Study examines cull sow condition prior to transport to slaughter

Researchers from Aarhus University among the first to study condition of cull sows on day of transportation to slaughter.

Knowledge on the clinical condition of culled sows prior to being transported to slaughter is very limited. Photo: Carsten Kjaerulf Christensen

On swine farms, unproductive or injured sows are often culled from the herd and sent to slaughter, but the condition of those cull sows has not been the focus of scientific study, according to researchers with Aarhus University in Denmark.

Previous international studies have focused on the condition of sows when they arrive at the abattoir. The results from these studies demonstrated that, compared to market-weight pigs, culled sows constituted the majority of animals showing signs of fatigue, being seriously lame or having a low body condition score at arrival, Aarhus said. So far, however, knowledge about the clinical condition of culled sows prior to being transported to the abattoir has been very limited.

"It seems paradoxical, as this knowledge is very relevant when it comes to assessing whether the animals are fit for transport," said Karen Thodberg with the Aarhus department of animal science and one of the authors of the study.

The Aarhus study utilized 12 herds, each of which were visited by trained technicians on the day of transportation. The technicians conducted thorough clinical examinations of all sows selected by the farmers for slaughter — a total of 522 animals. The clinical variables examined included body temperature, breathing frequency, body condition score, gait and various injuries, e.g.

Only four of the sows selected by the farmers were considered unfit for transportation. They remained in the herd and were not included in the study. A significant part of the rest of the sows had various injuries or disabilities that might affect their welfare during transport, the university said.

"The various injuries or lesions indicate that the sows are more sensitive to the strain related to transportation than other types of pigs," Thodberg said.

Fewer than 1% of the sows were lame, and a major part of the sows showed signs of various injuries such as wounds (approximately 55%), superficial skin lesions (approximately 30%) and udder lesions (approximately 25%) and 60 sows had at least one shoulder ulcer.

Lactating cull sows may be more sensitive

A significant number — almost 40% — of the sows came directly from the farrowing barn and were lactating at the day of transportation to slaughter. The lactating sows displayed a higher frequency of deviations from normal on clinical variables related to the udder, such as udder swellings and other signs of inflammation, Aarhus said.

In the scientific paper, the researchers discussed whether lactating cull sows have a higher sensitivity to heat stress caused by their high metabolism.

This study provides an overall insight into the extent as well as type of injuries and abnormalities in cull sows; however, there is a need for further knowledge about the sows’ behavior and welfare in the last days of their lives.

"Our results demonstrate that there is a need for further studies focusing on different aspects of the condition of cull sows in the interval from the culling decision is made until the time of slaughter. These should also comprise the housing systems and group size that best ensure sow welfare in this period, as well as the conditions during transportation to the abattoir. The conditions for lactating cull sows should be given special attention," Thodberg said.