Do physical and chemical characteristics of Greater Rhea eggs change throughout the laying season?.

LABAQUE, M.C.; MAESTRI, DM; HOYOS, L; MARTELLA, M.B.; NAVARRO, J.L.

MADRID, ESPAÑA

Congreso; 3r International Ratite Science Symposium; 2005

World´s Poultry Science Association

The quality of eggs is important for the correct development of the embryo. Physical and chemical characteristics of Greater and Lesser Rhea eggs have been described in previous works. However, whether they change throughout the laying season affecting hatchability is unknown. To explore this aspect, from September 2000 to January 2001, all the eggs (n=252) laid by 12 captive Greater Rhea females on a fixed diet were collected to determine their physical and chemical characteristics and hatching success. Eggs of each female were identified and classified into four periods according to their laying date. The egg weight, length, width and volume were measured, and up to four eggs of each female were randomly selected from each period to determine: specific weight, proportions of yolk, albumen and shell (based on entire egg weight), protein and lipid contents, and fatty acid composition. The rest of the eggs (n = 180) were artificially incubated and monitored until hatching. Physical and chemical data were subjected to a Friedman repeated measure ANOVA, with period as treatments and females as blocks, and hatchability to a Chi-squared contingency table test. Specific weight of eggs was lowest in September. On the other hand, yolk protein, stearic, and almost all unsaturated fatty acid (linoleic, linolenic, arachidonic) tended to increase as laying season progressed, particularly in the last period (December and January), while total yolk lipid content, oleic and palmitoleic acids showed an opposite trend. No significant variations were detected in other physical characteristics or albumen protein. Differences observed in the eggs seem to affect their hatchability, as it was invariant throughout the laying season (overall: 69%). Quality of eggs may also be related to females’ traits (genetic or physiological characteristics, age, weight, etc.) or to environmental conditions, and these relationships will be investigated in future research.