Implications of genetic selection on yolk proportion on the dry matter content of eggs in a White Leghorn population

Abstract

1. The responses to genetic selection on yolk proportion as a technique for increasing egg dry matter content, an important criterion for the egg-product industry, was investigated in a pedigree flock of White Leghorn hens.

2. Parents were preselected on high and low yolk proportion from a base population. The absolute estimated breeding value for yolk proportion of both groups differed by 3%. The realised selection difference in dry matter content of eggs between groups was more than 1% in the analysed offspring population.

3. Heritability estimates were moderate and dry matter had a lower heritability (h² = 0.39) than yolk proportion (h² = 0.44).

4. The genetic correlation between yolk proportion and dry matter content was highly positive (r_g = 0.91). Genetic correlations with egg weight were negative and would have to be compensated for in a breeding programme (r_g = −0.76 with yolk proportion and r_g = −0.64 with dry matter content). The genetic correlation between the laying performance and yolk proportion was r_g = 0.28 and close to zero (r_g = −0.05) for dry matter content.

5. Easy recording and lower undesirable correlations make yolk proportion more suitable for commercial selection compared with egg dry matter content in layer breeding.

ACKNOWLEDGEMENTS

We gratefully acknowledge the excellent technical assistance of Heinz Björnsen at the experimental station Frankenforst and Helga Brodeßer for performing egg quality measurements.