Description of the problem


There are 29 farms within the Canterbury region that supply Tegel with chickens, each farm has up to 9 sheds and the age of the birds in each shed are planned to meet Tegelís forecasted demand.

Tegel has a planner who generates weekly processing schedules. These are updated daily as required. The schedules are generally driven by the processing plantís demand except where processing is necessary to prevent the potential of overcrowding in the sheds.

The processing schedules consist of which order the farms are to be visited on each day and how many chickens are to be caught from each farm on each day.

Tegel delivers the processing schedule to the contracted catchers who are in charge of catching and transporting the birds to the processing plant. The contracted catchers employ a planner who decides the assignment of trucks to farms and how many catchers should catch at each of the farms. The planner does this task without the aid of computer software, relying on experience alone. The plannerís main objective is to prevent the processing plant from becoming idle throughout a shift.

The contractors operate a workforce of around 11 catchers who are often divided into gangs of 3 to 8 when catching, so that birds can be caught from more than one farm at a time. The makeup of the current fleet is given in the table below:

The contractorís resources comprise of a workforce of around 11 catchers. The workforce is often divided into gangs of 3 to 8 when catching to allow multiple farms to be caught from at the same time. The current vehicle fleet (as seen in figure 1) is comprised of three trucks. Two of the trucks carry loaders that are used to load the modules (bird transporters) on and off trucks. 



Truck 1

Truck 2

Truck 3

Module capacity









1. Fleet makeup




If desired, both truck 1 and 2 can choose not to carry a loader. If this is done an additional 2 modules can be carried on the trucks. This process takes negligible time and effectively increases the trucks capacity to 24 modules. An average total stock of 121 modules is currently available. The current fleet makeup causes restrictions on the assignments to be put in place. For instance, birds cannot be caught from a farm until a loader is present. From table 1, it can be seen that truck 3 can never be the only truck catching from a farm since it does not have a loader, therefore, truck 3 can only catch from a farm if another truck that carries a loader is present.

The catchers start catching at 2 a.m., this allows a stock of birds to build up at the plant before processing begins at 6 a.m.. There are breaks allotted to the catchers and the chicken processors. These halt the catching and processing of chickens respectively. The catchers usually break for breakfast at the second farm they catch from and the processing plant breaks three times.

Both the scheduling performed by Tegel and the contractors must take into account a large range of detail and various operating constraints. Chicken welfare is one of these constraints. 

2.1  Issues with the truck, trailer and loader

There are bio security requirements in place to prevent the likelihood of contamination between farms. These requirements affect the catching logistics such that, the trucks and loaders cannot visit farms consecutively as they must be cleaned at the plant before visiting the next farm.

A trucks trailer can be left at a farm or at the plant. This means that on occasion trucks leave farms without their trailer to return full modules to the plant with the possibility of returning with more clean modules.

Currently there is almost full utilisation of all the trucks and loaders and thus in the occurrence of a truck or loader breakdown, equipment resources become overly strained. Repair requires experts and hence when breakdowns occur there are delays in catching that can result in idle time at the plant.

2.2  Issues with the modules

At the processing plant, modules are cleaned on an 11-stage conveyor that has a stage movement time that is dependent on the plantís processing speed. This means that if the processing plant becomes idle, such as for breaks, the cleaning of modules is halted and trucks are delayed waiting for modules to be cleaned. If these delays are not considered in the scheduling, actual arrival times at the farms are likely to be later than scheduled.