A review of environmental enrichment for pigs housed in intensive housing systems

This paper critically reviews the literature concerning environmental enrichment for weaner, grower and finisher pigs housed in intensive (indoor) production systems. The thesis of our review is that successful enrichment should meet four criteria of success: (1) it should increase species-specific behaviour, (2) it should maintain or improve levels of health, (3) it should improve the economics of the production system, and (4) it should be practical to employ. We review the existing literature for three distinct classes of production systems; alternative enriched systems; straw-based systems, and barren systems enriched only with objects (‘point-source enrichment-objects’). Within each of these systems, we consider the effects of environmental enrichment on behaviour; health and physiology; animal performance, carcass quality and meat quality. We conclude that straw has the highest potential to meet the four successful enrichment criteria that we propose. However, we concede that it is possible to design successful point-source enrichment-objects if the wealth of knowledge available on enrichment for pigs is exploited. We also identify several knowledge gaps, especially in the area of the neurobiological effects of enrichment, which should be the focus of future research to advance the welfare of intensively reared pigs.