In utero heat stress alters postnatal phenotypes in swine

Authors: Johnson, Jay; STEWART, KARA - Purdue University; SAFRANSKI, TIM - University Of Missouri; ROSS, JASON - Iowa State University; BAUMGARD, LANCE - Iowa State University

Submitted to: Theriogenology
Publication Type: Review Article
Publication Acceptance Date: 5/10/2020
Publication Date: 5/18/2020
Citation: Johnson, J.S., Stewart, K.R., Safranski, T.J., Ross, J.W., Baumgard, L.H. 2020. In utero heat stress alters postnatal phenotypes in swine. Theriogenology. https://doi.org/10.1016/j.theriogenology.2020.05.013.
DOI: https://doi.org/10.1016/j.theriogenology.2020.05.013

Interpretive Summary: In utero HS threatens the sustainability of animal agriculture and puts the health and welfare of pigs at risk. Although the immediate impacts of in utero heat stress on sow and piglet performance at farrowing and lactation are readily apparent, the long-term negative impacts on postnatal development have only recently been elucidated. Evidence supports that the programmed phenotypes produced by in utero heat stress are contradictory to positive swine performance, health and welfare outcomes. Therefore, appropriate steps should be taken to prevent HS from occurring in gestating sows. Several technologies or management practices may be available to producers including the use of evaporative cooling pads, increasing air speed through the facility, direct cooling by use of sprinklers and fans, or recently developed cooling pads that conduct heat away from sows. Alternatively, selecting for sows that are more heat stress resistant may reduce the likelihood of in utero heat stress induced carryover effects on their offspring. Regardless of the methodology, it is imperative that steps are taken to reduce the effects of in utero heat stress in swine to improve profitability and ensure positive welfare.

Technical Abstract: The prenatal environment influences offspring health and development during postnatal life. This is readily apparent when considering the well-described effects of maternal nutrition and stress on future offspring metabolism, neural function, and stress response. Moreover, in laboratory species, sheep, and humans, the effects of in utero heat stress on offspring development have been described in detail for >50 years. Despite our extensive knowledge of the postnatal phenotypes elicited by in utero stressors, the carryover effects of in utero heat stress in pigs have only recently been elucidated. Pigs exposed to in utero heat stress develop a variety of postnatal phenotypes that are counterintuitive to positive production, health, and welfare outcomes in commercial production systems. Specifically, in utero heat stress increases the postnatal stress response, core body temperature, teratogenicity, and the innate immune response to a lipopolysaccharide challenge in pigs. In addition, in utero heat stress alters postnatal body composition through reductions in lean tissue accretion and increased adipose accretion. Furthermore, in utero heat stress has been shown to reduce swine birth weight, measures of growth performance, and reproductive efficiency. Although the economic impact of in utero heat stress in pigs has yet to be determined it may be substantial and could threaten the sustainability of swine production worldwide.