Production performance and temperature-humidity index of broilers reared in naturally ventilated houses in Botswana

Abstract

Production performance of straight-run Cobb 500 broilers under commercial management practices was investigated and their temperature humidity index developed. Birds were raised in three non-insulated naturally ventilated houses over a 6-week period. One trial was undertaken in winter and the other in summer. The environmental parameters measured were indoor and outdoor air temperature and relative humidity. Production responses measured were specific feed intake, average body mass and mortality while those derived were body mass gain and feed conversion. Due to lack of environmental control, the broiler house temperatures fell outside the thermoneutral temperature zone of the birds for a significant period which negatively affected their welfare and production performance. The mean specific feed intake ranged from 152 to 279 g feed/kg body mass while mean feed conversion ranged from 1.82 to 3.29 kg feed/kg body mass gain. The live weight of the birds at six weeks of age ranged from 1.8 to 2.3 kg while mortality ranged from 3.8 to 9.3%. Temperature humidity index developed at 3 to 4 and 5 to 6 weeks of age was THb-uk = 0.62Tdb + 0.38TWb or THls^uk = 0.7ITjb + 0.29Tub- This index can now be represented graphically and farmers can use it as a handy look-up management chart that guides them on proper strategies to employ to relieve the birds of heat stress.