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Why Weigh Broilers?(Part 2)

Types of automatic weigher
A) Platform weighers
These are normally metal boxes, which are placed on the litter and are linked by a cable to a control box in the broiler house. They weigh one bird at the time and are self-tareing when no birds are on the scale. In other words the empty weight of the scale is zeroed each time to allow for build up of muck on the scale.
When a bird gets on the scale, the scale records a higher weight. It allows for oscillation in the recorded weight, and when the weight is stable, it will be recorded if it meets certain criteria. The weight has to be within a set percentage of the expected weight for that day. If it is not, (for example, if two or more birds go on the same time), the weight is discarded as not valid weight. These scales can give reasonable accurate estimates of the average weight.

Disadvantages of a platform weigher
1) The scale has to be empty of birds before the next bird weight is recorded. So if several birds stay on the scale for some time, no weighings are possible before they ALL get off!
2) The load cell and the electronic equipment in the platform weigher itself are near the litter where a build up of dampness and ammonia may take place. Over time, this can get into the electronics and cause failure.
3) A cable has to lead from the scale to the control box. At least part of this is on or under the litter, and can be damaged by birds or otherwise.

B) Hanging scales
These work on a different principle. They comprise a larger, 50 cm round platform suspended via load cell and electronics from the ceiling. The platform is fixed in the centre which enables the birds to get on and off from all directions (see picture). Many birds can be on the platform at the same time, depending on their size.
A weight is recorded when a birds gets OFF the scale! As before, a stable weight has to be recorded before and after the bird gets off, and the weight has to be within a prescribed bandwidth. So if two birds get off together, no weight is recorded. Build up of muck on the scale does not matter, as it is the difference in weight that is recorded.

1. Produces more valid recorded weights than floor scales so the estimate average is better.
2. Broilers like to hop up to a higher level, so the scale is occupied most of the time.
3. The electronic and load cell are in the ceiling, well out of wet and ammonia, and is in situ between crops.
4. Cables are permanently fixed from the load cell and electronics, back to the control box, out of reach of the birds and are much less likely to be damaged.

1. Total weight on the scale can be high, so a really secure fixing to the ceiling is required. A flimsy screw hook can be pulled out.
2. The capital cost may be higher.

Current use of broiler scales
Hundreds are now in use in Europe and in America. Major companies are examining the various options and some are now buying in volume.

The future
We will need to get broilers to market age at more exact weights, (at least to within 2% of the target), to meet supermarket and consumer demand. To do this we will need to exercise better management control of broiler growing.

Whatever the industry, you cannot exercise management control if you do not have accurate management information!

Knowing what your broilers weigh on a day to day basis is essential if you want to get them to market age on the target weight in the best, most cost effective way.

If you see deviations from the proper growth curve starting to develop, you have the opportunity to do something about it quick enough to get them back on the correct growth curve again.

Without this information, you may not even know there is a problem until it may be too late to do anything about it!

What to do about it may involve looking at the daily feed intakes and the daily nutrient intakes of the birds compared to breed targets. There are proven computer programmes available to help you do just that like the OptiLink software from OPTICON.

For further information, contact Herman Fleuren of OPTICON AGRY SYSTEMS Tel: 00-31-77-32 31 200, email at or visit his website at

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No of weighings

Accuracy Percent of time

Average weight

400 gram

Average weight

800 gram

Average weight

1600 gram


Within 10%

40 g

80 g

160 g


Within 5%

20 g

40 g

80 g


Within 2,5%

10 g

20 g

40 g


Within 1%

4 g

8 g

16 g


Within 0,5%

2 g

4 g

8 g

Table 1 Limits of Accuracy related to Average weight

(source: Flockman, Ross, Cobb)