August 16, 2018

Why weigh broilers?

To meet processors’ demands, you need to get your broilers into the factory on the preprogrammed day, close to target weight. Factories are now getting more precise as to what they want growers to achieve. On farm weighing helps you to meet these requirements.

There are two types of weighings

A) Spot weighings

These are occasional weighings and give a snapshot picture of the situation at the time they are taken. They may be used in the last week or two, just to check that your broilers will be bear to the final target weight. Or they can take place at intervals through the crop to check that the weight for age is in line with the breeder’ target for that age. In other words, to see if they are growing along the growth curve recommended by the breed company supplying the birds.

The logic of this is that if you can keep them on or close to this prescribed growth curve all the time, they WILL be on target weight at kill!

B) Regular daily weighings

If you can weigh birds every day, you not only see if they are on the target weight for that day, BUT you can also see that the daily Live Weight Gain (LWG) is on target. Any fall off in daily LWG can give an early sign of impending disease or of a management problem.

How to weigh broilers

1) Hand weighing

Young broilers can be weighed in groups of 10, 20, 40 etc depending on their age and size of the container you use to weigh them in. This is normally slung or suspended from a mechanical scale from the ceiling. This method is reasonably quick, and does not stress the birds too much. We only need to know the average weight, so weighing the container full of birds, then subtracting the weight of the container empty and dividing this by the number of birds in the container, will give you the average weight. If you do this a number of times in different parts of the house, you will get a series of average weights. Taking the average of these will give you the best estimate of the house average. Bigger broilers need to be weighed individually. Some people put a loop of cord round their two feet and suspend them upside down from a scale hung from the ceiling. Broilers don’t like this and struggle and flap,making it difficult to read the scale properly. It is also very stressful to the birds and it takes them time to get over the trauma before they start growing normally again. There are openended weighing cones on the market, which hang from the scale. You put a bird into this head irst, and the sides of the cone stop their wings flapping.

Practical problems

A) The procedure is stressful to birds and slows their growth.

B) It is a time consuming and labour intensive method, not suitable for large-scale production.

Statistical problems

A) Number of birds

All birds in the flock do not weigh the same. Normally about two thirds of the birds are within 10% of the flock average, with about one sixth being more than 10% better than average and one sixth being more than 10% worse than average. We want to estimate the average weight of all the birds in the house by weighing a sample.

How many to weigh?

If you only weighed just one bird at random, then clearly, 2/3 of the time your estimate would
be only within 10% of the true flock average. This is not good enough, so you must weigh
more. Table 1 shows you how your estimate of the house average improves the more you
weigh. So, for example, if you weigh 100 birds at random, you will get an average within 1%
of the true house average within 2/3 of the time.

B) Bias

Catchers tend to catch heavier birds because the smaller ones get away! So the estimate of
flock average may be too optimistic.

2) Automatic bird weighing


1) No stress on the birds. Some scales are attractive to the birds because they like to hop up to a higher level.
2) Can get weights every day.
3) Large numbers are weighed, so the estimate of the house average is good.
4) Better mathematics can be build into the software programme involved to estimate the true average better.
5) Data can be observed on the control box in the broiler house or on a computer in your office via a cable linked to a large number of control boxes in different broiler houses.
6) These weights can be shown as graphs. For example:
• Actual daily weights compared to the breed target growth curve.
• Percentage deviation from each day’s target.
• Daily LWG compared to breed target.
7) Data and graphs can be accessed, via a modem from a remote computer, (say in the farmer’s house or a company head office).
8) Can be incorporated into management and nutrition control systems for profit optimisation.


There is a capital cost of installation of the equipment, though maintenance cost can be low.

Types of automatic weighers

A) Platform weighers




Disadvantages of a platform weigher


B) Hanging scales






  2. The capital cost may be higher.

Current use of broiler scales


The future







Contact us for more information

No of weighingsAccuracy
Percent of time
Average weight
400 gram
Average weight
800 gram
Average weight
1600 gram
1Within 10%40 g80 g160 g
4Within 5%20 g40 g80 g
16Within 2,5%10 g20 g40 g
100Within 1%4 g8 g16 g
400Within 0,5%2 g4 g8 g
Table 1 Limits of Accuracy related to Average weight (source: Flockman, Ross, Cobb)