Differentiation between females of ostrich breeding trios based on egg weights

Data, collected during the 1997-1998 breeding season from 14 ostrich trios, were used to determine whether two females in a trio could be differentiated based on egg size. For eight of the trios a difference between egg weights could be discerned and eggs could be assigned to one or to the other female. An average egg weight of approximately 1.5 kg and an average chick weight of approximately 0.9 kg was recorded. Coefficients of variation ranged from 9.8% for chick weight to 10.7% for egg weight. Overall hatchability was 53%. The repeatability of service sire observations for egg weight and chick weight were 0.32 and 0.28 respectively, whereas a higher repeatability of 0.82 and 0.67, respectively, was recorded for these traits when based on individual females. Four of the eight trios showed differences in the assumed hatchability between the females. These results suggest a preference of certain males for specific females. This study shows that the process of differentiating between females and their eggs based on the egg weight is feasible and could contribute to better data structures for ostrich breeders during genetic evaluation. South African Journal of Animal Science Supp 2 2004: 20-2