State of inbreeding and genetic trends for estimated breeding values in IVF embryos and oocyte donors in the Brazilian Guzerá cattle

Abstract The main objective of this study was to verify genetic trends for milk production (MY305) and age at first calving (AFC). Were also considered levels of inbreeding practiced in the Brazilian dual-purpose Guzera population (T POP ) comparing it with the same parameters estimated for two sub-populations derived from the reference (T POP ): female donors submitted to ovum-pick up (D POP ) and in vitro embryos produced (E POP ) between 2003 and 2013. Estimated breeding values (EBV) and inbreeding coefficients (F) were regressed by the year of birth (or year of in vitro fertilization) of each animal or embryo in order to obtain annual trends for these parameters separately for each of the three populations studied. A positive quadratic (β 2  = +0.000075) effect was detected for the F values in T POP . Both D POP and E POP showed positive linear coefficients (β 1 ), respectively, +0.00084 (P   0.05). Annual mean F for E POP was higher than T POP and D POP through the time series studied. The frequency of individuals with more than 7% F was higher in D POP . Genetic trends for AFC were −0.187 days/year (P > 0.05); −0.557 days/year (P  POP ; D POP and E POP . Genetic trends for MY305 were +6.75 kg/year (P  POP ; D POP and E POP . For both traits analyzed, E POP showed the highest regression coefficients, which confirms a higher selection pressure and lower generation intervals previously expected from this sub-population. Results reported in the present study suggest that mean F is increasing in the Guzera population. Efforts for controlling inbred mating on in vitro fertilization should be considered, as the presence of a bottleneck effect seems to be getting shape on D POP and E POP .