The value of conserved samples in gene banks for animal breeding in the MRIJ cattle breed

Population size of the Meuse-Rhine-Yssel cattle breed has decreased considerably between 1992 and 2014, while total genetic merit increased as a result of an effective breeding program. Genetic diversity decreased at the same time and inbreeding rate was 1.24% per generation. In addition to the genetic diversity in the live population, semen samples have been conserved in gene bank collections. We characterized genetic diversity in conserved samples and the current bull population by typing DNA with the 50K SNP chip, and investigated whether using conserved samples may help to restore genetic diversity in the breeding program, as measured by expected heterozygosity (Hexp), and what the effect is on total genetic merit. Hexp is 0.334 in the conserved bulls and 0.324 in the current breeding bulls. Hexp in the next generation can be maximised to 0.333 when using only current bulls, but to 0.344 when including conserved bulls. When the Hexp is constrained to 0.322 genetic merit can be maximised to 101 using current bulls only and to 105 when including conserved bulls. Under a more strict constraint of 0.331 genetic merit can increase to 56 for current and to 72 including conserved bulls. Conserved samples from gene bank collections may thus help to restore genetic diversity and even increase genetic merit when loss of diversity is constrained.