Assessing the combined effects of embryonic thermal conditioning and herbal feed additives on acquired thermotolerance of slow-growing poultry in a coastal climate

This study aimed to enhance thermotolerance in CARI-Debendra chickens under hot and humid climatic conditions by integrating embryonic thermal conditioning (ETC) and early post-hatch supplementation with natural herbal feed additives. About 224 chicks from the control and ETC groups were further divided into herbal-supplemented and nonsupplemented groups for 12 weeks using a 2 × 2 factorial design. Turmeric ( Curcuma longa ) and ginger ( Zingiber officinale ), screened using Fourier-transform infrared spectroscopy (FTIR) and gas chromatography–mass spectrometry (GC-MS), were added to the diet at a 1% inclusion level each. ETC group birds had higher body weight ( p < 0.01) but lower thigh % ( p < 0.05), spleen weight ( p < 0.05), and intestinal weight ( p < 0.01) than control birds. An interaction effect between ETC and posthatch herbal supplementation on body weight was observed only at the third and fifth weeks. The phytochemical profiling of turmeric ( Curcuma longa ) confirmed the presence of curcumin, 1-decanol, 2-hexyl- and 1-heptacosanol whereas ginger ( Zingiber officinale ) showed the presence of gingerols and shogaols, zingiberene, limonene, ethanone, 1-(2,2-dimethylcyclopentyl)-,1-but-2-enylpyrrolidine, N -butyric acid 2-ethylhexyl ester, which exhibit antioxidant and immunomodulatory activities and may serve as potential alternate candidates for further investigation to improve growth performance, egg quality, and economic efficiency in poultry. ETC had effects only on thigh weight, spleen weight, and intestinal weight without altering intestinal architecture compared with the control. Serum biochemical indicators, including thyroxine (T4) levels and creatine kinase activity, were elevated in the ETC + herbal supplementation group, while the heterophil-to-lymphocyte (H/L) ratio and triiodothyronine (T3) levels were lower, suggesting improved thermotolerance. In conclusion, the combination of ETC (39.5 °C and 60%–70% relative humidity for 5 h daily during embryonic days 11 to 16) and natural feed additives like turmeric and ginger improved heat resilience, immune competence, and productivity of CARI-Debendra poultry under tropical conditions.