Ventilation Systems for Livestock Trailers: A Study by the Kentucky Equine Research Staff
A study by the Kentucky Equine Research Staff assessed air exchange rates in trailers with various ventilation port configurations and with the transportation of differing numbers of horses. The researchers looked at air movement and temperature in several areas of the trailer. They also quantified the effect of:
- vehicle speed
- window openings
- number of horses on air exchange
Details of the Study
There was ten different locations to measure the air exchange rate using tracer gas concentration decay tests, both with and without horses present.
The use of three different speeds helped to determine the exchange rate to simulate driving of the following:
- in town
- on rural roads
- on limited-access highways
Arrangements of Ventilation Systems for Livestock Trailers
There was testing of three different arrangements of ventilation, which include:
- forward-facing roof vents and windows closed
- roof vents closed and windows open
- roof vents and windows open
For this study, four mature geldings (three Thoroughbreds and one Standard-bred) were necessary. These horses were familiar with transportation and with the particular trailer in the study.
Type of Livestock Trailer
The trailer was a four-horse, slant-load, Gooseneck model with:
- rear window
- window at the head and tail of each horse
- forward-facing roof vent over each horse’s head
All openings had a total area of 1.05 square meters (11.86 square feet). The positioning of horses was so that the angle of their head was toward the driver’s side of the vehicle. The number of stalls was one through four. This began the front of the trailer. Division of these stalls was with moveable partitions on the driver’s side.
Method Used for Ventilation Systems for Livestock Trailers
The method used to determine air flow was tracer gas concentration decay tests. To determine exchange rate, only relative changes in concentration are necessary. Every ten seconds, infrared sensors at various locations inside and outside the trailer would measure the concentration. Injection of carbon dioxide (the tracer gas) into the trailer was necessary until he concentration hit equilibrium at the upper end of the sensor range. Then, they took measurements of the dilution at fresh air entrance to the trailer.
They took measurement of outside air temperature by using a sensor to determine both temperature and relative humidity. Thermo-couples were used to measure the temperature in the trailer, which were with the carbon dioxide probes. At the beginning of each measurement, the trailer was allowed to achieve target speed and remain at that speed for two to three minutes to allow air flow patterns to develop. To promote dispersion and mixing within the trailer, carbon dioxide was injected throughout this period. Concentrations above 5000 ppm (the suggested human exposure limit), were avoided. Upon reaching the calibration level of the sensors, injection was stopped and the concentration was allowed to decay to equilibrium while the vehicle maintained a constant speed.
The Results of the Study
There was no valid data collection at the lowest speed that simulated town driving when horses were in the trailer. The sensors exceeded calibration limits with the injection of carbon dioxide, exhalations of the horses and low rates of air exchanged combined at this speed.
There was more air exchange due to increasing speed. Also, enhancement air exchange occurred when all windows and vents were open. Air exchange varied by location when horses were in the trailer. The lowest exchange rates were in the stall nearest to the front of the trailer.
The average air exchange rates were only about half the recommendations for stabled horses, even at the highest speed with all windows and vents open. While the outside temperature was never over 82°F during the study, heat stress conditions (air temperature exceeding 86°F) were inside the trailer during observation. Horses in the stall nearest the front of the trailer routinely showed more sweating than those in other locations.
What Can We Take from This Study?
The analysis of the data results shows the trailer in this study did not have proper ventilation.
Provide better air exchange and minimize heat stress of transported animals by:
- increasing window size
- opening upper rear doors
- removing upper rear doors
When comparing trailer models prior to purchase, an important aspect to look for maximum ventilation. In this study, there was data collection for only two conditions, empty trailer or trailer holding four horses. Air exchange rate was lower in front stalls than in rear stalls when transporting four horses. One way to possibly avoid overheating of multiple horses during transport is by placing the smallest or leanest horse in the first stall.
While it’s safe to assume that increased air exchange minimizes the buildup of dust and mold spores in trailer air, drafts due to increased speed can still blow particles of dust, hay and straw through the trailer. Placing fly masks on animals can help keep the dust and airborne materials from causing eye injuries.
Make sure to keep your animals from overheating through ventilation systems for livestock trailers. Contact Gooseneck Trailers with the link below for more information on our ventilation systems for livestock trailers!