Sow housing science inconclusive | Article

THE science does not currently exist to allow for rigid decisions on which type of housing is in the best interests of dry sows in commercial pork production, an international task force organized by the Council for Agricultural Science & Technology (CAST) has concluded.

The use of individual gestation accommodations (IGAs) for dry sows in commercial pork production is an issue that has raised much debate, and since public perceptions and misconceptions of welfare issues have the potential to dramatically affect swine production, CAST undertook the effort to provide an objective and scientific look at the subject.

"Too few statistically adequate, scientifically controlled trials on industry farms have been conducted; many reports are not useful for critical evaluation, thus for developing public policy," said task force chair Dr. Stanley Curtis with the department of animal sciences at the University of Illinois, Urbana-Champaign. "More large-scale, on-farm, multidisciplinary, scientifically robust research and development are needed before rigid regulations should be imposed."

For the sake of history, farmers started moving sows inside during the mid-20th century to provide them with relief from variable weather conditions, environmental protection pressures, predators and parasitic and enteric diseases.

Additionally, the job of managing breeding pigs is physically challenging, and the added stress to herdspeople caring for larger numbers of pigs during inclement weather was a contributing factor prompting the move indoors, according to Curtis.

Once the farms housed the sows indoors, Curtis said, it was a natural progression to develop systems that increased the efficiency of building utilization by considering the minimal space needed to accommodate a sow.

The success of IGAs in overcoming multiple production problems in an economical way led to an exponential increase in their use, he said.

Although farrowing crates have been used in one form or another for more than 100 years, U.S. farmers experimented with IGAs for sows starting in the 1950s. By the 1970s, sow IGAs were common, and by 1990, they were by far the most common sow-keeping system in the U.S.

Criticism of IGAs from consumers and activists started in the 1960s in the U.K. and Northern Europe. The tether was banned in the European Union beginning in 2006, and the gestation crate will be banned by 2013.

Major announcements in 2007 and 2008 reported that some U.S. production companies and some states will stop using IGAs in response to public animal welfare concerns articulated by animal activists.

Currently, producers of more than 25% of U.S. pork have committed to phasing out the gestation crate, and the trend continues with legislative or voluntary proscriptions now under way to eliminate use of IGAs.

Among other things, the CAST task force evaluated alternative sow accommodations in its recent review.

CAST explained that the dominance hierarchy in wild or feral bands of females is effectively managed because a female in an extensive setting can readily escape being attacked by moving away from an aggressive, dominant bandmate. In an artificial grouping of sows kept indoors, the same basic social interactions take place among sows.

When sows in a social group are given progressively less space, the rate of skin-lesion incidence has been shown to increase, most likely due to increased exposure to the physical components of the pen as well as greater social contact and more stress.

Sows kept in IGAs typically have fewer skin lesions and social stressors than those kept in groups with the same amount of individual floor space. Consequently, more barn space is required per sow when sows are kept in groups within gestation pens.

The task force explained that now that EU and U.S. farms either have decided to house sows in group pens or will be forced to do so, and because indoor floor space is expensive, methods are urgently needed to determine the minimum quantity and quality of space for pregnant sows kept in groups.

Pork producers started using group housing systems before complete scientific evaluations were done by developing and implementing creative group-keeping systems that remain untested at large-scale levels, they said.

The task force pointed out that although some scientists maintain that assessing an animal's state-of-being should be based mostly on its "feelings," and although this ultimately may be the ideal approach, it is still not possible to measure animal feelings objectively either in the laboratory or on the farm.

It is difficult to predict the future design and operation of pregnant sow accommodations, the task force said, noting that during the past decade, the cost of production has been the primary driving force behind the development of pork production systems.

Today, two science-based views are coming through in the current situation, and until a choice is settled on and accepted by a large majority of people in the U.S., the task force said the nature of accommodations for pregnant sows will remain a public issue.

As the choice is being made, the task force said the overall effect on the pregnant sow's state-of-being must be considered, in addition to consequences with respect to sow and piglet health, the cost of pork production and the availability and price of pork products.

In any case, the CAST task force said, the choice should be based on sound science, and further scientific research and development can be applied.

In addition to Curtis, the CAST task force members included Rodney B. Baker, veterinary diagnostic and production animal medicine at Iowa State University; Mark J. Estienne, Virginia Tech Tidewater Agricultural Research & Extension Center; P. Brendan Lynch, Pig Production Development Unit at Moorepark Research Centre, Ireland; John J. McGlone, animal and food sciences at Texas Tech University, and Bjarne K. Pedersen, Danish Farm Design A/S, Denmark.

The full text of the paper, "Scientific Assessment of the Welfare of Dry Sows Kept in Individual Accommodations" (Issue Paper 42), may be accessed free of charge at www.cast-science.org.

CAST is an international consortium of 36 scientific and professional societies. It assembles, interprets and communicates credible science-based information regionally, nationally and internationally to legislators, regulators, policy-makers, the media, the private sector and the public.

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