Managing heat stress in swine and ruminants remains a growing concern as rising temperatures negatively affect growth, fertility and milk production. Recent trials highlight long-term impacts of prenatal stress and late-gestation heat exposure. While nutritional strategies show encouraging results, particularly in improving feed efficiency and resilience, further details remain to be explored in the full article.
By CCPA
May 2025 marked the second hottest May on record, underscoring the increasing technical and economic impact of global warming on our farms. Heat stress is not only a welfare concern in livestock farming; it is a significant problem affecting productivity and farm economics in both swine and ruminant operations. As temperatures rise, farmers face challenges ranging from reduced growth rates and fertility to compromised milk production and feed efficiency.
HEAT STRESS IN SWINE
Performance and reproductive impacts
According to a recent study by INRAE, exposing gestating sows to chronic thermal discomfort does not affect the number or weight of piglets at birth. However, it does alter the feeding behaviour of growing pigs, with negative effects on their performance and slaughter weight. This prenatal stress could reduce the number of muscle fibres at birth, thereby limiting the animals’ ability to put on muscle during fattening. Pigs from these sows show slower growth (-52 g/day), reduced feed intake (-93 g/day) and a slaughter weight that is 5 kg lower. Maintaining a suitable ambient temperature throughout gestation therefore appears essential to preserve the growth potential of the offspring.
Heat tolerance does not eliminate heat stress
Humans perceive heat less intensely than most animals, and in pigs, sensitivity to heat stress increases with body weight. A trial conducted by CCPA in Mexico on crossbreed combining prolificacy, rapid growth, hardiness and meat quality evaluated the effect of thermal comfort. The animals were raised either at ambient temperature or under thermoneutral conditions in refrigerated buildings. The results show that even in pigs genetically adapted to the local climate, improved thermal comfort reduces behavioural and physiological heat protection responses, optimises intestinal absorption surface area and results in better performance: increased feed intake and growth, as well as improved feed efficiency.
Sows in maternity units under heat stress all year round
Thermal stress in sows in maternity units is often associated solely with episodes of high summer heat. However, measurements taken by CCPA in recent buildings equipped with piglet nests show average temperatures at sow level of 23°C from March onwards in Brittany (strong contrast with the exterior for the period). Although this temperature may seem moderate, it creates chronic discomfort for sows, whose comfort zone is around 18 to 20°C during lactation. In the maternity unit, sows are subject to intense metabolic stress linked to milk production, which increases their sensitivity to heat.
It is therefore essential to consider this often invisible but permanent heat stress and to adopt appropriate strategies to maintain the comfort of sows and ensure their performance throughout the year.
HEAT STRESS IN RUMINANTS
In ruminants, the effects of heat stress are equally concerning. A growing body of evidence shows that elevated temperatures during critical physiological periods — particularly late gestation — can have lasting repercussions on both the dam and her offspring.
CCPA has developed a product called Thermoplus® specifically to support ruminants during periods of heat stress. A Thermoplus® trial published in the Journal of Dairy Science (Daddam, 2023) showed a significant reduction in the duration of body temperatures above 39°C, an improvement in biomarkers of cell protection and an improvement in milk production. A trial conducted in Mexico showed a better start to lactation (+10%) with distribution starting 24 days before calving, as well as improved fertility performance and animal comfort.
Don’t forget dry cows
At our last international ruminant symposium held last April in Paris, Professor Jimena Laporta from the University of Wisconsin clearly demonstrated the consequences of heat stress at the end of gestation: Not only on her future lactation (-5kg/day) but also on the performance of her daughter (-12 months of longevity, loss of more than 2kg of milk per day over 3 lactations) and even her granddaughter (-27% survival rate, loss of 1.5kg of milk per day in her first lactation). This period is crucial for the development of reproductive and mammary tissue. Heat stress during this period directly damages the development of these tissues, leading to animals that perform less in the long term.
Young cattle for beef production either
Less well documented than milk production, animals for beef production are also affected by heat stress, particularly at the end of the fattening period. A trial was conducted in Mexico in 2024 on Prim ‘Holstein bull calves weighing 530 to 600 kg at the start of the trial. Animals that received Thermoplus® in their feed consumed more (+9%) and showed significantly improved growth (+197 g/day) and feed conversion ratio (-8.1%). The improvement in the feed conversion ratio indicates better feed efficiency. The economic calculation shows an excellent return on investment of 5.25, including the price of Thermoplus® in the feed.
CONCLUSION
The growing threat of heat stress demands proactive and scientifically grounded responses across livestock production systems. The trials presented here reaffirm that early intervention—especially during gestation or late fattening—can mitigate long-term performance losses in both swine and ruminants. By integrating targeted nutritional strategies into routine management, producers can not only protect animal welfare but also improve feed efficiency, fertility outcomes, and overall resilience.
