Why weigh broilers?
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
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
first, and the sides of the cone stop their wings flapping.
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
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.
Distribution of liveweights in a flock of as-hatched broilers (source: Ross)
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.
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
- No stress on the birds. Some scales are attractive to the birds because they like to hop
up to a higher level.
- Can get weights every day.
- Large numbers are weighed, so the estimate of the house average is good.
- Better mathematics can be build into the software programme involved to estimate the
true average better.
- 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.
- 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.
- Data and graphs can be accessed, via a modem from a remote computer, (say in the
farmer’s house or a company head office).
- Can be incorporated into management and nutrition control systems for profit
There is a capital cost of installation of the equipment, though maintenance cost can be low.
Types of automatic weighers
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...
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