Thermoregulation in newly hatched chicks.

Area of Science:

• Avian physiology and thermoregulation
• Poultry genetics and breeding

Background:

• Thermoregulation is critical for newly hatched chicks, influencing survival and growth.
• Body weight selection in chickens can impact physiological traits, including thermal regulation.

Purpose of the Study:

• To investigate thermoregulation in newly hatched chicks across different genetic lines.
• To analyze the effects of body weight selection and the sex-linked dwarf allele on chick thermoregulation.

Main Methods:

• Utilized seven early-feathering White Plymouth Rock chicken populations, including lines selected for high (HN) and low (LN) body weight, reciprocal crosses, F2 generation, and dwarf lines (HD, LD).
• Measured surface (foot pad) and core (rectal) temperatures, along with body weight, at multiple time points from 2 to 23 days of age, and at 105 days for HN and LN lines.
• Calculated surface-to-core temperature ratios to assess thermal regulation efficiency.

Main Results:

• Low-weight chicks (LN and LD) generally displayed lower surface temperatures from 11 to 23 days of age compared to other lines.
• LN chicks exhibited lower core temperatures through 23 days of age.
• Surface-to-core temperature ratios were lower in LD and LN chicks up to 23 days, but differences between HN and LN lines diminished by 105 days.

Conclusions:

• Body weight selection influences thermoregulation in young chicks, with low-weight lines showing distinct thermal profiles.
• The sex-linked dwarf allele did not significantly alter surface temperatures but showed a tendency to lower core temperatures in high-weight lines and increase them in low-weight lines.
• Thermoregulatory differences observed in young chicks between high and low body weight lines largely resolved by 105 days of age.