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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100105

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