Review: Concrete outdoor runs for organic growing-finishing pigs - a legislative, ethological and environmental perspective

Concrete Outdoor Runs (OUTRUNs) are a characteristic part of organic pig housing. They must allow species-specific behaviours such as rooting and elimination, as explicitly required by organic legislation of the European Union (EU). However, OUTRUN design often fails to fulfil behavioural needs, and excreta can cover large parts of the OUTRUN leading to poor pen hygiene and associated ammonia (NH3) emissions. This review integrates legislative, ethological and environmental requirements for OUTRUNs for organic growing-finishing pigs. While EU regulations specify some welfare-related standards for OUTRUNs (e.g. minimal space allowance), national and private standards interpret some aspects differently, e.g. the proportion of roofed and slatted floor area. Furthermore, reducing NH3 emissions is equally a challenge for organic systems, even though EU legislation does not explicitly refer to OUTRUNs. Depending on the actual use of the OUTRUN for elimination, higher space allowance compared to conventional production norms increases the potential for a large NH3-emitting surface. The design of pen features (e.g. roof, floor, enrichment) can encourage pigs to separate functional areas and consequently reduce the elimination area and associated NH3 emissions. While providing the main lying area indoors, resting outdoors should be possible for sub-groups during the day. A roof protects pigs and resources (e.g. bedding) from adverse weather, but the effect on pig welfare and NH3 emissions is site-specific. A floor design that ensures practicable manure removal and drainage is most important to reduce emissions. Providing opportunities for exploring and rooting in the OUTRUN has particular relevance for pigs' behavioural needs and can improve pen hygiene by reducing the elimination area. Cooling facilities are increasingly important to prevent heat stress and its detrimental effects on welfare and pen hygiene. Finally, practicability for farmers needs to be ensured for all resources provided in OUTRUNs, as good management is crucial. Research gaps emerge regarding the association between soiling and NH3 and the influence of certain pen features (shape, roof, feeder location, pen partitions and wet areas) on pig behaviour and soiling. (C) 2021 The Author(s). Published by Elsevier B.V. on behalf of The Animal Consortium. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

Concrete Outdoor Runs (OUTRUNs) are an essential part of organic pig housing, but their design often fails to meet the behavioral needs of pigs and results in poor pen hygiene and ammonia emissions. EU regulations provide some welfare standards for OUTRUNs, but national and private standards may interpret them differently. Reducing ammonia emissions in organic systems is a challenge, and the design of pen features can play a role in reducing emissions and improving pen hygiene. Providing opportunities for pigs to explore and root in OUTRUNs is important for their behavioral needs and pen hygiene. Cooling facilities are also important for preventing heat stress. Practical management is crucial for the success of OUTRUNs. Research gaps exist regarding the association between soiling and ammonia emissions and the influence of certain pen features on pig behavior and soiling.