Animal Health

Every picture tells a story

By Rod Dyson

AT OUR farm visits, we often take photos of key factors that we identify, and also the dairy shed layout — it helps us to quickly and easily recall the details later.

But as the collection of images has got larger, finding a specific image has got harder and harder!

So the slow and laborious task of collating and tagging all of these images into a digital photo album has begun.

Stepping through these images, I have been amazed at how many of them carry a story — and often multiple stories.

The accompanying image looks simple enough — in fact, it is a common sight during milking in many Australian dairies.

Taken just before cups off, the image shows a narrow stream of milk dribbling down the wall of the claw bowl from each of the two quarters that we can see.

This clearly shows what we call a “dribble finish” to milking, and a dribble finish is NOT normal!

There is usually a slight natural restriction at the point where the teat cistern meets the udder cistern.

Thus, excessive congestion and swelling in this area leads to a restriction of milk flow, commonly causing a dribble finish and/or incomplete milk out.

Also, if teats have extended far enough into the liner, it may lead to an increased risk of teat end damage.

The most common cause of this phenomenon is a failure of the cow to “let down” prior to cups on.

Let’s review the “let down” process.

A cow’s milk is not sitting in a large “tank” inside her udder, just waiting for you to put cups on and milk it out — the cow actually has to let her milk down for us to be able to extract it.

When a cow decides to let her milk down, commonly in response to familiar stimuli (such as feed arriving in the bail), her brain sends a message to the pituitary gland to release the hormone, oxytocin.

Oxytocin travels in the bloodstream to the udder where it causes all of the tiny milk producing alveoli to contract, squeezing the milk out into the ducts, from where it flows down into the udder cistern, then the teat cistern, and it can then be removed by the vacuum of our milking system.

To put it really simply — if there is no squeeze, you get no milk!

If cups go onto teats before the cow has let down, the lack of milk flow causes the vacuum she experiences at the teat end to be higher than when milk flow is occurring.

With no milk flow and high vacuum, she is likely to experience “cup crawl” at the start of milking — cups will crawl high on the teat at the start of milking, and congestion and swelling at the base of the teat is then quite likely.

Research has clearly shown that at the end of a “normal” milking, milk flow from each quarter stops independently and quite abruptly — they do not generally “dribble”!

So it is highly likely that the cow in the image did not “let down” properly prior to cups on.

At the individual cow level, if this happens repeatedly, the individual cow is at a significant risk of teat end damage and increased risk of mastitis.

At the herd level, if this is happening in a significant number of cows, then the overall milking will be slower and the herd level risk of mastitis will be higher.

If there is then a degree of over milking before cups come off, the risk of teat damage and the consequent risk of mastitis becomes even higher!

Hence, one of the key observations during a milking time assessment is to assess the level of “failure to let down” prior to cups on, as well as the degree of over milking.

But what other stories might this image be telling us?

Why didn’t she let down? What would cause a significant number of cows not to let down?

What if she did “let down” properly before cups on? Are there other factors that could be causing the “dribble finish”?

How does this relate to “rings” at the base of teats when cups come off? Do these “rings” make cup removal difficult?

Should the cups have already come off this cow? At what point should cups be removed? How do you, or your ACR’s choose the “end-point” of milking?

What if she was a freshly calved heifer?

Clearly, this image unlocks a host of possible scenarios, and for those who are interested, we have expanded and explored these scenarios further at the Dairy Focus website (www.dairyfocus.com.au).

Because every picture tells a story!

• Rod Dyson is a veterinary surgeon and mastitis adviser at www.dairyfocus.com.au