Calf-Level Factors Associated with Bovine Neonatal Pancytopenia – A Multi-Country Case-Control Study

Jones, Bryony A.; Sauter-Louis, Carola; Henning, Joerg; Stoll, Alexander; Nielen, Mirjam; Van Schaik, Gerdien; Smolenaars, Anja; Schouten, Matthijs; den Uijl, Ingrid; Fourichon, Christine; Guatteo, Raphael; Madouasse, Aurélien; Nusinovici, Simon; Deprez, Piet; De Vliegher, Sarne; Laureyns, Jozef; Booth, Richard; Cardwell, Jackie M.; Pfeiffer, Dirk U.

Data were collected for 502 suspected cases and 1583 potential controls from 410 farms. However, 62 suspected cases did not fit the case definition, 122 potential controls had incomplete blood results, and 210 potential controls had ''atypical'' blood results (thrombocytes ,300610 9 /litre and/or leucocytes ,5610 9 /litre). Exclusion of these led to the loss of 97 confirmed controls with no matching case and 35 confirmed cases with no matching control. The remaining 405 confirmed cases were matched to 1154 confirmed controls from 330 farms with an overall case control ratio of 1:2.8 ( Table 1 ). The proportions of dairy, beef and mixed farms that were included in the study from each country approximately reflected the proportions of those types of farms in each country. In the Netherlands, dairy farms predominate so almost all suspected calves came from dairy farms. In Germany a high proportion of cases recruited were from the south where beef farms are few so the high proportion of dairy farms reflects the regional distribution. The number of cases per farm varied from 1 to 3 and the number of controls from 1 to 9 (Table S1 ). The proportion of males amongst cases (41%) was higher than amongst controls (34%). In the Netherlands, cases were more likely than controls to be male probably due to the sale of male calves before one month of age so fewer were available to be selected as controls. This difference was not observed in the other countries. The most common breed of calf was Holstein-Friesian or Red Holstein-Friesian (56.0%), followed by Fleckvieh (13.7%), Belgian Blue (7.0%), Charolais (5.9%), other pure beef or dairy breeds (7.8%), and crossbreeds (9.6%) (Table S2 ). There was no evidence of a difference in breed distribution between cases and controls.