Linajes paternos del ganado vacuno Holstein Friesian criado en Ecuador

The Holstein Friesian cattle breed (Bos taurus) is predominant in dairy farming in Ecuador. The objective of this research was to analyze the genealogical information of the registered Holstein Friesian bull population in Ecuador to determine the paternal ancestors and their representation in the current male population, and to describe the historical variations between 1936-2021 and the effective population size. The national milk control database was evaluated (n=30,335 males), with 19,799 born and registered. Descriptive statistics were performed using the SPSS-v26 program. The contribution of ancestors from the reference population (males born between 2011-2021), inbreeding, and effective population size were evaluated using the ENDOG program. A total of 2,702 national and imported bulls were reported, where 92.97% were from Ecuador, with 52.04% corresponding to the current population. It was observed that, in general, there are more Ecuadorian bulls, with a lower average number of offspring compared to the USA, Canada, and the Netherlands. In a total of 32 ancestors, 75% of the genetic diversity was found, with an effective size of Ne=88.86 and ΔF=0.55%. The Neptune and Hulleman lineages are predominant. The bull PAWNEE FARM ARLINDA CHIEF from the Neptune lineage introduced a lethal gene causing spontaneous abortions and low fertility. Carlin-M Ivanhoe Bell is a carrier of BLAD (Bovine Leukocyte Adhesion Deficiency) and CVM (Complex Vertebral Malformation). The frequency (6.41%) of the ancestor Penstate Ivanhoe Star (carrier of CMV) was high compared to other countries. The paternal lineages in Holstein Friesian are mainly limited to two origins, and during the period included in this study (1936-2021), these two lineages replaced the others until they were extinguished. There is evidence of the need to conduct studies to determine carriers of lethal or deleterious alleles associated with lineages that make up the Holstein population and to establish proper management