The dairy industry is probably one of the most advanced when it comes to the weighing of livestock, with most modern commercial dairies, even in South Africa, having an electronic scale to weigh cows after milking.
In these operations, each cow is fitted with a radio frequency identification (RFID) tag and weight measurements are taken using a walk-over scale, usually installed in a walkway that guides the animals out of the dairy.
This scale is positioned between gates, with the front gate closing once the cow has entered the weighing station and opening again when the animal pushes against it.
The weight is incorporated electronically into the milking programme in real time, which is pre-programmed to flag and sound an alert when the live weight differs from a 10-day average weight by more than a previously set standard, usually 10%.
When this happens, a gate opens to let the cow into another walkway, where she will be inspected to determine the reason for the weight loss.
Benefits of regular weighing
Weighing cows regularly like this has a number of benefits, according to Dr Carel Muller, a research associate at Stellenbosch University.
Firstly, the system enables farmers to monitor individual animals and compare them with others in the group. Animals showing a sudden deviation in weight, for example, may be ill.
On physical examination, these animals may show signs of illness: for example, their eyes might be drooping, their ears hanging, or they may appear listless.
If nothing is wrong with the animal, the problem might be at the feeding station, which should be cleaned and checked for blockages.
“A physical examination, in combination with the use of milking, somatic count and feeding data, enables farmers to save thousands of rand through the early identification of problems and preventative treatment of diseases,” says Muller.
Cows will lose weight for up to 30 days after calving, after which they should return to a positive energy balance (the energy produced by feed consumed is sufficient for the animal’s energy needs), signaling that they are ready to be inseminated again.
Weight and feed measurements therefore also enable a farmer to identify as early as possible those animals that are losing too much weight or are not recovering as quickly as they should. These animals should be inspected for diseases and their rations adjusted to accelerate recovery.
Muller advises farmers to weigh heifers as soon as possible after birth, and at least once a month thereafter.
In this way, their growth rate can be tracked to adapt the feeding programme when they are below or above breed live-weight norms.
“We use breed-specific growth rate curves to track weight gain. Diets should be adapted for groups of animals that are not following the standard growth rate curves, otherwise a farmer might end up with a group of heifers that are not ready to be serviced by the time they are 12 to 15 months of age. Increasing the age at first calving increases the rearing cost of heifers, which extends the payback period once heifers are in milk,” he says.
Body condition should also be taken into consideration when cows and heifers are evaluated to determine whether they are ready for insemination, as a heavy cow might be underweight for its size, whereas a small cow might be the ideal weight for its size. Muller adds that overweight animals might also have problems becoming pregnant.
Weight and selection
The weighing of feed and cattle can be used to aid the selection of animals. According to Muller, breed shows have fostered a belief that bigger is better, as larger cows generally end up being crowned champions.
“Unfortunately, when milk yield doesn’t increase with size, these large animals are not as efficient as smaller cows because of higher maintenance requirements. Large cows are also more difficult to manage and are prone to injuries, as milking and housing systems in general have been designed for smaller animals,” he says.
Despite this, it is not that simple to replace large cows with smaller cows, as a large, older cow will still tend to produce more milk than a small, first-lactation cow.
Breeding for smaller cows without forfeiting milk yield is a challenge, as there is a positive correlation between milk yield and live weight. Recently, artificial insemination companies have been searching for sires to increase milk yield without increasing the live weight of cows at the same time. Therefore, reducing cow size is done through sire selection.
“Remember that it takes a few years before your newborns will be lactating. So keep the large cows until the end of their life cycle, but inseminate them with bulls that are known to produce more efficient progeny,” Muller advises.
Investing in the future
Muller says that farmers often shy away from investing in expensive infrastructure. However, viewed over the long run, the benefits of this infrastructure usually pay off.
“Farmers who keep small herds don’t have to buy a fancy electronic system to weigh cows. They can pick up a second-hand scale and use it as needed to keep track of the animals’ weights. They also don’t have to weigh the animals as regularly as in the modern milking systems, perhaps merely to keep track of heifers’ growth and recovery after calving.”
Afikim and Delaval manufacture robotic systems that allow for the incorporation of automatic scales. Both companies are represented in South Africa.
“These are expensive systems and perhaps not economically justifiable for small farms, but for a large farm they’ll repay the investment within a couple of years, as they can improve production efficiency and identify problems early,” says Muller.
Feed efficiency in feedlots and studs
Animals and feeding rations are generally weighed more frequently in feedlots these days, enabling feedlot companies to reward farmers for fast growers. As with the dairy cattle, beef cattle are chipped with RFID tags, with their feed intake and growth being monitored automatically at the feeding and weight stations.
The system enables feedlots to differentiate between efficient and inefficient growers, as well as adapt their regime to accommodate ‘shy eaters’, according to Dr Brink van Zyl, head of the Department of Animal Sciences at Stellenbosch University.
Various high-tech solutions that are easy to set up are available; they include the Canadian-developed GrowSafe system and the South African RFID Exports system, which is used in trials at Stellenbosch University.
Many feedlots share the information gathered with these measurements with their livestock suppliers, which allows these farmers to tweak their selection protocols to produce animals that are in higher demand at the feedlots.
“Production in South Africa is characterised by huge variation in efficiencies. Farmers tend to look only at large animals, for example the cow that produces 60kg of milk a day but needs to be fed 30kg of dry matter a day to maintain that output. The same happens with meat animals. We should rather be looking for the animal that produces the most output with the least input,” says Van Zyl.
One problem is that it is unknown how feed efficiency correlates with non-feedlot grazing conditions.
“We’re trying to develop a system to measure feed efficiency on the farm, but doing this is difficult if you don’t know the animals’ feed intake. Stellenbosch University’s research programme is currently investigating various options to predict the feed efficiency of livestock on grazing veld,” says Van Zyl.
Stud breeders generally weigh their livestock at birth and weaning, while some commercial farmers might do spot weighs during these times.
Too light or too heavy
Weighing calves within 24 hours of birth might help to identify birth problems, such as animals that are small and might need additional care, or animals that are particularly heavy.
A heavy birthweight could be a warning to use lighter sires on a specific female animal to prevent future potential birthing problems.
The weaning weight is used to evaluate differences in the growth potential of offspring and the milking ability of their dams.
In addition to this, sires are subjected to Phase C or Phase D testing. Van Zyl says that Phase C testing is more informative than Phase D, as it evaluates the performance of a sire against a contemporary group that receives the same rations under the same conditions, and measures intake, allowing feed efficiency to be determined.
“In Phase D testing, only the weight of the animal is measured, so there’s no indication of the animal’s feed efficiency. Phase C testing, amongst other [parameters], gives a good indication of the potential performance of a bull and his offspring within a feedlot,” he explains.
Email Dr Carel Muller at email@example.com, or Dr Brink van Zyl at firstname.lastname@example.org.