Factors associated with changes of state of foot conformation and lameness in a flock of sheep.

The aim of this research was to investigate transitions between foot conformation, lameness and footrot in sheep. Data came from one lowland flock of approximately 700 ewes studied for 18 months. Multilevel multistate analyses of transitions between good and poor foot conformation states in ewes, and lame and non-lame states in ewes and lambs were conducted. Key results were that the longer sheep had feet in good conformation, the more likely they were to stay in this state; similarly, the longer a ewe was not lame the more likely she was not to become lame. Ewes with poor foot conformation were more likely to become lame (OR: 1.83 (1.24-2.67)) and to be >4 years (OR: 1.50 (1.09-2.05)). Ewes with footrot were less likely to move to good foot conformation (OR: 0.48 (0.31-0.75)) and were more likely to become lame (OR: 3.81 (2.60-5.59)). Ewes lame for >4 days and not treated with parenteral antibacterials had a higher risk of developing (OR: 2.00 (1-3.61)), or remaining in (OR: 0.49 (0.29-0.95)), poor foot conformation compared with ewes never lame. Treatment of ewes lame with footrot with parenteral antibacterials increased the probability of transition from a lame to a non-lame state (OR: 1.46 (1.05-2.02)) and these ewes, even if lame for >4 days, were not more likely to develop poor foot conformation. The risk of a ewe becoming lame increased when at least one of her offspring was lame (OR: 2.03 (1.42-2.92)) and when the prevalence of lameness in the group was ≥5% (OR: 1.42 (1.06-1.92)). Lambs were at increased risk of becoming lame when they were male (OR: 1.42 (1.01-2.01)), single (OR: 1.86 (1.34-2.59)) or had a lame dam or sibling (OR: 3.10 (1.81-5.32)). There were no explanatory variables associated with lambs recovering from lameness. We conclude that poor foot conformation in ewes increases the susceptibility of ewes to become lame and that this can arise from untreated footrot. Treatment of ewes lame with footrot with parenteral antibacterials leads to recovery from lameness and prevents or resolves poor foot conformation which then reduces the susceptibility to further lameness with footrot.