Post on 24-Jun-2020
Optimization of delivery strategies for slaughter pigs
Merete Stenner Hansen28. oktober
2005
Disposition
● Aim of the project● Motivation● The Danish pricing system for slaughter pigs● Why LIMIDs?● Modelling of pig growth● Building the LIMID● Demonstration of the LIMID ● Future developments
Aim of the project
● The aim of the project is to determine if and how a decision support system, using Limited Memory Influence Diagrams (LIMIDs), can be developed, that can help the farmer find the optimal time of slaughter for the individual pigs in a pen, when knowledge of feed consumption and weight throughout the growth period is available.
Motivation
● PigVision project– Weight assesment from image analysis– Area of pig is calculated from image– Correlation between area and weight
● Other weighing systems under development– Mechanical scales
● Currently no single pig registration– Cost of ID vs profit from better decision– Increased precision?– Automatic sorting
The Danish pricing system for slaughter pigs
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Slaughter price
Weight, kg
DKK
/kg
Why LIMIDs?
● Alternative to MLHMP● Avoids the ”no forgetting” assumption in
traditional influence diagrams● Can be made dynamic with time steps
Modelling of pig growth
● Assumptions ● Growth capacity● Live weight● Observed live weight● Slaughterweight● Feed efficiency● Feed consumption
Assumptions
● Single pig registration– In order to get maximal effect of weighing
equipment.● Weekly registration of feed efficiency in the
pen● Lean meat percentage is not included
– It is hard to predict and would ad unknown precision.
● Growth capacity and feed efficiency– Linearity from time of insertion until start of
observation and from start of observation until time of slaughter.
Assumptions
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Development in live weight
Assumed weightTrue weight
Days post weaning
wei
ght,
kg
Growth capacity
● Pig specific● Initial value is based on herd average● Random variation over time
Live weight
● The live weight is increased as a function of the growth capacity
● Std. dev. of ν is the same as for ε
Observed live weight
● The weight as measured by the weighing system.
● e is the measurement error and depends on the weighing system.
Slaughterweight
● γs=0.79 is the slaughter factor● The pig grows d extra days from the decision
until slaughter
Feed efficiency
● The feed efficiency is registered on pen level
Feed consumption
● The feed consumption is the product of the current feed efficiency and weight gain.
● The d days from decision to slaughter is included in the interval from t=0 to t=tSO.
Building the LIMID
● Introduction to node structure– Stepwise expansion
● n-sigma intervals– Growth capacity– Feed efficiency
● Flexible number of states● The potential tables
Node structure I
Node structure II
Node structure III
Potential tables
● The probabilities for the node states given the state of the parent(s)
● Created as normal distribution
Demonstration of the LIMID
Future developments
● More pigs– Termination value– Live/dead counter