The Influence of Pen Space Quantity and Quality on Sheep Welfare in the Context of Australia's Live Export Industry

Abstract

<p>Australia is a major exporter of live animals, and around half a million sheep were exported in both 2021 and 2022. Countries of the Middle East represent the largest market demand for live Australian sheep, and most sheep exported to these destinations depart from Fremantle, WA, for a sea voyage that generally lasts between 14 to 21 days. In recent years, there has been extensive public concern regarding the welfare of animals, including sheep, on live export ships. The live export process is complex and involves various stages, including sourcing, handling, loading and the sea transport phase, which was the focus of the work described in this research. Specifically, this research investigated how sheep welfare is impacted by the quantity and quality of pen space during periods of intensive housing, such as what is experienced during live export voyages. An accumulated stressors approach was implemented to first investigate the impacts of stocking density severally, and then also in combination with restricted feed trough space, and then in combination with hot and humid conditions.</p> <p>Chapter 3 of this thesis examined how the quantity of pen space (i.e., stocking density) and the quality of pen space with regards to feed trough space restriction, impact the welfare of intensively housed sheep in a land-based experiment conducted in thermoneutral conditions. The provision of additional pen space was beneficial in reducing the time taken for sheep to behaviourally adapt to their environment, and in facilitating the expression of some preferred lying positions. Despite this, a lack of important impacts on the stress physiology and biological fitness characteristics of the sheep was observed. Unlike pen space, the trough space allowances investigated here had no important effects on the behaviour, stress physiology or biological fitness characteristics.</p> <p>Chapter 4 of this thesis built upon the findings from Chapter 3, to investigate the potential impacts of stocking density on the biological functioning and thermoregulation of sheep housed intensively on land, under continuously hot and humid conditions. The climatic conditions imposed were similar to what would be experienced by sheep travelling from Australia to the Middle East at certain times of the year that have been identified as problematic by the industry and the public, with regards to heat stress risk. Similar to the work described in Chapter 3, additional pen space facilitated the ability of sheep to lie in preferred positions, such as with legs outstretched from their body or in physical isolation from conspecifics in their pen, but the effects on stress physiology and biological fitness characteristics were limited. Stocking density did not have an effect on the thermoregulatory ability of the sheep, although results did indicate that the reliance on evaporative cooling through the respiratory tract may be reduced by providing more space at high temperatures. Importantly, individual variation and maximum rumen temperature and respiration rate values suggested that not all wethers were able to effectively regulate their core temperature under these conditions.</p> <p>In chapter 5, the presence and consistency of individual differences in aggressive behaviours expressed by wethers in a competitive feeding environment was investigated. Sheep were provided with restricted feed trough space and fed a maintenance quantity of pelleted feed, and the results indicated that sheep that displayed more aggression were at an advantage for accessing feed faster and more frequently within each feeding period. As such, the attempts of individuals to cope with the competitive feeding environment were not equal.</p> <p>This research provides evidence that while the provision of additional pen space may allow sheep to adapt to an intensive housing environment faster, and facilitates the expression of some lying positions, implications for stress physiology and the biological fitness of sheep are limited, at least under highly controlled experimental conditions. In addition, sheep do not have an equal ability to access feed in competitive feeding environments, so the provision of feed trough space which permits synchronous feeding, or an <i>ad libitum</i> quantity of feed are important for industries, such as during livestock export voyages, which feed sheep from troughs. This thesis also identified 5 clear recommendations for future research which continue to accumulate relevant stressors and build on the theories about stocking density reported here, so that potential interactions between stocking density and other relevant factors present during voyages can be explored.</p>