Managing mastitis in large dairy herds in China

Over the past two decades there has been a rapid expansion in dairy cow numbers in China. In 2020, there were just over six million dairy cows. Most people associate China with large dairy herds, but the average herd size in 2018 was 16 cows and the average production was 7,400 litres. The Chinese government wants to increase output of the dairy sector significantly by 2025.

One third of cows are on found on farms of over 1,000 cows. The number of small producers is decreasing and the number of big herds increasing. There are some companies milking over 50,000 cows distributed over a number of farms. These are run as commercial enterprises, processing and selling their milk under their individual brand names.

This article focuses on large dairy herds of over 5,000 cows. All large herds are built as green field sites with purpose-built facilities. Some start with 5,000 cows with the intention of expanding to 8-10,000 cows within two to three years. Most of the large farms milk three times a day, and some four times.

You can’t drive onto a dairy farm. Most have strict biosecurity where you have to park away from the dairy, sign in and change into farm uniform (clean overalls, boots, hat, mask and gloves) to avoid introducing disease.

There is limited experience of large-scale dairying and reliance on expertise from other parts of the world. The pool of well qualified farm managers, nutritionists and dairy veterinarians is quite small. There is a real desire to improve performance, improve milk quality and reduce disease.

Mastitis and cell count. The level of clinical mastitis is very variable. Cases commonly rise in the summer months when the temperature and humidity increase causing heat stress. Some herds have mastitis levels running at 3 to 5% of cows per month. The level of clinical mastitis in lactation 1 animals is generally lower at under 2% per month. Some newly established farms have much higher levels of mastitis due to teething problems, lack of training of farm staff and getting used to a new dairy farm.

Not all herds use internal teat sealants at dry off. Some have as many as 20% of cows with mastitis within 30 days of calving, compared to the target of 8%, suggesting significant problems with dry period infections.

Bacteriology testing is carried out on most clinical cases in the larger herds. Most of these have an on-farm laboratory which carries out a range of testing from bacteriology, metabolic profiles and feed analysis.

Bacteriology shows that Streptococcus uberis, Klebsiella, Escherichia coli and ‘no growth’ account for the majority of all clinical cases. Bacteriology results are not commonly used to make treatment decisions. Almost all clinical cases being treated with antibiotics. Streptococcus agalactiae is also a cause of clinical mastitis on some farms.

There are many herds which have cell counts running between 200 and 400,000/ml. S. uberis, Staphylococcus aureus and S. agalactiae are commonly isolated from high cell count cows.

Monthly cell count testing is not regularly carried out as there was no easy way to test large numbers of samples for cell count. There is no national system for cell count testing yet, but this could well change in the future.

While there is good biosecurity to prevent people entering a farm, herds will routinely buy cows from various sources to expand rapidly. The majority of animals will be heifers some of which may have calved and have been milked in other parlours. Cows in lactation 2 and 3 can also be purchased to build up herd numbers rapidly. This can be part of the reason for spread of contagious bacteria such as S. agalactiae and S. aureus.

Milking routine. Most farms have a full milking routine.  One 15,000 cow herd visited had a pool of 140 milkers for their four 80-point rotary parlours and the herringbone hospital parlour. Most milkers are female. Milkers work 6 to 8 hour shifts. They wear clean uniforms for each shift with aprons, hats, disposable gloves and masks. Labour is relatively cheap.

This farm had an ongoing monthly milker training programme. Staff turnover can be high if people find better offers for work elsewhere. There is no real loyalty to staying in one place or working on a dairy, especially as milking shifts can be long and tiring.

Milkers stood on mats in a designated marked area to ensure that the timing of each part of the prep process runs on time. The parlour and surroundings in all the farms visited are very clean and well maintained. There is a milking supervisor to oversee the milking process.

The first milker applied predip using a teat cup, the second person strips each cow. Hands are rinsed in a basin of iodine disinfectant after handling any teats.

All cows are forestripped for good teat stimulation and mastitis detection

30 seconds further on, the third milker was drying teats with individual cloth towels which were washed at 90°C and dried before the next miking. Units were attached by a fourth milker about 90 seconds after predipping.

Milker drying teats with individual cloths standing on their mat

On the far side of the rotary was one milker who will apply post dip using a teat dip cup. They also had someone manually disinfecting the clusters to reduce the risk of cross contamination.

Some farms manually disinfected clusters between cows

This farm inspected and graded the milk filters and if found to be dirty, the milkers were informed and steps taken to improve teat preparation.

There was often some confusion about the diagnosis of clinical mastitis. In one herd of 5,000 cows, the mastitis rate was 96 cases per 100 cows over the previous year, over three times the target level. They started milking nine months earlier and there appeared significant confusion about the routine. Milkers were away from their designated positions and at times seemed to be confused about what they should be doing. Training of milkers was given in the early stages and was not ongoing as management focussed on other areas.

They also had problems with mastitis diagnosis. Cows were treated if there were clots of abnormalities present after four squirts of milk. It was suggested that this be increased to ten squirts to ensure that milk from the mammary gland and not the teat cistern was examined.

Iodine products are most commonly used for pre and post dipping, hand rinsing and cluster disinfection. Some farms can have two rotaries running side by side where one supervisor can oversee both parlours. The hospital parlours generally follow the same milking routine.

One farm milked 80 cows though a 20-unit hospital parlour without disinfecting the clusters between cows increasing the risk of cross contamination. The milking routine was quite poor. Teats were not thoroughly cleaned. The timings of the routine were highly variable with up to five minutes from predipping to attaching the cluster.

Environmental management. Milking cows are generally housed in freestall barns with wide passageways, wide feed passages and fans and misters to assist cooling in the hot summer months. There can be a large variation in temperature throughout the year from as low as -15°C in the winter to a high of 35°C in the summer.

Many use freestalls with deeps beds made up of recycled manure solids often mixed with rice hulls or some other organic waste material. Barns have open sides in the summer and have drop down covers for the winter. Some dairies have sealed controlled environments with forced ventilation.

Disposal of manure is a big problem for many dairies as there are strict controls on disposal of cow manure. Use of recycled manure solids is common. Some of these solids are made up and stored for days or even several weeks before being applied to the beds. Freestalls for the milkers are applied daily or every second day. The beds are deep raked by tractor regularly to allow good draining of liquids.

Stocking density can be very variable. For many herds, the milkers had a stocking rate of 90% (90 cows for 100 cubicles). There was one herd that had a 115% stocking density as the owners wanted to push up milk production despite a significant increase in clinical mastitis that occurred. Their plan was to push this stocking density to 125% to boost profitability.

Passageways were either cleaned using automatic scrapers which were running every hour, were manually scraped when cows went to be milked or used flood gate irrigation. I saw flood gate irrigation being used when the milking cows were present and feeding. Dirty water splashing up against teats which is likely to have increased the risk of mastitis.

Flood gate cleaning also occurred in the exit passageways from the parlour in some herds and this was running as cows were walking back to their barns with dirty water splashing up against the udders and teats.

Many dairies had rubber matting on the walkways for cow comfort. It was interesting to watch cows queue up to walk on this soft surface rather than walk on concrete.

Hospital facilities have their own accommodation for cows which are generally freestalls and some loose lying areas for special need cows. Generally, there are enough freestalls unless there are large outbreaks of disease when these could be overcrowded for short periods of time.

Dry cows could be housed in freestalls at stocking rates of 80 – 85% or in large loose barns bedded with deep recycled manure solids with plenty of space. Cows were mostly removed to a separate calving area as soon as they started to calve. Maiden heifers were housed separately in similar facilities as the dry cows. Attention to detail for the environment for some of the dry cows was below that of the milkers with weekly bedding up.

One herd had overstocked it’s maiden heifers in dirty conditions. 12% of these heifers had mastitis within 30 days of calving indicating problems with dry period infections.

Milking parlours. The big dairies milk through large rotary parlours to maximise throughput. These are running 24 hours a day in some of the large herds with three breaks for plant washing. Good maintenance is essential to avoid breakdowns causing a backlog of cows to be milked.

Automatic cluster removers were set to come off at around 1,000 ml/minute for herds milking three times a day. Some herds milking four times a day were removing clusters at up to 1,350 ml/minute.

Liners are changed at the correct intervals to ensure that milking speed is optimised and the risk of spreading infection from cow to cow via the liner is minimised. Vadia testing and teat scoring is carried out monthly on the well managed herds.

Larger herds have a separate hospital parlour for milking all cows under treatment. This is where the dry off treatments take place. These are herringbone parlours as the number of cows going though these is generally low and there is no time pressure for milking.

There are individual bucket machines for milking freshly calved cows to harvest colostrum to feed to newborn calves.

Dry off management. Some herds were milking cows four times a day throughout lactation and immediately prior to dry off. Few herds reduced milking frequency to reduce yield prior to dry off.

There are many quality ‘branded’ antibiotic dry cow products and interna teat sealants, along with some locally made products. Almost all herds use blanket dry cow therapy as they do not carry out individual cell count testing. This is regarded as being very important in mastitis control. At present, there is little pressure on use of antibiotics in dairy cows. Understanding of the benefits and importance of internal teat sealants is low. Some farms would only look at using this in selected animals.

I observed cows bring dried off in one hospital parlour by the farm vets. This farm reported problems with cows leaking milk after dry off. Cows were CMT testing immediately after the last milking before dry off. Any high CMT quarters were treated with lactating cow intramammary tubes and dry off was delayed until the end of this treatment.

All four teats were thoroughly disinfected using cotton wool and surgical spirit. Antibiotic dry cow tubes were infused and massaged up the teat followed by a locally made internal teat sealant while pinching the teat to ensure that the sealant remained at the base of the teat and in the teat canal. Hygiene at infusion was good. Teats were post dipped.

These cows came back into the parlour for the following three days immediately after the last batch of cows was milked to have their teats dipped and this is when the cows were starting to leak milk. The machine was still running at this time.

The locally made internal teat sealant was compared to a branded product and this showed that it had very poor viscosity. It seemed to be a very inferior product. The locally made product was very cheap and the low price was the decision to use this product.

It was suggested that they switched to a proven branded product and did not bring the cows back into the parlour after dry off as this will stimulate the milk let-down reflex increasing the risk of milk leakage.

Data management. All dairies are computerised and all cow events are entered. Some use western programmes which allow extensive data analysis which can help pinpoint mastitis problem areas.

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