Gestational heat stress alters postnatal thermoregulation

Study characterized postnatal thermoregulation indices in pigs from differing in-utero thermal environments.

Gestational heat stress (GHS) is an insult that negatively affects development in a variety of species, but how it alters postnatal thermoregulation in offspring is not well-understood, according to J.S. Johnson, M.V. Sanz-Fernandez, S.K. Stoakes, M. Abuajamieh, J.W. Ross and L.H. Baumgard of Iowa State Univeristy, M.C. Lucy and T.J. Safranski of the University of Missouri and R.P. Rhoads of Virginia Tech in a presentation at JAM2013. 

Johnson et al. conducted a study to characterize postnatal thermoregulation indices in pigs from differing in-utero thermal environments. They exposed 13 first-parity gilts to one of four ambient temperature treatments -- heat stress or thermoneutral, applied for the entire gestation, the frst half or second half. Of the resultant offspring, 24 barrows were housed in Zumwalt climactic chambers in thermoneutral (21.7°C) conditions and then exposed to two separate but identical heat stress periods of six days during which the temperature was cycled diurnally between 28 and 36°C.

According to Johnson et al., in thermoneutal conditions, all GHS pigs had elevated (P < 0.01; 0.35°C) core temperatures compared with pigs that did not experience GHS. There was also no statistical differences in the methods of heat mitigation among pigs and no gestational differences were detected for either average daily gain or feed intake.

Johnson et al. concluded that GHS pigs (especially if the stress occurred during the frst half of gestation) had increased core body temperatures compared with controls, and the magnitude of difference was maintained in subsequent thermoneutral and heat stress conditions. This suggests that in-utero HS increases (0.33°C) the thermoregulatory set-point, but how this infuences whole body bioenergetics remains unknown, they said.


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