The study, conducted by Fiona C. Rioja-Lang, Jennifer A. Brown, Egan J. Brockhoff and Luigi Faucitano, aimed to present the best available scientific knowledge on key animal welfare issues during swine transport based on their impact on stress, injury, fatigue, dehydration, body temperature, mortality, and carcass and meat quality.

The review focuses primarily on research related to the transport of market pigs (100–135 kg) which is a reflection of the current literature available on pig transportation.

The priority welfare issues identified by the Scientific Committee and other stakeholders specifically focused on the effect of transport duration, time off feed and water, rest intervals (where appropriate by species), environmental conditions, and loading density, as single factors or in combination, on animal welfare.

Some conclusions from the study

Transport duration and distance

The literature indicates that, contrary to assumption, longer transport journeys show lower mortality rates than shorter journeys, perhaps due to pigs acclimatising to transportation conditions in between the stressful experiences of loading and unloading. It has also been observed that after 20-30 minutes of travelling, pigs tend to sit or lie down, meaning the risks of falling or being thrown around due to vehicle movements are higher during the initial period of transport when pigs are more likely to be standing up.

On the other hand, in this study there were large differences in mortality risk between producers (94 percent of the producers had no deaths), meaning it is possible that there were confounding factors between producers and distance to the slaughter plants. To confirm these results, controlled studies, where the farm (or herd) and travel distance factors are blocked, are needed.

Animal welfare is still an issue where longer journeys are concerned as heat stress, fatigue, hunger, dehydration and discomfort continue to be experienced by all transported animals. The longer the journey, the longer animals are subjected to aversive environments.

Time off feed and water

The literature recommends a fasting period prior to transport; previous studies illustrate that fewer deaths are observed and the risks of travel sickness are reduced when pigs are fasted.

This said, other reports have found that groups of pigs fasted 18 h prior to loading may be more difficult to handle at loading indicated by more pigs going backwards, making 180° turns, and vocalising. Such behaviours may be a reflection of increased frustration, fatigue, and excitement caused by hunger.

The study findings indicate that pigs will lose approximately 4 percent of body weight during the first 18 to 24 h of the fasting interval and extending the fasting period past 24 hours, sometimes into 72 hours, can result in physiological and behavioural changes. Reduced blood glucose levels, increased fighting rate in mixed groups due to hunger-related irritability and excitement, and increased drinking rate have all been observed.

A compromise for welfare, food safety, and meat quality suggests a fasting period of between 16 and 24 hours.

Loading density

According to the findings of the current study, optimum loading density for pigs during transport involves a trade-off between economic pressure to increase loading density in order to minimise transport costs from a single journey, and the respect of the welfare of animals during transport.

The study concludes that the impact of loading density varies with ambient conditions, but in general a greater loading density increases the risk of a pig becoming non-ambulatory or dying.

The full report and findings are published online in Frontiers in Veterinary Science.