The effect of duration of thermal manipulation during broiler chick embryogenesis on body weight and body temperature of post-hatched chicks

摘要

The significant developments in the genetic selection of fast-growing meat-type broiler chickens, coupled with insufficient development of theii visceral systems, have enhanced the interest for thermal manipulations (TM) during susceptible periods ofbroiler embryogenesis, in order to improve thermotolerance acquisition. The duration of TM may affect both body weight (BW) and body temperature (T_b) of the chicks. This study was aimed at elucidating the effect of different duration periods of TM during broiler embryogenesis on the hatching rate, BW and T_b at hatch and following thermal challenge (41 °C for 6 hours) at the age of 3 days (Challenged C or Naive N, i.e. non-challenged chicks) Control embryos were incubated at 37.8 °C, whereas the TM-embryos were treated for 3 (D1), 6 (D2), 12 (D3) or 24 (D4) hours per day at 39.5 °C during late embryogenesis from E16 to E18. Different durations of TM did not affect BW of the hatched chicks, but significantly affected hatchability, which was higher in the D3 and D4 treatments compared to the D1 treatment. It further affected the T_b of the treated chicks, which was significantly lower in all treatments than in the controls. During the challenge (C), all 4 treatments (D1C to D4C) exhibited a significantly lower T_b compared to the controls. Eighteen hours post-challenge, D1C chicks maintained significantly lower T_b than D2C, D3C and D4C chicks. The BW of the naive chicks continued to be similar, whereas that of the challenged ones demonstrated a significantly higher value for D2C and D.3C chicks compared to the Controls and D1C's. It can be concluded that out of the four TM durations, the best one to initiate improvement of thermo tolerance acquisition requires 3 hours of TM per day during E16 toE18, whereas 6 and 12 hours per day may be the best to reach higher hatchability and initiate growth. However, further research is required to follow both responses during the whoie life span of the chicks.