A recent AHDB webinar highlighted the importance of getting calf housing right, especially when calves come in from multiple sources.
Mixing calves from more than 10 sources results in more than 70 per cent being treated for pneumonia according to trial data.
Discussing the trial findings in a recent AHDB-organised webinar, vet Nick Gibbon, from Belmont Farm and Equine vets in Herefordshire, explained the study, carried out by AHDB, involved eight calf rearers who each reared between 500 and 1,200 beef cross dairy calves a year.
Calves were reared from about three-weeks-old to 140-150kg, mostly on contract, and came to the farms from multiple sources.
Data was recorded and AHDB received weight data samples for 3,000 calves. Full health records were detailed for 1,500 calves, along with their weights.
Most of the calf rearers took in calves from multiple farms and the results showed when batches of calves were drawn from more than 10 sources, more than 70 per cent of them were eventually treated for pneumonia.
This figure dropped to about 25 per cent when calves were sourced from one or two units.
Dr Gibbon said: “When you mix calves from a large number of farms, there are many more viruses and bacteria which the calves will be naive and not immune to, increasing their risk of illness.”
The findings revealed extra costs associated with pneumonia were not just down to the cost of treatment and potential losses, but also through lost efficiency and slower growth.
Calves with pneumonia spent a longer period on-farm than calves which did not have pneumonia which also added to these costs.
“The focus has to be on preventing pneumonia. Pneumonia is the biggest reason for antibiotic usage in the calf rearing system and presents challenges to costs and welfare,” said Dr Gibbon.
He explained part of the trial looked at factors which created the greatest risk of pneumonia, and the factor which has the greatest influence on whether calves were treated for pneumonia or not was season of arrival on farm. During the trial, winter and spring posed the biggest threat due to prolonged periods of cold, wet weather.
Breed also had an effect and dairy bulls came out worst. Dr Gibbon said this may have been down to a number of factors, including a lack of hybrid vigour or early treatment on the farm of origin.
Other factors which were important were air quality and ventilation in calf housing.
Dr Gibbon said: “Poor housing leads to poor air quality. Poor quality air is described as air which contains anything which is an insult to the calf’s airway, such as viruses, bacteria, dust or ammonia.
“Dust and ammonia will cause damage to the hairs lining the windpipe which will allow secondary infection as it is easier for bacteria and viruses to invade.
“Air quality problems are exacerbated by a lack of air turnover,” he added.
Dr Gibbon outlined research by Kenneth Nordlund, University of Wisconsin, who found a strong relationship between air quality and respiratory diseases.
The study showed calves which were able to nest in deep bedding with no draught were at the least risk of developing pneumonia.
This was only an issue when air quality became very poor.
Conversely, calves with no deep bedding and the absence of a solid barrier, meaning draughts were likely, were most at risk.
He said farmers could maximise air quality by ensuring excellent ventilation without draught and keeping environmental moisture to a minimum.
“Excessive amounts of humidity or environmental moisture will allow calves to get a chill, especially in cold weather.
“Potentially extra moisture in the air acts as a way pathogens are able to transit between calves. Excessive moisture around feeders and water troughs is usually the source of this,” he said.
Importance of air flow
DR Gibbon said there should be at least eight to 10 ‘air changes’ per hour even in winter. The requirement could be as much as 60 times an hour in hot weather.
“This is rarely achieved in traditional sheds. In winter, people tend to close sheds down to keep calves as warm as they can, this compromises air changes,” he said.
The number of air changes can be measured using smoke bombs. Dr Gibbon explained: “For every sq.m of inlet space you need 0.5 to 0.25 times the amount of outlet space. If air is flowing out you must provide as little resistance as possible for air to flow in behind it. Often the inlet is acting as outlet too.”
Dr Gibbon said other examples of natural ventilation were doors and windows, shuttered sides and gale breaker blinds, but he said these were often left closed.
Alternatively, he said air could be forced in mechanically using energy, which was often the only option, especially when a building was designed or required for another use as well as for housing calves.
Dr Gibbon said calf rearers should not over-rely on the stack of ridge effect, as calves did not generate enough body heat to make the hot air rise out of the ridge.
“Air tends to circulate just above the calves, often it does not make it out of the ridge to escape, therefore not driving the draw through the inlets.”
However, Dr Gibbon said another potential option was to create a space within an environment with lots of air movement that calves could nest and escape from the draughts. He suggested igloos or large hutches within a very open building could work well.