Comparison of Selection and Mating Systems for Maintenance of Closed Poultry Lines Using Several Breeding Cages

Abstract

In a typical maintenance plan of closed poultry lines, breeding individuals are divided into several groups each with one male and several females. The groups are put into different breeding cages and mating within cages is carried out to produce their replacements. To reduce the inbreeding rate or increase the effective population size in this plan, following four selection and mating systems were considered. In the first system (RS-RM), parents of the next generation are randomly selected from the progeny pooled over cages, and breeding groups are re-established by randomly dividing the selected progeny. In the second system (WS-RM), selection is carried out within progeny from each cage, and breeding groups of next generation are re-established in the same way as RS-RM. In the third system (WS-RGM), after the within-cage selection as in WS-RM, the females selected from same cage and a randomly selected male over cages are formed a breeding group of the next generation. The final system (WS-NGM) is similar to WS-RGM, but in the assignment of selected males, sib-mating is completely avoided. These systems were compared in terms of the inbreeding coefficient and the effective population size. Compared to RS-RM, the three systems with within-cage selection (WS-RM, WS-RGM and WS-NGM) effectively reduced the inbreeding coefficient in the initial generations. Among the three systems, WS-NGM gave the lowest initial inbreeding coefficient. Although the largest effective population size was attained under WS-RGM, many generations were required for WS-RGM to give a lower inbreeding coefficient than WS-NGM. It was concluded that WS-NGM is a practically recommended system.