DANA O. PORTER
Environmental Control Considerations for Baby Chicks
Proper ventilation rates and thermal conditions are critical issues in shipping breeder chicks. Compared to chicks in production facilities, chicks in transit are often subjected to suboptimal environmental conditions, water deprivation, and nutritional deficiency. Information about response of the chicks to environmental conditions can aid in improved design and operation of ventilation and environmental control systems during transport.
Hongwei Xin and Jay Harmon of the Department of Agricultural and Biosystems Engineering at Iowa State University studied moisture production, sensible heat production, total heat production, respiratory quotient, and body mass loss of breeder chicks during a 50-hour posthatch holding period. According to the authors, thermal neutrality (no body heating or cooling and no change in evaporative heat loss) for the unfed, group-housed neonatal chicks was between 30o C (86o F ) and 32o C (90 oF). At thermal neutrality, the metabolic rate of fasting chicks was 77 kcal.day-1/kg0.75.
Xin, H. and J.D. Harmon. 1996. Responses of group-housed neonatal chicks to posthatch holding environment. Transactions of the ASAE 36(6):2249-2254.
Heat and Moisture Production of Broilers
Substantial differences have been observed in heat and moisture production by broilers during light and dark periods. According to Hongwei Xin, et al. of Iowa State University, moisture production, sensible heat production, and total heat production by broilers during dark periods were approximately 74%-76% of the values during light periods. During eight-hour lighting periods, 3 kg broilers under conditions of 24o C (75o F) and 52% relative humidity produced 6.1 g H2O/(kg-h) moisture, 4.3 W/kg sensible heat, and 8.4 W/kg total heat. During four-hour dark periods, moisture production, sensible heat production, and total heat production were 4.7 g H2O/(kg-h), 3.1 W/kg, and 6.3 W/kg, respectively. Lower dark period heat and moisture production levels previously were noted with layers and pullets.
According to the authors and other cited studies, design heat and moisture production values commonly used were developed for housing the broilers under continuous lighting conditions. Intermittent lighting has become more commonly practiced because of improved feed conversion and reduced growth abnormalities. Light-dependent responses in heat and moisture production should be taken into consideration in the design of environmental control systems.
Xin, H., J.L. Sell, and D.U. Ahn. 1996. Effects of light and darkness on heat and moisture production of broilers. Transactions of the ASAE 36(6):2255-2258.