Profitable cattle are those which produce the greatest weight of saleable meat in the shortest time. The only way to directly measure this performance trait in live animals is to weigh them at intervals and compare results for different animals. Considerable progress has been made in developing instruments to indirectly assess lean meat percentage in live animals. These offer you a useful extra measure of growth performance, but they can only be an adjunct to weighing. A set of scales is an essential component of every cattle recording scheme. The information it provides is the foundation of decisions on selection of breeding cows and sires. Scales also contribute enormously to accurate decision making in a whole range of farm management activities such as culling, feed management, animal health and buying.
Types of scales
Because cattle scales must accommodate large, strong animals which can object violently to close handling, the weighing bail and scales must be robustly constructed and designed to be as easy to use as possible. Bail gates must close easily and lock positively, and have a fast, easy-to¬use release mechanism.
There are three main types of weighing mechanisms — spring balance (clock face), hydraulic and electronic — but both the two mechanical types are steadily being superseded by electronic models. Electronic scales are more accurate, more flexible and possess several benefits for both livestock recording and management activities. Consequently we strongly recommend their use over the other types. Cattle scales require a range from 0 kg to 1000 kg in 1 kg steps.
The main strength of electronic scales is the fact that unlike mechanical scales they can be programmed to do more than simply indicate the weight of the animal standing on the weighing platform.
Because of its ability to store and manipulate data and display instant statistics, the electronic scale can be used to provide on-the-spot management information such as grading weights. Because the calculations are done both accurately and rapidly it improves the chances of making correct management decisions.
The programmability and data storage capacity of electronic scales overcomes the main problem with mechanical scales, which is that the animal weights must first be separately recorded, then the necessary calculations done. Inevitably copying of lists of figures and working out averages etc leads to errors and delays before decision-making information becomes available.
For example an electronic scale can be programmed to calculate and display the mean weight of a mob immediately after a weighing session. Management decisions can then be made while the mob is still in the yards.
Location and setting up
Design the yard so cattle flow easily and smoothly into the weighing race. The race leading up to the weigh bail must be narrow enough to prevent animals turning around. The area beyond the weigh bail should open out and encourage the animal to move through the bail to reach open space. Well thought out yard design which enables animals to be weighed with a minimum of fuss and effort is an essential element of a good cattle recording scheme.
Place scales on a clean, level site, preferably a concrete pad. Secure them firmly ensuring they are unable to move. Motor cycle tie downs do the job well. The weigh bail must be free to move through its full travel without touching any obstructions. Cattle leaning on the back gate (if the gate is not attached), or other cattle behind leaning on the back gate of the scale (if the gate is attached) will seriously affect accuracy.
Scales must be kept clean and dry and moving parts lubricated according to the manufacturer’s instructions. They must not be left out in the weather. They are precision instruments and should be handled carefully when being moved.
Using scales
Obviously scales must be accurate. Before beginning a weighing session check the accuracy of the scales with a known weight. Some scale makers supply check weights, but if they are not available you can make your own. One method is to fill empty drench containers with water —1 litre of water equals 1 kg. Or if you know your own weight accurately, weigh yourself. If you are weighing stock in different weight ranges you will need a suitable range of check weights.
Check there is no mud, stones or dung on or under the weighing platform interfering with its free movement. Once weighing begins check the scales after the first 10 animals then after every 100. Electronic scales have an automatic tare feature. Mud and dung is automatically tared, up to a certain weight, e.g. 800 g. If build-up exceeds that weight you simply press the Zero key to start afresh.
Quiet handling of cattle to be weighed is particularly important as they remember bad experiences and will be reluctant to go onto the scales the next time. Don’t use sticks, electric goads or excessive pressure from dogs, and avoid rough handling. If stock are consistently reluctant to go onto the scales you may have to rethink their positioning and/or the general layout of yards and races.
Diagram of the layout of a good yard for beef cattle
To ensure fast throughput and a good flow of cattle over the scales read the tags in the race before the animal enters the weigh bail. The importance of placing tags correctly for easy reading quickly becomes apparent. Cattle will quickly become shy of scales if the tag reader has to pull and twist their ear to read the number, plus it slows down throughput.
The same person should read the scales throughout each session as this will ensure that any operator error is consistent. Some electronic scales feature a stable weight indicator whereby the display is constantly updated with the best estimate of the animal’s weight. The display alerts the operator when the weight is ready to be recorded.
Ensuring weighing accuracy
You must ensure all liveweights recorded are made on animals in the same physical condition so that the figures between one weighing and the next are strictly comparable. This is particularly important when monitoring weight gain for management purposes.
Gut fill can significantly affect apparent liveweight. Therefore cattle should have similar gut fill at each weighing. The best option is to hold the cattle in the yards overnight and weigh them next morning.
If this is not practical try to weigh straight off the grass at the same stage of the grazing period. For example if the first weighing was on the fifth day of a 10-day break, weigh them at the same grazing stage at the next weighing. If you do have to weigh cattle with different gut fill from the previous weighing note this in the records.
If you are weighing a large mob and they have not been held in yards overnight be aware that cattle weighed in the evening will be lighter than if they had been weighed in the morning. You must adjust cut-off weights accordingly.
