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Abstract
1. This study was conducted to evaluate the influence of diet composition on egg number, physical and chemical characteristics of eggs and weight and survival of chicks throughout a breeding season in a captive-bred population of greater rheas (Rhea americana).
2. From August to December, individuals were offered two diets: processed feed for rheas and processed feed for chicken (which is the feed most commonly offered to farmed rheas in Argentina). Reproductive performance of 15 females was monitored and female body weight was recorded before egg-laying onset. Within each experimental group, the following variables were determined: egg morphometric variables and percentage of components, fatty acid composition, hatching success and initial weight of chicks and mortality during the first week of life.
3. Females that were fed on processed feed for rheas delayed onset of laying and reduced laying period and number of eggs produced. However, females of this group laid larger eggs, with higher percentages of yolk and yolk lipids, and exhibited higher hatching success and chick weight compared with those that received chicken diet. Survivorship of chicks in their first week of life was not affected by composition of the diet offered to parental female.
4. Some reproductive parameters of captive greater rhea females fed on processed feed for rheas were higher than those of individuals receiving processed feed for chicken.
ACKNOWLEDGEMENTS
The authors are grateful to the Córdoba Zoo for allowing us to conduct this research on its property, and to the Zoo personnel and Veterinarians V.C. Asís and M. Carello, for their helpful assistance and services. We also appreciate the useful statistical advice provided by J. Di Rienzo. The authors are researchers of the Consejo Nacional de Investigaciones Cientificas y Técnicas (CONICET). This work was funded by grants to M.B.M. from the Agencia Córdoba Ciencia S.E., The Secretaría de Ciencia y Técnica of the Universidad Nacional de Córdoba, CONICET and the Agencia de Promoción Científica de Argentina.