The Cost of Rising Temperatures

Seasonal warm temperatures are upon us, and for swine production that means managing heat stress is at the top of the list of daily challenges. Heat stress is a predictable and recurring issue within animal agriculture, yet it continues to have lasting impacts on animal performance. The economic toll is significant, with losses attributed to heat stress costing producers over $520 million annually (Johnson and Stewart, 2025). Perhaps one of the most detrimental aspects of heat stress in the swine industry is the decline of sow reproductive performance. When temperatures rise, sows struggle to regulate their body temperature, particularly during periods of high metabolic demand like late gestation and lactation. Reproductive implications can include factors such as smaller litter sizes, extended wean-to-estrus intervals, increased early embryonic mortality, and poor piglet viability. While heat stress is the proximate cause, understanding what this implies at the underlying cellular level is essential for employing effective mitigation strategies.

Heat Stress to Oxidative Stress: The Reproductive Consequences

During periods of stress, nutrients and energy are directed towards survival, with other processes like reproduction taking less priority. There are a variety of environmental stressors that can shift energy towards preserving the sow herself rather than supporting reproductive function. Heat stress is a common concern in swine production, and it occurs when environmental temperatures exceed the upper limits of the thermoneutral zone, causing internal body heat to surpass the animal’s capacity for heat dissipation. Upper thresholds for heat tolerance in swine differ based on factors such as age, stage of production, and weight, with gestating and lactating sows having lower thermal thresholds due to increased heat production during those stages (National Research Council, 2012).

Heat stress has been documented to increase embryo mortality and impair oocyte maturation in sows (Tompkins et al., 1967; Omtvedt et al., 1971; Lee et al., 2021; Liu et al., 2022), which has an effect on litter size and farrowing rates. To offset rising body temperatures, the metabolic pathways that produce energy alter in a manner to reduce heat generated per unit of ATP, but in doing so this results in the overproduction of reactive oxygen species (ROS), and in effect oxidative damage. Developing oocytes and embryos are particularly vulnerable to oxidative damage because of their antioxidant defense systems are relatively immature (Dennery, 2007). The mammalian embryo relies primarily on oxidative phosphorylation for energy production during the early stages of development, a process that already generates ROS under normal conditions. However, under additional thermal stress, ROS production rates increase and accumulate, compromising embryonic competency, pregnancy establishment, and pregnancy retention.

The impact of heat stress is not limited to only these effects. Suppression of feed intake is also a common observation of heat-stressed sows during gestation and lactation (Prunier et al., 1997; Renaudeau et al., 2012). It was noted by Bjerg et al (2020) that during lactation, for every 1 °C increase above 25 °C, sow feed intake was reduced by 270 g/day and milk production was decreased by 184 g/day. Consequently, sows resulted in poor body condition coming out of lactation, with a 1.5 kg loss in body weight. In addition to impacts on body condition and milk production, reductions in feed intake decrease the consumption of dietary antioxidants, widening the gap between oxidative load and the sow’s capacity to manage it. Each of these factors creates a compounding cycle with significant consequences for the productivity of both sows and their piglets.

Targeting Heat-Induced Oxidative Stress Through Nutrition

Managing heat stress requires a multi-layered approach, addressed at both the environmental and nutritional levels. Of course, environmental management – proper ventilation, cooling techniques, and consistent fresh water supply – is a main priority for managing thermal challenges. However, nutrition can also be an effective and targeted approach at the cellular level, mitigating potential damage that can occur within the animal due to heat-induced oxidative stress.

Traditionally, dietary antioxidants like vitamins E and C are the primary tools for defense against oxidative stress. However, global vitamin E prices are historically volatile and expensive to maintain at commercially preferred levels in swine diets. Polyphenols can potentially offer a cost-effective complement to synthetic antioxidants such as vitamin E, working across both water- and lipid-based environments and supporting the body’s own antioxidant systems. Elife®, a synergistic blend of carefully selected polyphenols, is designed to support the animal’s response to oxidative stress through several mechanisms. This includes upregulation of endogenous antioxidant enzymes, sparing of vitamin E, and neutralization of ROS. This activity may be especially valuable in heat-stressed sows with suppressed feed intake, where every pound of feed consumed is crucial.

Data from an internal mechanistic study observing the effect of Elife® on oxidative markers suggests the potential benefits for use of polyphenols in swine production. Serum biomarkers indicating oxidative status for sows receiving Elife® were improved in late gestation and lactation, characterized by significant increases in glutathione peroxidase and superoxide dismutase as well as a reduction in malondialdehyde concentrations.

In a separate study, litters from Elife® supplemented sows had a greater number of piglets born alive (+0.75 piglets / litter) and piglet pre-weaning performance showed a 2.6% increase in average litter weight gain. Additionally, time intervals between weaning and successful mating for Elife® sows were reduced by 2.7 days compared to controls, as well as a 4-day reduction from weaning to subsequent farrowing. Altogether, these outcomes reflect improved oxidative status in sows and additional benefits in piglet performance during critical production windows.

Heat stress is a common issue with complex implications, and its relationship to oxidative stress is easy to overlook. Yet the cellular consequences – lipid peroxidation, mitochondrial dysfunction, and suppressed antioxidant defenses – can be a silent driver of reproductive loss. The unique properties of polyphenols allow them to directly counteract these disruptions through targeted support of metabolic pathways and antioxidant functionalities. Together with environmental management, nutritional support through a blend of polyphenols such as Elife® represents a practical, cost-effective step towards mitigating oxidative challenges associated with heat stress.

To learn more about Elife® and how it can support your sow’s antioxidant defenses, contact your Feedworks USA representative or reach out to us directly.

References

Bjerg, B., P. Brandt, P. Pedersen, and G. Zhang. 2020. Sows’ responses to increased heat load – A review. Journal of Thermal Biology. 94:102758. doi:10.1016/j.jtherbio.2020.102758.

Dennery, P. A. 2007. Effects of oxidative stress on embryonic development. Birth Defects Research Part C: Embryo Today: Reviews. 81:155–162. doi:10.1002/bdrc.20098.

Johnson, J. S., and K. R. Stewart. 2025. Heat stress matters: insights from United States swine producers. Trans Anim Sci. 9:txaf001. doi:10.1093/tas/txaf001.

Lee, S., H.-G. Kang, P.-S. Jeong, M. J. Kim, S.-H. Park, B.-S. Song, B.-W. Sim, and S.-U. Kim. 2021. Heat stress impairs oocyte maturation through ceramide-mediated apoptosis in pigs. Science of The Total Environment. 755:144144. doi:10.1016/j.scitotenv.2020.144144.

Liu, F., W. Zhao, H. H. Le, J. J. Cottrell, M. P. Green, B. J. Leury, F. R. Dunshea, and A. W. Bell. 2022. Review: What have we learned about the effects of heat stress on the pig industry? animal. 16:100349. doi:10.1016/j.animal.2021.100349.

National Research Council. 2012. Nutrient Requirements of Swine: Eleventh Revised Edition. The National Academies Press, Washington, DC. Available from: https://nap.nationalacademies.org/catalog/13298/nutrient-requirements-of-swine-eleventh-revised-edition

Omtvedt, I. T., R. E. Nelson, R. L. Edwards, D. F. Stephens, and E. J. Turman. 1971. Influence of Heat Stress During Early, Mid and Late Pregnancy of Gilts. J Anim Sci. 32:312–317. doi:10.2527/jas1971.322312x.

Prunier, A., M. M. de Bragança, and J. Le Dividich. 1997. Influence of high ambient temperature on performance of reproductive sows. Livestock Production Science. 52:123–133. doi:10.1016/S0301-6226(97)00137-1.

Renaudeau, D., A. Collin, S. Yahav, V. de Basilio, J. L. Gourdine, and R. J. Collier. 2012. Adaptation to hot climate and strategies to alleviate heat stress in livestock production. Animal. 6:707–728. doi:10.1017/S1751731111002448.

Tompkins, E. C., C. J. Heidenreich, and M. Stob. 1967. Effect of Post-Breeding Thermal Stress on Embryonic Mortality in Swine. J Anim Sci. 26:377–380. doi:10.2527/jas1967.262377x.