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Improving Air Quality and Effective Cowside Velocity (ECV) inside Modern Dairy Facilities

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  10th International Livestock Environment Symposium (ILES X)  .(doi:10.13031/iles.18-063)
Authors:   Michael J Wolf, John McBride
Keywords:   Air quality, effective cowside velocity (ECV), heat stress, cooling

Abstract. The dairy industry‘s barn designs have improved significantly over the past few decades, especially in temperate zones but also in tropical and desert environments. Also, the modern dairy cow has a greater genetic potential to produce milk more efficiently in terms of the amount of feed and forage dry matter required and the amount of manure excreted per kilo of milk produced. However, these efficiencies require a more precise management of a cow‘s environment in order to help her remain in her thermoneutral zone (TNZ), and as a result, housing and manure-management costs per animal have increased. Guarding the modern dairy cow‘s health also requires more aggressive ventilation strategies aimed at maintaining healthy air quality and exchange rates inside the dairy barn. For this reason, tunnel and cross-ventilation barn designs, given their ventilation advantages, have become the more common choices, as have negative pressure systems coupled with adequate curtain inlets and exhaust fans. The baffles used in these systems reduce the size of the barn‘s cross-sectional areas, thereby increasing airflow at the animal level. Agricultural engineers typically refer to an adequate flow, which can be defined as the Effective Cowside Velocity (ECV), and if baffles are used to direct airflow downward, achieving ECV depends largely on their placement and orientation above the freestalls. As an alternative, recirculation fans, properly installed, will serve as powered baffles. These fans create additional ECV and also direct air towards the barn‘s exhaust fans to reduce the static pressure imposed on the recirculation fans. Such measures have improved air quality while maintaining ECV more effectively than can barns equipped only with static baffles, between which foul air can become trapped. The incorporation of louvered recirculation fans has further improved ECV delivery (to more than 450 fpm) over a greater square footage and at the level where the cows reside. Cooling systems, combined with systems designed to improve ECV, can also include soakers at the feed rails and in the holding pens, and low-pressure misters/high pressure foggers and evaporative cooling systems. All these components require controls that can efficiently manage the environment and also manage electrical energy and water use economically.

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