|JOHNSON, JAY - Iowa State University|
|SANS-FERNANDEZ, VICTORIA - Iowa State University|
|SEIBERT, JACOB - Iowa State University|
|ROSS, JASON - Iowa State University|
|LUCY, MATTHEW - University Of Missouri|
|SAFRANSKI, TIM - University Of Missouri|
|Kahl, Stanislaw - Stass|
|RHOADS, ROBERT - Virginia Tech|
|BAUMGARD, LANCE - Iowa State University|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/10/2015
Publication Date: 9/8/2015
Citation: Johnson, J.S., Sans-Fernandez, V.M., Seibert, J.T., Ross, J.W., Lucy, M.C., Safranski, T.J., Elsasser, T.H., Kahl, S., Rhoads, R.P., Baumgard, L. 2015. In utero heat stress increases postnatal core body temperature in pigs. Journal of Animal Science. 93:4312-4322.
Interpretive Summary: In various regions of the country, environmental heat stress challenges swine producers to achieve high levels of production efficiency in regards to the growth of piglets born from sows that were heat stressed. The experiments conducted here provide new information on important observations and health regulating mechanisms in the piglets that could be built into management practices that reduce the impact of heat stress. The application of an environmental heat challenge, consistent with daily temperature changes capable of occurring in the southeastern U.S., caused not only an increase in the core temperature of the piglets in utero, but also a maintained elevated core temperature after birth where the piglets were further reared in ambient conditions of no heat stress. Hormone data reflecting changes in the important heat regulating aspects of the thyroid axis suggest that readjustments in the ratios of thyroid hormones in blood participate in the levels of control needed to maintain a healthy body core temperature in the heat-stressed piglets. However, this added level of control may compromise the rates of body weight gain wanted by producers. These adjusted hormone levels when measured and their interactions with tissues would be consistent with a tendency to reduce the metabolism of growth in the heat-stressed piglets in a manner in which the body heat otherwise generated by metabolizing nutrients is decreased at the expense of body weight gain.
Technical Abstract: In utero heat stress (IUHS) negatively impacts postnatal development, but how it alters future body temperature parameters and energetic metabolism is not well-understood. Objectives were to characterize future temperature indices and bioenergetic markers in pigs originating from differing in utero thermal environments during both postnatal thermal neutral (TN) and cyclical heat stress (HS) exposure. First parity pregnant pigs (n = 13) were exposed to one of four ambient temperature (Ta) treatments [HS (cyclic 28 to 34°C) or TN (cyclic 18 to 22°C)], applied for the entire gestation (HSHS; TNTN), HS the first half (HSTN), or second half (TNHS) of gestation. Twenty-four offspring (30 ± 3 kg BW; n=6 HSHS, n=6 TNTN, n=6 HSTN, n=6 TNHS) were housed in TN (21.7 ± 0.7°C) conditions, and then exposed to two separate but similar HS periods (HS1 = 6 d; HS2 = 6 d; cycling 28 to 36°C). Core body temperature (Tcore) was assessed every 15 minutes using surgically implanted temperature recorders. Regardless of in utero treatment, Tcore increased during both HS periods (p < 0.01; 0.58°C). In TN, IUHS pigs had increased (p < 0.01; 0.36°C) Tcore compared to TNTN controls. During HS1 and HS2, IUHS pigs had increased Tcore (p < 0.04; 0.20 and 0.16°C, respectively) compared to TNTN controls. No in utero area under the Tcore response curve differences were detected within either HS1 or HS2 (p > 0.35). Although unaffected by in utero environment, the ratio of total plasma thyroxine to triiodothyronine was reduced (p < 0.01) during HS1 and HS2 (39 and 29%, respectively) compared to TN. In summary, pigs originating from IUHS maintained an increased body temperature compared to TNTN controls regardless of external ambient temperature, and this thermal differential may have practical implications in animal agriculture.