Mortality in near‐term ostrich embryos during artificial incubation

1. The ostrich industry in South Africa (and elsewhere) experiences a high rate of embryo mortality during artificial incubation of eggs. Most of this mortality takes place in the last 10–14 d of incubation.

2. We carried out post‐mortem examinations on 111 embryos that died within this period to assess the causes of this mortality.

3. Malpositioning and severe oedema were the predominant symptoms of dead‐in‐shell embryos with 55% being malpositioned and 41% showing severe oedema. Of these, 22 embryos (24%) showed both symptoms. Malpositioning generally results from incorrect setting of the eggs or inadequate turning and oedema was significantly correlated with the amount of water lost from the eggs which in turn was correlated with egg size.

4. Myopathy, gross lesions of internal organs, haemorrhage, bacterial infections and congenital deformities were found in less than 10% of chicks examined for these symptoms.     

Influence of temperature during growth on responses of hens to high or low temperatures during lay

1. Commercial pullets were grown at cool (10°‐20°C) or hot (25°‐35°C) temperatures to similar bodyweights at 18 weeks of age. Between 18 and 50 weeks the birds were either kept at the same temperatures as during growth or transferred to the alternate temperature.

2. Birds kept at the cool temperatures throughout life ate most food and gave the best production during lay. Minimum food intake and poorest performance were obtained with birds kept at the hot temperatures throughout life.

3. Performance in the hot environment during lay was improved by rearing birds in the cool environment, the response being related to an increased food intake. Food intake in the cool environment during lay was reduced, with only minor effects on performance, in birds which had been reared in the hot environment.

4. The results of the present study show that production responses during lay are affected by the temperatures experienced by hens during both growth and lay.