As summer temperatures rise, transport loss becomes an increasingly important topic for pork producers and processors. Seasonal heat stress, combined with ongoing industry pressures such as heavier market weights and transportation costs considerations, can create conditions that increase the risk of losses during loading and transport.
Higher hog values may encourage producers to market pigs at heavier weights, while rising diesel costs can increase pressure to maximize trailer utilization. At the same time, heat and humidity place additional physiological stress on pigs before, during and after transport. These factors can create challenges for maintaining animal welfare and minimizing losses.
Transport loss is influenced by a combination of animal handling, environmental conditions and transportation practices. While no single management strategy can eliminate risk, proactive planning and communication across the transport chain can help reduce losses and support pig welfare during the summer months.
Transport loss as a welfare and economic concern
Transportation is one of the most stressful events in a pig’s life. Pigs experience significant physiological and behavioral stress responses during the process, including elevated cortisol and increased heart rate, triggered by loading, handling, unfamiliar environments, mixing with other animals and changes in temperature.1These stressors can compromise welfare, and in some cases, result in dead or non-ambulatory animals at the plant.
The economic impact is significant. Analysis of transport loss data from approximately 385 million market pigs across 15 USDA-inspected pork slaughter plants between 2016 and 2022 found industry averages of 0.23% dead pigs, 0.40% non-ambulatory pigs and 0.63% total transport losses.2Across the industry, those losses are estimated to cost approximately $215 million annually, or roughly about $0.56 per pig marketed.
Summer conditions create elevated transport risk
Heat and humidity are among the most significant contributors to transport loss and total dead-on-arrival percentages are consistently highest during summer months.3
Pigs are particularly vulnerable to heat stress because they have a limited ability to cool themselves. They lack functional sweat glands and rely heavily on respiratory panting to dissipate body heat.4 When ambient temperature and humidity are high, that mechanism becomes increasingly ineffective.
Several factors can compound summer risk:
- Heavier pigs generate more metabolic heat: As market weights climb, the heat output per animal increases. Research has shown that heavier pigs are disproportionately represented in transport loss events, partly due to increased metabolic heat production and reduced surface-area-to-body mass ratios.2
- Reduced airflow increases trailer heat accumulation: Trailers that are stationary, moving slowly in traffic or inadequately ventilated can quickly become dangerously warm.
- High humidity limits cooling: When relative humidity is elevated, pigs’ ability to dissipate heat through respiration is reduced, accelerating onset of heat stress and increasing the risk of death.
- Tighter stocking densities reduce airflow between animals: Even small increases in load density can reduce a pig’s ability to cool down and increase competition for space.
Optimal load weight matters
Stocking density and trailer load weight are among the most important decisions made before a transport event.
Optimal load weight, while primarily influenced by pig weight, can vary depending on several factors:
- Pig weight: Heavier pigs require more space and generate more heat per animal.
- Weather conditions: Hot, humid days warrant reduced loads to preserve airflow and minimize thermal stress
- Trailer design and ventilation: The airflow capacity of a given trailer affects how many pigs can safely travel at a given temperature.
- Transport duration: Longer hauls increase cumulative stress, requiring load weights to be adjusted accordingly.
- Pig health status: Compromised animals are at elevated risk and should be evaluated carefully before loading.
Elanco Technical Consultants work with producers to establish load weight guidelines that reflect local conditions and seasonal risk factors.
Practical strategies to reduce transport loss
No single action eliminates transport risk, but a combination of thoughtful practices across trailer management, pig handling and chain-wide communication can help reduce losses.
Trailer management and environment
- Adjust boarding: Proper boarding helps maintain airflow within trailer compartments and prevents heat from becoming trapped around pigs.
- Monitor airflow and ventilation: Check vents and airflow systems before loading to help prevent excessive heat buildup during transport.
- Ensure misters and hoses are operational: Wetting pigs before loading and during staging can help reduce body temperature and improve heat tolerance.
- Avoid overcrowding: Adjust stocking density based on pig weight and weather conditions to promote airflow and minimize thermal stress.
- Reduce stationary time: Heat can accumulate quickly in parked trailers, making it important to minimize delays whenever possible.
- Transport during cooler hours: Early morning or late evening transportation can help reduce pigs' exposure to high temperatures.
Low-stress pig handling
- Move pigs at a steady pace: Rushing pigs increases stress and fatigue before transport begins.
- Avoid overcrowding in alleys and loading areas: Maintaining pig flow can reduce agitation and minimize bottlenecks.
- Use proper handling tools appropriately: Tools should guide movement rather than force it.
- Identify compromised pigs before loading: Pigs that appear physically stressed or show signs of respiratory distress should be evaluated before being loaded.
Communication across the transport chain
- Monitor weather conditions: Sharing information about forecasted heat events allows teams to adjust plans before pigs are loaded.
- Coordinate plant schedules: Communication between farms, transporters and processing facilities can help reduce wait times and unnecessary delays.
- Plan for traffic and disruptions: Having contingency plans in place can help minimize the impact of unexpected delays.
- Maintain communication throughout the process: Strong coordination across the transport chain allows teams to identify risks and respond quickly when conditions change.
Summer transport losses are influenced by many factors, but proactive planning can make a meaningful difference. Evaluating trailer conditions, adjusting load densities, handling pigs calmly and maintaining communication throughout the transport process can help protect pig welfare and reduce economic losses during the year's most challenging transportation season.
Elanco technical consultants work alongside producers and their teams to evaluate transport practices, assess load density guidelines and identify opportunities to reduce losses and improve pig welfare throughout the summer months.
1Flores-Peinado, S., Mota-Rojas, D. et al. 2020. "Physiological responses of pigs to preslaughter handling: infrared and thermal imaging applications." International Journal of Veterinary Science and Medicine. 8.1: 71–84. doi: 10.1080/23144599.2020.1821574.
2Calvo-Lorenzo, M., Gooding, J. et al. 2024. "Transport of Market Pigs: Improvements in Welfare and Economics." In: Grandin, T. (ed.) Livestock Handling and Transport, 6th Edition. CAB International, pp. 390–407.
3Hernandez, R., Rocha, A. et al. Aug. 2025. "Effects of microclimate during transport on physiological indicators of market pig welfare: a systematic review with meta-analysis." Frontiers in Veterinary Science. 12: 1657185. doi: 10.3389/fvets.2025.1657185.
4Gómez-Prado, J., Pereira, A. et al. Dec. 2022. "Thermoregulation mechanisms and perspectives for validating thermal windows in pigs with hypothermia and hyperthermia: An overview" Frontiers in Veterinary Science. 9: 1023294. doi: 10.3389/fvets.2022.1023294.
