In utero heat stress increases postnatal core body temperature in pigs

Area of Science:

• Animal physiology
• Developmental biology
• Environmental stress physiology

Background:

• In utero heat stress (IUHS) is known to negatively affect postnatal development.
• The specific impacts of IUHS on future body temperature regulation and bioenergetic metabolism remain poorly understood.

Purpose of the Study:

• To characterize future body temperature indices and bioenergetic markers in pigs exposed to different in utero thermal environments.
• To investigate the effects of postnatal thermoneutral (TN) and cyclical heat stress (HS) on these parameters.

Main Methods:

• Pregnant gilts were exposed to four gestation temperature treatments: continuous HS, continuous TN, HS in the first half of gestation, or HS in the second half.
• Offspring were housed in TN conditions and then subjected to two periods of cyclical HS.
• Core body temperature was continuously monitored using implanted temperature recorders, and plasma thyroid hormone ratios were analyzed.

Main Results:

• Pigs exposed to IUHS maintained a higher core body temperature compared to controls, irrespective of postnatal thermal environment.
• Postnatal heat stress exposure increased body temperature in all groups.
• The ratio of thyroxine to triiodothyronine decreased during postnatal heat stress, indicating altered thyroid hormone metabolism.

Conclusions:

• In utero heat stress establishes a persistent elevation in body temperature in pigs, independent of external thermal conditions.
• These findings suggest that IUHS has lasting implications for thermoregulation and energetic metabolism, with potential consequences for animal development and bioenergetics.