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ALFS 2 > PRINCIPLES OF NUTRITION > Flashcards

PRINCIPLES OF NUTRITION Flashcards

1
Q

What is neutral detergent fibre (NDF)?

A
  • Plant cell wall material
  • Fibre insoluble in neutral detergent
  • Residue containing CW materials = Hemicellulose + Cellulose + Lignin
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2
Q

What is acid detergent fibre (ADF)?

A
  • Fibre insoluble in acid detergent
  • Residue contains CW material = lignin + cellulose
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3
Q

What does NSC stand for?
And what is NSC fraction composed of?

A
  • Non-structural carbohydrates
  • NSC fraction composed of Starch + WSC (water-soluble carbohydrates)
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4
Q

What is WSC fraction composed of?

A

Simple sugars + fructan

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5
Q

State some factors that affect grass growth/productivity and briefly describe them.

A

Stage of growth
- Most important factor in nutritional value of grass
- e.g. increased lignin content lowers grass nutritional value

Time of year
- Most rapid in spring & early summer (April - June)

Environment
- Season e.g. reduced growth below 5C
- Climate, topography, soil type
- Light, temperature, rainfall
- Increased productivity in warm & wet conditions

Soil status
- Nitrogen, Phosphorus, Potassium
- Nitrogen fixing plant species
- Soil pH i.e. most grasses thrive on slightly acidic pH

Grass species
- Ryegrass, Timothy, fescue, cocksfoot are high yielding
General management
Cutting & grazing strategies

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6
Q

What are the desirable characteristics of low DM silage?

A

Low pH, low butyrate, low NH3-N, high lactate

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7
Q

Why is HT forage high in nutritional value?

A

Young herbage utilised

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8
Q

Rank the starch content of oats, barley and maize from highest to lowest.

A

Maize, barley, oats

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9
Q

What oilseed meal is most commonly used?

A

Soya bean meal

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10
Q

What term is most often used for digestibility?

A

Apparent digestibility

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11
Q

How is in vitro digestibility assessed?

A

Through work in labs

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12
Q

How does increased feeding level in ruminants change ruminal retention time and thus digestibility?

A

Reduces ruminal retention time and digestibility

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13
Q

State the relationship between GE (Gross energy), DE (Apparent digestive energy), ME (Metabolisable energy) and NE (Net energy).

A

GE (Gross energy) is measured by converting food to heat energy;

GE - Faecal energy = DE
DE - (urine + gaseous energy) = ME
ME - heat increment = NE

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14
Q

State the energy system for ruminants, pigs, poultry, dogs & cats, and horses.

Briefly explain why that energy system is used when possible.

A

Ruminants (ME)
- Use k factor for maintenance, milk production, work & growth

Poultry (ME)
- Easy to measure, since urine and faeces are voided together
- Less fibre in diet, limited range of feeds

Dogs & cats (ME)
- Effectively linked to BW

Pigs (DE)
- Rationale, simpler system than ruminant with less fibre in diet & limited range of feeds

Horses (DE)
- Calculated based on BW basis

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15
Q

Which nutrient has the greatest nutrient density?

A

Fat

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16
Q

Which nutrient provides the most energy in farm animal nutrition?

A

CHO

17
Q

What are the 2 components of Metabolisable protein (MP) system in ruminants?

Briefly describe the two.

A
  1. Digestible microbial true protein (DMTP)
    - Synthesised by microbes in rumen
    - digested in abomasum & SI
  2. Digestible undegraded feed protein (DUP)
    - Fraction of feed not degraded during passage through rumen
    - digested in abomasum & SI
18
Q

What are the 2 components of Feed crude protein?

A
  1. Rumen degradable protein (RDP)
    - Fraction of feed CP that can be degraded in rumen
  2. Undegradable dietary protein (UDP)
    - Fraction of feed that is not degraded in rumen
    - Digested in abomasum & SI
19
Q

Briefly summarised how true proteins are synthesised.

A
  1. Rumen degradable protein
  2. Effective rumen degradable protein (ERDP)
  3. Microbial crude protein (MCP)
  4. Microbial true protein (MTP) synthesise by microbes
20
Q

How is crude protein determined?

A

Measuring Nitrogen (N) content of feed

21
Q

Why is crude protein 6.25 x N?

A

Because protein contains 16% N

22
Q

Briefly describe how the level of crude protein in foods is determined, and why is it called “crude” protein.

A

Protein content - calculated from analysing N content of a substance (feed, faeces, excreta), expressed in g/kg fresh or DM;

Protein contains 16% N - N multiplied by 6.25 to get crude protein;

2 assumptions are made: All N present = protein; all protein contains 16% N

Both assumptions are unsound, since not all N in feed is protein, and that different feed proteins have different N contents. So crude protein level is normally an overestimation.

23
Q

Briefly describe the effect of maturation on cell content to cell wall ratio and grass nutritional value.

A

Grass nutritional value decrease with growth because the older grass contains more lignin;

Cell contents (as grass matures):
- Protein level reduced
- Lipid level reduced
- Mineral level reduced
- NSC level increased!!!

Cell wall:
- Hemicellulose increased
- Cellulose increased
- Lignin increased

24
Q

What would be the best time of the day to cut grass for conservation purposes, and briefly why.

A
25
Q

Briefly explain how and why supplementary feeds are often processed.

A

Cereal grain processing:
Improves availability of nutrients i.e. increase nutritional value
e.g. Cattle & sheep
- Better rumen degradability
- Prevents grains passing to abomasum undigested
E.g. Improves SI digestibility

Simple mechanical processing
- Rolling, grinding

More sophisticated techniques:
- Micronisation (heat & mechanical pressure; infrared techniques)
- Extrusion (high temperature & pressure, with or without steam)

26
Q

Name 5 factors that can affect the digestibility of a foodstuff, and briefly outline why each does

A
  1. Food composition (chemical composition)
    - Cell contents are highly digestible
    - For cell wall, digestibility of fibrous fractions depends on quantity and chemical form
  2. Food processing
    - Treatment e.g. rolling, grinding, chopping, cooking
    - Chemical treatment e.g. alkali or urea treatment increase digestibility of straw
  3. Level of feeding
    - Especially important in ruminants, since rumen retention time is sensitive to level of feeding; the higher the level of feeding, the lower the rumen retention time(faster); Reduced exposure time of feeds to microbial degradation
  4. Ration composition
    - Associative effects i.e. when 2 or more feeds fed together, digestibility of each feed is affected (usually negative); greatest impact when combining roughage with high starch concentrate
  5. Animals
    - Food digested differently in different species e.g. digestibility of low fibre foods in ruminants an non-ruminants is relatively similar; digestibility of high fibre food is better in ruminants; sheep digests cereal better than cattle, but cattle digest low quality roughage better than sheep
27
Q

Briefly describe partitioning of food energy in animals (use a diagram if you want)

A

Gross energy - faecal energy = Apparent digestible energy
Apparent digestible energy - (urine + gaseous energy) = Metabolisable energy
Metabolisable energy - heat increment* = Net energy

*Heat increment from digestion/metabolism

28
Q

Briefly describe the metabolisable protein system used in ruminant feeding.

A

Metabolisable protein (MP) = DUP (digestible undegradable protein) + DMTP (Digestible microbial true protein)

DMTP
- Synthesised by microbes in rumen
- digested in abomasum & SI
1. Rumen degradable protein
2. Slowly degradable & quickly degradable
3. Forms microbial crude protein
4. Forms microbial true protein

DUP
- Fraction of feed not degraded during passage through rumen
- digested in abomasum & SI

29
Q

Briefly describe the basis for ration formulation, and what type of questions need to be asked.

A

Ration formulation = Feed ingredients combined to provide animal with required nutrients

Basis:
- Combine ingredients to meet energy requirements
- Adjust to meet protein/AA requirements
- Check major minerals (supplement if required)
- Check trace mineral/vitamins

Requires knowledge of:
- Nutrient requirements
- Feedstuffs available
- Feed intake achieved
- Any ingredient limitations

ALFS 2 (5 decks)

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