There are no approved drug treatments for analgesia use in swine, and the identification and validation of objective, repeatable pain measurements is fundamental for the development of effective analgesic drug regimens and management strategies for use in lame pigs. Induction of lameness allows for controlled evaluation of lameness pain in animals because pre- and post lameness measurements can be taken from the same animal, thereby reducing the confounding effects of individual differences. Therefore, the objective of this pilot study was to characterize differences in weight bearing that result from the amphotericin B chemical synovitis model in sows and test a prototype embedded prototype micro-computer based force plate system plate to determine its usefulness in detecting lameness in sows. A total of 24 mixed parity sows were used. Six sows were allocated to one of four treatment groups: sows that were injected on the front left hoof (n = 6), front right hoof (n = 6), rear right hoof (n = 6) and left rear hoof (n = 6). Each sow served as her own control and weight carried by each of all four legs was measured individually at all time periods. Pigs were anesthetized and injected with 10 mg of amphotericin B in both of the most distal interdigital joint spaces of the assigned foot. Data were collected on the embedded force plate the day before induction of lameness (D0; baseline), the day after induction (D2; most lame) and 7 days after induction of lameness (D8; recovery and resolution of lameness). Data for this pilot study was analyzed using the PROC MIXED procedure in SAS. When clinically sound (baseline; B) sows placed equal amount of weight over the four hooves, but on the day after injection when they were clinically the most severely lame, (L) regardless of the hoof treated, sows placed less weight on that injected hoof and dispersed their weight over the three unaffected hooves. Seven days after injection, lameness had resolved (R) clinically, and sows were placing equal weight over their four hooves as measured on the prototype (Figure 3a-d). This pilot study demonstrated that injection of 10 mg of amphotericin B in the distal interphalangeal joints of the foot causes clinical lameness in sows that is distinguishable from their pretreatment gait by observational lameness score and using an embedded microcomputer based force plate system. Additionally, this lameness spontaneously resolved in this study by 7-days post injection.
Available at: http://works.bepress.com/kenneth_stalder/46/