title: Performance of naked neck and normal broilers in hot, warm, and temperate climates.
abstract: Chickens suffer at high ambient temperatures because their feather coverage hinders internal heat dissipation. Naked neck broilers (Na/na) and their normally feathered sibs (na/na) were evaluated in three natural climates. Three experiments were conducted in Turkey, during the summer 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 averaged 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 was lower by about 20% in Na/na broilers than in na/na ones, independent of climate, sex, and age (6 or 7 wk). The Na/na broilers exhibited higher 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 reflected the differences in ambient temperature among climates. The effect 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 exhibited a highly significant advantage over their na/na counterparts. In the more moderate climate (Iz-Sm), the Na/na genotype exhibited superior 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 and BW7 (BW at 7 wk) means were similar for both genotypes. In Iz-Sp, feed efficiency (FE) of the Na/na birds was lower by about 4%, but in the two summer climates (Iz-Sm and Ad-Sm), FE of the Na/na birds was about 9% higher than that of their na/na counterparts. Body temperature was lower in the Na/na broilers than in their na/na counterparts; in all cases, the difference increasing with ambient temperature. The results indicate that the reduction in feather coverage provided relative heat tolerance, and therefore, under hot climates the Na/na broiler were superior to their normally feathered counterparts. It is concluded that naked neck broilers should be preferred in hot climates.
authors.affiliation: Aegean University, Faculty of Agriculture, Izmir, Turkey.
authors.forename: S
authors.initials: S
authors.lastname: Yalçin
authors.forename: A
authors.initials: A
authors.lastname: Testik
authors.forename: S
authors.initials: S
authors.lastname: Ozkan
authors.forename: P
authors.initials: P
authors.lastname: Settar
authors.forename: F
authors.initials: F
authors.lastname: Celen
authors.forename: A
authors.initials: A
authors.lastname: Cahaner
mesh_terms: D000818:Animals; D001831:Body Temperature / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D002645:Chickens / Q000235:genetics* / Q000254:growth & development* / Q000502:physiology; D002980:Climate; D004435:Eating / Q000502:physiology; D005241:Feathers; D005260:Female; D005838:Genotype; D006579:Heterozygote; D008297:Male; D009333:Neck / Q000033:anatomy & histology*; D012621:Seasons; D013696:Temperature; D014421:Turkey; D015430:Weight Gain / Q000502:physiology