Although the diagnosis of SR was based on field observations by a number of veterinary surgeons, the diagnoses are considered reliable as the morphology of SR is probably well known to veterinarians. Detailed morphological descriptions were not available, although additional defects as e.g. fissure of the genitals and polypodia were reported.
Pedigree analyses included seven generations in most cases, while nine generations pedigrees were available in some cases. In a number of cases, pedigrees were incomplete due to unregistered descent. One case was omitted from the calculations as the descent of dam of an affected calf was unknown. The 29 SR cases were progeny of 29 sires.
Twenty-one SR affected calves were genetically related (Figure ). Of these, 18 SR cases had a common ancestor in the paternal and maternal pedigrees (inbreeding loops). All sires producing SR cases were purebred Holsteins. Overall 106 ancestors with multiple occurrences were identified by analysis of the individual SR pedigrees. Usually the number of repetitions ranged from two (48 ancestors) to seven (six ancestors). However, three sires (I/2, II/1 and III/2 in Figure ) were repeated 61, 58 and 22 times, respectively. In addition to the pedigree including 21 cases, a minor pedigree with a few cases of SR were identified (Figure ). Three cases of SR were progeny of the same grandfather, and two of the grandmothers were related while the third was of unknown descent.
Figure 1 Pedigree of 21 schistosoma reflexum affected calves. The animals in Figure 2 are not included here. Generations are numbered from the top of the pedigree in uppercase Roman numerals. Individuals in each generation are numbered from the left in Arabic (more ...)
Figure 2 Pedigree of three schistosoma reflexum affected calves. The common grandfather V/2 is crossbred Holstein (75%) and Simmental (25%). Sires VI/1 and VI/3 are crossbred Simmental (63%) and Holstein (37%). Sire VI/2 is crossbred Simmental (51%) and Holstein (more ...)
For comparison, 15 additional sires not fathering SR affected calves were analysed. These 15 sires were not of the same lines as the sires fathering SR calves. Of the three sires (I/2, II/1 and III/2) often present in the pedigrees of SR calves (Figure ), solely I/2 occurred in these comparative pedigrees but only rarely. Other ancestors with repeated occurrence in SR pedigrees hardly appeared in the comparative pedigrees thus indicating that affected calves shared common ancestors different from those shared by the unaffected offspring.
The inbreeding coefficient was calculated for SR calves and the sires selected for comparison. The coefficient was calculated only for calves with common ancestors up to and including the 5th generation in the parental pedigrees. For SR calves, only 11 individuals complied with this requirement. All 11 calves were included in the pedigree shown in Figure , and they had an average Fx of 0.94% (range: 0.20% to 2.34%). The average inbreeding coefficient of the sires fathering SR calves was 1.55%. The Fx of control Holstein sires not having registered SR affected offspring was 0.03%, while the average coefficient of all sires in the Czech registry was 0.67%. If only registered sires with a coefficient greater than zero were included, the average inbreeding coefficient was 2.49%.
During the period 1986-2001, 2740 Holstein sires entered the Holstein pedigree herd book in the Czech Republic. Thus, 0.84% of Holstein sires fathered a SR calf.