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Thymus atrophy and regeneration following dexamethasone administration to beef cattle
  1. F. T. Cannizzo, PhD1,
  2. F. Spada, DVM1,
  3. R. Benevelli, DVM2,
  4. C. Nebbia, DVM3,
  5. P. Giorgi4,
  6. N. Brina, DVM4,
  7. E. Bollo, DVM1 and
  8. B. Biolatti, DVM1
  1. 1 Dipartimento di Patologia Animale, Sez. Anatomia patologica
  2. 2 Quinto valore spa, Via Due Canali, 13 42100 Reggio Emilia, Italy
  3. 3 Dipartimento di Patologia Animale, Sez. Farmacologia e Tossicologia, Facoltá di Medicina Veterinaria di Torino, Universitá di Torino, Via L. da Vinci 44, 10095 Grugliasco (TO), Italy
  4. 4 Coop italia, Via del Iavoro 6/8, 40033 Casalecchio di Reno (Bo), Italy
  1. E-mail for correspondence: tiziana.cannizzo{at}unito.it

Abstract

Thymus atrophy and regeneration were studied in 13- to 22-month-old beef calves treated with dexamethasone (DMT), using anabolic dosages and implementing different withdrawal times. Two trials were conducted. In trial 1, group A (n=6) received 0.7 mg/day DMT orally for 40 days, group B (n=6) received 1.4 mg/day orally for 40 days and group C (n=6) was the control. In trial 2, group D (n=6) received 0.7 mg/day DMT orally for 40 days, group E (n=6) received 1.4 mg/day orally for 40 days and group K (n=6) was the control. DMT withdrawal times before slaughter were six days (groups A and B) and 26 days (groups D and E). At slaughter, thymus atrophy was severe and progressive in animals from groups A and B. In contrast, thymus weight and volume of the animals from groups D and E were almost normal. Slight atrophy was also detected in the calves in these groups. Histological changes and Ki67 immunostaining revealed a large number of positive lymphoid cells, mostly in the cortical area, associated with higher expression of apoptosis in the medulla compared with controls. This demonstrated that the thymus of beef cattle is still able to regenerate following DMT administration.

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