Influence of dystocia on white blood cell and blood neutrophil counts in mares.

A retrospective study was done on total white blood cell (WBC) and blood neutrophil counts of 41 mares referred to one of two veterinary hospitals for correction of dystocia. The mares were 2 to 19 years of age and included draft, light, and pony breeds. The WBC and neutrophil counts were performed at varying intervals from time of admission to 10 d after delivery of the feti. Retrospective analyses of WBC and neutrophil counts from 10 normal foaling mares from two Pennsylvania breeding farms (Thoroughbred and Trakehner) and from 14 normal foaling pony mares were done as controls. Mean WBC (10446 +/- 2296 cells/mul) and neutrophil (6850 +/- 2136 cells/mul) counts on the day of delivery in mares with normal parturition were slightly elevated over values reported as normal in the literature. The mean blood cell counts gradually declined to 6124 +/- 1255 WBC/mul and 3692 +/- 409 neutrophils/mul on Day 2 postpartum and returned to normal baseline values by Day 3 postpartum (8868 +/- 2693 WBC/mul, 4298 +/- 1966 neutrophils/mul). No toxic neutrophils were present in mares with normal delivery. Mean WBC (11346 +/- 3298 cells/mul) was elevated on the day of delivery in mares with dystocia as a result of neutrophilia with a left shift (9297 +/- 3298 neutrophils/mul). An apparently faster decline occurred in WBC and neutrophil counts of mares with dystocia than in mares with normal delivery, until a marked leukopenia (3905 +/- 1292 WBC/mul) and neutropenia (1570 +/- 1340 neutrophils/mul) occurred on Day 3 postpartum. The leukopenia and neutropenia persisted until Day 5 postpartum. Toxic neutrophils were present in several mares with dystocia.