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ASC273 > L21: Energy Systems > Flashcards

L21: Energy Systems Flashcards

1
Q

How do we calculate the energy of a feed?

A
  • in vitro method
  • formulas (Oddy et al)
  • feeding table
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2
Q

What is the basis for forming a feed ration?

A
  • knowing energy content of feed
  • knowing the energy requirement of the animal
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3
Q

Animals tend to show a …… response to increasing energy

A

increasing

-not always for other nutrients

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4
Q

What are energy systems?

A
  • Relates energy intake of animal to its peformance to predict:
  • peformance of animal on energy intake
  • energy req. for performance
  • Feeds work on ME
  • Reqs work on NR
  • Why?
    -different efficiencies w/ each process Lm, Kg, Kl etc
    How do we convert b/w ME and NE?
  • K values (efficiencies)
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5
Q

*List and describe common ruminant energy systems

A
  • OLD:
    -Armsby’s NE sys
    -Kellner’s starch equivalents
    both have problems; NE valoues of same food differed depending on function
    -TDN (total digestible nutrients)
  • CURRENT:
    -ARC system
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6
Q

_*List and describe common ruminant energy systems_

Describe ARC ME system

A
  • Current british system
  • Provides estimates of energy reqs of growing, lactating and pregnant sheep/cattle
  • Food energy expressed as ME
  • Animal energy reqs expressed as NE
  • Uses series of equations to predict efficiency
  • based on ME/GE ratio (metabolisibility or qm)
  • assumes constant GE of ruminant feeds
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7
Q

What do we use to predicr animal peformance?

A
  • Calculate metabolisability (qm of feed)
    - ME of feed / GE of feed (as a proportion)
  • eg. 11 MJME/kgDM (GE = 18.4 MJ/kg DM) = 0.6
  • Calculate k values
    km
    Kg
    Kl
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8
Q

What is the calculation for Km (maintenance)?

A

Km = 0.35qm + 0.503

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9
Q

What is the calculation for Kg (growth)?

A

Kg = 0.78qm + 0.006

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10
Q

What is the calculation for Kl (lactation)?

A

Kl = 0.35qm + 0.420

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11
Q

Please look in lecture at calculation diagram

A

DO IT.

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12
Q

What is the issue with calculating metabolisability for a ration formulation?

A

Method difficult for ration formulation as we often don’t know the total diet ME

  • May know part of it (e.g. roughage) but not the rest (grain content) • Often trial and error qm values until we get a match
  • Works on the assumption GE = 18.4 MJ/kg DM

Also may not know how much each feed will contribute to maintenance and production

Energy partitioning

Use kmp (average efficiency with which ME used for maintenance and

production)

Kmp = (NEm+NEp)/(NEm/km+ NEp/kp)

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13
Q

What is the current Australian energy system? (ruminant)

A
  • SCA system (Australian Standing Committee on Agriculture)
  • Includes modications for grazing animals
  • Different Kg for forage diets (incl. tropical forages)
  • Includes Kwool
  • 10% ME for production is added to maintenance when feeding above maintenance level
  • feeding for production
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14
Q

Describe the NRC system (ruminants)

A
  • National Research Council USA
  • NE sys for beef/dairy
  • Foods given in NE values for both maintenance and gain
  • ***Under predicts NE compared to ARC system
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15
Q

Why do energy systems tend to be more accurate for dairy cows?

A
  • less variability in diet
  • milk fairly consistent
  • Aus sys appears most accurate
  • don’t need to put on weight
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16
Q

Why do monogastric energy systems tend to be simpler?

A
  • Less variability in food energy
  • Efficiency of ME use (Km, Kg etc) less variable
17
Q

What are the two monogastric energy systems? (horse)

A
  • NRC (USA) DE system
  • little diff in equine DE & ME due to digestive sys
  • DE is what seperates feed e values most
  • maintenance is calculated (Km)
  • preg, growth, lact, work are multiples of maintenance
  • INRA (France) system
  • Based on NE
  • relationships b/w NE and DE much morr variable, so not as accurate
18
Q

Equations were developed to predict ME of feeds for different animals based on:

A
  • fibre content
  • digestibility
  • protein content
  • fat content
  • starch
19
Q

Energy requirements are maintenance plus:

A
  • growth
  • lactation
  • pregnancy
  • work
  • pelage growth
20
Q

What is meant by maintenance?

A
  • body compositition does not chnage
  • produces no product
  • not in work
21
Q

What is meant by maintenance requirement?

A
  • quantity req. for no net gain or loss of nutrients
  • steady state
22
Q

What is basal metabolism?

A
  • Energy expended (heat) for a fasting animal w/ no activity
  • influenced by age/sex
  • no energy input (feed)
  • animals offered feed will produce extra heat
23
Q

Briefly describe factors to be considered when estimating energy requirements

describe maintenance energy

A
  • Amount required for zero energy equilibrium (balance)
  • Calculate from fasting metabolism allowing for:
  • exercise
  • Environment

• level of feeding will affect it
- Increase feeding increases efficiency for maintenance

• Age affects energy requirement for maintenance - Development

  • Young = more
  • Old = less
24
Q

Briefly describe factors to be considered when estimating energy requirements

describe energy for growth

A

• Requirements vary with age

  • Young = rapid growth
  • Old = Storage as fat
  • NE in fat higher than in muscle
  • Younger animals lay down more muscle than fat
  • less energy/kg liveweight gain
  • Older animal have greater energy storage / kg BW (FAT!!!)
  • Depends on physiological state
  • In horses also depends on whether in training
25
Q

Briefly describe factors to be considered when estimating energy requirements

describe energy for lactation

A

• Greatest energy requirement
• May not be able to eat enough to meet energy demands:

  • fat reserves
  • NEFAs
  • Concentrates

• After parturition

  • milk yield increases
  • protein and minerals decrease

• Energy requirement calculated days post-partum or based on yield

  • E.g. mare. First 3 months vs later
  • (first 3 months highest production)
26
Q

Briefly describe factors to be considered when estimating energy requirements

describe energy for work (horses)

A

• Difficult to quantify requirement as may be influenced by:

  • horse condition
  • climate
  • rider characteristics
  • ration composition

• NRC categorise requirements on general workload

  • Light
  • Moderate
  • Intense

• Other equations available based on workload (km x kg) and speed

27
Q

Briefly describe factors to be considered when estimating energy requirements

describe environmental effects

A

• Efficiency with which ME will be used by animals will be affected by:

  • *- temperature
  • wind
  • precipitation
  • humidity
  • heat radiation**

ASC273 (30 decks)

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