The Relationship between Egg Production, Egg Weight and Body Weight in Laying Hens

SUMMARY

An analysis of the results obtained from the Central Egg Laying Test, Glen, revealed the close relationship between egg production, egg weight and body weight.

With the South African White Leghorns it was found that the optimum body weight at sexual maturity for egg production seems to range between 1·59 to 1·82 kg. If egg weight is considered, the optimum body weight is increased to 2·04–2·27 kg. Young birds which weigh more than 2·27 kg. at sexual maturity should be discarded for egg production. At a body weight of 1·36–2·27 kg. the correlation between egg production, egg weight and body weight is positive with an antagonistic relationship when the birds weighed more than 2·27 kg.

At mature body weight the position is about the same. The only difference is that birds of a low mature body weight are not only poor egg producers but on an average also produced about 58 eggs below standard weight.

As far as the South African Black Australorps are concerned we have a somewhat different situation from that found in White Leghorns. Contrary to the findings with White Leghorns there is no relationship between total egg production and body weight at sexual maturity. Here early maturity might be the deciding factor because it is known that birds of early maturity are poor egg producers during the winter months.

Perhaps there is a genetic difference in these characteristics between the two breeds. This is quite understandable as these two breeds have genetically been segregated for more than half a century.

The position is somewhat different with mature body weight in White Leghorns where there is an increase in egg production of standard size (56·75 g.) eggs as the body weight increases. The difference between the two breeds is, however, explained by the fact that in the Black Australorps there is no optimum body weight at sexual maturity for the production of standard sized eggs. This is difficult to explain. The relationship between egg production and mature body weight seems to be the same in both breeds, namely an optimum body weight for egg production. The ideal body weight for mature Australorps seems to be about 2·72 kg.

In conclusion it might safely be stated that breeders should concentrate on improving the body weight of young birds, both White Leghorns and Black Australorps. From a practical point of view it would be best to increase the age at sexual maturity. This will increase body weight at the first egg and at the same time improve production in the winter months. (Lerner and Taylor (1939)).

Against all expectations it has also been found that the efficiency of egg production depends in no way on body weight because the production of standard weight eggs is positively correlated with body weight.

Une analyse des résultats du testage Central pour la Ponte (Central Egg Laying Test) à GLEN, République d'Afrique du Sud, révèle une relation étroite entre la production d'oeufs, le poids des oeufs et le poids corporel. Le poids optimum en vue de la ponte pour des Leghorns blanches Sud-Africaines à maturité sexuelle était de 1,59 à 1,82kg. Pour une production et un poids d'oeufs optimum, il passait à 2,04–2,27kg. Quand le poids corporel dépassait 2,27kg, il était en corrélation négative avec le poids des oeufs et la ponte.

Par contraste, aucune relation n'a été observée entre la ponte totale et le poids corporel à maturité sexuelle chez des Australorp noires. Le poids corporel idéal à maturité pour les Australorps apparait être voisin de 2,72kg. Contrairement aux prévisions, le rendement de la production d'oeufs dans les deux races ne dépendait pas du poids corporel.