Assessment of Broiler Surface Temperature Variation When Exposed to Different Air Temperatures

This study was conducted to determine the effect of the air temperature variation on the mean surface temperature (MST) of 7to 35-day-old broiler chickens using infrared thermometry to estimate MST, and to study surface temperature variation of the wings, head, legs, back and comb as affected by air temperature and broiler age. One hundred Cobb broilers were used in the experiment. Starting on day 7, 10 birds were weekly selected at random, housed in an environmental chamber and reared under three distinct temperatures (18, 25 and 32 oC) to record their thermal profile using an infrared thermal camera. The recorded images were processed to estimate MST by selecting the whole area of the bird within the picture and comparing it with the values obtained using selected equations in literature, and to record the surface temperatures of the body parts. The MST estimated by infrared images were not statistically different (p > 0.05) from the values obtained by the equations. MST values significantly increased (p < 0.05) when the air temperature increased, but were not affected by bird age. However, age influenced the difference between MST and air temperature, which was highest on day 14. The technique of infrared thermal image analysis was useful to estimate the mean surface temperature of broiler chickens. INTRODUCTION Broiler production in tropical countries like Brazil faces the challenge of controlling heat stress, especially during the warmer periods of the year. Live performance is impaired when birds are reared at temperatures above their comfort zone due to reduced feed intake because dietary energy is used to maintain constant body temperature, instead of converting feed into meat (Fukayama et al., 2005; Laganá et al., 2007). Zhou & Yamamoto (1997) found that broiler body temperature increased three degrees Celsius (41 44 oC), and skin temperature increased 6 °C (37-43 oC) when exposed to heat stress (36 °C) for three hours. Increasing sensible heat loss may promote heat tolerance in broilers, and this seems to be more beneficial than heat loss by evaporation, which may lead to dehydration. The difference between surface temperature and ambient temperature is the main parameter to determine sensible heat loss (Yahav et al., 2008). Different body parts present different heat during the rearing period, and this is related to environmental air temperature and birds’ feathering index (Nääs et al., 2010). Infrared cameras measure the amount of invisible heat energy emitted by surfaces and convert them into surface temperature, producing thermal images. These measuring instruments have been used to estimate the surface temperature of broiler chickens in studies Assessment of Broiler Surface Temperature Variation When Exposed to Different Air Temperatures nAuthor(s) Nascimento GR Nääs IA Pereira DF Baracho MS Garcia R 1 School of Agriculture Engineering FEAGRI/ UNICAMP. Campinas, SP, Brazil. 2 UNESP. Tupã, SP, Brazil. 3 FCA/UFGD. nMail Adress GR Nascimento FEAGRI/UNICAMP. Campinas, SP, Brazil. E-mail: [email protected] n