Antimicrobial Dry Cow Therapy Update

Last month we wrote an article on the recently released changes around the use of selective dry cow

antibiotic therapy (DCAT).

The changes have been instigated by the ACVM and will be overseen by the New Zealand Veterinary Council with the full endorsement of DairyNZ and all NZ milk processors. The primary reason is to reduce antimicrobial use in our dairy industry, thereby lowering the risk of Antimicrobial Resistance (AMR) development. Also, our Free Trade Agreement with the EU is based on “equivalence” – the use of antibiotics to prevent mastitis over the dry period is not permitted in many parts of the EU.

The key areas to take note of:

1. DCAT must only be authorized following a consultation where the veterinarian has collected sufficient information. That vet must be involved in an ongoing udder-health program.

2. Selective dry cow therapy involves the targeted use of ITS and DCAT.

3. Internal Teat Sealants (ITS) are used to:

a. Reduce the risk that uninfected quarters become infected during the dry period.

b. Extend the period of reduced risk when used in combination with DCAT.

4. DCAT is used only to:

a. Treat existing infections (cows with ISCC >150,000 to 200,000 SCC/ml)

5. When authorizing DCAT, veterinarians are expected to review individual cow records and only authorize DCAT for use in those cows likely to be infected.

6. Veterinarians must be able to justify each individual’s treatment decision by ensuring there is sufficient evidence to support it.

7. Only herds with an average BMSCC of >200,000 by January, which increases by a further 50,000 average over the last 3 months of lactation are eligible for blanket DCAT. It has been calculated that this represents less than 5% of herds in the country.

8. Where no herd test data exists, RMT testing should be performed to identify infected and uninfected cows. Uninfected cows are more likely to be young cows, that have not had clinical mastitis, that have good udder conformation and teat health.

9. A history of clinical mastitis or other specific risk factors such as production over 15L at the last herd test and an age greater than 4 years will also make a cow eligible for DCAT.

10. Culling of cows unlikely to respond to DCAT treatment is an important part of herd control.

Between now and drying off start thinking about the logistics of drying off some cows without antibiotics.

• A good nutritional dry-off plan is paramount to success.

• Insertion of teat sealants does take longer.

• You need to be meticulously clean.

• Who will do it?

• If your staff need training, when does this need to happen – book it in!

• Can you talk with your neighbors who have been doing it successfully and get some tips from them.

• Don’t plan on cutting corners, it will “bite you” eventually.

• If it seems like a short-cut, you won’t get away with it every time.

Selective Dry Cow is now the Default

Selective Dry Cow for your herd is now the default – Blanket Dry Cow (whole herd dry cow) will be the exception.

The rules we operate under have changed and it is now going to be much harder to authorize the use of antibiotic dry cow therapy (ABDCT) to a whole herd. We now must prescribe for each cow, not for a herd.

There is justifiable concern that the widespread use of antibiotics will lead to the selection of antibiotic resistance (this has been found overseas and some weak evidence of it in NZ). Perhaps a more tangible reason why we need to shift from blanket use of antibiotic dry cow therapy is that we have Free Trade Agreement with the EU that is based on “equivalence” – the use of antibiotics to prevent mastitis over the dry period is not permitted in many parts of the EU.

Many of you have already transitioned to using teat-sealants alone for uninfected cows and only using ABDCT for cows likely to be infected so this really won’t affect you, except we will be providing you with more paperwork to file to prove this is what are you doing.

For those of you who are thinking that you may still be able to use ABDCT on the whole herd, unless your BMSCC is averaging over 200,000 and rising from February, we will probably not be able to authorise blanket treatment.

We need good records to make the best decisions for each individual cow, this means we need to know a cow’s mastitis history, (please enter all mastitis events into MINDA), her herd test history, age and predicted production level at drying off. Nationally we know that 77.1% of cows in the national herd got herd tested in the 2023/24 season. What we are expected do for the herds that are not herd testing has not been fully addressed but the advice suggests using RMT to define a cow as infected or uninfected. If your herd is in a position where blanket ABDCT might be justifiable perhaps yours is a herd that would really benefit most from herd testing.

For those farms that are not used to using teat-sealants alone at dry off, please talk to us, and your farming mates who are doing it successfully, as it does take planning and meticulous attention to detail and hygiene, and you can’t just decide “lets dry off tomorrow” and expect a great result.

This change has been forecasted and is supported by DCANZ and DairyNZ. We will help you identify cows that will be suitable for not receiving an antibiotic at drying off and get a teat sealant alone. Between now and drying off start thinking about the logistics of drying off some cows without antibiotics.

• It does take longer

• You need to be meticulously clean

• Who will do it?

• Can you talk with your neighbors who have been doing it successfully and get some tips from them.

• Don’t plan on cutting corners, it will “bite you” eventually.

• If it seems like a short cut you won’t get away with it every time.

The NEW 5-Day Heifer CIDR Synchrony Programs – Outstanding Results Achieved

This season we have had 23 farms use the 5-Day Heifer CIDR Synchrony program, on the back of the study we conducted last season.

17 of these heifer lines have had an aged pregnancy test so far and we hope to have the remainder done in the next week.

The results have been outstanding, and I would have scarcely believed some of the results had I not scanned them myself.

Overall, the average conception rate to the first AI has been 67%, with 85% pregnant in total after a further cycle. The best two farms achieved 79% and 82% pregnant to first insemination and the lowest being 55%.

There were some slight differences in protocol between different farms heifer groups –some used heat detection over two days and some chose a blanket AI approach. We will breakdown and analyse differences once we have a full data set.

The practice has also conducted a funded study in 100 heifers, which looked to measure the range and average time to ovulation after CIDR removal in heifers using the 5-Day CIDR protocol. This involved scanning heifer ovaries up to 10 times to detect the time of ovulation (animal ethics approval gained). Going forward we hope to be able further refine optimal insemination timing when using different semen technologies – i.e. fresh versus, frozen, versus sexed. These have differences in maturation and survival time in the female reproductive tract.

TeatCHECK – the cow’s early warning system!!

Two seasons ago we launched TeatCHECK, a service where our tech team scores teats, teat spraying, and other mastitis risk factors to pre-emptively find farms that may benefit from making some changes (NOW) to help ensure the cows are dried off at the end of the season in the best teat condition possible.

What did we find?

Teat Condition: A lot of farms had significant amounts of teat end damage. This is worrying when you consider that there are still five more months of milking, during a period of reducing milk volumes which only tends to increase the risk factors for teat end damage. On average 1 in 4 teats scored were rough – these teats are at higher risk of mastitis, AND will be more difficult to clean properly when drying off with teat seal.

Teat Spray Coverage: On some farms as few as 35% of cows were getting adequate teat spray on all 4 teats. Only 7/50 farms had a system that was getting “every teat, every milking”. Given that we know correct teat spraying will reduce the risk of mastitis by 50%, there are a lot of cows being put at unnecessary risk! These farms were a mix of manual and automatic teat sprayers.

There were also a lot of issues with teat spray mixing, often due to unclear instructions for staff who were mixing at incorrect rates.

Got a problem, what can you do?

For farms with major issues we recommend a follow-up visit to investigate any risk factors that may be affecting teat health. Here we can work through a plan specific to your farm to help make changes that should minimise the impact on the teats over the remainder of the season. Some of the common findings have been:

• High vacuum pressure

• ACR settings keeping cups on too long (haven’t been adjusted for stage of season)

• Milking routine (especially in herringbones)

• Faulty gauges

• Insufficient pressure in automatic teat sprayers (+ incorrect angling/ sensors)

• Untrimmed tails

• Staff awareness / training (including cupping technique, teatspray technique etc)

One of the interesting findings has been that some low cell count herds are still starting to see significant amounts of teat end damage. Currently they aren’t seeing increases in cell count or mastitis, BUT they have typically had excellent teat spray coverage, good tail/udder hygiene, and low mastitis pressure within the herd. They therefore have a very low mastitis bug challenge at the moment so the damage isn’t causing clinical issues. HOWEVER, we are concerned that if the trend continues that they may put themselves at risk in Spring when the challenge markedly increases.

How do you sign up?

We will be in touch with all farms in the next 2 months to find out if you would like to sign up for a TeatCHECK visit, however if you want to find out your score ASAP then please get in touch. We will be charging $175 (incl) + travel per farm, which will include the visit itself, a comprehensive report, and some practice wide benchmarking. As discussed some farms may require a further visit from one of our trained mastitis advisors if we need to help diagnose the underlying cause of teat issues – note this would be a separate offering/ charge.

Herds coming off Peak Lactation

Most herd in this district hit peak lactation figures in early November. Ideally the lactation peak holds for as long as possible. A >7% drop in production/month after peak is considered excessive and likely indicates issues with a net reduction in ME intakes of cows.

A significant drop in production in the pre-mate and mating period will often see cows dropping in condition at the same time. This is not an ideal situation for optimising embryo quality and pregnancy maintenance.

So, what are the most common reasons for herds coming off peak lactation?

Dry matter percentage

• The excessive intracellular water (internal), as opposed to rain on the surface of grass (external), has been shown to restrict voluntary intake. Studies have shown a reduction of dry matter intake of 0.2-0.3kg DM for each percentage drop in dry matter below 15-18%. After a period of wet weather and good growing conditions this might see voluntary intakes drop from 18kgDM/day to 15kgDM/day if the dry matter percentage dropped from e.g. 18% to 12%.

• Mowing in front of cows several hours before grazing to get wilt should increase intakes if dry matter % is low but of good quality.

Quality of pasture

• Grazing pastures more mature than the 3-leaf stage (2-3 is optimal) will show a marked drop in ME. Grazing to low residuals where previously rounds have been lax means a higher percentage of mature/dead DM must be eaten, this reduces ME of the grass eaten as well as voluntary intake.

• If pasture cover is greater than 3,400kgDM you are best to top behind cows rather than mow in front, so as to not force them to eat poor quality feed.

Quantity offered

• Low pre-entry covers, restricted areas and simultaneous removal of concentrate supplements.

• Continue to calculate pre-graze covers and adjust break size or supplement as appropriate.

NDF percentage

• Cows cannot eat more than 1.3-1.5% of their body weight in NDF (this would be 7.5kg for a 500kg cow). If targeting cows to eat ≥18kgDM, the maximum NDF content would be about 40% of the diet.

• Ensure that covers do not exceed 3,400kgDM/ha at this time of year, and don’t force them to eat low quality residual.

Weed takeover

• Californian thistles and dock can become a significant problem on some farms at this time of the year. They effectively reduce the grazing area.

Heat stress and water restriction

• Temperature Humidity Index, air movement and solar radiation in combination will have a combined effect on the cows ability to maintain a normal body temperature. This in turn will affect grazing behaviour and grass harvest. Having shade and available drinking water (exit races) is pertinent to regulating body temp. Bringing cows together in close proximity in the yards/shed over the hottest hours in summer increases this risk.

• Watch for cows panting. Aim to provide the biggest feed allocation in the coolest part of the day in hot weather and adjust milking times.

Concentrate removal

• Often in-shed concentrates are removed as financial budget for purchases is reached or there is an anticipated excess in grass. The removal may coincide with any of the above to reduce total ME intake at what may be a crucial time.

Lameness

• If a significant percentage of the herd does become lame (and this could be slight), there is an associated increase in lying time as cows try to rest their feet.

• Monitor walking times of cows. If this is slow due to lameness adjust management or seek help from your Prime vet.

Milking interval

• It is generally considered that dropping from TAD to 16hrs while cows are producing more than 1.6kgMS/day will result in a milk drop.