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Machines and Mastitis Risk: A Storm in a Teatcup. Graeme Mein , Australia Douglas Reinemann , UW-Madison, USA Norm Schuring , Westfalia-Surge, USA Ian Ohnstad , ADAS, UK. Relative Effects on Mastitis. Feeding Herd health Calving areas Muddy lanes Clean udders. Milking

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slide1

Machines and Mastitis Risk:A Storm in a Teatcup

  • Graeme Mein, Australia
  • Douglas Reinemann, UW-Madison, USA
  • Norm Schuring, Westfalia-Surge, USA
  • Ian Ohnstad, ADAS, UK
slide2

Relative Effects on Mastitis

Feeding

Herd health

Calving areas

Muddy lanes

Clean udders

Milking

management

Herd & farm

management

Cow

Machine

Yield

Teat characteristics

Immune system

slide3

Effects of milking

on new infection rate

Hygiene

Calm cows

Visibly clean teats

Timing of cup attachment

Cluster removal technique

Teat disinfection

Milking

management

}

Machine

Contamination

Table 1 IDF,

1987

Teat health / colonization

Bacterial penetration

Dispersing pathogens in udder

Frequency /degree of emptying udder

slide4

Machines and Mastitis Risk:A Storm in a Teatcup?

“What percentage of all infections are due to milking machine factors?”(Eberhard, Montreal, 1987)

Range of responses:

“We don’t really know”

“ Probably quite low”

“Anywhere between 0% and 100%”

slide5

Most new infections are due to factors other than the machine

Hygiene

Calm cows

Clean teats

Teat disinfection

Cluster removal

Timing of cups on

Milking

management

}

Machine

Contamination

6-20%

Teat health, colonization

Liner slip, rough removal

RPGs, other effects???

slide6

Extreme effects of the first three mechanisms

Infected Quarters (%)

Peak Milking Rate (kg/qtr/min)

Grindal & Hillerton, 1991

slide7

1. Contamination:

A storm in a teatcup ?

  • Teatcup liners are damp, drippy places and contamination of teat skin is common
  • Contamination of teat skin does not necessarily lead to new infections:
    • NIRs remain low in control quarters of most milking studies involving high bacterial challenge
    • Two other instructive examples ...
slide8

Examples of low NIR

despite high bacterial challenge

  • High cyclic plus high irregular vacuum fluctuations failed to produce high NIRs in:
    • the first series of challenge experiments in the UK when teatcups were not joined by a common claw (Thiel et al. 1973)
    • the second series of challenge experiments in Ireland when a stable liner was used(O’Shea & O’Callaghan, 1978)
slide9

1. Conclusions: contamination

A storm in a teatcup ?

Machine-induced IMIs are low in the absence of teat damage (which assists colonization in or near the teat canal) or high local winds (that might impel pathogens into the canal)

Milking machine effects are low relative to the effects of herd and milking management

slide10

2. Changing the resistance of the

teat canal to bacterial invasion

“Milking machines influence the level of exposure to pathogens by their direct effect on the health of the teat duct or teat skin” (Dodd, 1987 & 2003)

Teat canal integrity

Congestion or edema

Skin or orifice lesions

slide11

Wide pulsator ratios increase the risk of mastitis

100:1

100:1

75:25

Infected Quarters (%)

Infected Quarters (%)

70:30

60:40

50:50

Duration of C+D phases (sec)

(from Reitsma et al. 1981)

pulsation failure and mastitis
No pulsation

Short C + D phase

Short liners

Short liners + o/milking

No pulsation

x 5-20 (Bramley, 1978)

x 2 (Reitsma, 1981)

x 2 (Mein et al. 83)

x 9 (Mein et al. 86)

7 vs 0 (Lacy-Hulbert, 98)

Pulsation failure and mastitis
slide13

Effect of pulsation

on teat-end condition

VR

R

Teat-end condition

S

N

None

Gentle

Aggressive

Positive

pressure

Increasing “strength” of pulsation

slide14

Association with NIR ?

New infection risk

VR

Teat-end condition

R

S

N

None

Gentle

Aggressive

Positive

pressure

Increasing “strength” of pulsation

slide15

2. Teat damage & colonization:

A storm in a teatcup ?

NIR is increased by machine-induced changes in teat-end condition:

Increased congestion or edema

Increased hyperkeratosis

Slower removal & re-growth of keratin Teat orifice more ‘open’ after milking

slide16

Teat health and “teat massage”

NIR is reduced if teat massage is effective

(= compressive load or over-pressure)

Compressive load depends on:

Pulsator ratio, B & D phases, rate

Vacuum inside the liner barrel

Liner material, geometry and tension Teat size and shape

slide17

3. Producing forces to impel pathogens

into or through the teat canal

  • ‘Impacts’ due to acceleration and inertia of small milk droplets that hit the teat-end.
  • ‘Impacts’ may result in partial penetration of the teat canal:
  • Liner slips, machine stripping, rough take-off
  • Effects confined within an individual cluster
  • Higher infection risk late in milking
  • Lower risk with free-draining claws and tubes
slide19

Effect of sudden air

admission into a teatcup

Managing Milk Quality, Levesque, 1998

slide20

Effect of sudden air

admission into a teatcup

150 kPa/s (45 inHg/sec)

slide21

Vacuum changes in milkline affect claw vacuum but rate of vacuum change is slow

Managing Milk Quality, Levesque, 1998

slide22

Vacuum changes in milkline affect claw vacuum but rate of vacuum change is slow

15 kPa/s

(4.5 inHg/sec)

slide23

3. Impacts and penetration:

A storm in a teatcup ?

Teat duct penetrated by 6 m/s jet speed (20 ft/s) but 2 m/s (6.5 ft/s) is too slow(Thiel et al. 1969)

Liners move much too slowly to generate high air speeds(Spencer, 2003)

Sudden air admission into a teatcup can generate air speeds > 6 m/s(Woolford et al. 1980)

Prime causes: liner slips, abrupt cluster detachment, vigorous machine stripping

slide24

Likely conditions for ‘impacts’

12

6

inHg

inHg

7.5

inHg

(from Levesque, 1998)

slide25

Impacts and penetration:

A storm in a teatcup ?

Vacuum changes in milklines or receiver are too slow to generate air speeds > 2 m/s within a cluster

Unstable milkline or receiver vacuum may be associated with higher NIR but this is unlikely to be a cause/effect relationship

slide26

5. Frequency and degree of

udder evacuation

New Infection Risk is lower during lactation than in the dry period

Regular milking has a positive effect !

- NIR reduced by regular flushing of canal

Complete milk-out seems important but may be less so with more frequent milking per day

slide27

Reducing the risk

  • Reduce transient air inrush, especially late in milking:
    • Stable liners, cluster positioning
    • Free draining SMTs, claw and hose
    • Calm cows (to reduce kick-offs)
    • Gentle removal, no stripping
    • Maintain effective teat massage
  • Maintain healthy teat-ends