64 No difference in health and fertility characteristics between offspring arising from in vitro production or multiple ovulation embryo transfer

The production of in vitro-produced (IVP) embryos is growing worldwide, despite the fact that, in general, IVP embryos show lower pregnancy rates, higher abortion rates, and result in offspring with a higher chance of abnormal birthweights (Siqueira et al. 2020 Reprod. Fertil. Dev. 32, 82-97). In addition, very limited information is available on the performance of IVP offspring later in life. One study (Bonilla et al. 2013 J. Dairy Sci. 97, 229-239) showed that there were no differences in milk production, but no information on health and fertility is available from IVP offspring. The aim of this study was to compare the health and fertility of offspring arising from IVP compared with offspring from multiple-ovulation embryo transfer (MOET). IVP and MOET embryos are produced using HF donors and bulls in our facility using standard conditions and are transferred to recipients in the field. Breeding values and phenotypes for health (mastitis and hoof health) and fertility (number of straws needed to become pregnant, nonreturn rate at 56 days, and interval from calving to first insemination) were monitored in offspring arising from these IVP and MOET embryos. In total, we compared 2736 offspring arising from IVP and 3436 offspring from MOET born between 2009 and 2019 (i.e. all IVP and MOET offspring that had phenotypic data in this period). Data in this retrospective study were analysed by chi-squared or t-test analysis. The average breeding values of the IVP and MOET offspring for the different traits showed no significant differences (mean of 101.0 for IVP and 100.8 for MOET; P > 0.05), indicating that they were genetically comparable. When we compared fertility and health parameters, we saw a small but significantly better performance in offspring arising from IVP for two fertility parameters (number of inseminations per pregnancy and nonreturn at 56 days) and one health parameter (somatic cell count) compared with offspring from MOET (Table 1). For the interval calving to first insemination and hoof health, no signficant differences between IVP and MOET offspring were observed. When the data were divided per birth year, a clear genetic trend could be observed. However, the same pattern of differences in the health and fertility phenotypes between offspring arising from IVP and MOET was observed, as shown in Table 1, although less significant because of lower numbers of animals per birth year). We therefore concluded, based on this large study, that offspring arising from IVP perform similar or even slightly better during later life with respect to health and fertility parameters than offspring from MOET. This is a very important conclusion because most cattle breeding programs today rely heavily on the use of IVP in creating the next generation.

Table 1.  Fertility and health parameters of offspring derived from IVP and MOET