Can probiotics protect growth rates when temperatures rise?

We previously discussed how gut health support may help pigs cope with heat stress. However, the question for the pig industry is simple: can these gut-level effects translate into measurable performance benefits when temperatures rise?

This question is becoming increasingly relevant. Heatwaves across Europe have highlighted the growing vulnerability of pig production to climate extremes. Reports from the sector described widespread production disruptions following recent heat episodes, with impacts extending beyond immediate mortality to include reduced growth rates, lighter market weights, reproductive challenges, lower future pig availability, and economic pressure associated with higher production costs. Industry observers have also noted reductions in carcass weights exceeding 1 kg per pig.

To evaluate whether a gut microbiota strategy could help maintain performance under these conditions, a study was conducted in a commercial farm in collaboration with the Agricultural University of Athens. Seven hundred grower pigs (13 weeks of age) were allocated to either a control group or a group receiving feed supplemented with Bacillus velezensis PB6 at 2 x 10⁸ CFU/kg feed (CLOSTAT®, Kemin Europa NV). The probiotic was administered through feed during the study, but administration is also possible through drinking water. Animals were monitored from 13 to 18 weeks of age under commercial conditions. During most of this study period, average temperatures remained close to 29°C with relative humidity between 40% and 44%, conditions that placed the animals within the heat-stress danger zone.

Figure 1: Average Daily Gain of Pigs Supplemented with B. velezensis PB6 Compared with Control Pigs during heat stress

Performance results improved during the heat-stress period. Between 13 and 18 weeks of age, pigs receiving the probiotic achieved a significantly higher average daily gain than control animals (0.64 vs. 0.62 kg/day; P < 0.05). This translated into greater body weight gain during the heat-stress period and a significantly higher final body weight afterwards, with an advantage of 1.58 kg per pig.

How could a probiotic influence growth during heat stress? Heat stress affects performance through multiple mechanisms. Pigs redirect blood flow away from the intestine to dissipate heat. At the same time, feed intake declines and inflammatory pressure may increase, creating conditions that are unfavorable for growth. Scientific literature suggests that heat stress disrupts intestinal barrier function, microbiota balance, and nutrient utilization. Probiotic Bacillus strains have been shown to support microbial stability and promote beneficial bacterial populations. By preserving a healthier intestinal environment, more nutrients may remain available for growth rather than being diverted toward inflammatory and stress-related responses. This is consistent with lower physiological stress markers previously observed in PB6-supplemented pigs, notably reduced D-lactate dehydrogenase levels.

Ventilation, cooling systems, water availability, and nutritional management remain the first lines of defense against heat stress. However, as summers become increasingly challenging, supporting gut resilience offers an additional opportunity to help maintain growth performance and ultimately protect production.

References:

Husson, E. (2026).
 Marché du porc : l’offre recule en raison des pics de chaleur. Porc Magazine (PorcMag). Published July 15, 2026.

Liu, F., Zhao, W., Le, H.H., Cottrell, J.J., Green, M.P., Leury, B.J., Dunshea, F.R., & Bell, A.W. (2022).
 What have we learned about the effects of heat stress on the pig industry? Animal, 16, 100349.

Ringseis, R., & Eder, K. (2023).
 Heat stress in pigs and broilers: role of gut dysbiosis in the impairment of the gut–liver axis and restoration of these effects by probiotics, prebiotics and synbiotics. Journal of Animal Science and Biotechnology, 14, 2

Tang, X., Zeng, Y.Y., Xiong, K., & Zhong, J. (2024).
 Bacillus spp. as potential probiotics: promoting piglet growth by improving intestinal health. Frontiers in Veterinary Science, 11.