Changes in hemostatic mechanism of broiler chickens in response to overcrowdness

The present investigation was done to study the effect of overcrowdness as a stress factor on the hemostatic mechanism in broiler chickens. Birds were allocated into 2 groups. The first group acted as control [100 baby chicks/m 2] and the second was crowded group [200 baby chicks/m 2]. Blood samples were collected by cardiac puncture from birds of both groups every week for 7 successive weeks. Some blood coagulation parameters were determined including prothrombin time [PT], activated partial thromboplastin time [APTT], activities of clotting factor 8 and 9, fibrinogen concentration and platelet count. The results revealed that no changes in the tested blood coagulation parameters were recorded during the first three weeks of experiment except a significant increase in the platelet count that occurred between the 2nd and 5th weeks of the experimental period. No changes were recorded in PT all over the experimental period. Activated partial thromboplastin time and fibrinogen concentration were significantly decreased from the 4th and 5th weeks till the end of the experimental period, respectively. Activities of clotting factors 8 and 9 were significantly increased from the 4th week till the end of the experiment. So, it is clear that overcrowdness may affect the hemostatic mechanism of broilers in the form of enhanced intrinsic blood coagulation pathway that detected after the first three weeks of life. This may lead to intravascular coagulation that considered as a possible cause of increased mortality in stressed chickens