Risk Factors for Chronic Stress in Sows Housed in Groups, and Associated Risks of Prenatal Stress in Their Offspring

Abstract

Chronic stress has a detrimental effect on sow welfare and productivity, as well as on the welfare and resilience of their piglets, mediated prenatally. Despite this, the specific risk factors for chronic stress in pregnant sows are understudied. Group-housed pregnant sows continuously face numerous challenges associated with aspects of the physical (group type and size, flooring, feeding system) and social (stocking density, mixing strategy) environment. There are many well-known potent stressors for pigs that likely contribute to chronic, physiological stress, including overcrowding, hot temperatures, feed restriction, inability to forage, uncomfortable floors, and poor handling. Some of these stressors also contribute to the development of production diseases such as lameness, which in turn are also likely causes of chronic stress because of the associated pain and difficulty accessing resources. The aim of this review is to discuss potential risk factors for chronic stress in pregnant sows such as space allowance, group size and type (stable/dynamic), feeding level, lameness, pen design, feed system, enrichment and rooting material, floor type, the quality of stockmanship, environmental conditions, and individual sow factors. The mechanisms of action of both chronic and prenatal stress, as well as the effects of the latter on offspring are also discussed. Gaps in existing research and recommendations for future work are outlined.

Indicators of improved gestation housing of sows. Part I: Effects on behaviour, skin lesions, locomotion, and tear staining

“…Hence, a drawback of rooting towers and racks is the risk of competition (and thus sustained aggression), due to the potential for such structures to be monopolised by dominant individuals (Stewart et al 2008 ). Nevertheless, this could be mitigated by strategic placement and provision of a number of straw delivery structures (Lagoda et al 2021 [Au: 2021a ], 2022 ). Natural fibre rope could also help satisfy sows’ behavioural motivation to chew, as it is destructible, chewable, manipulable, and investigable (Horback et al.…”

“…There are several methods of estimating chronic stress in sows (Lagoda et al 2022 ), besides physiological measurements such as cortisol level (Herman et al 2016 ; Carroll et al 2018 ). One is through observation of stereotypical behaviours; these become established when animals are unable to cope with a challenge, or have no control over their environment (Martinez-Miro et al 2016 ).…”

“…However, this approach could provide additional benefits over research targeting individual risk factors for chronic stress (e.g. Stewart et al 2008 ; Horback et al 2016 ; Merlot et al 2017 ), as in reality sows rarely experience stressors in isolation (Lagoda et al 2022 ). Hence, the aim of this study was to investigate the effect of housing sows in a physically more comfortable and enriched environment on indicators of chronic stress and animal welfare.…”

Effects of a Phytogenic Feed Additive on Redox Status, Blood Haematology, and Piglet Mortality in Primiparous Sows

“…Piglet mortality and especially the increased number of stillborn and crushed piglets is an important welfare issue for modern sows. Chronic stress has a detrimental effect on sow welfare and productivity, as well as on the welfare and resilience of their piglets, which is mediated prenatally [20]. Crushing usually occurs during the first 3 days after birth with around half occurring during the first 24 h when the sow changes posture [92].…”

“…Farrowing sows could experience chronic stress for an extended period [16][17][18], inducing negative effects not only on the sow's health and metabolism but also on foetal development and offspring's survival [19]. This is known as prenatal stress and could have negative implications on the health, welfare, and growth performance of newborn piglets [20].…”