UNDERSTANDING - 10 - AOC_Forces Applied and Teat Responses

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* 1. Enter your first and last name

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* 2. Select all that apply. Teat tissues are stressed during the milking process through the:

accumulation of fluids in the soft inner tissues of the teat (congestion and oedema)

stretching of teat skin, resulting in hyperplasia and hyperkeratosis of the teat end

excessive drying of the teat skin

decrease in the normal removal rate of the teat skin

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* 3. The teat canal opens primarily by:

the stretching of the elastic of the canal wall

the unfolding of the canal wall

producing extra skin cells

changing its shape from flat to round

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* 4. The teat canal is pulled open when forces generated by the milking vacuum stretch and expand the free end of the teat to such an extent that the biological closing forces within the teat apex are overcome.

True

False

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* 5. The forces of the vacuum cause the teat to stretch along its length (longitudinally) as well increase its diameter (circumferentially).

True

False

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* 6. Select all that match the engineering terms with their definitions.

tissue stress: the force exerted on the tissue, or the amount of pull

tissue strain: the force exerted on the tissue, or the amount of pull

tissue strain: the change in tissue length, or stretch

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* 7. After teat skin is fully unfolded, a further increase in length will cause the skin to:

become congested

rupture

develop hyperkeratosis

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* 8. The Poisson effect supposes that as the stretched teat diameter is increased (circumferential stretching) its maximum stretched length (longitudinal stretching) will be:

decreased

increased

about the same

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* 9. The fibrous layer of the teat skin surrounds and protects the middle and inner layers of the teat wall. The amount of teat strain (stretch) is ________ the fibrous layer.

limited by

independent of

increased by

proportional to the age of

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* 10. Circumferential strain (ballooning of the teat to increase its diameter) can be limited by the supporting liner. For typical liners, teat end diameter increases by about 33%, and teat length increases by 40 to 50%, during milking.

True

False

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* 11. The teat canal is fully open at a milking vacuum of:

50 kPa

30 kPa

40 kPa

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* 12. As the depth of penetration of the teat into the open liner increases:

the teat canal closes

nothing changes

the duration of the peak flow increases

the effective teat canal diameter increases

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* 13. Select all that match each period of milking with its characteristics.

Period 1: peak flow: The teat wall is thin; the teat sinus volume is relatively large; there is a wide connection to milk in the udder sinus; and the vacuum level in the mouthpiece chamber is low (10 kPa).

Period 2: transition from peak flow to low flow: There is a small spike in mouthpiece chamber vacuum (MPCV); there is an increase in the average MPCV; there is an increase in the amplitude MPCV; there is a sudden movement of the teatcup up or down the teat; the teat moves in about 20 mm (0.8 inches); and the teat may start squawking as air leaks past it.

Period 3: beginning of low flow: There is increased teat wall thickness (the connection to the udder is restricted); the vacuum develops in the teat sinus, reducing flow rate; and the teat sinus volume is reduced (reduced pressure and friction between teat and liner walls).

Period 4: late in low flow: There is little additional change in the outer shape of the teat; there is additional thickening of the wall as the sinus becomes smaller; and the connection to milk in the udder sinus appears even more tenuous.

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* 14. Why does the milk flow rate increase early in milking if the teat penetrates farther into the liner?

the teat skin is stretched more, causing the teat canal to be pulled open more completely

the teat skin is ruptured

teat congestion is reduced

none of the above

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* 15. Select all that apply. During the peak flow rate period, the main factors influencing changes in the milk flow rate are:

the external teat diameter

the pressure difference across the canal

the effective diameter of the teat canal

the effective teat length

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* 16. During the peak flow period, the rate of milk flow is governed by the dimensions of the teat canal and the pressure difference.

True

False

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* 17. What is the main reason for the differences in the peak flow rates among cows?

the variation in teat lengths

the variation in teat canal sizes

the difference between the cows’ ages

the difference between the cows' levels of milk production

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* 18. Why does milk flow fall at the end of the peak flow period?

because the action of oxytocin ends very quickly after the peak of milk flow

because the b-phase becomes shorter

because the intra-mammary pressure falls throughout the peak flow rate period as milk is removed

because the cows are not comfortable

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* 19. Once the IMP falls to approximately atmospheric pressure, what is the limiting factor for the rate of milk withdrawal?

the rate at which milk can drain into the udder cistern from the duct system, and then into the teat sinus past the constriction applied by the teatcup mouthpiece to the teat base

the rate at which milk drains from the teat sinus trough the orifice of the teat canal

the diameter of the liner

the vacuum level

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* 20. Select all of the correct statements regarding friction between the teat and teatcup liner.

Friction increases during milking as the soft teat tissue conforms to the harder rubber surface of the liner, increasing the area of true contact.

The friction between the teat and liner is reduced when liners absorb butterfat and become slippery.

The friction between the teat and liner is determined by the pulsation rate and ratio

There are no differences in the frictional properties of different liner materials.

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* 21. During the low flow period, the mouthpiece flexes downward when the liner opens because:

the mouthpiece vacuum rises

the mouthpiece vacuum decreases

the diameter of the teat increases

none of the above

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* 22. Mark ALL that apply. “When the liner opens and the mouthpiece flexes downwards, …”:

the mouthpiece lip diameter is increased slightly by flexing

the constricted pathway between udder and teat may partially re-open and withdraw drainage milk

milk stops flowing

milk flowrate doubles

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* 23. Mark all the correct answers. Which of these describe the action of “machine stripping”:

Applies extra downward pressure to the teatcups

Re-stretches tissues around the base of the teat temporarily re-opening of the milk passageway to the teat sinus

Reduces teat congestion

Reduces the risk of liner slip

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* 24. Select all that match the condition of veins and inner mucosal surfaces of the teat sinus for these levels of teat sinus pressure:

High sinus pressure (IMP is high because of full udder and ejection): Veins flattened but little congestion in surrounding mucosal tissue

High sinus pressure (IMP is high because of full udder and ejection):

Sinus pressure near atmospheric pressure (IMP nears atmospheric pressure milk is removed): Veins flattened but little congestion in surrounding mucosal tissue

Sinus pressure near atmospheric pressure (IMP nears atmospheric pressure milk is removed): Veins full and round with little congestion in surrounding mucosal tissue

Low sinus pressure (vacuum developed in sinus during overmilking): Veins full and round with congestion and thickening of surrounding mucosal tissue