Effect of misting on the performance of male broilers in an enclosed environment

S. Shanmugavelu, G. Burnett and W. Michie

Abstract

A study was done to evaluate the effect of evaporative cooling on the performance of Ross male broilers. The temperature in the treatment groups was fluctuated with time of day from 24 °C to 28 °C. Birds in one of the treatment groups were evaporatively cooled by misting. The control group was maintained at 21 °C. Two experiments (1 and 2) were conducted with two different sets of misting equipment. The first with a misting system available commercially, operating at 414 kPa to generate a coarse mist and the second custom designed with oil-jet nozzles operating at about 1 380 kPa that create a fine mist. The mean temperature drop achieved with misting was 1.3 °C and 1.6 °C while the relative humidity was 71% and 83% in experiment 1 and 2 respectively. There was no difference between the non-misted and misted groups at week 4 and 6 but both were significantly (p <0.05) heavier than the control group at 3 weeks of age. At 7 weeks, however all three groups were significantly different with the heaviest bird in the control group and the lightest bird in the non-misted group. A similar trend was observed with average daily gain, average daily feed intake and feed conversion ratio with the control ranking the highest and non-cooled the lowest. The mean water intake (both experiments) of the birds in the non-misted group was significantly (p <0.05) higher than the misted or the control, especially after 35 days of age. The pattern of water to feed intake ratio was similar to those of water intake. Despite a high relative humidity (71% and 83%) in the misted group, there was no increase in the ammonia level (≤5 ppm) or the degree of hock burn. The control group had a significantly (p <0.05) higher cumulative mortality rate (18.6%), compared to either the misted (12.9%) or the non-misted group (12.4%) at 49 days of age. The main cause of death was ascites, which is associated with increased growth rate. The dust levels were also reduced (53%) with misting.

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