Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/2000
Publication Date: N/A
Citation: Interpretive Summary: Economic losses each year in the swine industry resulting from neonatal morbidity and mortality are substantial. While these losses cannot be attributed to any one factor, losses associated with chilling and infectious diseases are recognized as major contributing factors. Currently there is limited information regarding the impact of environmental temperature on the baby pig's ability to cope with an infectious challenge The objective of this study was to determine what role environmental temperature may play in a neonatal pig's immune and stress responses to an immune challenge. In this study, we found that environmental temperature plays a critical role in the baby pig's ability to cope with an infectious insult. Results indicate that when combined, but not singly, cold stress and exposure to an infectious challenge induces a rapid and potentially fatal loss of body temperature in the baby pig. This information will be of finterest to scientists in academia, industry and government who are evaluating the effects of environmental inputs on neonatal pig survival. Additionally, this information may aid swine producers in evaluating the adequacy of their farrowing facilities.
Technical Abstract: This study evaluated interactions between environmental temperature (ET) and the neonatal pig's ability to cope with an endotoxin challenge. Male pigs (n=28; 24 h old) were placed in environmentally controlled chambers kept at 18 deg C or 34 deg C (n=14/ET). Rectal temperatures (RT) were recorded every 15 min for 3 h after an intraperitoneal injection of saline (Cont; n=7/ET) or lipopolysaccharide (LPS; 150 ug/kg; n=7/ET). Pigs were then sacrificed for tissue and blood collection. LPS pigs kept at 18 deg C experienced a period of hypothermia while RT for LPS pigs at 34 deg C did not differ from their respective Cont (P<.0001). LPS pigs kept at 18 deg C lost the most body weight during the 3 h (P<.015). LPS pigs kept at 18 deg C had a greater increase in serum cortisol as compared to LPS pigs at 34 deg C (P<.025). LPS increased serum tumor-necrosis factor alpha (TNF-alpha) in pigs at 18 deg C, but had no effect on serum TNF-alpha in pigs at 34 deg gC (P<.014). Serum prolactin (PRL) was reduced (P<.012) in pigs at 18 deg C as compared to pigs at 34 deg C. LPS increased serum PRL at 18 deg C but had no effect on serum PRL at 34 deg C (P<.05). LPS increased CRH mRNA expression (P<.04) in all pigs, and pigs exposed to 18 deg C expressed less ACTH receptor mRNA (P=.015). The LPS-induced increase in POMC mRNA expression tended (P<.08) to be greater in pigs kept at 18 deg C. These results suggest that ET can greatly influence a neonatal pig's ability to cope with an endotoxin challenge.