The objective of an animal welfare study at Iowa State University was to compare blood cortisol levels in sows of various parities to assess painful and non-painful hoof lameness.

Lameness disorders can be associated with neurological disorders, lesions of the hoof or limb, mechanical-structural problems, trauma or metabolic or infectious diseases.

Lameness is a common reason sows are culled from the breeding herd. Producers and veterinarians need a robust and repeatable means of determining levels of animal lameness.

One such measure is cortisol, which is the most abundant circulating steroid and the major glucocorticoid secreted by the adrenal cortex. Cortisol concentration has been used in other studies to assess stress levels in livestock.

Ten commercial, mixed-parity, crossbred sows were housed in individual pens measuring 12.2 ft. long x 4.6 ft. wide and 4.0 ft. high. A rubber mat was provided for sow comfort. Sows had ad-lib access to a nipple waterer. Lights were on a 12:12 light-dark cycle. Sows were acclimated 10 days before treatments.

In a crossover design, lameness was induced in the right rear leg of five sows and the left rear leg of five sows using amphotericin B. Blood was collected when sows were sound, when they were most lame and when lameness was resolved. After completion of the first round, sows were given a 10-day rest and then the trial was repeated.

The process of lameness induction started with all sows being restrained in a standing position and then anesthetized. The assigned claws to be injected were washed with mild soap and water to remove fecal contamination. Then they were scrubbed for three minutes with an iodine-based surgical scrub. Ten mg. of amphotericin B was injected in the distal interphalagneal joint space in both claws of one rear foot. All sows were monitored continuously until fully recovered.

No differences were observed for sows that had lameness induced in the left leg vs. right leg or during the two rounds of treatment.

There was also no difference between cortisol levels taken when sows were sound and lameness was resolved; cortisol concentration was greatest on the day when sows were most lame.

Lameness induced with amphotericin B was associated with elevated plasma cortisol levels relative to baseline (sound) and resolution (of lameness).

Researchers: C. Mohling, A.K. Johnson, L.A. Karriker, K.J. Stalder, S.M. Millman and J. Coetzee, Iowa State University. For more information, contact Johnson by phone (515) 294-2098, fax (515) 294-4471 or e-mail johnsona@iastate.edu.