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Abstract
1. This research was carried out to investigate changes in egg production and hatchability as influenced by age and breeding season of 10 trios (two females, one male) of ostrich (Struthio camellus) during 1998 to 2002.
2. Breeding season affected number of eggs laid per female per season, average egg weight, length of laying period and clutch sequence.
3. The number of eggs laid per female per season was 25 in the first breeding season and 57 by the fifth breeding season. The laying period lasted 169 d in the first season whereas it was 210 d by the fifth season. The breeding season became longer year by year.
4. The number of clutches was two in the first season, three in the second and 4 in the later breeding seasons: the mean interval between cycles was 9 to 10·6 d and the mean number of eggs in one cycle varied from 12 to 14·4.
5. The breeding season affected the hatchability of fertile eggs, chick weight at hatching, hatchability of total eggs, fertility, malpositioned embryos, deformed chicks and assisted chicks during hatching. The first 4 variables increased and the last three decreased, with each breeding season.
6. Weight loss of eggs and length of incubation were unaffected by the breeding season. Hatchability which was 64·3% in the first season increased progressively and reached 73·1% in the fifth breeding season.