Effect of low incubation temperature and low ambient temperature until 21 days of age on performance and body temperature in fast-growing chickens

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English. Thermal manipulation during embryogenesis was previously reported to decrease the occurrence of ascites and to potentially improve cold tolerance of broilers. The objective of our study was to explore the effects of the interaction of cold incubation temperatures and cool ambient temperatures until 21 d of age on performance and body temperature. Ross 308 eggs were incubated either under control conditions I-0 (37.6A degrees C) or with cyclic cold stimulations I-1 (6 h/d at 36.6A degrees C from d 10 to 18 of incubation) or with 2 cold stimulations I-2 (30 min at 15A degrees C) at d 18 and 19 of incubation. These treatments were followed by individual rearing and postnatal exposure to either standard rearing temperature T-0 (from 33A degrees C at hatching to 21A degrees C at d 21) or continuously lower temperature T-2 (from 28A degrees C at hatching to 21A degrees C at d 21) or exposure to cyclically lower temperature T-1 (with circadian temperature oscillations). Treatments I-1 and I-2 did not significantly alter hatchability compared to control incubation (with 94.8, 95.1, and 92.3%, respectively), or hatching BW and overall chick quality. Hatching body temperature (Tb) was 0.5 and 0.3A degrees C higher in I-1 than in I-0 and I-2 groups, respectively (P = 0.007). A doubled occurrence of health problems was observed with T-2 condition, regardless of incubation or sex. At d 3, BW was 2% lower with treatment I-1 than with I-0 and I-2 and was 3% higher in T-1 and T-2 groups than in T-0, but these effects disappeared with age. Group T-2 presented a 5% higher feed intake than the control group T-0 between 3 and 21 d of age (P = 0.025). Feed conversion ratio (FCR) was affected by experimental conditions (P < 0.001), with low FCR values obtained with I-2 incubation in control or cyclically cold postnatal conditions. Maximal FCR values were observed in the continuously cold postnatal conditions, in males submitted to control incubation and in females submitted to I-1 incubation, revealing sex-dependent effects of the treatments on performance.