Effect of Pasteurella multocida toxin on physeal growth in young pigs

To determine whether Pasteurella multocida toxin (PMT) affects growth of the proximal portion of the humerus of young pigs.

20 colostrum-deprived, cesarean-derived pigs.

5 groups (n = 4/group) of pigs were formed. Group-1 pigs received 0.1 ml of phosphate-buffered saline solution for 4 weeks; group-2 pigs received 0.05 microgram of PMT/kg of body weight at 14 and 21 days; group-3 pigs received 0.05 microgram of PMT/kg at 28 and 35 days; group-4 pigs received 0.1 microgram of PMT/kg at 14 and 21 days; and group-5 pigs received hyperimmune serum (from a sow given purified toxin) on days 13, 20, 27, and 34, and 0.1 microgram of PMT/kg on days 14, 21, 28, and 35.

All pigs given 0.1 microgram of PMT/kg without serum died or were euthanatized, as were 4 pigs given 0.05 microgram of PMT/kg. These pigs had increased serum interleukin 1 and 6 bioactivities. Pigs surviving 0.05 microgram of PMT had decreased weight gain, rough coat, marked atrophy of the ventral concha (as determined by turbinate perimeter ratios), and small stature. The surviving pigs also had reduced area and decreased proliferation indices in physeal chondrocytes on the basis of bromodeoxyuridine immunoreactivity. Control and serum-treated pigs gained weight, had no clinical effects, had similar physeal areas, and had higher cell proliferation indices.

PMT inhibits endochondral bone formation by reducing physeal area and chondrocyte proliferation in vivo. Hyperimmune serum neutralizes the effects of toxin on weight gain, clinical appearance, physeal area, and chondrocyte proliferation.

PMT may affect growth of the skeletal system. Antiserum to PMT is protective.