Effects of Structural and Stacking Configuration of Containers for Transporting Chicks in their Microenvironment

摘要

Breeder (layer) chicks in transit are vulnerable to oxygen shortages that stem from the lack of mechanical ventilation in holding areas such as warehouse and cargo compartments of aircraft. Such vulnerable periods tend to occur around departure time of an aircraft when the cargo door is closed but the compartment has not been pressurized, and vice versa upon landing. To maintain the well-being of the chicks, sufficient air exchange through the containers is essential during these periods. This study examined the air flow rates and internal thermal conditions of a commercial chick container as influenced by its structural and stacking configurations. Specifically, a 2×2 factorial arrangement of container structures was examined that consisted of a regular cardboard box (62 × 47 × 15 cm) and a box modified by adding extra vent holes (128 vs 92) on the side walls; each type of box was covered with either the regular cardboard lid or a modified plastic poultry grid lid. The effects on air flow rate of vertical distances (VD) from 2.5 cm (currently used) to 17.8 cm between the boxes were evaluated with one stack of four containers. The effects on air flow rate of horizontal distances (HD) from 5.1 to 15.2 cm between the stacks were evaluated with four stacks of six containers each. NI/CR electrical heating wires evenly located above the excelsior bedding were used to simulate sensible heat production rate (21 W at 30°C) of 88 unfed day-old chicks that are normally held per container.The results revealed that the measured ventilation rate under the current box structure and stacking arrangement (averaging 0.013 L/s/chick or 0.028 CFM/chick) seemed sufficient during cold weather but was considerably below values recommended for mild to hot weather. An improved, practical container structure and stacking configuration features the regular container body with the grid lid, 7.6 cm VD between boxes, 5.1 cm HD between stacks linked with the existing cardboard spacers. The improved structure and stacking configurations had an average air flow rate of 0.062 L/s/chick. The corresponding internal temperature rise of the containers relative to the test room temperature was 3.4, 4.7, 4.8, 5.0, 5.5, and 4.8 K for layer 1 (bottom layer), 2, 3, 4, 5 and 6 (top layer), respectively, compared to 5.5, 8.1, 9.1, 9.8, 9.9, 7.8 K for the current box structure and stacking arrangement. Because of the excessive air flow rate and potential cold draft for the top layer, the original cardboard lid was recommended for the top containers.