Clinical Forum Assessment of milking systems

Clinical ForumAssessment ofmilking systems

Ian Ohnstad BSc

MILKING TECHNOLOGY SPECIALIST

THE DAIRY GROUP

CATTLE ● CLINICAL FORUM 1

THE INFLUENCE OF THE MILKING MACHINE

ON MASTITIS AND MILK QUALITY

Although the milking machine is the only piece ofmachinery on a dairy farm in direct contact with the cow,it is often the most neglected. As long as the vacuum pumpstarts, the pulsation system appears to be working and theteat cups stay on the cow’s teat, in many cases, the plant isassumed to be working satisfactorily.

However, in reality, the impact of the milking equipmenton mastitis and milk quality can be considerably moreprofound.

It needs to be remembered that, just like a modern motorcar, if the machine is well maintained and carefully andsympathetically operated, it causes few problems. However,even when well maintained, when it is put in the hands ofan inexperienced operator, the results can be catastrophic.

The role of the milking machine in milk quality is welldocumented. It can either act as a vector and spreadpathogens between cows or quarters or alternativelyadversely affect the condition of the cows’ teats which inturn impairs the first line of udder defence.

In any milk quality programme, it is therefore essential tobe confident that not only is the milking machineoperating satisfactorily but that it is being used correctly.

TESTING OF THE MILKING EQUIPMENT

A full assessment of any milking machine can beconsidered to fall into four categories:i. A static or dry test - carried out between milkings to

measure vacuum levels, effective vacuum reserve,pulsation characteristics and air leakage.

ii. A dynamic test - carried out during milking tomeasure vacuum levels and vacuum stability, milkflows, ACR take off settings, cow behaviour and postmilking teat condition.

iii. A plant cleaning assessment - carried out after milkingand measuring wash temperatures, flow rates, solutiondistribution and chemical concentrations.

iv. An operator assessment - carried out during milking toassess operator technique and effectiveness of practices.

It is essential that the milking equipment is tested, servicedand maintained by a suitably trained dairy engineer. Thisengineer should undertake a static test of the milkingequipment in accordance with the requirements of BS ISO6690:1996.

The requirement for service will vary depending on hoursrun but as a general rule, milking equipment requires amajor service every 1500 hours and an interim serviceevery 750 hours. It is important to realise the differencebetween a plant test and a plant service. Regular testingdoes not equate to regular servicing. A number of dairyengineers and consultants are able to provide a dynamictesting service which can provide useful additionalinformation on plant performance, particularly whenaddressing a problem.

In my opinion, a dynamic plant test should be carried outa minimum of once a year and more frequently if the plantis operating for extended periods.

Nigel Cook Panel members:Roger Blowey BSc BVSc FRCVS

Neil Frame BVM&S CertEP CertVA MRCVS

Richard Laven BVetMed PhD MRCVS

Andrew Norton BVetMed CertBR DBR MRCVS

Andrew White BVMS CertBR DBR MRCVS

Fig. 1: Fullwood 30 degree rapid exit milkingmachine.

Fig. 2: Plant testing.

CATTLE ● CLINICAL FORUM2

Many garages now carry out a road test as part of a routineservice. I suggest that carrying out a dynamic plant test issimilar to a road test and it will allow you to assess just howwell the plant is operating. However, a word of caution!

While BS 6690:1996 clearly describes performanceparameters to which a plant must comply, the guidelines fordynamic testing are less specific. The dynamic observationsmust be viewed in conjunction with the operatortechnique and the condition of the teats post milking.

OPTIMISATION OF THE MILKING MACHINE

To ensure that milking equipment is performing at anoptimum level, as well as regular service and maintenanceinput from a qualified dairy engineer, the operators musttake their share of responsibility. There are a number ofdaily physical checks to carry out to ensure optimalperformance.It is also important to take advantage of other monitoringtechniques such as cow behaviour and post milking teatcondition.

i. Vacuum Level

The plant vacuum level should be checked on the farmgauge at the start of every milking session. It is essential the

gauge is accurate and it can be helpful if the dairy engineermarks the correct vacuum level on the face of the gauge.

Plant type Working vacuum level (kPa)

Low level 40– 44

High level 45– 48

The gauge should be checked periodically during themilking.

ii. Pulsation

The operation of the pulsators should be checked bystarting the milking unit, closing three of the teat cups andinserting a thumb in the fourth. The speed of the pulsatorsshould be measured and the movement of the linerassessed.

The pulsation speed will be between 55 – 62ppm. Theliner should move away from the thumb during the lineropen phase and collapse around the thumb, applying acompressive load, in the liner closed phase.

iii. Cluster air bleeds

The cluster air bleeds should be checked and cleaned witha piece of fuse wire at the start of every milking. Duringmilking, blocked or partially blocked air bleeds willresulted in flooded claws and residual milk running out ofthe bowl when the unit is removed.

iv. Vacuum stability

Removing a long milk tube under vacuum should notresult in any vacuum fluctuation. If two long milk tubes areremoved, a slight fall of less than 2 kPa may be noted.When the long milk tubes are re-attached, the vacuumshould rapidly recover.

This test should be done periodically to ensure satisfactoryeffective vacuum reserve.

v. Completeness of milking

A cow, which has been efficiently milked, will have littleresidual milk left in her udder. If the milking machine isoperating well and the cow has been well stimulated, itshould not be possible to draw more than 100 ml of milkfrom each quarter in 15 seconds.

This assessment should be carried out whenever asignificant change is made to the milking machine settingsor routine.

TEAT CONDITION

Various agents and mechanisms can influence thecondition of the teats of a dairy cow. Milking machineinduced changes or environmental factors can cause short,medium or long-term changes in teat condition. The mainshort-term (single milking) effects may include changes incolour, swelling and firmness of the teat end and barrel andthe degree of openness of the external teat orifice. Themain medium-term effects (requiring a few days or weeks)include changes in teat skin condition, and incidence ofpetechial haemorrhages.

Changes in orifice hyperkeratosis levels appear to developin the longer term (typically 2–8 weeks) but may happenmore rapidly in the presence of extreme weather or harshenvironmental conditions.

i. Short-term changes in teat condition

Faults in milking machines or milking management are theprimary cause of short-term changes in colour, firmness,thickness or swelling of teats, or degree of ‘openness’ of theteat orifice.

Colour changes

Some teats are noticeably red, either at the teat-end or overthe entire teat, when the cluster is removed. Others maybecome reddened within 30-60 seconds of cluster removal.In extreme cases, teats become blue or already appear bluewhen the cluster is removed.

Poor teat colour after milking may be worse for short orslender teats. Colour changes are exacerbated by overmilking,especially with wide-bore liners or tapered liners with wideupper barrels, unusually heavy cluster weight, high milking

Fig. 3: Hyperkeratosis score 5.


vacuum, faulty pulsation, or a mismatch between type ofliner used and mean teat size within a herd.

Clearly black teats must be excluded from any colour-based evaluation. Changes can be classified according tothe proportion of light-coloured teats that, whenexamined within 60 seconds of cluster removal, are:? Normal (pink)? Reddened (part of or all the teat-end or barrel may be

discoloured)? Blue-coloured (part of or all the teat surface appears to

be tinged with blue or purple).

Swelling at or near the teat base

When examined after milking, the upper part of the teatmay have a visible line or mark caused by contact with theliner mouthpiece lip. Alternatively or in addition, theremay be visible swelling (with a palpable, thickened ring) inthe unsupported area that was inside the liner mouthpiecechamber near the end of milking.

Factors commonly responsible for swelling around the topof the teat as a direct result of milking include: highmouthpiece vacuum associated with wide-bore liners,overmilking, especially with wide-bore liners or taperedliners with wide upper barrels, teatcup crawling or linermouthpiece lips that are unusually stiff or narrow inrelation to teat size.

These effects can be evaluated according to the proportionof teats that, when examined within 60 seconds of clusterremoval, are:? Normal (no ring, little or no swelling)? Visible mouthpiece lip mark or ‘garter mark’? Marked swelling or palpable thickened ring

Hardness at or near the teat-end

Many teats feel soft and compliant after milking and theycontract when touched. However, some teats feel swollenor firm or, in extreme cases, hard and unresponsive totouch. Teats often look flat or ‘wedge-shaped’ after milking.‘Wedging’ describes the flattened shape of the teat-end dueto the compressive load applied by the opposing walls of acollapsed liner.

Severe wedging which induces a reduction in teat endvolume may result from hard liners, liners mounted underhigh tension, a prolonged liner closed D-phase or failure ofthe liners to open fully.Teat-ends can be classified by simple visual examinationsupported by manual palpation, as:? Normal (soft and supple)? Firm, swollen or hard, or severely wedged.

Openness of the teat orifice

When examined immediately after milking, the externalteat orifice may appear to be closed, slightly open or, inextreme cases, with a funnel-shaped opening about the sizeof a match-head.

Factors linked with short-term, post-milking openness ofthe teat orifice include high milking vacuum, overmilking,design of liner mouthpiece, unusually heavy cluster weight,or high liner mounting tension.

Teat orifices can be classified, by qualitative assessmentwithin 60 seconds of cluster removal, as:? Closed? Open (more than 2 mm wide or deep).

A clean paper towel can be used to remove milk residuefrom the teat end. When estimating the degree ofopenness, it is helpful to compare the width or depth of anopen orifice with a common object such as a match-head(about 3 mm in diameter) or the shaft of the match (about2 mm).

ii. Medium-term changes in teat condition (responses

visible within a few days or weeks)

Teat skin condition

Healthy teat skin is coated with a protective mantle of fattyacids that are derived from the dermal layer and whichretard the growth of bacterial pathogens. When exposed tocold, wet and windy conditions, the skin of machine-milked teats often becomes scaly, irritated or chapped(broken skin) and the protective surface coating may beremoved, thereby allowing colonisation of contagiouspathogens such as Staphylococcus aureus.

Cold, wet or muddy conditions induce hardening orthickening of the teat skin. Mud, as it dries, draws moisturefrom the skin with a consequent loss of elasticity of the teatskin. Machine milking exacerbates problems of chapping orcracking. Chemical irritation associated with disinfectanttype or concentration, or inappropriate type orconcentration of emollients, may exacerbate the effects ofharsh weather conditions and promote teat chapping.

The dryness of black teats tends to be over-estimated byobservation alone. Evaluation is improved by lightlyrubbing the teat skin with a finger. In the absence of cracksand sores, differences in skin condition classed as smooth orrough do not seem to influence new mastitis infectionrates.

When examining teats for dryness, the evaluation shouldbe carried out before teat preparation.

Teat can be considered as:? Normal (smooth sheen, soft, healthy skin)? Dry (scaly, flaky or rough skin but with no cracking)? Open lesions (chapped, cracked, blackspot)

Vascular damage

The proportion of teats with petechial haemorrhages, ormore extensive haemorrhaging, is one indication of theextent of any vascular damage. Vascular damage usuallyreflects some type of pulsation failure, often associated withhigh vacuum and/or prolonged over-milking.


iii. Longer-term changes in teat-end condition

(response visible within a few weeks)

The degree of teat-end hyperkeratosis is a dynamiccondition. Status of teat-ends for an individual cow or herdcan change within days, especially in regions subject to harshweather conditions or sudden weather changes. Seasonalconditions may affect dryness and hardness of keratin.

In the absence of unusually harsh weather conditions,however, changes in teat-end status occur over a period of2-8 weeks.

Apart from seasonal weather conditions, major factorsaffecting teat-end hyperkeratosis include teat-end shape,production level and stage of lactation, and interactionsbetween milking management and machine factors(especially slow milking and over-milking).

In general, teat-end hyperkeratosis is more marked in cowswith long pointed teats, slow milking cows or higher-producing cows.TEAT CONDITION SCORING

In most of the described parameters it is important to haveintervention levels which indicate a problem. I wouldsuggest for all these parameter, if more than 10% of teatsexamined are ‘not normal’, this should raise concerns.

COW BEHAVIOUR

Animals who are milked by a well maintained milkingmachine, which complies with all the relevant standards,will not dung or urinate frequently. They will standcomfortably, often chewing their cud. Fidgeting, liftingtheir feet or kicking at units is a good indication of a cowthat is not happy with the milking environment.

CONCLUSION

A well maintained milking machine with a good operatoris seldom the cause of a milk quality problem.

Taking a more active role in the milking process andspending time monitoring changes can be very helpful. Inmany cases, operating conditions, operator technique, teatcondition and machine performance have deterioratedover a period of time, but because the deterioration wasslow, the poor environment just becomes the norm.

Static milking machine testing is an essential managementtool. However, it should not be seen as a stand aloneservice and should be supported by dynamic assessmentsand frequent monitoring of milking routines, cowbehaviour and teat condition.

Identifying changes in teat condition before a problem canbecome established can prove to be very cost effective.

QUESTIONS TO THE PANEL

1. What is your view on the value of regular milking

time visits?

Roger Blowey replies:

It would be nice to be able to doregular milking time visits, but wedon’t seem to do it. As herd sizeincreases the cost per cow willdecrease and perhaps we will do itmore. We certainly ought to chatabout the parlour routine

whenever the opportunity arises, and just pop into the pitfor a few minutes if we are there during milking. Whatsurprises me is how often the routine is changed. I supposeevery herdsman wants to try to improve things, and if hehas been speaking to someone he will want to give newideas a try.

Neil Frame replies:

Absolutely essential. So often afarmer's description of his routineis very different from what oneobserves after he has relaxed intohis usual procedure. It would begood to do more of these visitspro-actively but it is usually

requested only as a response to a milk hygiene problem.

Richard Laven replies:

For the larger farms very valuableas you get to see how the systemworks and how all the milkers fitinto that system. Useful addedpart of the veterinary carepackage. May not be cost effectivefor smaller farms.

Andrew Norton replies:

I am sure regular milking time visitscan be of enormous value inmonitoring milking parlour routineand cow teat condition. However,for me the idea is unfortunatelymore theoretical than practical, as Ifind significant client resistance -

both farmer and cowman - to paying for this time unlessmajor problems with mastitis have developed, and the dayswhen I was regularly on the farms at milking time on various ‘fire-brigade’ calls and could just look in the parlourare long gone.

Andrew White replies:

Regular milking time visits aresomething that we do not, as apractice, normally do. Theadvantages are obvious but usuallythe time and vet required do notalways coincide to do this on ourfarms. We have over 100 dairy


farms in this practice. If we are investigating a problemwith mastitis or some other factor which would indicate aproblem, such as poor milk let down for instance, then avisit at milking time is essential. The difficulty is topersuade the farmer not to alter his routine purely becausewe are watching!

2. Do you routinely teat score herds?


The main occasions I would score herds are a) before andafter they have had a new plant installed. I have seen somany herds where the installation of new equipment hasled to increased teat damage that I strongly recommendthis as a routine. Secondly b) if they have a problem withcell counts or increased mastitis and c) if they have hadproblems in the past and I want to make sure that thingsare OK. I do think that handling of teats is an importantpart of teat scoring. If I find more than 20% of teats are‘hard’ when the unit is removed I would suspect a machinemilking problem. In my opinion this can cause an increasein cell count without any increase in infection rate,although if not corrected no doubt new infections wouldstart to increase.

Neil Frame replies:

Yes, as part of a milking visit teats are assessed by scoringfor levels of hyperkeratosis and other teat lesions are noted.We hope to see a herd score less than 1, on a scale of 0 to5. A score of 3 or over has a good correlation with apositive California test.


As part of any mastitis investigation I would look at andscore teat end and skin condition. I find numbers veryuseful for persuading farmers to change systems. They aremuch more effective than generalities such as ‘teatcondition isn’t very good’ – they are also useful for settingtargets.


Teat scoring of herds is something that I tend to do whena problem with either clinical mastitis or SCCs hasoccurred; visits on a regular basis are not performed. WhatI have suggested to a couple of more pro-active cowmen isthat they store regular data themselves by using a digitalcamera and home computer to keep pictures of teat endsof a batch of first and second lactation animals every twoto three months throughout the lactation. In this way I feelthat they can monitor teat end damage using ‘before andafter’ shots which can be available for me, the farmer, andthe machine engineer if problems develop, or more ideally,before they develop too far.


We do not routinely teat score herds. The examination ofthe teats during the first minute after teat removal can yielda considerable amount of useful information both positiveand negative. Teat inspection, as part of our milking timeinvestigation of a problem, forms an important part of that

investigation as the colour, shape and hardness of the teatcan lead to suggestions of faults with vacuum, and maysuggest reasons for cows reluctant to come into the parlouror a poor ‘let down’ reflex.

3. Do your clients appreciate the importance of a

well maintained milking machine?


I think most do, yes. Farm Assurance schemes obviouslyrequire that all machines are tested regularly, and when Iam discussing cell count problems I would prefer to lookat the recent test reports. As more herds have dedicatedherdsmen, and they have to show that they can maintainquality milk production, testing is becoming a part of theroutine.

Neil Frame replies:

Mostly they don’t appreciate the importance of a wellmaintained system until there is a problem with cell countor Bactoscan penalties. It is always worth reading the testreport for oneself and checking that advice given is beingfollowed.


Yes, but often their definition of well maintained isdifferent from mine!


In theory clients understand how important a wellmaintained milking machine is, in just the same way asthey appreciate the importance of a regular service of theirmotor car. However, as with the car, provided they havehad a service at approximately the right time they then dono further checking - as many of them perform daily andweekly checks on the machine as the rest of us check tyrepressures and oil levels in our car!


Difficult to answer this question. I suggest that thefarmers’ attitude to a well maintained milking machine issimilar to mine with regard to the routine servicing of mymotor car. I know it has to be done, if only because Irealise that things will go wrong if it is not carried out.The value of the regular service is difficult to state interms of increased efficiency. The vast majority of ourfarms have their milking machines serviced at regularintervals and usually at the correct time interval, only afew following the argument of ‘If it ain’t broke, why fixit?’

4. Do you believe that standards of installation and

service within the milking machine industry are

improving?


Yes, I think that they are. There have been a number offairly high profile legal cases where the farmer hassuccessfully sued the manufacturers/suppliers for faultyinstallation, and so most plants are now installed to acarefully listed specification. In addition, as electronic


equipment becomes more sophisticated there is anincreased opportunity to use the machine itself tomonitor what is happening in the parlour. A goodexample of this is the monitoring of milk flow rates percow. If the mean peak flow rate of the high yielder groupis less than 4 litres per minute, or their average milk flowis less than 2.5 litres per minute, then you know that youhave a problem. This information is now easily accessibleon many systems. However, when faced with teat endproblems, it sometimes worries me that manufacturersspend longer looking at aspects of the milking routinethan at plant performance itself.

Neil Frame replies:

Yes, although we see some problems with parlours that havebeen altered or extended by the farmer himself.


Bigger farms are able to get better deals from themanufacturers. After sales service is now an obligatory partof the package.


Marginally perhaps, but major errors still seem to occurquite frequently.


Over time, I have seen changes in the standards of theinstallation and service of milking parlours and equipment.Over the past three or four years I feel that standards haveimproved. This is perhaps because the parlours now beinginstalled are becoming so high tech that the installing teamsreally have to be much better trained.

5. What is your view on dynamic plant testing?


One of the best dynamic tests is to do a teat score - i.e. askthe cow what she thinks about the effects of the machineon her teat ends! This will give you quite lot ofinformation.

Although I have no personal experience of its use, I knowthat the graphical printouts of milk flow rates that theLactocorder gives can be invaluable in the investigation oflet down and teat lesion problems. Dynamic testing is ofcourse the only way that you can really get any idea of teatend vacuum fluctuations, and this has an influence on newinfection rates.

Neil Frame replies:

We strongly recommend dynamic testing especially if aproblem has been demonstrated on the static test. It doesseem difficult to persuade testers in this area to performdynamic tests - possibly because there are no fixed guide-linesto the test and results are open to interpretation. We findassessing cow teat condition after milking a useful guide to thefunction of the milking machine.


I don’t believe that you can properly evaluate the milkingmachine without a dynamic test.


Dynamic testing has to be a good thing but isn't carriedout often enough. However, there often seems to be aproblem arranging for an engineer to make these visits andthey often seem to take a defensive stance as soon as one isrequested.


I feel that dynamic plant testing is a very useful addition tothe static test. I always ask for it to be done if I am askedto investigate a mastitis problem which I feel is being madeworse by a faulty plant. Many of the machines on ourfarms have been constructed as ‘add ons’ to existingparlours and sometimes the vacuum reserves need checking.I feel that this is much easier to test with a dynamic test,particularly whilst the high yielders are being milked. Inaddition to the mechanical testing normally carried out, Ifeel it important to watch the cows. They should enter theparlour willingly and show no signs of discomfort duringthe milking procedure.

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Clinical Forum Assessment of milking systems