An Example for the “Transit-Heterosis” in the Non-Return Rate of Upgraded Dairy Genotypes

The research aim of the authors was to evaluate the success of the heterosis manifested in the non-return rate regarding an upgrading breeding system in Serbia. The data base contains altogether 27,241 records of the initial purebred Simmental and Holstein-Friesian cows as well as of the six intermediate Holstein-Frisian crossed genotypes, from the last four decades (1971-2008). In the non-return rate calculated by pp day 70 and 210 the Simmentals, together with the F1-R3 genotypes, regularly reached higher values than the purebred Holsteins, together with the R4-R5 genotypes, to a significant degree (p<0.001). The heterosis appeared at dissimilar direction and extent in the non-return rate calculated by different pp days. With regards to the success of re-breeding by pp day 70, a statistically proven, positive complementary effect, which was emerging in R2, occurred in all the crossed generations. Evaluating the re-breeding by pp days 210, the recombination along with the heterosis became negative in R5 generation, while the heterosis remained positive, also favourable in all the other genotypes. The authors presented the transit-heterosis in case of R2 and R5, where the previous superiority became lost and the advantage became negative over time, respectively.