Advice on the use of positive pressure tube ventilation in calf barns


Most calf houses could benefit from positive pressure tube ventilation (PPTV) systems that ensure fresh, clean and still air is supplied at calf height to every location in the shed.

The PPTV is made up of a long tube that runs along the internal length of a calf house with an external fan at one end.

The fan draws clean air from the outside which is blown into the tube and out of a series of holes along the tube. This means that the air is distributed evenly throughout the shed.

The goal is to ensure that each animal is exposed to the same environment and that the air is still when it reaches the calf.

A study on a US farm found that the absence of PPTV was associated with an 81% increase in the number of calves detected with fever.

Livestock Management Systems consultant Jamie Robertson believes most calf barns in the UK could benefit from their installation.

See also: How to improve old calf barns on a budget

“Almost all calf buildings, except for very small ones (like hutches), need mechanical ventilation, which is most likely and optimally provided by positive pressure tube ventilation,” says -he.

His reasoning is based on several factors:

1. Baby calves cannot generate enough heat to generate the chimney effect.

The chimney effect occurs when warm air rises, leaves the building through an outlet and sucks in clean air through the air inlets. It depends on sufficient body heat, but also sufficient entry and exit.

2. Insufficient entry and exit

An opening cannot be considered as entry and exit. Even if it is a large area, the chimney effect will not be created and there will be no directional air flow.

Opening the back can help in a small building, but for larger buildings the only way to create this airflow is through mechanical ventilation.

3. More days

There will always be days when there will be no air movement.

PPTV helps with these factors, although it does not compensate for insufficient market opportunity. “Getting the right ‘in’ doesn’t solve the problem.

If you don’t get the right result with PPTV, it can make it worse, ”says Robertson.

Cost / benefit

At around £ 1,200 to £ 2,000, the cost of PST can often discourage farmers. However, Mr. Robertson believes the industry should focus on upgrading fresh air. PPTV can:

  • Create a drier environment, reducing the risk of aerosol spread and potentially bedding costs
  • Help reduce respiratory disease – AFBI study put the cost of respiratory disease at £ 700-900 per head at the end of the second lactation if an animal was treated twice or more during the lactation period .

Tips for getting the most out of PPTV

  • Make sure the system is installed by a competent person
  • PPTV will not solve hygiene, nutrition or general management issues
  • Maintenance is essential – dirty fans and / or dirty and torn tubes will never function properly. Fans and tubes should be cleaned two to three times a year
  • Be prepared to change the fan every five years and the tube every two years

Design Tips

There is no one-size-fits-all approach to PPTV. It’s critical that any system be designed for an individual hangar, and ideally by someone who has taken the University of Wisconsin’s PPTV design course, says Robertson.

The size of the barn, the number of calves and their location will influence the design.

Considerations include:

1. Fan size

  • Fan capacity must provide a minimum ventilation rate of four air changes per hour
  • The size of the fan will influence the diameter of the tube – for example, if the tube is too narrow and the pressure too high, the air will rush to the end and not be distributed evenly

2. Height and position of the tube

  • The location and height of the tube will influence the size and position of the hole
  • If the tube is at the back of a shed, the holes will need to blow down and at 4 o’clock to push air into the building
  • If the tube is in the middle, there might be a line of holes at 4 and 8 o’clock

3. Hole size

  • The size of the holes should be customized so that the calf resting area is covered with fresh air. If the holes are too large, the calves can be refrigerated; if the holes are too small, the fresh air will not reach them
  • Holes can vary in size to ensure air is supplied to all areas of the shed.

The system is operated from a simple control panel © Hugh Nutt

Case Study – William Holmes, High House Farm, Dorset

Installation of a positive pressure tube ventilation (PPTV) system in a shed used to raise calves up to one week of age reduced calf mortality by 63% and reduced antibiotic use 86% off at William Holmes’ High House, Dorset.

In 2019, high speed and a lack of ventilation on calm days – due to the fact that small calves are not able to generate the chimney effect – were identified as contributing factors to calf pneumonia in the shed open to a single lot.

Will holmes

Will Holmes © Hugh Nutt

Heifers and veal calves from the 420-cow fall block calving herd are housed in this shed for the first week after birth and managed in groups of 12 in eight pens.

Synergy Farm Health vet Tom Shardlow advised placing two staggered straw bales in each pen – one in the front and one in the middle.

Windbreaks were also installed at the top of the open facade of the building. This provided the calves with reduced shelter and drafts.

After completing the PPTV design course at the University of Wisconsin, Mr. Shardlow went on to design a system for the hangar. Features include:

  • The tube is located at the front of the building, which is higher than the rear, to allow clearance of machinery
  • The hangar measures approximately 1,600 m² with the fan moving over 7,000 m² of air per hour to provide more than four air changes
  • Holes are located on one side, facing the shed, to route air to the rear

Mr Holmes discussed the management of colostrum to ensure that calves receive 10% of their body weight within six hours of birth.

He also tightened hygiene protocols and increased milk feeding rates.

“Between the closing of the hangar and the installation of the positive pressure tube, we no longer have pneumonia in this hangar.

We haven’t stung a calf in this shed for two years, ”he says.

Since most antibiotics were associated with this period, reducing pneumonia at this stage reduced the overall level of antibiotics, as well as the mortality of the young (see table below).

The calves are also stronger when they leave this shed and group together by 45.

After paying £ 1,410 for the system, Mr Holmes believes it paid off in two months. “In the first year alone, we had nine fewer calves that died.

If we work on £ 250 per calf, that’s £ 2,250 just on deaths, ”he says.

At the same time, 251 fewer doses of antibiotics equates to savings of around £ 750 to £ 1,000 in the first year.

Improvements since installing PPTV in 2019

2018

2019

2020

Young mortality (total calf deaths from birth to calving for any reason. Half is estimated to be related to pneumonia)

27

18

ten

Number of doses of antibiotics given to young animals (for any reason, until calving)

307

56

43

In 2018, around 130 heifers were bred. As of 2019, veal calves and heifers have been bred, totaling approximately 570 head.

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