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Doc's Corner Article 102

January 1, 2005

Brazil’s Hypothesis - “Teat End Pressure Change”

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 see it.

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 milk out.

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 reduction.



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