Nutritive Value of Feedstuffs Flashcards

1
Q

What are some steps involved in determining nutritive value?

A
  1. Chemical Analysis (complete, proximate, Van Soest, NIR)
  2. Palatability
  3. Digestibility
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2
Q

What is a complete chemical analysis?

A

This test examines every nutrient in a feed, and takes a long time.

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3
Q

What is a proximate analysis and what does it determine?

A

A proximate analysis determines the following factors in feedstuffs:

  1. Water
  2. EE
  3. CF
  4. CP
  5. Ash
  6. NFE
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4
Q

How is water content determined in a proximate analysis?

A

by drying the sample

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5
Q

What is EE?

A

EE is ether extract, or crude fat. It’s simply a measurement of crude fat.

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6
Q

What is CF?

A

CF is crude fiber, and it measures cellulose, lignin, and hemicellulose content.

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7
Q

What is CP?

A

CP is crude protein, an estimate of the protein content of a feed based on the nitrogen content. It is found by multiplying the %N in a feed by 6.25.

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8
Q

What is ash?

A

Minerals; the inorganic residue left behind after burning food

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9
Q

What is NFE?

A

NFE is Nitrogen-Free Extract, and it is obtained mathematically. It consists of mostly sugars and starches.

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10
Q

What is the Van Soest method?

A

This method analyzes fibers in feed.

Acid Detergent Fiber
Neutral Detergent Fiber

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11
Q

What is the Acid Detergent Fiber (ADF)?

A

This measurement contains cellulose and lignin, and is usually associated with digestibility. Since it contains more non-digestible contents, a high ADF is bad.

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12
Q

What is the Neutral Detergent Fiber (NDF)?

A

A measurement containing cellulose, hemicellulose, and lignin; it indicates intake, or the amount an animal may consume. The NDF is always a higher number than the ADF.

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13
Q

What is NIR?

A

NIR is Near Infrared Spectroscopy. It is a rapid method that uses IR light to analyze bonds in feeds and determine moisture, fat, protein, etc.

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14
Q

Define palatability

A

the fact or quality of being acceptable or agreeable to the taste; will the animal eat it?

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15
Q

What are some limitations to chemical analysis, Van Soest method, and NIR?

A

They don’t tell us anything about palatability, toxicity, or digestibility.

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16
Q

Define digestibility

A

The ability of a nutrient to be digested and absorbed by the animal rather than be eliminated in the feces.

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17
Q

Describe a digestion trial

A

An animal is given a feed, and if it does not exit in the feces, it is considered digestible

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18
Q

How is the Apparent Digestion Coefficient (ADC) calculated?

A

D/C = weight of nutrient consumed - weight of nutrient excreted in feces/ weight of nutrient consumed

example: an animal eats 12 grams of feed dry matter and excretes 6 grams of feed dry matter in its feces. What is the feed’s ADC?
(12-6)/12 = 0.5 ADC

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19
Q

What factors influence digestibility?

A

fiber content, rates of passage, preparation, and processing

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20
Q

What is the easiest way to alter a feed’s digestibility?

A

Altering the fiber content of the feed

higher fiber content is harder to digest, especially in monogastrics

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21
Q

What is TDN?

A

Total Digestible Nutrients: an estimate of energy content in a feed, it does not really measure digestion

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22
Q

What is the significance of CP?

A

CP (crude protein) can be used to find the N content of a feed and vice versa using the conversion factor of 6.25

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23
Q

How much more energy do lipids contain than carbs or proteins?

A

2.25 times more energy

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24
Q

What is GE?

A

Gross Energy, the total energy in the feed, and always the highest number when estimating feed energy

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25
Q

What is bomb calorimetry and what does it measure?

A

It is a type of measurement that burns feed to determine the energy released, and it measures the GE of a feed

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26
Q

What is DE and how is it calculated?

A

DE is Digestible Energy, it measures the energy absorbed in the GI tract

DE= GE - FE

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27
Q

What is FE?

A

Feces Energy

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28
Q

What is UE?

A

Urinary Energy

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29
Q

What is GPDE?

A

Gaseous Products of Digestion Energy

30
Q

What is HI?

A

Heat Increment

31
Q

What is ME and how is it calculated?

A

ME is metabolizable energy, it measures energy available for use in cells

ME= GE - FE - UE - GPDE

32
Q

What is NE and how is it calculated?

A

NE is Net Energy, it measures the available energy for maintenance, growth, and lactation (accounts for E used in consumption and digestion of food)

NE= GE - FE - UE - GPDE - HI

33
Q

What does a respiration calorimeter measure?

A

It measures the gaseous products of digestion energy (GDPE), heat increment (HI), feces energy (FE), and urinary energy (UE)

34
Q

What is a specific instance where ME is used?

A

ME is used to measure the energy for birds because of the fluidity of their feces.

35
Q

What factors influence energy requirements?

A
  1. species
  2. age
  3. activity level
  4. production level
  5. environmental temperature
  6. nutritional deficiencies
  7. surface area of the animal
36
Q

What are some effects of energy deficiency?

A

decrease in weight (catabolic rxns. occur as animal breaks down macromolecules to acquire energy)

decrease in body fat (emaciation)

lower fertility

lower production

37
Q

What is total protein?

A

the total amount of protein in a feed

38
Q

What is digestible protein?

A

the amount of protein an animal can digest and use

39
Q

How can protein quality be determined?

A

chemical procedures like amino acid analysis

biological procedures

40
Q

What is biological value (BV)?

A

BV is the amount of retained nitrogen.

BV = (N retained/N digested) x 100%

41
Q

What are some relative protein values?

A

Eggs 100
Milk 92
Meat 82
Rumen Protein 80
Plants variable

42
Q

What are some protein sources for feeds?

A

animal sources: fish meal, blood meal, meat and bone meal

plant sources: soybeans, cottonseed meal, etc

43
Q

What are some issues with animal and plant sources of protein?

A

animal sources: regulation of contents, palatability issues

plant sources: lower quality protein

44
Q

What are byproduct feeds?

A

Feed components resulting from manufacturing processes.

ex. distiller’s grains, brewer’s grains, bakery waste

45
Q

What are the consequences of too little dietary protein?

A

lower growth
decreased efficiency
lower reproductive performance

46
Q

What are the consequences of too much dietary protein?

A

too expensive
good growth
excess water intake
enlarged kidneys

47
Q

How are vitamins expressed in feedstuffs?

A

They are measured as IU’s (international units) for fat soluble vitamins, % mg, etc.

48
Q

How are minerals expressed in feedstuffs?

A

Minerals are expressed as ppm, % mg, etc

Macrominerals are in animal carcasses at a measurement greater than 100 ppm

49
Q

Describe feed intake

A

Animals eat to meet their energy needs. The input impacts energy balance, which in turn affects the output (feces, urine, work, heat, milk, etc)

50
Q

What are concentrates?

A

they contain less than 18% CF (ex. grains)

51
Q

What are roughages?

A

they contain greater than 18% CF (ex. hay)

more often consumed by ruminants

52
Q

Describe the quantity and kind of foods that ruminants consume

A

Ruminants usually eat 2-3% of their bodyweight a day, and they usually eat roughages

53
Q

Describe the quantity and kind of foods that monogastrics consume

A

Monogastrics usually eat 2-6% of their bodyweight per day, with very young monogastrics possibly eating up to 13% of their bodyweight in a day. They typically consume grains or other concentrates.

54
Q

What percent do animals typically eat of their bodyweight per day on average, even if we are unsure of the species?

A

2-3% of their bodyweight

55
Q

What is gut fill?

A

What the animal can hold in its GI tract; it is a type of physical regulation

56
Q

What type of feed is the usual cause of gut fill?

A

Low energy density feed usually causes gut fill and physical regulation because the animal has to eat more of it to meet their energy needs

57
Q

What type of feed is usually the cause of chemical regulation?

A

High energy density feed is the usual cause of chemical regulation.

58
Q

What will an animal do if they are consuming a low energy density feed?

A

They will eat a higher amount of it to reach their energy needs.

59
Q

What will an animal do if they are consuming a high energy density feed?

A

They will consume a lower amount of the feed because they do not have to eat as much of it to meet their energy requirements.

60
Q

What factors influence feed intake?

A
  1. physiological state
  2. weight
  3. activity level
  4. temperature
  5. disease status
  6. palatability
61
Q

How is the hypothalamus involved in feed intake?

A
  1. Feed center controls eating
  2. Satiety center tells the animal to stop eating
62
Q

What are short term mechanisms of regulating food intake?

A

physical and chemical regulation

63
Q

What are the respective short term mechanisms of regulating food intake in monogastrics and ruminants?

A
  1. Monogastrics
    gut fill (physical)
    glucose (chemical)
  2. Ruminants
    gut fill (physical)
    VFA’s (chemical)
64
Q

Describe how glucose is involved in a monogastric’s feed intake

A

Blood glucose is a chemical regulator of feed intake. High blood glucose levels tell the animal when to stop eating, unless it has already hit gut fill.

65
Q

Describe how VFA’s are involved in a ruminant’s feed intake

A

VFA’s are a chemical regulator of feed intake. High blood VFA’s tell the ruminant when to stop eating, unless is has already reached gut fill.

66
Q

What hormones are involved in appetite control?

A
  1. cholecystokinin (CCK)
  2. Neuropeptide Y (NPY)
  3. Leptin
67
Q

What role does CCK play in regulating appetite?

A

CCK (produced in the small intestine) influences the hypothalamus to decrease appetite

68
Q

What role does NPY play in regulating appetite?

A

NPY comes from the hypothalamus and increases appetite

69
Q

What role does leptin play in regulating appetite?

A

Leptin, which comes from adipose tissue, decreases appetite by stimulating the hypothalamus

70
Q

What is the lipostatic theory?

A

Lipostatic theory is a proposed long term regulation system for appetite that sees appetite regulated by fat reserves