Abstract
The ostrich industry experiences a high rate of embryonic mortalities during artificial incubation of eggs. Embryonic deaths were studied from data recorded on 37,740 fertile eggs incubated artificially during the 1998-2005 breeding seasons. Roughly 10,000 eggs that sustained embryonic mortalities were classified according to the stage and nature of death, i.e. before 21 days of incubation, after 21 days of incubation, deaths after pipping and rotten eggs. Although infection may have played a role in approximately 1300 rotten eggs, no detailed knowledge of the pathogens involved was available. The remainder of deaths could not be related to pathogens and the deaths were thus generally referred to as non-infectious. The overall level of embryonic mortality in all the eggs studied was 28.5 %. Overall embryonic mortality was affected by incubator, with higher levels (57.0 %) found in eggs incubated in an African Incubator and also in eggs that were transferred between incubators during incubation (38.1%). Overall embryonic mortality also increased in eggs produced by older females. Eggs produced in the autumn had the highest level of embryonic mortality at 53.6 %, whereas eggs produced in the winter had a marginally higher level of embryonic mortalities of 29.2 % compared with eggs produced during summer (27.4 %). Eggs produced by South African (SA) Black males crossed to Zimbabwean Blue females had high levels of embryonic losses of 45.7 %. The embryonic mortality of eggs produced by SA Blacks or Zimbabwean Blue breeding birds subjected to pure breeding was similar at approximately 33-34 %, but embryonic mortality was improved in eggs produced by Zimbabwean Blue males crossed to SA Black females (27 %). Embryonic mortality was increased in eggs that were set directly (32.0 %) or subjected to longer than 6 days of storage (43.5 %). Embryonic mortality was affected by year. The results that were obtained will assist in determining non-infectious factors that have a negative effect on hatching success. Steps can thus be taken to eliminate such factors that may compromise hatching success.
Highlights
Artificial incubation has become an essential part of any commercial poultry enterprise[3]
Eggs produced by South African Black females mated to Zimbabwean Blue males had the lowest proportion of embryonic mortality (0.270; Table 1)
The latter proportion is significantly lower than those derived for purebred South African Black eggs (0.338) and from an uncharacteristically high proportion of overall embryonic deaths in the South African Black male × Zimbabwean Blue female combination (0.457) (P < 0.05)
Summary
Artificial incubation has become an essential part of any commercial poultry enterprise[3]. Every fertile egg should produce a healthy hatchling. In reality this situation is never achieved in a commercial hatchery. Despite substantial advances in incubator design and incubation techniques since the ostrich industry in South Africa began in the 1800s, problems with embryonic mortality during artificial incubation is still one of the main aDepartment of Animal Sciences, University of Stellenbosch, Private Bag X1, Matieland, 7602 South Africa. CInstitute for Animal Production, Private Bag X1, Elsenburg, 7607, South Africa. The physiological requirements of the developing ostrich embryo are met by the control of temperature[35], humidity[30], gaseous environment[37] and the turning of eggs[36]. Hatchability of artificially incubated ostrich eggs can reach
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