Pa. Gentry et al., AN INHERITED PLATELET-FUNCTION DEFECT IN A SIMMENTAL CROSSBRED HERD, Canadian journal of veterinary research, 61(2), 1997, pp. 128-133
An inherited bleeding disorder, resembling Simmental hereditary throma
bopathy (SPIT), has been identified in a Simmental crossbred herd. In
an affected bull calf, initially evaluated because of excessive bleedi
ng from a vaccination site, the platelet aggregation response to the a
gonist, adenosine-diphosphate (ADP) was essentially absent and the agg
regation response to platelet activating factor (PAF(16)) was reduced
by at least 70%, The initial laboratory assessment of platelet functio
n in the dam and sire yielded results which were within normal limits,
The sire was mot available for further testing, The dam, also a daugh
ter of this sire, was subsequently shown to have a partially reduced a
ggregation response to ADP. Of 18 other offspring of the sire evaluate
d, 6 were also identified as having a partially impaired aggregation r
esponse, The maximum aggregation response to ADP and PAF(16) in these
6 calves was approximately 50% of the level exhibited by unaffected an
imals, In contrast, the coagulation profiles were normal for all anima
ls except for a heifer calf which also exhibited a partially impaired
aggregation response, The plasma level of the coagulation protein, fac
tor XI, was reduced in this heifer calf which suffered a fatal hemorrh
age following dehorning, This report appears to be the Ist to have ide
ntified animals putatively heterozygous for SHT on the basis of the in
vitro platelet aggregation response to ADP.