It is tiny, but it is im­por­tant

Dairy News Australia - - ANIMAL HEALTH - • Rod Dyson is a vet­eri­nary sur­geon and mas­ti­tis ad­viser at www.dairy­fo­cus.com.au ROD DYSON

IT IS only a tiny part of your milk­ing plant, and it can some­times be very un­ob­tru­sively placed, but it is crit­i­cal to the abil­ity of your milk­ing plant to func­tion cor­rectly. Nat­u­rally this tiny part of your plant is the claw air ad­mis­sion hole. Usu­ally be­tween 0.8 mm and 1 mm in di­am­e­ter, the claw air ad­mis­sion hole is com­monly lo­cated in the claw it­self, ei­ther in the metal body of the claw or some­times in the claw bowl it­self. In some cases the air ad­mis­sion hole is lo­cated in each of the lin­ers, ei­ther in the short milk tube or near the mouth­piece of the liner. This tiny hole has two key func­tions in the milk­ing process. Firstly, the air ad­mis­sion hole al­lows milk to move away from the claw to the milk­line. Milk, like all liq­uids, does not run “up­hill”. To be able to move up­wards in any part of its path­way to the milk­line, milk will need to form “slugs” in or­der to defy grav­ity, and it needs air to form those slugs. The air en­ter­ing the claw through the air ad­mis­sion hole al­lows those slugs to form and milk can then travel to the milk­line. Hence one of the first signs of a blocked air ad­mis­sion hole is the claw fill­ing with milk as a cow is be­ing milked — be­cause the milk is un­able to get away prop­erly. The sec­ond key func­tion of the air ad­mis­sion hole is to al­low air to en­ter the claw at a con­trolled rate when vac­uum is bro­ken at the end of milk­ing to al­low cups to be re­moved. Oth­er­wise, if there is an ef­fec­tive seal be­tween lin­ers and teats, and no air can en­ter the claw af­ter vac­uum is bro­ken at the end of milk­ing, the clus­ter will be un­able to fall away from the cow, and the only way re­moval can then oc­cur is by pulling the cups off the cow. The end re­sult of pulling cups from the cow is to al­low blasts of air into the claw as the first cup breaks vac­uum away from the teat. This causes “im­pacts” which are blasts of air and milk which travel into the other three quar- ters of the cow with a very high risk of trans­mit­ting mas­ti­tis bac­te­ria. Hence this tiny air ad­mis­sion hole plays a key role in ef­fi­cient milk­ing and ef­fec­tive mas­ti­tis con­trol, so it is very im­por­tant to en­sure these holes are kept clean. The signs of a blocked air ad­mis­sion hole are twofold as de­scribed above — the claw bowl fill­ing with milk dur­ing milk­ing, and the clus­ter fail­ing to fall away from the cow af­ter vac­uum is bro­ken at the end of milk­ing. All milk­ers should be trained to be on the look­out for these clues to a blocked air ad­mis­sion hole. The air ad­mis­sion hole is com­monly blocked by dirt, bits of grass or ma­nure, and in sum­mer it is also quite com­mon for flies to get stuck in the hole. Nat­u­rally these for­eign bod­ies are to some ex­tent as­sisted to block the hole by the air move­ment into the hole and hence it is not un­com­mon to see a fly “stuck” in the air ad­mis­sion hole. How com­monly block­ages of the air ad­mis­sion hole oc­cur can vary dra­mat­i­cally from farm to farm. Some farms hardly ever see the hole blocked whilst some other farms need to have a milk­ing pro­to­col where the cups on op­er­a­tor ac­tu­ally wipes the hole clean prior to the ap­pli­ca­tion of the cups to ev­ery cow. Ev­ery farm should en­sure that all milk­ers are aware of the lo­ca­tion of the air ad­mis­sion hole, the signs when the hole is blocked, and the im­por­tance of clear­ing those block­ages. In ad­di­tion, a rou­tine of clean­ing the air ad­mis­sion hole on a reg­u­lar ba­sis us­ing an ap­pro­pri­ately sized probe to en­sure there is no build up in the aper­ture of the hole should be stan­dard on ev­ery farm. En­sure that you check with your milk­ing ma­chine tech that you have the cor­rect sized probe, as un­nec­es­sar­ily en­larg­ing the air ad­mis­sion hole can some­times have un­in­tended con­se­quences!

Usu­ally be­tween 0.8 mm and 1 mm in di­am­e­ter, the claw air ad­mis­sion hole is com­monly lo­cated in the claw it­self, ei­ther in the metal body of the claw or some­times in the claw bowl it­self.

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