Knowledge
Dossier: Group-housing and mixing of sows
This page provides background information and practical knowledge on the welfare issues related to group-housing and mixing of sows, and how welfare problems can be limited in practice.
Important welfare needs of sows that live in groups are described. Four important key areas challenging sow welfare are highlighted:
- Mixing of unfamiliar animals
- Competition for resources
- Restrictive feeding
- Climatic and resting comfort
Guidance and recommendations for actions to improve the sows’ welfare on farms is given within each key area.
Mixing of unfamiliar animals
Social group structure:
- In nature, sows live in small maternal groups of two to four sows with their offspring and juveniles.
- In nature, unfamiliar sows are rarely allowed to incorporate into a group.
- Within each social group long-time social relationships exist.
- Most often mature sows are dominant over sub-adults.
- Social relationships are maintained by subordinate animals avoiding physically stronger animals.
Read more & relevant links
Options to improve the welfare of sows around mixing:
- Provide sufficient space, especially the first days after mixing, to reduce stress and agonistic interactions (see also ‘Mixing pens’ under ‘Inspiring examples’).
- Mix sows at weaning or in the first week after insemination to reduce the risk of embryo mortality and therefore smaller litter sizes.
- Provide good quality flooring to prevent slipping, falling and lameness.
- Provide opportunities to escape from other sows to reduce stress and skin lesions.
- Preferably keep sows in static groups where they are mixed only once during gestation, and preferably return sows to their previous group following lactation.
- Select non-aggressive traits in sows to reduce agonistic interactions.
Relevant links
- Effects of group housing on sow welfare: a review, Verdon et al, Journal of Animal Science, 93(5), pp. 1999-2017, 2015
- Group housing of sows in early pregnancy: a review of success and risk factors, Spoolder et al., Livestock Science, 125(1), pp. 1-14, 2009
- Welfare of dry sows, Marchant-Forde, In ‘The welfare of pigs (pp. 95-140)’, 2009
- Council Directive 2008/120/EC laying down minimum standards for the protection of pigs, EC, 2008
- The accumulation of skin lesions and their use as a predictor of individual aggressiveness in pigs, Turner et al., Applied Animal Behaviour Science, 96, pp. 245-259, 2006
Competition for resources
For access to resources:
- Sows generally prefer to synchronise behaviour, i.e. have access to resources (especially food and lying areas) more or less at the same time.
- In nature, within a social group, aggression is rare, but may occur during competition for resources such as for food.
- Sows need static space, behavioural space and interaction space.
Read more & relevant links
Reducing competition for resources may be done by:
- Adequate access to resources in space (no narrow passageways or placement in corners) and time (permanent access to enrichment materials).
- Spreading food widely in case of floor feeding, allowing all sows access to food simultaneously.
- Lockable feeding stalls allowing sows to eat simultaneously and protecting subordinate sows from food stealing by dominant ones.
- Adequate design of feeding stalls to prevent sows from being attacked, leading to e.g. vulva biting.
- Electronic sow feeding, which is a localised resource and does not allow simultaneous feeding, should be positioned away from busy areas and other resources.
- Additional roughage offered ad libitum with easy access to the racks.
- Sufficient lying space, i.e. enough space such that all animals can lie at the same time.
- Lying areas should be separate from the activity and dunging areas, and provide shelter and a view of the surroundings.
Relevant links
- Effects of group housing on sow welfare: a review, Verdon et al, Journal of Animal Science, 93(5), pp. 1999-2017, 2015
- Welfare of dry sows, Marchant-Forde, In ‘The welfare of pigs (pp. 95-140)’, 2009
- Group housing of sows in early pregnancy: A review of success and risk factors, Spoolder et al., Livestock Science, 125(1), pp. 1-14, 2009
- Council Directive 2008/120/EC laying down minimum standards for the protection of pigs, EC, 2008
- Lying characteristics as determinants for space requirements in pigs, Ekkel et al., Applied Animal Behaviour Science, 80, pp. 19-30, 2003
Restrictive feeding
For foraging and feeding:
- Sows spend 75% of their daytime activity with foraging-related activities in semi-natural environments and are highly food motivated.
However, in commercial systems:
- Pregnant sows are commonly kept on a restricted diet to prevent excessive body weight gain, fat deposition and reproductive problems.
- The diet is often rapidly consumed and does not keep the sows satiated for more than 1 or 2 h.
- Restrictive feeding is very likely to lead to chronic and persistent hunger, stereotypies, and frustration.
Read more & relevant links
The adverse consequences of restrictive feeding may be mitigated by:
- Including more fibre in the diet, allowing a larger volume of food without increasing the energy level and nutrient composition.
- Offering fibrous materials separately in racks or on the floor. Racks should be readily accessible, 40-45 cm high and have 11-13 cm between bars (see also ‘Inspiring examples)’.
- Providing both fibrous ingredients in the diet and ad libitum access to roughage is the most effective way to increase satiety.
Relevant links
- Trough half empty: Pregnant sows are fed under half of their ad libitum intake, Read et al., Animal Welfare, 29(2), pp. 151-162, 2020
- Inclusion of intensively manipulated silage in total mixed ration to growing pigs – influence on silage consumption, nutrient digestibility and pig behaviour, Presto Åkerfeldt et al., Acta Agriculturae Scandinavica, Section A — Animal Science, 68(4), pp. 190-201, 2018
- Mitigating hunger in pregnant sows, D'Eath et al., In: ‘Advances in Pig Welfare’, pp. 199-234, 2018
- Effects of group housing on sow welfare: a review, Verdon et al, Journal of Animal Science, 93(5), pp. 1999-2017, 2015
- Effects of feeding different roughage components to sows in gestation on bacteriological and immunological parameters in colostrum and immune response of piglets, Werner et al., Archives of Animal Nutrition, 68, pp. 29-41, 2014
- Council Directive 2008/120/EC laying down minimum standards for the protection of pigs, EC, 2008
- The behaviour of pigs in a semi-natural environment, Stolba, A., and Wood-Gush, D. G. M. (1989). Animal Science, 48(2), pp. 419-425
Climatic and resting comfort
Characteristics of climatic and resting comfort:
- Sows in nature rest together in a communal nest and they cushion their lying area with bedding material such as straw if available.
- Sows spend approximately 80% of their time lying.
- When given the choice, pregnant sows prefer soft, followed by hard rubber mats for lying in comparison to a concrete floor.
- The sows’ thermo-neutral zone is around 15-20°C, and they cannot sweat.
- Heat stress starts above 20°C and is critical above 26°C. A high relative humidity makes heat stress worse.
Read more & relevant links
Improving climatic and resting comfort involves:
- Clean, dry bedding (e.g. straw) or cushioning, e.g. using rubber mats (see also ‘Inspiring examples’), to improve resting comfort and reduce leg and claw problems.
- Proper heat disposition (cooled air, floor cooling, misting and sprinkling systems, etc.).
- Warm and cool surfaces for resting (e.g. a partly-slatted floor).
- Adjusted management (e.g. feeding and thermal control) during periods of hot weather.
Relevant links
- Heat stress in pregnant sows: Thermal responses and subsequent performance of sows and their offspring, Lucy and Safranski, Molecular Reproduction and Development, 84(9), pp. 946-956, 2017
- Longitudinal study of the effect of rubber slat mats on locomotory ability, body, limb and claw lesions, and dirtiness of group housed sows, Diaz et al., Journal of Animal Science, 91, pp. 3940-3954, 2013
- Review of wallowing in pigs: Description of the behaviour and its motivational basis, Bracke, Applied Animal Behaviour Science, 132, pp. 1-13, 2011
- Use of different cooling systems by pregnant sows in experimental pen, Barbari and Conti, Biosystems Engineering, 103, pp. 239-244, 2009
- Council Directive 2008/120/EC laying down minimum standards for the protection of pigs, EC, 2008
- Thermal behaviour of growing pigs in response to high temperature and humidity, Huynh et al., Applied Animal Behaviour Science, 91(1), pp. 1-16, 2005