Ventilation

Why is natural ventilation so important in cattle buildings?

• • If air can't circulate around and out the building efficiently the animals can be more prone to catching air borne illnesses such as pneumonia

  • In dairy heifers, pneumonia during the first three months of life has been found to reduce first lactation milk yield by 2.2 per cent and increase age at first calving by two weeks. 

  • In beef cattle with lung damage research shows a 6 per cent live weight penalty compared with healthy cattle. Over a six month winter, this means affected cattle would take 11 days longer than healthy ones to reach the same live weight.

  • In some circumstances, vaccination can play an important role in helping to prevent calf pneumonia. Various vaccines are available to help protect against viruses, bacteria or a combination of both and their use should be discussed with your veterinary surgeon, who can advise on possible vaccination strategies.

  • When cattle become visibly infected with pneumonia, they should be isolated as soon as they are identified to help prevent the spread to others within the group. Fast and effective treatment is critical to minimising any potential lung damage, and ensuring a speedy recovery.

What we can do to help

Agri Design have become known for there expertise and knowledge in the natural ventilation of cattle sheds.

We can provide advice, reports and designs to get the best form your cattle and buildings. We can typically provide a report for shed ventilation for £400 if you are able to provide the required information without the need for a site visit. Contact us for further information and a quote.

Some things that affect ventilation and points to note:

• • The ridge is the most important part for natural ventilation to work

  • Crown crank ridges don't provide adequate ventilation for anything other than small numbers of calves

  • Lots of cobwebs are a sign of poor ventilation

  • The building size, shape and site can all affect the sheds ventilation characteristics

  • Stock size and number affect ventilation

  • Ventilation fans are normally covering an underlying problem. They don't normally sort out the problems, this is especially true in calf sheds.

Things that help to reduce the risk of respiratory disease

• Good colostrum management

• Avoid overstocking 

• Don’t mix animals of different ages 

• Good ventilation 

• Regular cleaning and good hygiene 

• Minimise animals stress

Extract about shed ventilation from the Scottish Farmer December 2010

Keep cattle warm and dry through winter by all means. But don’t stifle the airflow that gives them an essential supply of fresh air. That is the key advice from experts in livestock building design.

“The over-riding principles of dairy building ventilation are often not well applied, especially when it comes to the ridge structure, where air is extracted from the building,” says designer David Mair of Agri Design, Ayrshire. “On new builds, the quickest and easiest solution for the builder, and the cheapest for customer, is not necessarily the best for cattle health.”ventilation to producers looking to adapt or improve existing cattle housing or specifying new builds.

While many cattle buildings end up with ridges formed from cranked crown ridge panels interspersed with ventilating sections, the amount of airflow they allow is never sufficient for housed cattle and will lead to increased health problems.

“An open or protected open ridge will involve more work for the builder and may cost £10-£15 per metre more for the client,” says Mr Mair. “But as long as this style of ridge is specified and installed correctly, it will provide a good healthy atmosphere for the cattle and farmer.”

Air exchange rate is the key consideration. Cattle require enormous quantities of oxygen to support their metabolism and exhale around 5-litres of moisture every day.

That large volume of warm, moist air has to be exhausted from the building and replaced with fresh air; experts say a complete exchange every six minutes is a sensible target. And since hot air rises, the key 

requirement is to have sufficient airflow through ridge ventilation.

The size, number of cattle and function of a building should determine the most appropriate ridge configuration. An open ridge is a simple and low cost solution for situations where the design does not have to be entirely weather-proof – over a collecting yard, for example.

Where it does, a protected open ridge – one with an angled sheet above the opening – will provide an effective and largely weather-proof solution, as long as it is constructed to the correct dimensions.

“With both fully open and protected open ridge designs, upstands formed from fibre cement or steel sheet create a draw as the wind blows across the opening and this extracts moisture-laden air from the roof space,” explains David Mair. “But there is an important relationship between the width of the opening between the top purlins and the height of the cap above them.”

“Fitting the angled flat sheet forming the cap too low will reduce optimum airflow,” he points out. “The details have to be right for the installation to work as intended.”

Although an open ridge construction of one form or another will usually provide the main source of air extraction, other techniques can also be employed – such as raised roof sheeting and spaced roof panels. These can be especially useful in large or multi-span buildings involvement movement of large volumes of air.

“Inserting wooden battens or nylon mesh between profiled sheet courses will create a ‘breathing roof’ that will still be weather-proof as long as the sheet overlap recommendations are followed,” notes David Mair. “Another approach is to lay specially trimmed sheets 12-15mm apart to provide air inlets at the lower level and extraction outlets higher in the roof.

“This will not be weatherproof but heat updraft from cattle when it is occupied will help keep the rain out – and it doesn’t really matter if it gets in when the shed’s empty in summer,” he suggests.

For further reading see some of the links here

The Dairy Site 

DAIRY EVENT: Pneumonia Costs More Than£100/head,    Wednesday, September 08, 2010

Calf Pneumonia – Merial Report The Hidden Costs,    Friday, September 09, 2011

Fresh Air To Fight Pneumonia,    Tuesday, November 10, 2009

EBLEX

How good are your buildings?

VET GRAD

The Prevention and Control of Bovine Pneumonia,    Lindsay Rochford BVM&S MRCVS,    November 21, 2010