Lairage behavior, carcass lesions, blood biomarkers, and meat quality in pigs transported over two distances across season

The journey from farm to table is a critical, yet often overlooked, chapter in the life of a pig. Before an animal reaches the slaughterhouse, it must be transported, a process that involves loading, travel, and a period of rest in a holding pen known as lairage. This transition is far from passive; it is a time of significant physical and mental challenge for the animal. Factors such as the length of the trip, the weather outside, and the conditions inside the holding pens can trigger stress responses that alter the animal's body chemistry. These changes do not just affect the pig's well-being in the moment; they can leave a lasting imprint on the quality of the meat itself. For producers and consumers alike, understanding how these pre-slaughter conditions shape the final product is essential, as the stress an animal experiences can determine whether the resulting meat is tender and juicy or tough and dry.

A team of researchers at the State University of Londrina in Brazil set out to investigate exactly how the distance a pig travels and the season in which it travels influence its behavior, its physical health, and the quality of its meat. They observed 256 male pigs under commercial conditions, tracking two specific groups: one group traveled a short distance of roughly 28 kilometers, while the other traveled a much longer route of about 112 kilometers. To see how weather played a role, they conducted these observations during both winter and summer. The scientists watched the pigs closely in their holding pens, measured their blood for signs of stress and dehydration, and then examined the carcasses and meat after slaughter to see how the journey had affected the final product.

The researchers found that the pigs' behavior in the holding pens was surprisingly consistent, regardless of how far they had traveled or what time of year it was. Upon arrival, the animals spent the first hour standing, likely exploring their new surroundings, before settling down to lie for the remainder of the three-hour rest period. This pattern of standing first and then lying down was a natural rhythm that the pigs followed in all conditions. However, the season did change how the pigs interacted with their water. During the summer, the pigs spent significantly more time drinking water than they did in the winter, a logical response to the heat as they tried to cool their bodies. Interestingly, the distance of the trip did not change how much they drank or how long it took them to start drinking, suggesting that the heat of the summer was a stronger driver of thirst than the length of the journey.

When the scientists looked inside the pigs' bodies through blood tests, the story of stress became clearer. The animals transported during the summer showed much higher levels of lactate in their blood compared to those transported in winter. Lactate is a substance that builds up in muscles when an animal is fatigued or under heat stress, indicating that the summer journey was physically more demanding. The season also influenced the pigs' blood sugar and protein levels. Pigs that traveled the longer distance had higher blood sugar levels, a sign that their bodies were working hard to cope with the stress of the journey. Furthermore, the pigs transported in the summer showed signs of dehydration, indicated by higher levels of a protein called albumin in their blood. This suggests that the combination of travel and hot weather left the animals more dehydrated than those traveling in cooler conditions.

These physiological changes had a direct and measurable impact on the meat. The pigs transported during the summer ended up with more severe skin lesions on their carcasses, likely due to increased agitation and aggression caused by the heat. The meat from these summer-transported pigs also suffered in quality. It lost more water, a trait known as drip loss, which makes meat less juicy and less valuable. Additionally, the meat from the summer group was redder in color, a change often associated with stress. In contrast, the distance of the trip had a more subtle effect; pigs that traveled the longer distance had a slightly higher final pH level in their leg muscle, which can influence how the meat ages and stores, but the season remained the dominant factor affecting the overall quality.

The study concludes that while the distance of the transport matters, the season in which the transport occurs is the most powerful force shaping the pig's experience and the resulting meat quality. The heat of the summer created a perfect storm of stress, dehydration, and fatigue that the animals could not fully recover from during their short rest period. This resulted in more injuries, greater physiological strain, and meat that was less able to hold onto its moisture. The findings highlight that managing the environment and the timing of transport is just as critical as the journey itself. By understanding that heat stress is a primary driver of poor outcomes, producers can better protect animal welfare and ensure a higher quality product for the consumer, proving that the conditions of the final hours before slaughter are as important as the miles traveled to get there.