Unpedigreed populations and worst-case scenarios

A population in which parentage information is not recorded is considered a pedigree "black hole" in terms of genetic management. Integration of anima ls from such an unpedigreed population into a genetically managed populatio n is often accomplished by assuming a worst-case scenario and recording all animals as highly interrelated (e.g., full siblings). The assumption that a worst-case scenario is appropriate under a wide variety of circumstances is evaluated. It was determined that the genetic costs of overestimating re lationships among animals from an unpedigreed population are always greater than the genetic costs of underestimating relationships by the same amount . This demonstrates that worst-case scenarios, which are by definition inte ntional overestimates, are not generally appropriate. A method of obtaining an estimate that will yield the lowest overall genetic cost using the poss ible maximum and minimum levels of relatedness among animals from the unped igreed population is presented along with two methods for implementation. F inally, for cases in which the estimated average relatedness among animals from an unpedigreed population is low, it is recommended that different ana lytical studbook datasets be used for calculation of inbreeding coefficient s and mean kinship coefficients. This strategy would allow close estimation of average relatedness without risking inadvertent pairing of highly relat ed animals from the unpedigreed population. Zoo Biol 20:305-314, 2001. (C) 2001 Wiley-Liss, Inc.