Effects of Indoor Temperature, Relative Humidity, and Carbon Dioxide Conditions on Wean-to-Finish Swine Survivability

In swine production, it is broadly recognized that ventilation rates and indoor environmental conditions influence pig productivity. However, sparse scientific data are available on the combined effects and potential interactions of these factors in commercial production systems. This study investigated indoor environmental and management factors influencing wean-to-finish pig mortality in a commercial system. Temperature, relative humidity (RH), and carbon dioxide (CO 2 ) were recorded every 10 min in the front and back of 16 barns across five grow-finish sites in eastern North Carolina for two turns (four barns) or three turns (12 barns) for a total of 44 pig groups. Proportional weekly mortality was modeled using a generalized linear mixed model. Results showed that pigs in environments warmer than the desired room temperature had lower mortality ( p < 0.001), suggesting cold stress was more detrimental than heat stress. Elevated RH and CO 2 at the back of the barn were linked to increased mortality ( p < 0.001), highlighting air exchange rates as a key indicator. Mortality was greatest in pig groups placed during Spring and lowest in Summer ( p < 0.05), and mortality declined as pigs aged ( p = 0.0134). Surprisingly, greater barn occupancy correlated with lower mortality ( p = 0.0012), potentially related to piglet quality at placement. The predictive power of the model varied with the turn of pigs, with R 2 averaging 0.24 (ranging from 0.001 to 0.61) and an average RMSE of 0.36% (ranging from 0.17% to 0.77%). Ammonia (NH 3 ) was recorded at the back of six barns, and concentrations were modeled. Greater NH 3 concentrations were associated with increased pig age, RH, and CO 2 , as well as lower deviation from desired room temperature and lower barn occupancy. Collectively, these findings highlight the importance of proper ventilation and management on swine productivity.