Sex difference in mortality rates of Leghorn-Red reciprocal crosses.

Mortality rates among White Leghorn-Rhode Island Red pure-line and reciprocal cross adult female progeny were recorded for 8 years. The mortality rate among progeny of White Leghorn males exceeded that of the progeny of Rhode Island Red males in both pure-line and crossbreds. White Leghorn X Rhode Island Red crossbred progeny had the highest mortality rate. In a second phase of the study, a comparison was made between mortality rates of male and female progeny of White Leghorn-Rhode Island Red reciprocal crosses. Rate of loss was significantly lower in males than in females but did not differ between crosses. These results support a conclusion that sex linkage is a major factor in differential mortality rates between progeny of White Longhorn-heavy breed reciprocal crosses.