Blood Cortisol as an Objective Tool to Measure Painful and Non-painful Hoof Lameness States in Multiparous Sows
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The objective of this study was to compare blood plasma cortisol concentrations from sows in painful and non-painful hoof lameness states. Ten, clinically healthy, mixed-parity, crossbred sows were used. The sow was the experimental unit and a cross-over design with a 2 (legs) x 3 (days) factorial arrangement of treatments were compared.On D 0, Ten mg of amphotericin B were injected in the distal interphalagneal joint space in both claws of one rear foot. All sows served as their own control and treatment. After completion of the first round, sows were given a 10-d rest period and then the trial was repeated. Blood cortisol was measured on sound (D-1; 1 day before induction), most lame (D+1; first day after injection of amphotericin B to induce lameness) and resolved day (D+6; 6th day after the induction of lameness). Cortisol sample analysis was completed with the IMMULITE®1000 cortisol assay. All data were statistically analyzed using the PROC MIXED procedure in SAS. A P value of ≤ 0.05 was considered to be significant. No differences were observed for foot (P = 0.78) or round (P = 0.86). There was no difference in cortisol levels between D -1 and D +6 (P = 0.35), but sows expressed higher cortisol concentrations on most lame day (D +1; Figure 3; P=0.0013). In conclusion, lameness induced with amphotericin B was associated with elevated plasma cortisol levels relative to baseline (day-1) and resolution (day+6).