Gestational group-housing: Widely discussed, limited in applied research
MSU’s new facility allows a look at intergenerational effects of social stress
By Andrea Luttman, Kevin Turner, Dale Rozeboom, Simon Collier and Catherine Ernst
Producers are acutely aware of legislative changes and consumer pressure towards banning controversial practices in animal production including gestation stalls. Arizona, Colorado, Florida, Maine, Michigan, Ohio, Oregon and Rhode Island have already passed legislation banning gestation stalls although not all of these bans are in effect yet. California and Massachusetts banned gestation stalls as well as the sale of pork products from out-of-state farms using gestation stalls.
This change in management of gestating females introduces challenges for producers including how to feed for body condition score, aggression, lameness, detection of early abortions, and potential worker safety issues when providing medical care or moving animals in and out of large groups.
What do we know and where are we headed?Unfortunately, there are many gaps in research specific to gestational group-housing. The bulk of research to date has focused on characterizing the impact gestational group-housing has on the animal’s welfare, reproductive performance and performance of their offspring. Researchers have observed that group size isn’t associated with frequency of aggression, serum cortisol concentration or reproductive performance.1,2 In regard to group composition, there are mixed findings on if dynamic groups are truly more aggressive than static groups. Some studies observed greater aggression in dynamic groups, while others have observed more tolerance from sows in dynamic groups.3-6
Type of feeding system is probably the most challenging decision for producers facing the transition to gestational group-housing. Floor feeding is the simplest but can cause low rank sows to lose body condition.7 Free access stalls reduce aggression and plasm cortisol but are also associated with an increase in vulvar biting.8,9 Individual feeding is best addressed by electronic sow feeders (ESF) but sequential feeding invites queueing of animals at the ESF gate, with one study finding a handful of sows queued at any given time.10
As detailed above, the scientific community has learned a lot about how transitioning to gestational group housing may influence the animals and their production. However, research now needs to focus on genetic selection strategies and management interventions to help mitigate the negative impacts of group-housing. For example, can we select for less aggressive and more resilient breeding females? In the meantime, could products such as the AllBite block (Alltech) or other enrichment items be implemented to reduce aggression and therefore social stress in gestating females? There is also a need for research in developing and implementing precision livestock farming technologies for automated estrus detection, cough detection, lameness detection and body condition monitoring.
New facility supports new researchThe Michigan State University (MSU) Swine Teaching & Research Center (STRC) as an institutional research farm is exempt from Michigan’s legislative mandate banning gestational stalls. However, to enable traditional and applied research in gestational group-housing systems, a facility was constructed in 2022 thanks to funding support from the Michigan Alliance for Animal Agriculture.
This new facility is adjoined to the existing facility by a connecting hallway consisting of sorting pens, a loading dock and mechanical room. It was built over a 4’ shallow slurry pit with fully automated ventilation, heating and feed systems. The facility can house approximately 200 females in either free-access stalls or pens operating on an ESF system. The first group of bred sows entered the facility in January 2023 and the facility is now in full use including the first research project in gestational group-housing.
This research being conducted by the Ernst lab is investigating resilience to social stress in gestating females and will be detailing molecular changes in the offspring that occur as a result of prenatal social stress. The project titled ‘Characterizing intergenerational resilience in pigs: Impacts of group-housing on epigenetic modifications associated with behavioral and physiological stress phenotypes’ is funded by the Agriculture and Food Research Initiative from the USDA National Institute of Food and Agriculture.
The project has three aims:
Classification of resilience to weaning stress and characterization of molecular differences between purebred gilts identified as resilient or vulnerable.
Classification of resilience to gestational social stress and characterization of molecular differences in the neonatal offspring born to resilient and vulnerable females.
Description of the growth and behavior differences of offspring born to resilient or vulnerable females.
The first aim of the project was completed on-farm in April 2023 and molecular data generation and analysis is underway. There are currently five pens (n=8/pen) of gestating gilts and sows on project due to farrow in November 2023 and January 2024. We are particularly excited as some of the Yorkshire gilts from the first aim were retained for breeding and are now gestating as a part of the later aims of the project. This is giving us a rare opportunity to investigate if resilience to weaning stress is associated with how they respond to subsequent stress of gestational group-housing. We plan to then retain their daughters for breeding as well, allowing us to investigate not only intergenerational effects but also transgenerational effects of social stress from group-housing.
Having research animals in a free access stall system provides many opportunities. In addition to measuring and recording salivary cortisol, skin lesion counts and tear staining scores surrounding the main mixing event to provide insight to the stress levels of the animals, we are utilizing overhead video to explore behavior of gestating females in a free access stall system. We plan to answer questions such as, how much time are the animals spending in the stalls vs. in the loafing area? What time of day do we see the most or least activity? When animals are in the loafing area, how are they spending their time?
Undergraduate research assistant and MSU STRC student employee, Simon Collier, is taking the lead in decoding the video for stall utilization data and plans to present his findings at the American Society of Animal Science Midwest meeting. Preliminary data is already revealing some interesting findings. In the first three days post-mixing, first parity (P1) sows spend significantly less time in stalls than gilts (p=0.046), with P1 sows spending only 70% of their time in stalls vs. gilts who spend 87% of their time in stalls. As we look at the time spent in stalls over time, there is little difference between P1 sows and gilts in the first 24 hours but by day 3 post-mixing the difference is obvious (Figure 1). However, there doesn’t appear to be any differences in the number of times the animals visit a stall (p=0.860).
We will be combining this data set with our salivary cortisol, skin lesion and tear staining score data to determine if there is any association between stalling preference of the animals and their stress response to mixing. The Ernst lab looks forward to providing the research community as well as producers valuable insight into the stress response to gestational group-housing, behavior within a free access stall system, and the molecular mechanisms underlying intergenerational effects of prenatal social stress resulting from group-housing.
Beyond the dataThe Ernst lab is not the only ones taking full advantage of MSU’s new gestational group-housing facility. The role of a university facility, particularly a land grant university, is to not only lead the way in research but also in education. The original facility built in 1997 has provided students, researchers and visitors with the opportunity to experience all stages of swine production under one roof.
While the new group gestation facility has only been in full operation for about a year, it is already providing the chance to compare and contrast traditional gestation stalls to different styles of group housing systems, expanding the efforts of educating on all aspects of swine production. In a typical year, the MSU STRC sees approximately 1000 students utilizing the facility for class tours or working labs in addition to tours given to the public or various groups.
For university farm staff, educators and researchers, being a part of moving forward with the swine industry and sharing that with others is an incredibly rewarding experience.
AcknowledgementsThe Ernst lab’s project is funded by Agriculture and Food Research Initiative (award number 2022-67015-36865) and AML is supported by a pre-doctoral fellowship (award number 2022-67011-36562) from the USDA National Institute of Food and Agriculture.
References
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Luttman is a PhD candidate in Genetics and Genome Science, Turner is the farm manager at the MSU STRC, Rozeboom is a professor emeritus of Animal Science, Collier is an undergraduate student in Animal Science, and Ernst is a professor of Animal Science, all at Michigan State University. Photos courtesy of MSU.
