by ANDREW BOURNE, broiler specialist – World Technical Support, Cobb-Vantress This is the 3rd of our five essentials series of articles. All five brooding essentials are equally weighted in their importance. Fresh air – Ventilation and air quality are the most common challenges facing the broiler grower in both conventional and closed environment housing. The best return on capital investment a grower can make is in the minimum ventilation system which is responsible for both meeting the oxygen demand of the modern broiler chick and removing excess moisture. Adequate oxygen supply during early growth will ensure healthy cardiovascular development, particularly in winter conditions, preventing problems such as ascites. The minimum ventilation system should have a fan capacity equal to at least 12.5 percent of the house volume. Air should enter the house at a pressure drop and velocity to ensure it reaches halfway across the ceiling before falling. Inlets should always have a minimum opening of at least 2 – 3cm and incoming air should be drawn along a smooth surface to ensure good airflow. Adjustments to the inlet area, along with the required corresponding air speed and pressure drop, will ensure good air fl ow and the all-important moisture removal. Minimum ventilation is always easiest to manage when operating on a five-minute cycle timer with a minimum run time of one minute, ensuring cold incoming air has enough time to be adequately mixed and heated with warm air in the ceiling before reaching chick level. The following table can be used as a reference guide for different widths of poultry houses in determining the required inlet air speed, pressure difference and inlet area. The inlet area is always dependent the operating fan capacity. The importance of the inlet system is often overlooked. Without an efficient, well-designed inlet it is difficult to manage air fl ow, especially in very cold climates. Installing a cross flow minimum ventilation system, even in tropical countries, will ensure minimal airspeed at chick level. Early feed intake is easily compromised by using the tunnel inlet during minimum ventilation. When considering the design of any new housing or when upgrading current facilities, one of the most important uses of capital lies in the choice of inlet and minimum ventilation design. Careful consideration of the five essentials driving early feed consumption and growth will ensure the grower benefits fully from the least cost advantage provided by the Cobb500.