production reaches five litres or less a day might suit some but if you’re lacking feed, drying-off early is your best bet, Laven says.

“You want to get the cows into a good body condition score (BCS) for calving, so if you don’t have the feed then dry them off early. It’s going to save you money, rather than trying to stretch out the lactation and then struggling to get body condition on them with no feed.”

There can be a knock-on effect into the next lactation if cows don’t reach target BCS.

“Your cows aren’t going to produce as much, so your income’s going to drop. They’re not going to reproduce as well so you can get a knock-on effect for the next two or even three years.”

Drying-off needs to happen abruptly. Switching to once-a-day milking has no benefits and increases the risk of mastitis during the dry-off period.

Drying-off properly

Historically drying-off has included large amounts of antibiotics and teat sealants but Laven says there is a shift to using teat sealants on their own. The process of the udder shutting up shop includes the natural creation of a keratin plug in the teat. However, this plug doesn’t form immediately so teat sealants provide a physical barrier of defence from new infections immediately after drying-off and before calving while the udder is ‘waking up’ again.

“As a profession in the veterinary industry there is a push towards using less antibiotics and not using antibiotics on uninfected cows. So with using teat sealants alone, hygiene has to be really good.”

There have been many stories in the past of farmers having problems with mastitis because of teat seals, but often the issue of poor hygiene was masked by using an antibiotic.

“People were getting away with it because they’re putting in bacteria and antibiotics at the same time. World-wide we have to get better at administering dry cow therapy.”

Infections because of poor hygiene can also cause the mammary gland involution process to slow down, giving disease-causing bacteria more chance to get in.

Whether you’re drying off a small or large herd it’s important to administer dry-cow therapy after milking so you’re not trying to do it while milking cows. Teat spraying after treatment to clean the teat and standing for an hour in a clean environment before putting them back on the paddock is important, particularly when conditions are wet.

“Restricting feed intake as well is important – less feed, less milk produced – and it helps reduce leakage. After this you really just need to leave the cow alone as much as possible.”

Maintenance feeding for the first 7-14 days after drying off is normally about 8 kg DM/day.

Making the most of your money

In low payout years it’s easy to run a red pen through certain items on the list, but dry-cow therapy shouldn’t be one. Herd testing is the best thing to do to save money with dry cows because it allows farmers to select and treat the animals that require it, Laven says.

“It’s not expensive per-cow. Get a herd test, look at her mastitis history, cell counts everything. If you have a bulk cell count over 200,000 for cows and 150,000 for heifers, then you can choose which cows to give antibiotics to.”

Laven says on No 4 Massey dairy farm they are expecting to use antibiotics on 40-50 cows out of a herd of 600.

“The milk price would have to be about $2/kg milksolids (MS) before dry cow therapy in the right cows is not economically effective.”

Taking the opportunity to cull high cell count cows is important, no matter how well-producing they are.

“She would have to be producing at least four times the herd average in order for her to be worth keeping. If you combine selective dry cow therapy and getting rid of high cell count cows, then you’ve got a low risk of spreading it to the rest of the herd and saving money.”

Selective antibiotic dry cow therapy and whole-herd teat sealing is the direction Laven would like to see the industry go.

“If you have 10-15% of your cows that usually get mastitis in the period immediately after calving, then teat sealing pays for itself quite nicely. But if people want to save money by not teat sealing the whole herd then using combination therapy on selected dry cows and being less restrictive about it is an option.”

Talking to your vet is important when exploring options for dry-cow therapy, and reducing antibiotics as a go-to remedy means better advice is being given.

“It’s a win for everybody – farmers aren’t having to spend as much on antibiotics and vets are relying on it less, meaning farmers get better advice to help reduce mastitis and save them money.”

Mammary gland magic: The dry period

During drying-off the mammary gland undergoes the process of involution – a process by which the gland returns to its non-lactating state. This function is regulated by environmental and hormonal controls. The dry period is important for udder heath, particularly in terms of mastitis control.

“The shut down and immune response you get from drying-off gives you a much better cure for infection. So if you have mastitis you need the dry period to get that cure, and using antibiotics on top of that works much better than just giving antibiotics and continuing milking.”

During lactation the primary function of the mammary gland is one of constant synthesis and milk secretion. During the dry period it goes through two distinct stages before involution is complete.

1) Gradual decline in milk production: This stage follows peak milk yield and is a result of programmed cell death – apoptosis. Fewer mammary cells, less milk produced.

In the first few days of the dry period, the synthesis and secretion of milk constituents such as casein, lactose and fat steadily decrease and the alveolar cells start to shrink in size.

Concentrations of immunoglobulins, lactoferrin, sodium and chloride bicarbonate and serum albumin increase as lactation gradually ceases.

2) Abrupt cessation of milk: The process of cessation of milk takes about two weeks. During this time the mammary gland continues to synthesise and secrete milk, which accumulates in the gland. The build-up in pressure in the udder along with chemical feedback by milk constituents can lead to the loss of secretory function, meaning no more milk is produced and the cow is “dry”.

“It’s a real shut down and reduction in the size and activity of the milk producing cells – there are changes in milk composition and things like lactoferrin and then the formation of the natural keratin teat seal.”

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