GTP meeting 2000: Case No 11

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Species:

Pig

Strain/breeder:

German cross bred

Sex:

Female

Age:

2.5 months

Study type:

Nutritional intoxication

Treatment:

Animal status:

Euthanasia

Clinical findings:

Lameness, hoof sloughing, paralysis, recumbency

Organ:

Spinal cord

Macroscopic
finding(s):

Hemorrhages, bilateral grey-yellow discoloration of the ventral columns of the cervical enlargement

Staining:

H&E

Literature:

	Summers BA, Cumming JF, deLahunta A (1995) Veterinary neuropathology. Mosby, St. Louis, Baltimore, pp 208-350
	Wilson TM, Scholz RW, Drake TR (1983) Selenium toxicity and porcine focal symmetrical poliomyelomalacia: description of a field outbreak and experimental reproduction. Can J Comp Med 47: 412-421
	Casteel SW, Osweiler GD, Cook WO, Daniels G, Kadlec R (1985) Selenium toxicosis in swine. J Am Vet Med Assoc 186: 1084-1085
	Harrison LH, Colvin BM, Stuart BP, Sangster LT, Gorgacz EJ, Gosser HS (1983) Paralysis in swine due to focal symmetrical poliomyelomalacia: possible selenium toxicosis. Vet Pathol 20: 265-273

(71k)

Abstract

POLIOMYELOMALACIA IN FATTENING PIGS DUE TO SELENIUM POISONING

Aim of the study
The feeding management has significant influence on the performance and health of weaned pigs. Supplementation of zinc oxide to creep feed has been reported to have beneficial effects on diarrhoea incidence and performance.

Materials & methods
In a fattening herd a sudden onset of hoof sloughing, lameness, canibalism and recumbency with tetraparesis was observed in approximately 20% of the weaned pigs.

Results
Clinically, affected animals were afebrile, alert and maintained appetite. Coronary bands were swollen and showed exsudation. The animals were lame and some lost their hoofs. Three affected pigs were submitted for necropsy. Pathomorphologically, gradually variable pododermatitis was present on the parietal and solear surface of the hoofs. The main findings in the central nervous system were poorly demarcated yellow-greyish areas with occasional hemorrhages confined to the ventral grey horns of the cervical and lumbar enlargements of the spinal cord. Histological examination revealed a bilaterally symmetric, focal poliomyelomalacia with degeneration and necrosis of neurons, vacuolisation of the neuropil, proliferation of capillaries and infiltration of gitter cells. The toxicological analysis of serum and liver samples of the affected animals resulted in extraordinary elevated levels of selenium. As source of the intoxication the mineral feed was identified with a selenium content of 613.0 mg/kg. The normal range of selenium in supplementary mineral feed is about 15.0 mg/kg.

Conclusions
The history of this case revealed that for the zinc supplementation of the creeping feed inexpensive zinc sulfate was used, which originated from the zinc industry and which was not certified as feeding supplement. The high contamination with selenium was responsible for this toxicosis in fattening pigs.

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