Factors influencing embryo quantity and quality in donor cows from Latvian Blue, Latvian Brown, and Danish Red breeds at risk in Latvia

•Sufficient number of transferable embryos can be produced from several local dairy breeds at risk of extinction in Latvia.•By selecting donors with a lower milk somatic cell count, national breeding programs have an opportunity to produce more transferable embryos.•Air temperature in temperate climate affects the outcome of embryo quantity and quality. The aim of this study was to find out what general factors influenced embryo quantity and quality in the framework of multiple ovulation and embryo transfer done in Latvia 2018–2020. The gene-pool cows from the cattle breeds Latvian Blue, Latvian Brown, and Danish Red (n = 30) were selected. Such factors as the donor`s blood biochemical and hematological parameters value, ovarian steroid hormones level, milk somatic cell count (SCC), parity, and environmental temperature were analyzed using a negative-binomial regression method. The variables significant at a liberal alpha level of 0.20 in univariable regression models were included in two multivariable models. The first model showed that the number of embryos (nE) was associated (P