Doc's Corner Article 102
January 1, 2005
Brazil’s Hypothesis - “Teat End Pressure
Present applied research conducted by Lionel H. Brazil DVM
suggests that the major causes of increased mastitis and SCC
levels are related to the abrupt pressure changes at the teat
end that propel the infecting bacteria into the mammary gland
during the milking period. This, obviously, is not a new
concept, but perhaps we now have the additional data to
enlighten and suggest how else these forces can be applied and
how this activity can, and must, be curtailed.
Ever since the concept of reverse gradient impacts propelling
bacteria into the mammary gland have been suggested to be a
major cause, we have been very concerned about audible sounds
suggesting rapid pressure changes at teat end. Many have
suggested that many incidents of non-audible pressure changes
contribute to the reverse flow of milk into the mammary gland
and contribute to the increased mastitis levels observed on many
dairies. Along with these facts, we have concluded that the more
prevalent the bacteria population at teat end the greater the
mastitis infection level and rate.
Recent discoveries have suggested that several very important
areas have been neglected and demand greater attention. These
facts in no way reverse the need for vacuum stability and
improved sanitary levels at teat end during the milking process.
The development of pulsation monitoring systems have shown that
many more pressure changes occur at teat end than previously
recognized and at the same time many more fall-offs and
re-attachments occur during the milking period than is desired.
The assumption being that these pressure changes directly relate
to reverse pressure changes that contribute to many more impacts
of bacteria into the mammary gland.
It is my opinion that future data will provide even greater
support to the above conclusions. Let us take a quick look at
the many potential factors that create pressure changes at teat
end during the milking period, in the order of importance as I
1. Periodic compression of one or more of the three hoses that
convey vacuum and pressure to the teat end during milking.
Notably the effects of the cows hoofs applying pressure at
various intervals during the milking process which very often
influence pressure differences at teat end which can propel
bacteria into the mammary gland.
2. Fluctuating vacuum levels that often fall below the vacuum
retention levels necessary to keep the mouthpiece of liner
firmly attached to the upper portion of the teat.
3. Failure to routinely maintain milk line closure valves. The
return to atmospheric pressure must be quick, consistent and
complete every time the milk sensor sends signal to close.
4. Lack of adequate positive pressure in the system to assure
that positive pressure at all times exceeds the requirements of
the milk line closure valves.
5. Lack of complete assurance that all other pressure requiring
equipment (such as crowd gates and exit gates) does not rob the
milking system of adequate positive pressure to close the milk
line closure valves.
6. Improper maintenance of cluster bleed hole to enable quick
and adequate decay time. Repeat cleaning of bleed hole must be
done with device sized the same diameter as the original hole.
7. Improper udder preparation which contributes to early
fall-off because of lack of friction between teat and liner.
8. Erratic signals for milking unit removal at time of proper
9. Failure of removal of pre-dipping solutions which very often
reduce friction between teat and liner.
10. Improper weight of milking cluster in relation to cluster
vacuum level. Balance of these two components is very important
for proper and consistent attachment.
11. Low cluster vacuum levels.
12. Faulty or worn liner mouthpieces.
Even when most recognize the
importance of the above statements, many fail to constantly
recognize the importance of high levels of persistency and the
demand for constant surveillance to assure a high level of
success. Regardless of management levels, the growing size of
dairies and the complexity of equipment requires constant
mandatory procedures to assure that all major and minor concerns
are constant and persistent to assure the desired levels of
success to assure survival.
Doc's Corner is a contribution of Lionel H. Brazil, DVM
(1928-2007). Dr. Brazil offered dairy consultation
services worldwide for many years. His services covered the following areas: milking management, vacuum system evaluation; and all management procedures relating to mastitis control and SCC