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Title: ENDOCRINE AND THERMOREGULATORY RESPONSES TO ACUTE THERMAL EXPOSURES IN SIX-MONTH OLD PIGS REARED IN DIFFERENT NEONATAL ENVIRONMENTS

Author
item BECKER, BARBARA - SELF-EMPLOYED
item Klir, John
item Matteri, Robert
item SPIERS DONALD E - UNIVERSITY OF MISSOURI
item ELLERSIEK MARK - UNIVERSITY OF MISSOURI
item MISFELDT MICHAEL - UNIVERSITY OF MISSOURI

Submitted to: Journal of Thermal Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/23/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Our interest in this research was whether environmental conditions during the neonatal period (period right after birth in the pig) have long-lasting or even permanent effects on hormonal and thermoregulatory responses to acute thermal exposures. Pigs reared in a hot and cool environment during their first 28 days of life were exposed to acute heat and cold at 6 months sof age. The results indicate that hormonal and thermoregulatory responses to selected acute thermal exposures in 6-month-old pigs were not affected by prior thermal environment in which the pigs were reared during the neonatal period. However, neonatal thermal environment did influence the magnitude of the adult day-night cycle in body temperature. This information contributes to our understanding of the complex biological processes involved with environmental stress and well-being. The results are of interest to scientists studying environmental stress and body temperature control and provides useful information pertinent to environmental management and housing design for neonatal pigs.

Technical Abstract: Numerous reports demonstrate that exposure to physiological and behavioral stressors during the neonatal period permanently alters adult response to those stressors. However, there is no information whether exposure to different ambient temperatures during the neonatal period results in long-term alterations of endocrine and thermoregulatory responses to acute thermal exposures. Pigs were reared in either a cycling upper (27-32 deg C) or lower (21 deg C) thermal environment for the first 28 d of life. At 6 mo of age, endocrine and thermoregulatory responses to acute heat (34 deg C) and cold (10 deg C) exposures were determined. Neonatal thermal environment did not influence any acute endocrine responses. Cortisol increased during both acute thermal exposures (P=0.0001) although the response was greater in heat (P=0.003). Prolactin increased during acute heat (P=0.004). Growth hormone increased during acute cold (P=0.001). There was a strong tendency for increased epinephrine during both acute exposures (P=0.06). No significant effects of either exposure were found on norepinephrine (P=0.9) or triiodothyronine (P=0.11). Neonatal environment did not affect daily core body temperature (Tc) before acute exposures, but did alter amplitude of the 24-h Tc cycle. The amplitude was significantly greater in animals reared in the lower thermal environment (P<0.001). Acute heat exposure resulted in increases in Tc (P<0.001) and heat production (P<0.01). Neonatal thermal environment had no significant effect on Tc and heat production responses to acute thermal exposures. Although early neonatal thermal environment has no long-lasting effects on endocrine and thermoregulatory responses to acute thermal exposure, it does have prolonged effects on the amplitude of the 24-h Tc cycle.