Lifetime Reproductive Planning
In light of the need to ensure the sustainability of ex situ animal populations, the RMC is developing alternative approaches to reproductive management. Lifetime Reproductive Planning (LRP) recognizes that fertility is best established and maintained by allowing reproduction not long after puberty and then at regular intervals throughout a female’s life, until her genetic contribution to the population is reached. However, early and regular reproduction must be balanced with effects on the gene diversity of the population, its age structure, and the current holding capacity for the species in zoos. We are currently developing models to test the effects of various potential reproductive management scenarios on population genetics, long-term population sustainability, and population size. Running these models will allow us to see how using a certain strategy will affect the population before we actually implement the strategy for reproductive management.
Ideally, animal breeding programs would breed every female after puberty in order to establish her fertility. Then, depending on her genetic value, she would follow one of many possible trajectories, either spacing out subsequent pregnancies using contraceptives, breeding her several times before putting her on long-term contraception (or spaying her), or she may be put on long term contraception at a younger age if her genetic line is overrepresented in the population. Unfortunately, in most populations, breeding all females at puberty will likely have significant negative genetic and demographic consequences; therefore, the reproductive strategies that we are investigating include delaying the age of first reproduction in some females and excluding some females from the breeding population entirely.
Though the original concept for LRP was to predetermine a female’s reproductive future based on her genetic value at puberty, LRP will more realistically look like more of a decision tree that determines a female’s reproductive status based on several factors at the time of population planning. In addition to her genetic value, other factors such as her age, prior parity, and how close the population is to its target population size should be considered. This may be particularly important in populations where a female’s position on the mean kinship list changes significantly between breeding and transfer planning periods. Using this approach also allows us to incorporate more flexibility in the reproductive management strategy based on how the population is performing. See the schematic below for a conceptual look at LRP.