PERFORMANCE OF NAKED NECK AND NORMAL BROILERS IN HOT, WARM, AND TEMPERATE CLIMATES

Chickens suffer at high ambient temperatures because their feather cov erage hinders internal heat dissipation. Naked neck broilers (Na/na) a nd their normally feathered sibs (na/na) were evaluated in three natur al climates. Three experiments were conducted in Turkey, during the su mmer in the extremely hot region of Adana (Ad-Sm), and in the moderate region of Izmir during the spring (Iz-Sp) and summer (Iz-Sm), always following the same experimental protocol. Ambient temperatures average d 19, 28, and 32 C in Iz-Sp, Iz-Sm, and Ad-Sm, respectively. About 300 birds per genotype were included in each experiment. Feather weight w as lower by about 20% in Na/na broilers than in na/na ones, independen t of climate, sex, and age (6 or 7 wk). The Na/na broilers exhibited h igher breast weight in all cases, from 2.5 to 10.9% higher than their na/na counterparts. Body weight gain from 4 to 7 wk (BWG4-7) clearly r eflected the differences in ambient temperature among climates. The ef fect of the Na/na genotype on BWG4-7 interacted with climate and sex. In the hottest climate (Ad-Sm), both male and female Na/na broilers ex hibited a highly significant advantage over their na/na counterparts. In the more moderate climate (Iz-Sm), the Na/na genotype exhibited sup erior growth only among males, and the magnitude of this advantage was lower than in Ad-Sm. In the cool temperate climate (Iz-Sp), BWG4-7 an d BW7 (BW at 7 wk) means were similar for both genotypes. In Iz-Sp, fe ed efficiency (FE) of the Na/na birds was lower by about 4%, but in th e two summer climates (Iz-Sm and Ad-Sm), FE of the Na/na birds was abo ut 9% higher than that of their na/na counterparts. Body temperature w as lower in the Na/na broilers than in their na/na counterparts; in al l cases, the difference increasing with ambient temperature. The resul ts indicate that the reduction in feather coverage provided relative h eat tolerance, and therefore, under hot climates the Na/na broilers we re superior to their normally feathered counterparts. It is concluded that naked neck broilers should be preferred in hot climates.