Tip of The Day - October 6, 2016

Photo by Tom Semadeni

An inukshut

1987 Strategy for Selecting Egg-Laying Chickens

Charlie Smith evaluated the usefulness of juvenile selection in terms of rates of genetic change. Egg laying chickens are normally selected for breeding on part records at about 39 weeks of age based on an index from family records. The generation interval is about one year and the genetic correlation with the whole record is about 0.7. An alternative would be to mate early in the laying period, and to select the next generation of breeders as juveniles before they start to lay, based on the average genetic merit of their parents. Selection of individuals from the best indexed matings rather than the best indexed individuals would reduce the annual response by half, but the generation interval could be reduced by 0.63 and the accuracy of selection increased by using part records of 202 days (rather than 133 days) so that the genetic correlation between part and whole records would increase to 0.85. Put together, the increase in annual response would be 1.3 to 1.4 times greater. This juvenile scheme would require larger numbers of hatched and reared animals than the current system, but the same number tested. Individuals not selected for breeding could be used as multipliers or crossing stocks. Males not selected for breeding could be discarded at 160 days of age rather than 294.

Photo by Tom Semadeni