L23: Dairy Cattle Feeding Standards: Energy Flashcards Preview

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Flashcards in L23: Dairy Cattle Feeding Standards: Energy Deck (10)
1

What is energy required for maintenance?

  • Mean steady state, no loss, no production
  • Zero energy retention
    -theoretically stable live weight
  • British ARC system
    -MEM = 8.3 + 0.091W plus 5-10% for grazing

2

Describe this equation

  • #1 formula for ME requirement!!!!!!!
  • IS IN THE EXAM
    KSM = 1.4 where:
    K = 1 for sheep and goats; 1.2 for Bos indicus; 1.4 for Bos taurus
    S = 1 for females and castrates; 1.15 for males
    M = 1 + (0.23 x proportion of DE from milk) • W0.75 = Biological weight
    A = Age in years (maximum 6)
    Km = efficiency of ME utilisation for maintenance
    MEp = ME used directly for production
    MEgraze = Additional energy expenditure of grazing
    ECold = Additional energy expenditure when temperature below thermal neutral zone

3

Describe this equation:

 

Where:

H = horizontal equiv. of distance walked in km

C = 0.0025 for cattle, or 0.02 for sheep

DMI = dry matter intake from pasture in kg/d

D = dry matter digestibility as a proportion

W = Weight

4

Describe this equation

Milk Production

• EVL= (0.0381xF) + (0.0245xP) + (0.0165xL)

• Energy value of milk depends on components

• EVL= (0.0381xF) + (0.0245xP) + (0.0165xL)

• F = Fat content (g/kg)

• P = Protein content (g/kg)

• L = Lactose content (g/kg)

• Alternatives calculations:

• EVL= 0.0386F + 0.0205SNF - 0.236

- SNF = Solid non-fat concentrations (g/kg)

• EVL= 0.0458F + 1.222****

• KL = (0.02M/D) + 0.4 (or approx. 0.6)

- M/D = MJ ME/kg DM per Day

MEL = Y x EVL /KL

- Where Y = Milk yield/day

5

What is a standard reference weight (SRW)?

  • Liveweight of an animal when skeletal development complete w/ a BC score of 3 (mid range)
  • Brings all breeds to a common weight for inclusion in energy value (EB) calculations
  • Used in the prediction of:
    -composition of empty body gain (EBG)
    -feed intake

6

Describe how energy from liveweight loss can be used for lactation****

 

  • transition state in cow preg=>lactating has largest e demand -this is wen LWL comes into play
  • Net Energy in body tissue = 20MJ/kg (potential amount available)
  • Used with 84% efficiency
    - i.e. supplies 16.8MJ Net Energy
  • This replaces 16.8/KL of dietary ME
    -or about 28MJ ME for lactation
    - Assuming efficiency of lactation 60%
  • Net energy from LWL varies with condition
  • Calculated Net Energy in body tissue
    - MJ/kg = 10.1 + 2.47CS

    - Higher the condition score = higher energy available from weight loss

7

Describe this equation

 

• Z = W/SRW (Liveweight divided by Standard Reference Weight)

• R = [(0.92 x weight change/d)/(4SRWkg0.75)]-1

8

What is the equation for ME(pregnancy)?

• MEp = 1.13exp0.0106t

• t = days after conception

• Mainly used for dry cows and heifers

9

What is the equation for dry matter intake capacity?
What is DMI influenced by?

Mid-late lactation

• DMI = 0.025W + 0.1Y

• Y = Milk yield (L/day)

• W = Weight (kg)

• Early lactation 2-3kg below this

• Influenced by

- size

- physiological state

- genotype

- digestibility

- substitution

- climate

10

Solve this:
LEARN HOW TO DO IT. THIS QUESTION IS IN EXAM W/ DIFF FIGURES.!!!!!!

Housed 5 yr old 600kg cow producing 30kg milk/d (36g/kg butter fat (F); 86g/kg Solid non-fat conc. (SNF)) not pregnant and offered a diet of 11MJ/kg DM.

WHAT IS THE ENERGY REQUIREMENT?

look at lecture slides for assistance if necessary