The performance of farmed ostrich eggs in eastern Australia

A prospective observational epidemiological study was undertaken in the south-eastern region of Queensland in eastern Australia to collect accurate information on the performance of farmed ostriches, and to identify the most important constraints facing on-farm production. This paper (the second in a series of three) focuses upon the performance of 910 ostrich eggs laid on 12 farms in this region between 1 July 1993 and 30 June 1994. Each egg was observed from lay until it hatched, was permanently removed from the incubator unhatched, or reached the 46th day of incubation without hatching (whichever occurred first). Eggs weighed on average 1301.9 g at lay, were stored for a mean of 3.7 days prior to the start of incubation, and lost an average of 15.5% of the initial set weight during the period of incubation. Overall fertility and hatchability percentages of 68.1% and 67.0%, respectively, were achieved. Laboratory examination was performed on some eggs that were infertile or failed to hatch. Although bacteria were isolated from some of these eggs, bacterial infection may not have been an important cause of incubation failure. Egg-level factors were examined for association with egg fertility and with egg hatchability using random-effects logistic regression modelling. There was no unconditional association between egg fertility and either egg weight at the start of incubation, the season of lay or the duration of egg storage prior to incubation. There was evidence, however, indicating a relationship between egg fertility and nonexamined pair and farm-level factors. Egg hatchability was conditionally associated with egg weight at the start of incubation, the percentage egg weight loss during incubation and the season of lay, and random pair-level extra-binomial variation was also demonstrated. The relationship between hatchability and weight loss was curvilinear; fertile eggs were most likely to hatch with weight loss during incubation of between 12 and 15% of the egg weight at the beginning of incubation.