As the debate over the use of gestation stalls continues, it has become clearer that science is not the trump card in decision making, but it is still an incredibly valuable component. One of the most valuable characteristics about scientific quantification is its objectivity. This is what allows a scientist to clearly measure variables that are associated with a question. For example, a scientist could ask the question, “Are gestation stalls better for the welfare of pregnant sows?”
After the question has been established, a study could be designed to compare gestation stalls to other types of sow-housing systems through the measurement of the levels of substances in the blood that change in relation to a stressful environment, such as cortisol (a stress hormone) and glucose — or “blood sugar.”
The behavior of the sows also would need to be quantified, because the behavior of the animal is the best indicator of an animal’s psychological state. This could be accomplished through the measurement of the amount of time sows spend performing their typical behaviors, which may include sitting, standing, feeding, bar-biting (chewing on the bars of the crate or pen), and so on. The level of production that the individual sows can achieve has to be considered as well. This data is perhaps the easiest to quantify because the industry has been collecting it for years.
After all of the biological, behavioral and production data is collected and analyzed, scientists can determine if differences between gestation stalls and an alternative housing system exist. Since science is objective, the differences are easy to detect through the use of objective statistical tests. The information gleaned from a well-designed study that is tightly managed and appropriately analyzed will result in “sound science.”
The next step for the scientist is usually the most difficult. Since science is objective, the scientist must interpret the results and explain what happened. This is where judgment calls are made. The science helps the scientist to decide which housing system may be better based on the variables that were measured, but it does not make the decision for the scientist. This is why multiple studies have to be considered by the industry before making decisions on an issue as impactful as sow housing.
Overall, “sound science” is a tool that is used to help guide decisions made by scientists, veterinarians, producers, processors and their customers. Unfortunately, “sound science” does not have the ability to make ethical decisions for us — we have to determine what is acceptable and what is not.
In 2005, a task force from the American Veterinary Medical Association (AVMA) set out to thoroughly and objectively review all relevant scientific literature regarding the impact of gestation-stall housing on the welfare of pregnant sows. The review[1] covered approximately 1,500 pages of peer-reviewed scientific literature. The 14-member task force was comprised of highly respected researchers and veterinarians who represented many of the stakeholders in the sow-housing issue.
As the task force began to investigate the impact of gestation stalls on sow welfare, they came to the agreement that an accurate assessment of sow welfare must focus on all possible indicators of sow welfare that are available. The group recognized that paying attention to physiological function without considering sow behavior, health or productivity would not fully answer the question. In fact, failure to consider any single factor would have eroded the integrity of the conclusions made by the task force.
Ultimately, the task force was unable to identify a housing system that was clearly superior to all others. At first glance this may sound rather inconclusive, but it is actually an indication of the task force’s success in assessing as many indicators of sow welfare as possible.
Overall, the group did not identify a difference in sow physiology or productivity between gestation stalls and group-housing systems. Some of the individual studies that were considered by the task force reported improvement in physiological indicators of sow welfare and sow productivity as a result of gestation stall housing and other studies reported negative implications of gestation stalls.
It was determined that gestation stalls improved sow health by reducing the incidence of injuries. However, gestation stalls were not as conducive to the expression of natural behaviors by sows — and this conclusion was not just based on the restriction of movement. Reduced caloric consumption, reduced opportunity to forage, absence of bedding and restricted social interaction were implicated in the observed behavioral differences between gestation-stall and group-housed sows.
It is important to note that some of these conditions, such as reduced caloric intake, absence of bedding and reduced opportunity to forage, are not isolated to gestation-stall systems. Many group-housing systems have to limit the amount of feed offered to sows each day to maintain their body condition and do not include bedding and foraging material in their pens because of the challenges these materials present in liquid manure-handling systems.
Throughout the task force’s report, management emerged as a major factor in maintaining sow welfare. The group concluded that gestation stalls and group housing both had intrinsic strengths and weaknesses over each other, and management played a key role in maintaining productivity and animal welfare in both systems.
Over the past few months, several large quick-service restaurant chains, food retailers and foodservice companies have committed to sourcing at least part of their pork supplies from systems that do not use gestation stalls in their current form. Many representatives of the swine industry have expressed their concern with the likely increase in pork-production cost associated with such a transition.
The costs associated with a transition away from gestation stalls are difficult to accurately estimate, but post-transition studies in the European Union — whose member countries have vowed to discontinue use of gestation stalls by January 2013 — have estimated that pork-production cost increased by approximately 0.6 % to 2.7%.
The AVMA task force suggested that the production cost may have been greater than the reported figures because of the difficulty associated with estimating additional labor, construction and training costs. An additional challenge in estimating the cost of the transition away from gestation stalls is the difficulty to estimate the cost to build and operate systems that have not been fully developed and tested yet. But this is where an opportunity may exist for the swine industry to showcase its ingenuity.
In the 1950s and 1960s, the swine industry began widespread implementation of gestation-stall systems with the intuition that such systems would make sow management easier and more consistent and make space utilization more efficient. These systems were developed and implemented with little guidance by scientific literature. Instead, the gestation-stall system was implemented and fine-tuned in the real-time industry setting with great success.
It appears that the time has come for another period of innovation in sow housing for the swine industry. This time, the industry must find systems that improve sow welfare and still achieve efficiency in production and reasonable product cost. Anyone who claims the industry is being asked to step back a half century is clearly misguided.
There is a growing pool of scientific literature to guide the process, but most of the innovation will likely come through industry implementation and testing. In order for the effort to adopt group-housing systems to be successful, the swine industry must determine the amount of time needed to develop systems that are good for the welfare of sows, producers and consumers.
Time is arguably the most important factor in this transition. If the change is too sudden, the best of intentions could yield unfavorable results.
[1]Rhodes, R. T., M. C. Appleby, K. Chinn, L. Douglas, L. D. Firkins, K. A. Houpt, C. Irwin, J. J. McGlone, P. Sundberg, L. Tokach, R. W. Wills, D. Fraser, D. Hayes, and G. C. Golab. 2005. A comprehensive review of housing for pregnant sows. J. Am. Vet. Med. Assoc. 227:1580-1590.
