of the technique. Coherently, the two countries with greatest IVEP (Brazil and USA) are also those with the two largest commercial cattle herds
in the world. Nevertheless, it is noticeable that an increasing proportion of countries in all regions (overall 41.9% in 2018) has IVEP as the main
source of transferable cattle embryos. The increase in the use of in vitro technologies was also not restricted to cattle. Although the majority of
embryos from other species are still IVD, the number of IVP embryos increased +675.8% in sheep, +1,241.0% in goats, and +85.6% in horses.
The features of IVEP may also have favored the adoption of other technologies that requires embryo micromanipulation, explaining the different
tendencies observed for sexing and genotyping in IVD vs IVP embryos (+8.3% and -15.6%% vs. +447.9% and +429.8%; respectively). In this
regard, the expansion in the number of countries adopting IVEP may have created a platform for the further development of other embryo
technologies.
The rising of IVEP worldwide in the past decade was associated with a decrease in the numbers of collected IVD embryos. However,
changes were not proportional and the positive balance resulted in the increase in total global numbers (+38.7% from 2009 to 2018). In fact,
the adoption of IVEP usually causes a remarkable rise in the embryo industry numbers, as previously observed in Brazil, Argentina and, more
recently, the USA. The relatively slow growth observed in global numbers in the beginning of the past decade can be partially explained by the
decline in ET records from Asia after 2010, where lack of consistent data impairs a clear interpretation of the current trends. For instance, there
is no data from Peoples Republic of China since 2008 and from Japan since 2017 (Thibier 2009, Viana 2018). These two countries were leaders
of the Asian embryo industry in the early 2000s’. In 2006, for example, this region accounted for 27.4% and 28.2% of the world IVD and IVP
records, respectively (Thibier 2007). The Japanese Embryo Transfer Society is currently discussing how to resume data retrieval in the country.
The balance between the trends for IVP and IVD embryos, mainly in the last two years, allowed world ET numbers to reach approximately
1.5 million embryos recorded in a year. This clearly demonstrates that the worldwide growth of IVEP involved the emergence of new potential
markets. On the other hand, in spite of the consistent inclination for the reduction in the collection of IVD embryos over the years, more frozen
IVD embryos were transferred in the past 10 years than in the decade before (2,960,811 [58.4% of total] from 2009 to 2018 vs. 2,741,023
[49.6% of total] from 1999 to 2008, respectively), as shown in Figure 4. This can be a reflex of the lower proportion of transfers of frozen-thawed
IVP embryos (26.8%). Thus, it is likely that collection of IVD embryos has been used as an alternative to overcome the low cryotolerance of IVP
embryos, in situations requiring cryopreservation. Coherently, the number of exported IVD embryos increased (+7.8%), whereas IVP embryo
exports decreased (-35.4%).
This technological shift from IVD to IVP embryos occurred in a manner that affected different aspects of ET activity, such as global
distribution, species, livestock sector involved, use of sex-sorted semen, cryopreservation, micromanipulation etc. The possible forecast for the
evolution of the world embryo industry in the years to come is positive. In this regard, these recent changes also highlight the importance of
data retrieval as a strategy to objectively study and understand the potentials and technical limitations of in vitro technologies, based on the
large-scale use in a commercial scenario. The correct identification of technological gaps and opportunities is crucial to define research focus
and public policies.
6. Acknowledgements