PRODUCTIVE AND PHYSIOLOGICAL ADAPTIVE RESPONSES OF ETHIOPIAN NAKED-NECK CHICKENS AND THEIR F1 CROSSES WITH COMMERCIAL CHICKEN BREEDS TO HIGH ENVIRONMENTAL TEMPERATURE

  • Aberra Melesse Hawassa University
  • S. Maak Leibniz Institute for Farm Animal Biology
  • G. von Lengerken Martin-Luther University Halle-Wittenberg
Keywords: 3, 5, 3-triiodothyronine, corticosterone, F1 crosses, heat stress, Naked-neck chicken

Abstract

The objective of this study was to evaluate the effects of the interaction between chicken genotypes (Naked-neck, Na, from Ethiopia; New Hampshire, NH; Lohmann White, LW; and F1 crosses of Na males with females of NH [Na´NH] and LW [Na´LW]) and ambient temperatures (normal and high) on physiological indicators and performance traits. Two-hundred forty female chickens were assigned to a completely randomized design of 2 × 5 factorial arrangements (2 temperatures and 5 genotypes). Eggs were collected daily while feed intake was determined at 28-d intervals and egg shell thickness at 4 age points. Corticosterone (CS) and 3,5,3¢-triiodothyronine (T3) levels were determined from 480 blood samples taken at 4 age points. Commercial hens reared at high temperature showed significant (p<0.05) performance reductions in egg production (33%), feed intake (15%) and shell thickness (24.3%). The effect of heat stress on T3 levels was significant (p<0.001) and consistent across heat-stressed genotypes resulting in an overall reduction of 29% compared with those reared at normal temperature. Moreover, significant (p<0.05) differences in plasma T3 levels were observed between heat-stressed genotypes. Although the CS levels uniformly increased due to heat stress, the response of genotypes with advancing age was inconsistent. In conclusion, the Na´LW crosses at high temperature outperformed other genotypes and thus, appeared to be suitable genetic combinations. The Na chickens and their F1 crosses demonstrated reduced thyroid gland activity suggesting improved thermo-tolerance to long-term heat-exposure. The present findings suggest that levels of T3 hormone might be considered as reliable indicator of long-term heat stress in chickens.
Published
2013-04-13
Section
Research articles

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eISSN: 2520–7997
print ISSN: 0379-2897