Impact of immunosuppression in transition and calving cows

It’s fair to say vets have long advocated the idea that by getting the bit before calving right – and the bit after – you can expect smooth sailing for the rest of the year.

However, a mismatch exists between this and the time spent attending to cows in early lactation.

As well as the obvious sick cows, this may also include the routine post-calving checks and the not-seen-bulling cows that make up the bread and butter of routine fertility time on dairy farms.

The problem with only intervening here is it leads vets to treat, rather than prevent, disease, leading to disappointing outcomes and demoralising both the vet and farmer.

This article focuses on one farm, looking at the immunosuppressive effect of being a transition and calving cow, and how this links with the farmer recognising a peak in cases of retained foetal membrane (RFM) and endometritis.

The farm

Data from the farm revealed a greater-than-expected rate of early lactation mastitis.

This farm had an obvious disparity in its housing. At one end of the spectrum, the milking cow accommodation passed all tests – be it the technical “knee test” (McFarland and Graves, 1995) or more simplistic signals of comfort and ability to express behaviour. Wide passageways and multiple access point water troughs allowed for relatively low cow stress (Figure 1).

At the other end, the dry and transition yards were the alpine bunkhouse to the milking cows’ Claridge’s (Figures 2 and 3).

So why did the farmer want to make changes? The effect of the increased number of cases of endometritis is seen in the allied submission at the 80-day rates (Figure 4).

This two-year profile showed a reduction in 80-day submission during the warm months of both years.

It was this, rather than any intrauterine antimicrobial use or other perceived failures, that made the farmer take action to improve transition cow management.

Examination of the dry and transition areas started in October 2015 – while we had done this before, it was not with enough vigour by the author or the farmer, meaning a lack of any behaviour changes.

This time, they looked hard at environmental conditions, air flow, bedding comfort, and feed and water access. They identified two issues needing immediate remedy.

• Air flow

The shed had originally been built as a sheep shed and, typical of designs of its time, had a low-pitched roof and a lot of Yorkshire boarding.

While the ridge of the shed had already been removed to enable some air exit, and enough exits were present, insufficient air intakes meant the Yorkshire boarding was too closed.

However, the farmer could not bring himself to simply knock out every other panel. Instead, he agreed to mount every other panel on a rolling frame.

That way, he could try the author’s idea of sliding the frame behind the fixed boards. Then, when it got cold, he could slide the panel back into place to stop any drafts.

One year on, the panel has never been moved from the open position and is no longer discussed.

• Water access

Insufficient access to water troughs existed, while the one trough available was too small (Figure 5).

Dry cows require 10cm access each and should, ideally, have access at more than two points around the shed to avoid bullying.

Although the farmer said he was keen to amend the shape of the loose yard to improve this access, it had not happened.

These problems were highlighted using Elanco Animal Health’s healthy start checklist (HSCL). It works through environment, nutrition, water and cow condition methodically, using a traffic light reporting system, to indicate areas of good practice and those requiring improvement.

This approach delivers good pedagogy through encouraging positive comment and open questioning.

Collating data

The farm records milk with the Cattle Information Service. This is analysed through the practice using commercially available software.

Putting the evidence of the HSCL with reports of metritis, ketosis and RFMs identified the farm’s annual mean transition period failure – defined as an adverse event in the first 30 days of lactation – was 21%.

It was simple to record, for example, the incidence of RFM, cystic ovaries, left displaced abomasum and metritis on a wall chart, since the attending vet largely observed these on routine visits.

However, it was harder to encourage active recording of first 30-day mastitis rates. Therefore, this was added to the data through a trawl of medicine records, pairing each index case of mastitis to days in milk at that time.

Adding the cows affected by mastitis, and if measured as the first 30 days of lactation, gave an overall transition failure rate of 37%.

As Figure 6 shows, mastitis in the first 30 days accounted in the previous three months for nearly a third of all cases on the farm. This had not been recognised by the farmer and was, therefore, a surprise when first discussed with him.

The figure for cows sold in the first 100 days of lactation due to mastitis is included in the overall total of 14% of cows removed from the herd in the first 100 days – some of these are sold as part of the farm’s strategy. Excluding these reduces the percentage removed from the herd in the first 100 days to about 7%.

As well as identifying the reduction in 80-day submission rates seen around the times of increased failure of innate immune function, the milk recording data was also used to demonstrate the ongoing elevated levels of first-recorded high cell counts.

An average of 1:9.4 cows had a high cell count at first recording (range 10 days to 40 days). This compared to an industry target of 1:12, meaning the farm is 28% above target.

Taking our case farm and putting it in a wider context, Figure 7 shows data from a 12-month period recorded by a vet across his herd (John Cook, Elanco; personal communication). This relied on farmer reports, so may be considered under-reporting.

On a data set of 33,136 animals, this represents about 21% of animals undergoing some failure of transition during the first 60 days of lactation. In our case farm, while we were unable to record lameness rates, the mastitis rate in the first 30 days, as well as metritis and sold rates, were broadly in line with this larger data set.

This indicated the farm in question was not significantly outside the expected transition failure rate seen more widely.

Immunosuppression role

Immunosuppression is a natural process around parturition. In fact, Kimura et al (2002) concluded all cows – regardless of health status – were immunosuppressed at this time.

The process is likely to be an unintended consequence as the innate part of the immune system is required to down regulate the adaptive part of the immune system. This prevents excessive response to the antigenic stimulus of the calf as the placenta detaches, breaching biological barriers (Kehrli, 2016).

However, no similar requirement exists to down regulate the innate immune system. This process is nonselective and based largely on phagocytic cells, principally neutrophils.

To better understand which animals to target with any immunomodulatory treatment, it would help to be able to predict the cows likely to suffer the clinical effects of immunosuppression.

An encouraging US study used pedometers to identify mobility, lying events, lying time and feeding time, which led to a suggestion it was possible to predict the cows that would become ill as much as 21 days before calving.

It was also possible to predict the production disease they would get.

However, this data has been contradicted by a further study, which identified alterations in routine on a farm seen on most commercial units – where, for example, feed times and group numbers may vary – led to a greater variation in the results in the prediction, or even the presence, of disease.

This, therefore, makes this system unsuitable for commercial use, but represents a challenge to find early, reliable warning signs to identify animals most likely to benefit from immunomodulatory therapy.

It also means – for the time being, anyway – we must recognise any improvement in transition cow immunity has to be applied at herd level to deliver the benefits.

Helping the herd

Pegalated-granulocyte colony stimulating factor (PEG-GCSF) is a novel product acting at the level of the myeloproliferative cells to increase both the number and function of neutrophils; it aims to improve the function of the innate immune system.

This body-wide effect will have been further tested on a number of the practice’s farms before congress, where the impact on disease levels will be discussed. Initial results, however, appear favourable for improved transition function.

At the World Buiatrics Congress, Krohn et al (2016) stated the best way to reduce the need to treat the effects of immunosuppression was to stop an animal getting sick in the first place.

This is a chance for both management and therapeutic inputs to improve outcomes for our case farm’s transition cows and would be measured by no adverse event rates in the first 30 days of lactation.

Looking forward

Tom Brownlie, of the Livestock Improvement Corporation, believes the technology for in-line milk recording of pregnancy-associated hormone detection from day 16 of the pregnancy is likely to reduce the requirement for traditional rectal ultrasound diagnosis of pregnancy (Brownlie, 2016).

It is important, therefore, to identify new access points to these cows now, to deliver the welfare and productivity improvements we lay claim to.

The author believes a focus on transition cows and modulation – whether through management alone or including PEG-GCSF – represents an area where vets have historically failed to deliver consistently good advice, namely a secure future revenue source that will add value to our clients’ businesses.

Returning to the farmer, it was important to recognise his aspirations. He did not wish to invest heavily in rebuilding sheds, nor spend considerable amounts on individual cow treatments – he produces more heifers than the farm requires, so is comfortable with his 42% culling rate.

While this may not really fit with advice from Denmark that the most profitable cows are those that give five good lactations, it is important to pick up the aspirations of the client to deliver improved outcomes, cattle welfare and client satisfaction.

In this case, we’re striving for a young and highly productive herd. Where this does fit with the Danish advice is in evidence showing these older cows are more profitable through their improved transition period.

Through increasing the availability of lying time, and reducing the impact of a periparturient dip in immunity, the animals were able to deliver higher yields for longer.

This was a consistent finding among the top 1% of Danish dairy herds by Joep Driessen of CowSignals Training Company.

Conclusion

By focusing on transition cow management and early lactation success, we should be in a position to reduce the level of culling, and improve the average age and overall profitability of this herd without undermining the farmer’s aspiration for highly productive cows.

By the time of writing this article, PEG-GCSF will have been used on this farm for long enough to know what impact it has had on supporting the transition period.

The author expects this will have augmented the changes already implemented and looks forward to sharing the results.