The effect of elevated non-esterified fatty acid concentrations on bovine spermatozoa and on oocyte in vitro fertilisation

Abstract

Elevated non-esterified fatty acid (NEFA) concentrations, present in follicular and oviductal fluid, have been postulated as a causative link between metabolic disorders and subfertility. High NEFA conditions can directly disrupt oocyte maturation and developmental capacity after fertilisation. However, their influence on sperm function and the fertilisation process is not known. This study investigated the fertilisation process under high NEFA conditions. To differentiate between effects on both spermatozoa and oocytes or on spermatozoa only, different experiments were conducted. In the first experiment both gametes were simultaneously incubated during IVF under different conditions: (1) NEFA-free, solvent-free control conditions, (2) solvent control, (3) physiological concentrations of oleic (OA), palmitic (PA) and stearic (SA) acids or (4) pathophysiological concentrations of OA, PA and SA. In the second experiment spermatozoa were incubated (4h) under the same treatment conditions prior to routine IVF. Gamete co-incubation resulted in reduced fertilisation and cleavage rates and increased prevalence of polyspermy. In the second experiment embryo developmental capacity and quality were not affected, although sperm motility and plasma membrane integrity were decreased. In conclusion, lipolytic conditions affected the fertilisation process mainly through an effect on the oocyte. Spermatozoa were still able to fertilise even though these conditions reduced sperm function.

Impact of negative energy balance and postpartum diseases during the transition period on oocyte quality and embryonic development in dairy cows

“…Increased dry-matter intake leads to urea accumulation and it negatively affects embryonic development by reducing hatching rate as well as through increased apoptotic rate in the embryo (61). A similar effect has been observed for NEFA, as cell differentiation and hatching are impaired in developing embryos; remarkably, this adverse effect seems to be of maternal and not paternal origin (62). In order to detect alterations of the embryonic development occurring at a later stage, for example after transfer, we followed up on the produced embryos until day 9 after IVF and also checked their hatching capability.…”

Motility, oxidative status and morphology of frozen‐thawed bovine semen are not impacted by fatty acid exposure in vitro

“…Additionally, our experiments were carried out in vitro, and in vivo studies are imperative to validate these findings in a real‐life setting, specifically to assess the impact of the cow's uterine and oviduct conditions in a NEB on spermatozoa for fertilization. This study represents one of the initial efforts focusing on the effects of fatty acids on bovine spermatozoa (Desmet et al., 2018; Islam et al., 2021; Kiernan et al., 2013).…”