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Simple Summary: Sheep in Australia are transported to abattoirs for slaughter by trucks and usually left in lairage (holding pens) overnight. They are then moved through the abattoir via a series of pens that ultimately leads to a single file race immediately before slaughter. This movement has the potential to induce considerable stress among the sheep, thus compromising welfare. This study introduces the concept of 'Optimal Flow', where sheep movement through the abattoir is the most efficient balance between speed and minimising overt signs of distress in sheep. The results of the pilot study suggest that Optimal Flow at this abattoir occurs when sheep are given enough space to move freely. Abattoirs are faced with the challenge of moving livestock efficiently through the plant, while also engaging in handling practices that assure good animal welfare. Achieving optimal outcomes for both of these goals can bring them into conflict. An additional source of conflict can arise from the design of the abattoir. These problems are compounded by the dearth of research available to inform how livestock should be handled to achieve all of these goals. We applied the concept of 'Optimal Flow' to describe conditions under which rate of movement is maximised while overt signs of distress in sheep are minimised. Effectively, this represents the point at which trade-offs between speed and welfare converge. The current pilot study examined the behavioural interactions between humans (n = 5), livestock herding dogs (n = 7), and sheep (n = 3235) in a large Australian abattoir to describe the factors associated with an increase or decrease in rate of sheep movement per minute. It revealed that distress behaviours in sheep were associated with dog presence and with a decrease in livestock movement rate. However, we found that as sheep density increased, there was increased livestock movement rate as well as an elevated incidence of distress behaviours. Optimal Flow at this abattoir was achieved by maintaining sheep at lower densities. Our report discusses the possible confounds in this interpretation. [ABSTRACT FROM AUTHOR]