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Lab Test > Lab Test > Flashcards

Lab Test Flashcards

1
Q

What is one of the best tools available for the dairy fieldman?

A

The microscope

The microscope is used to study bacterial types in milk.

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2
Q

What can careful study of bacterial types in milk tell you?

A

Much about its bacterial quality

This analysis is important for assessing milk safety and quality.

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3
Q

What type of reference have dairy fieldmen often requested?

A

A collection of photomicrographs

These images assist in the microscopic evaluation of milk.

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4
Q

What do stained smears indicate in milk evaluation?

A

The history of a milk sample

They are useful but should not be the sole criterion for quality.

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5
Q

True or False: No single test can provide a complete picture of the bacteriological history of milk.

A

True

Multiple tests are necessary for thorough evaluation.

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6
Q

What can affect the meaningfulness of deductions about milk quality?

A

Accurate sampling and proper care of milk samples

Poor practices can lead to misleading results.

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7
Q

What are vacuoles in milk caused by?

A

The removal of fat droplets from the dried milk solids

They appear as white circular areas against a blue background.

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8
Q

What should good quality milk never show in large numbers?

A

Leucocytes or bacterial cells

Occasional presence is acceptable, but not in large quantities.

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9
Q

What is a characteristic of mastitis milk?

A

Presence of long-chain Streptococcus agalactiae and associated leucocytes

These indicate infection and poor milk quality.

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10
Q

What can the use of a strip cup reveal in mastitis milk?

A

Flaky particles (garget)

This is a sign of milk quality issues due to udder damage.

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11
Q

Fill in the blank: Good quality milk may contain an occasional _______ or bacterial cell.

A

leucocyte

Good quality milk should not have large numbers of these cells.

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12
Q

What type of streptococci is associated with massive numbers of leucocytes in milk?

A

Short-chain streptococci and long-chain Streptococcus agalactiae

These organisms indicate an infection that may affect milk production in cows.

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13
Q

What is phagocytosis?

A

The actual engulfing of bacterial chains by leucocytes

This process is part of the immune response to destroy pathogens.

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14
Q

In mastitis-infected cows, how many quarters may yield infected milk?

A

One or two quarters

The remainder of the udder may still produce normal milk.

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15
Q

What characteristic grouping is typical of staphylococci?

A

Irregular groupings resembling a clump of grapes

This morphology is indicative of staphylococcal infection.

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16
Q

What are the common sources of staphylococci contamination in milk?

A

Contact with residues in open seams and crevices of utensils

Poor sanitation practices lead to contamination from milking equipment.

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17
Q

What may cause the presence of clumps of staphylococci in milk?

A

Improperly cleaned milking machines or rubber parts

Hygiene practices are crucial to prevent bacterial contamination.

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18
Q

What type of cell growth is associated with contaminated utensils?

A

Mixed cell growth

This includes clumps of staphylococci, diplococci, yeasts, rods, and chains.

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19
Q

What can cause the same bacterial picture as contaminated utensils in milk?

A

Contamination by dust

Environmental factors can also contribute to milk contamination.

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20
Q

What do paired round cells (diplococci) or short chains of round cells (streptococci) indicate in milk?

A

Poor cooling

This is typically associated with Streptococcus lactis, the sour-milk organism.

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21
Q

What does a milk sample on the verge of souring show under the microscope?

A

Many pairs of cells, double pairs, and short chains with a high bacterial count

This indicates that the milk is almost sour.

22
Q

What does a mixed bacteria field in milk suggest?

A

Poor production methods

It shows clumps of micrococci, short chains, and paired bacilli, indicating contamination.

23
Q

What impact does contamination have on milk quality?

A

It can ruin the quality of a large volume of milk

The lowered quality persists in pasteurized or manufactured products.

24
Q

Fill in the blank: The presence of _______ in milk usually indicates poor cooling.

A

paired round cells (diplococci)

25
Q

True or False: A sample showing a variety of bacteria is a good sign of milk quality.

A

False

A variety of bacteria suggests poor production methods.

26
Q

What is indicated by the presence of large numbers of paired cells or diplococci in milk?

A

Evidence of poor cooling and mixed bacteria

This condition leads to actively growing organisms and off-flavors.

27
Q

What type of organisms are indicated by contamination from hay and dirt?

A

Heavy, paired, rod-shaped organisms

These are spore-formers and quite heat resistant.

28
Q

True or False: Poor cooling in milk can lead to quick spoilage.

A

True

Poor cooling allows for contamination and growth of spoilage organisms.

29
Q

What do filter pads remove from milk?

A

Visible particles of manure or manure-contaminated soil or bedding

However, organisms can still pass through the filter.

30
Q

What is the consequence of manure contamination in milk?

A

Breakdown of milk proteins leading to off-flavors and sweet curdling

Short rods from manure can separate from solid particles.

31
Q

Fill in the blank: The presence of _______ in milk indicates contamination by organisms from hay and soil.

A

large bacilli

32
Q

What characteristic of heavy, paired rod-shaped organisms indicates they are spore-formers?

A

Heat resistance

This trait allows them to survive in various conditions.

33
Q

What happens when milk is contaminated with actively growing organisms?

A

It develops off-flavors

This is often a result of poor cooling and mixed bacteria.

34
Q

What type of contamination is indicated by heavy sediment in milk?

A

Dust contamination

This can come from manure and affects milk quality.

35
Q

What is the typical arrangement of four micrococci often associated with milkstone called?

A

Tetrads

Tetrads are heat loving and may originate from the teat canal.

36
Q

How resistant are tetrads to germicidal agents?

A

Relatively resistant

Tetrads are generally considered inert and cause little if any damage to the milk.

37
Q

What type of bacteria are short, rod-shaped with rounded ends commonly associated with?

A

Soil

These bacteria may enter milk through a contaminated water supply.

38
Q

What indicates poor production practices in milk?

A

Large numbers of short, rod-shaped bacteria

A few of these bacteria are normally present in raw milk.

39
Q

What condition can be caused by some short, rod-shaped bacteria?

A

Acute and chronic mastitis

These bacteria may produce an acute form of mastitis and occasionally chronic infections.

40
Q

What is the mild form of mastitis associated with staphylococci called?

A

Nonspecific mastitis

Laboratory analyses are needed to determine the pathogenicity of staphylococci.

41
Q

What do mastitic staphylococci appear like under the microscope?

A

Similar to those in milk contaminated by dirty utensils

They are typically accompanied by more leucocytes than normal.

42
Q

What are yeast cells typically like in shape?

A

Normally spherical or slightly elongated

Yeast cells frequently show small buds and are larger than bacteria cells.

43
Q

Why are yeasts normally present in milk?

A

Due to contamination by dirty rubber parts in milking machines

Yeasts may also invade in cases of mastitis, though this is not common.

44
Q

What effect do yeasts have in cheese and milk?

A

They produce a gassy, yeasty breakdown

This breakdown occurs more frequently in cheese than in milk.

45
Q

What are the characteristics of mold contamination in fresh milk?

A

Not commonly found unless in contact with moldy scum of milk solids

Neglected rubber parts can also cause mold contamination.

46
Q

What are the advantages of direct microscopic examination of milk?

A

Rapid, inexpensive, and slides can be preserved for review

Dead bacterial cells stain differently than live ones, providing insights into milk quality.

47
Q

What can be deduced by reviewing a series of fields of a milk sample under a microscope?

A

Valuable index of the relative number of several types of bacteria present

This helps evaluate a producer’s quality program.

48
Q

True or False: It is common to obtain milk samples with only one type of bacteria present.

A

False

Under farm conditions, milk samples usually contain multiple types of bacteria.

49
Q

What is essential to know in order to evaluate the evidence obtained with a microscope?

A

All of the conditions under which milk is produced at a farm

This knowledge is crucial for accurate evaluation.

50
Q

Fill in the blank: Properly used, the microscope can greatly decrease the time spent on each _______.

A

quality call

This efficiency is important for laboratory workers and fieldmen.

Lab Test (13 decks)

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