Submitted 2020-06-26 | Accepted 2020-08-18 | Available 2020-12-01 https://doi.org/10.15414/afz.2020.23.mi-fpap.52-57 In this study, inbreeding and effective population size of the Latvian gene conservation cattle breeds Latvian Brown (LB) and Latvian Blue (LZ) were analysed. The study was based on the pedigree data of 319 LB and 712 LZ cows that were alive at the time of data selection. The inbreeding level in LB and LZ has been increasing during the last decade and at the end of the year 2019, it was 2.61% and 5.20% for LB and LZ, respectively. The average increase of inbreeding from 2010 to 2019 was 1.80% for LB and 2.26% for LZ. The proportions of inbred animals with an inbreeding level greater than 10% were 0.60% and 2.14% in LB and LZ, respectively. Effective population size based on the rate of inbreeding decreased and was close or within the minimum range of recommended effective population size. The current study demonstrates that the inbreeding has increased, and the effective population size decreased in both populations. Therefore, the breeding organizations have to monitor and control the rate of inbreeding in LB and LZ populations over time. Keywords: inbreeding, Latvian Brown, Latvian Blue, native breed References Addo, S., Schäler, J., Hinrichs, D. and Thaller, G. E. (2017). Genetic diversity and ancestral history of the German Angler and the Red-and-White dual-purpose cattle breeds assessed through pedigree analysis. Agricultural Sciences, 8, 1033-1047. https://doi.org/10.4236/as.2017.89075 Doekes, H. P., Veerkamp, R. F., Bijma, P., de Jong, G., Hiemstra, S. J. and Windig, J. J. (2019). Inbreeding depression due to recent and ancient inbreeding in Dutch Holstein-Friesian dairy cattle. Genetics Selection Evolution, 51(1), 54. https://doi.org/10.1186/s12711-019-0497-z FAO. ©2019. Domestic Animal Diversity Information System (DAD-IS). Retrieved May 2, 2020 from http://www.fao.org/dad-is. GrÄ«slis, Z. (2006). Blue cows in Vidzeme. Jelgava. BÅ SA âZilÄ govsâ, 1â36. In Latvian. GrÄ«slis, Z. and Å imkevica, D. (2018). Latvian Blue selection. BÅ SA âZilÄ govsâ, Jelgava, 1â43. In Latvian. GrÄ«slis, Z., Markey, L. and Zutere, R. (2005). The inbreeding analysis in Latvian Blue cow population. Proceedings of the 11th Baltic animal breeding and genetics conference, Lithuania, 65â69. Groeneveld, E., Westhuizen, B.v.d., Maiwashe, A., Voordewind, F. and Ferraz, J. B. S. (2009). POPREP: a generic report for population management. Genetics and Molecular Research, 8(3), 1158â1178. https://doi.org/10.4238/vol8-3gmr648 Jonkus, D., Paura, L. and Cielava, L. (2020). Longevity and milk production efficiency of Latvian local breeds during last decades. Agronomy Research, 18(S2), 1316â1322. https://doi.org/10.15159/ar.20.064 LDC. (2019). Latvian brown cow conservation program from 2019 and nearest future. Retrieved May 26, 2020 from https://www.ldc.gov.lv/upload/doc/doc20.pdf. In Latvian Mäki-Tanila, A., Fernandez, J., Toro, M. and Meuwissen, T. (2010) Assessment and management or genetic variation. In Mäki-Tanila, A. et al. (eds.) Local cattle breeds in Europe. Development of policies and strategies for self-sustaining breeds. The Netherlands: Wageningen Academic Publishers (pp. 98â119) Mc Parland, S., Kearney, F. and Berry, D. P. (2009). Purging of inbreeding depression within the Irish Holstein-Friesian population. Genetics Selection Evolution, 41, 16. https://doi.org/10.1186/1297-9686-41-16 Mc Parland, S., Kearney, J. F., Rath, M. and Berry, D. P. (2007). Inbreeding effects on milk production, calving performance, fertility, and conformation in Irish Holstein-Friesians. Journal of Dairy Science, 90(9), 4411â4419. https://doi.org/10.3168/jds.2007-0227 Oldenbroek, K. and Van der Waaij, L. (2015). Animal Breeding and Genetics for BSc students. Centre for Genetic Resources and Animal Breeding and Genomics Group, Wageningen University and Research Centre, the Netherlands. Retrieved May 26, 2020 from https://wiki.groenkennisnet.nl/display/TAB/ Sørensen, A. C., Sørensen, M. K. and Berg, P. (2005). Inbreeding in Danish dairy cattle breeds. Journal of Dairy Science, 88(5), 1865â1872. https://doi.org/10.3168/jds.S0022-0302(05)72861-7 Zutere, R., GrÄ«slis, Z. and Sjakste, T. 2006. Breeding programs in Latvian livestock. Proceedings of the 12th Baltic animal breeding conference. Jurmala, Latvia, 6â13.   Â