Long-term metabolic and developmental effects of in vitro embryo technologies in female cattle

Assisted reproductive technologies (ART) may exert long-term effects on offspring, which have not yet been addressed in dairy cattle. This longitudinal study examined reproductive outcomes and intergenerational effects of embryo recipients conceived by different ART, including artificial insemination (AI) and embryo transfer (ET) with fresh, frozen, and vitrified embryos. For this purpose, in vitro-produced (IVP) embryos were transferred to synchronized recipients (n = 298 ET from AI, and n = 84 ET from IVP-ET origin). Pregnancy on d 40 and 62, gestation term at birth, and gestation length were recorded. From birth until adulthood, calf morphometry (weight, withers height, and chest circumference) was monitored (n = 142 animals), and IGF2 methylation and expression were analyzed in peripheral blood lymphocytes (n = 113 samples). The plasma metabolome on d 0 (n = 179 samples) and d 7 (n = 176 samples) and metabolically regulated pathways were compared between estrus-synchronized recipients born by AI and ET. Data were analyzed with generalized mixed models (parametric) and Kruskal-Wallis test (nonparametric). Pregnancy and birth rates did not differ between AI and ET recipients. However, mothers from ET-born recipients were heavier at calving, and their calves showed intergenerational effects, including greater birth weight, withers height, gestation length, and daily weight gain compared with those from AI recipients. Only calves born from frozen embryos displayed transient IGF2 hypomethylation on d 30, which disappeared later on. In contrast, IGF2 expression decreased on d 0 and 30 in calves born from cryopreserved embryos, and increased in calves aged 2 to14 mo from vitrified embryos, but did not differ thereafter between any group. Among females >6 mo old, those from frozen embryos and AI were heavier and taller than females from vitrified and fresh embryos. Certain metabolite concentrations on d 0 and d 7 differed among recipient groups, mainly in essential amino acids and metabolites related to 1-carbon metabolism. Overall metabolic differences (Mahalanobis distance matrix) between females were higher in AI than in ET-cryopreserved females on d 0, and in AI versus ET-fresh females on d 7. These findings suggest that ART induces epigenetic and metabolic variations, potentially influencing nutritional efficiency.