Pattern of Eimeria oocyst output and repeatability in naturally infected suckling Rhön lambs.

The faeces of 14 Rhön lambs were examined every second day between 7 and 99 days of age for the presence of Eimeria oocysts. Eimeria absata, E. bakuensis, E. faurei, E. granulosa, E. intricata, E. ovinoidalis, E. pallida, E. parva and E. crandallis/weybridgensis were identified. The predominant species were E. ovinoidalis, E. parva, E. crandallis/weybridgensis and E. bakuensis. Using a statistical model, the oocyst excretion rate was described as a sequence of periods with decreasing levels and varying length ('excretion periods') interrupted by intervals with no or very low oocyst counts. Several variables could be deduced from these two parameters, including the length of an excretion period and the maximum output during an excretion period. Thc estimated repeatability for oocyst counts for the different species ranged from 0.05 to 0.41. This result provides a starting point for possible genetic selection based on faecal oocyst counts of Rhön sheep for resistance to Eimeria infections.