The effects of breeding young bulls and cows in vitro
Sirard, Marc Andre
Abstract In the bovine dairy sector, the pursuit of rapid genetic advancement has prompted the adoption of increasingly younger parental figures for both males and females. While physiological limitations and access to gametes impose certain restrictions, the impact of age on gamete quality remains crucial yet poorly understood. We propose that the age effect encompasses environmental factors, which include the metabolic state of the parents and the conditions surrounding gametes and embryos within the reproductive tracts of both sexes. Emerging evidence indicates that this environment significantly influences not only the functionality of gametes and early embryos but also the future phenotype of the offspring. Recent research utilizing transcriptomic and epigenetic molecular analyses in bovine models has demonstrated that the age of both females and males gamete donors, can alter gene expression and programming within the embryo in a similar way that metabolic post partum conditions can. This embryo adaptation to parent's age is similarly noted in variations related to different culture conditions and the in vitro fertilization (IVF) process. A common outcome from these circumstances is the development of embryos operating in "economy" mode, where translation, cell division, and ATP production are diminished, seemingly as an anticipated adaptation to environmental conditions. Furthermore, new epidemiological studies have shown that these alterations can lead to distinct phenotypes, particularly in animals conceived through IVF, underscoring the long-term consequences that may unfold later in their lives.
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