Einfluss der Lagerungsdauer auf die Brutergebnisse von Straußeneiern (Struthio camelus)

Environmental conditions influence hatchability of ostrich eggs as these include the length of the storage period, temperature, humidity, gaseous environment, and orientation of the eggs (MELLET, 1993). There is a decrease in hatchability of the egg during storage (MEIJERHOF, 1992). A study in poultry (BUTLER, 1991) suggests that longer storage delays hatch time and reduces chick quality and growth rate. However, species variation exists. For example, KosIN (1964) has indicated that chicken eggs when stored for 14 days show a severely reduced hatchability, whereas hatchability of Bobwhite quail eggs may only be slightly affected (WILSON, 1984). Very little research has been conducted on the effects of storage length on the hatchability of ostrich eggs. Due to the exceedingly high price of fertile ostrich eggs it was not possible to conduct storage experiments with large numbers of eggs. DEEMING (1993) found that storage for langer than seven days will result in a gradual decline in hatchability with a significant reduction after 14 days. By contrast, GONZALEZ et al. (1999) determined that ostrich eggs can be stored for a minirnum of 10 days without negatively impacting on hatchability. In the wild, ostrich adults are capable of incubating up to 22 eggs per nest. Oviposition in ostriches is approxirnately at 2-d intervals. The eggs laid early in a nest thus typically remain in the nest for 2 to 3 weeks before being incubated naturally (BERTRAM and BURGER, 1981) and all eggs in the clutch hatch at the same time. In the wild, the ambient temperature reaches 30-40 °C during the day and in the sun may exceed even 50 °C. As already mentioned, an exposure of eggs to direct sun significantly decreases the hatchability of eggs, thus leading to a considerable variability within one nest. However, in some cases despite high air temperature hatchability reaches even over 80% (HORBANCZUK, 2002) if the period from the laying of the first egg to the time when the ostrich starts sitting does not exceed 7 -10 days and if the birds protect the eggs from füll sun exposure. BRAKE et al. (1994) suggest that this is caused by differences between eggs in albumen quality. The first eggs in the clutch have a superior viscosity of albumen and can withstand langer storage and high temperatures than the later eggs. In the ostrich at the start and end of the laying season, storage may be even longer in order to ensure that sufficient ostrich eggs are set (DEEMING and AR, 1999). In addition, when the number of eggs laid on the farm is small, this period may even be extended to 14 days. Therefore, it