The environmental impact of sheep confinement feeding systems

Abstract

Confinement feeding systems are being used increasingly in dryland Australia for the finishing of lambs, and for maintenance of the flock in drought conditions. They have great potential as part of the farming system to address other major issues, such as herbicide resistance, soil compaction and improved management of pastures through deferred grazing. Whilst the benefits of confinement feeding systems are well documented, the environmental risks they pose and how can these risks be minimised through site selection, design and management are less well understood. Current legislation and guidelines consider sheep to be mini cows, but there are significant physiological and production differences between intensive cattle and sheep systems that may influence their relative potential to cause environmental harm. This paper examines the key differences between the 2 systems, particularly the pollution potential of cattle and sheep manure that is influenced by levels of moisture, nutrients and biochemical oxygen demand. It also questions how a grain-based diet may influence levels of pathogens in sheep manure, and the potential impact on food safety. There are large gaps in our knowledge of the environmental impact of sheep confinement feeding systems in Australia. Producers need guidelines on site selection, design and management of sheep confinement feeding systems to minimise environmental harm, but these must be based on sound research if sheep meat and wool are to retain their product integrity.