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Nutrition > Energy systems, digestibility > Flashcards

Energy systems, digestibility Flashcards

1
Q

What is digestible feed?

A

The portion of the feed which is not excreted in feces and is assumed to be absorbed by the animal.

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2
Q

How is digestibility usually estimated and expressed?

A

Estimated in DM basis.

Expressed as a coefficient or percentage.

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3
Q

What is the formula for DM digestibilty?

A

(consumed-excreted)/consumed

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4
Q

What is apparent digestibility?

A

An estimation = feed ingested - feces excreted

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5
Q

What is true digestibility?

A

True digestibility involves correction for endogenous losses.

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6
Q

What information do you need to determine true digestibility?

A
  • Sloughed off intestinal cells
  • Digestive secretions (enzymes, mucus)
  • Microbial matter
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7
Q

Which is higher, true or apparent digestibility?

A

True is higher than apparent

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8
Q

Which digestibility is more difficult and costly to determine?

A

True digestibility.

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9
Q

What are the different ways to measure digestibility in vivo?

A
  • Growth trials
  • Direct (total collection)
  • Difference (basal + test food)
  • Regression
  • Tracer or indicator
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10
Q

Which in vivo measurement of digestibility is the most accurate?

A

Direct (total collection)

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11
Q

What are in vitro methods of digestibility measurement?

A
  • Digestion stimulation
  • Gas production
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12
Q

What is the adaptation period for direct measurement of digestibility?

A

1-2 weeks

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13
Q

How is direct (total collecttion) measurement of digestibility done?

A
  1. Feed a known quantity to the animal at the same time every day.
  2. The amounts of food eaten should not vary from day to day.
  3. Collect total fecal output for 5-14 days (during diet feeding period).
  4. Chemical analysis of feed and feces.
  5. Apparent digestibility calculation.
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14
Q

What are the lab conditions for sheep and cattle digestibility studies?

A
  • Metabolic crates or chambers
  • Animals are fitted with strap-on canvas fecal collection bags
  • Urinary catheters are placed to prevent the contamination of feces with urine

NOTE: lab conditions impact digestibility

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15
Q

When are tracers or indicators used?

A

When it is impossible to measure total intake and fecal output (ex. group feeding or grazing animals).

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16
Q

What are the characteristics of a tracer?

A
  • Indigestible
  • Non-absorbable
  • Non-toxic
  • Easy to analyze
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17
Q

How are tracer studies done?

A
  • Known tracer amount and known feed amount are given.
  • Collection of fecal samples for at least one week of marker feeding.
  • The marker is given continuously during the trial period until it is stabilized in the feces.
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18
Q

What are internal markers/tracers?

A
  • Lignin
  • Acid insoluble ash (silica)
  • N-alkanes
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19
Q

What are external markers/tracers?

A
  • Cr2O3 (ruminants)
  • TiO2 (pigs, poultry)
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20
Q

What are the pros of using a tracer?

A
  • Total feces collection is not necessary.
  • Total intake determination is not necessary.
  • Easier, less labor.
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21
Q

What are the cons of using a tracer?

A
  • Representative sampling is essential.
  • Accurate estimation of nutrient or marker concentration is essential.
  • It assumes complete excretion of the marker and hence the recovery of the marker determines accuracy.
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22
Q

What is the definition of in vitro measurement of digestibility?

A

Lab methods to simulate digestion by the animal.

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23
Q

How is in vitro measurement of digestibility used for non-ruminants?

A

Protein digestion is determined by digesting the feed in pepsin and HCl.

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24
Q

How is in vitro measurement of digestibility used for ruminants?

A

The feed is incubated with rumen fluid under anaerobic conditions. The bacteria are then killed by acidifying with HCl and digested in pepsin.

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25
Q

What temperature is rumen fluid incubated at?

A

39 C

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26
Q

How is digestibility in different GIT portions measured?

A

In situ - fistulated animals (surgical procedure)

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27
Q

What is digestibility more associated to, feed characteristics or animal factors?

A

More associated to feed characteristics.

28
Q

What are animal factors that affect digestibility?

A
  • Species
  • Individual factors
  • Level of feed intake
  • Frequency of feed intake
  • Age
  • Adaptation to feed
  • Infectious disease or parasites
29
Q

How does age affect digestibility?

A

Better in adults since young animals have less enzyme secretion

30
Q

How does changing feed affect digestibility?

A

Sudden changes in feed composition usually decreases digestibility.

31
Q

Which has less variability in digestibility: grain or forage?

A

Grain is less variable due to a more constant composition.

32
Q

What feed factor has the greatest impact on digestibility?

A

Fibre fraction

33
Q

How does grain processing impact digestibility?

A

Increases digestibility

34
Q

What are associative effects?

A

Interaction between nutrients in different ingredients resulting in higher or lower digestibility than expected for individual ingredients

35
Q

What are positive associative effects in ruminants?

A

Increased fibre utilization after N supplementation in N-deficient forages and supplementation of roughages with small quantities of sugars (do not ask me what he means by this)

36
Q

What are negative associative effects in ruminants?

A
  • Concentrate supplementation in excess can reduce fibre utilization
  • Excess fat supplementation reduces fibre digestion

(if u wanna know how its in the slides)

37
Q

What is the definition of energy?

A

The potential to do work.

38
Q

Is energy a nutrient?

A

NO, but it is a result of nutrient metabolism

39
Q

What is a calorie?

A

The amount of energy as heat required to raise by 1°C the temp of 1 g of water at a pressure of 1 atmosphere

40
Q

What is a general rule for livestock and energy requirements? (I FEEL LIKE THIS IS IMPORTANT)

A

Livestock eat to their energy requirements

41
Q

What is gross energy?

A

Total energy in feed

42
Q

What does gross energy not tell you?

A

Does not give any indication of energy availability to the animal (does not account for animal factors)

43
Q

What is gross energy dependent on?

A

The proportion of fat, CHO and protein in the feed.

44
Q

What is digestible energy?

A

DE = GE minus energy lost in feces

45
Q

How much energy is lost to feces?

A

Feces are a major source of energy loss (10-80%)

46
Q

What is used as the measure of energy supply for pigs and horses?

A

Digestible energy

47
Q

How does ADF affect digestibility?

A

Decreases DE

48
Q

What is total digestible nutrients (TDN)?

A

%TDN = DCP + DCF + DNFE + (DEE*2.25)

  • DCP = digestible crude protein
  • DCF = digestible crude fibre
  • DNFE = digestible nitrogen-free extract
  • DEE = digestible ether extract (fat)
49
Q

What is metabolizable energy?

A

ME = DE – (energy loss in urine + gas production)

50
Q

What is a better estimate of energy in feed available to the animal?

A

Metabolizable energy

51
Q

What is net energy?

A

NE = ME – heat lost during digestion process (Heat Increment, HI)

energy from feed retained and absorbed by the animal, fraction of total energy utilized for maintenance, growth and production

52
Q

How do you calculate the efficiency of ME utilization?

A

NE = ME × k, where k represents the efficiency in conversion of energy substrates to ATP

53
Q

What do you need to estimate in order to know NE?

A

heat loss

54
Q

How is heat loss estimated?

A

Direct / indirect calorimetry

55
Q

What is indirect calorimetry?

A

Respiration chambers

56
Q

What factors affect energy requirements?

A
  • Body weight
  • Growth
  • Age (life / production stage)
  • Sex (M>F); castration/spaying
  • Gestation / physiological stage
  • 3/3rd pregnancy = higher energy requirement
  • Disease = higher energy demands (?)
  • Lactation (or egg or wool production)
    0 Exercise (race horses, sled dogs, grazing large pastures)
  • Environment: temperature, wind, mud, condition of hair coat
57
Q

What are energy systems?

A

Abstract scientific-based system (equations) to quantify, estimate and predict requirements and how to satisfy them with feed provided to the animal

58
Q

What is usually the main limiting factor in animal production?

A

Energy

59
Q

What is the main limitation for energy systems?

A

Requires accurate laboratory methods for predicting the energy content of foods from their characteristics

60
Q

ME supplied as ____ is used more efficiently than ME supplied as ____

A

ME supplied as fat is used more efficiently than ME supplied as carbohydrate or protein

61
Q

Energy systems for ___ and ___ are simpler than those for ruminants and herbivores

A

Energy systems for pigs and poultry are simpler than those for ruminants and herbivores

62
Q

What energy system is used for dairy?

A

NE

63
Q

What energy system is used for beef?

A

NEm (breeding cows) and NEm+NEg for growing/fattening

64
Q

What energy system is used for swine?

A

NE system (NEm+NEg)

65
Q

What energy system is used for poultry?

A

ME system

66
Q

What energy system is used for horses?

A

DE (UK & US) and NE (France) system

67
Q

What energy system is used for companion animals?

A

ME system

Nutrition (10 decks)

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