In recent years, reproductive biotechniques have become increasingly pivotal, offering the potential for significant advancements in genetic gain and livestock production. In vitro embryo production is among the most promising assisted reproductive techniques today, particularly within the commercial sector, with a strong emphasis on its application in bovine species. However, despite its promising potential, the technique still faces limitations that challenge its widespread adoption. Notable among these limitations are the variable blastocyst production rates and, more significantly, the heterogeneity in pregnancy rates observed following the transfer of in vitro produced (IVP) embryos post-cryopreservation [1,2].

While cryopreservation facilitates embryo transport and storage logistics, it can have adverse effects on cell viability. Research indicates that the procedure can lead to changes, such as modifications in the transcriptional profile, an increase in apoptotic percentage, and a decrease in pregnancy rates [[3], [4], [5]]. The parameters that define the competence and cryosurvival of embryos are still not well established. One alternative that has been employed is the addition of synthetic molecules to the culture media, which are intended to enhance the quality of IVP embryos and enable them to withstand cryopreservation [[6], [7], [8]].

The female reproductive system supplies the conceptus with all the necessary conditions for complete development by secreting hormones, growth factors, and cytokines that regulate the embryo's physiology and differentiation [9]. Thus, supplementing the culture media with regulatory molecules can bring the in vitro environment closer to the physiological conditions, and the use of some of these supplements has already yielded positive results, such as fibroblast growth factor 2 (FGF2) [10], epidermal growth factor (EGF) [11], or the combination of several of them (FGF2, leukemia inhibitory factor (LIF), and insulin-like growth factors 1 (IGF1) [12].

Interleukins also have a significant role in embryonic development, as evidenced by the expression of certain cytokines and their receptors in endometrial tissue throughout the estrous cycle and in the blastocyst itself, such as IL6, IL8, IL16, IL18, IL6R, IL13RA, ILIR1, among others [13]. IL-13 is a non-glycosylated cytokine that shares common characteristics with IL-4, capable of inhibiting the production of TNFα, IL-1, IL-8, and MIP-1a [14]. Its biological properties have been extensively studied due to its anti-inflammatory action and ability to negatively modulate nuclear factor kappa B (NF-κB) activation and cellular inflammatory response [15]. When bovine embryos were produced in the presence of an antioxidant that downregulates the NF-κB pathway, there was an improvement in the developmental rate, a reduction in reactive oxygen species (ROS), attenuation of NF-κB protein expression, and a decrease in the number of apoptotic cells [16]. These characteristics are desirable for improving embryonic quality and may be predictive factors for improved cryosurvival.

The IL-13 gene expression was identified in the oviduct and endometrium of bovine females at the beginning of the estrous cycle, and the expression of the IL13RA receptor has already been documented in IVP blastocysts [13,17]. However, information about its actual role in embryonic development is still limited. Considering that the addition of IL-13 has not yet been tested in the culture of IVP bovine embryos and anticipating the potential benefits of its use, this study aimed to evaluate the effects of supplementing IL-13 at two different moments of in vitro bovine embryo production: during the final hours of culture (before cryopreservation) and during the period of recultivation after cryopreservation and warming. We assessed cryosurvival rates, total cell numbers, and embryo cell viability, determined by measuring the apoptotic percentage using the TUNEL technique.