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Astaxanthin in cryopreservation of bovine semen and embryos

Abstract

The cryopreservation of gametes and embryos allowed great advances for research and commercial application of Animal Reproduction biotechniques. However, one of the problems associated to this process is oxidative stress. In this context, the use of antioxidants, including astaxanthin, can mitigate cell damage caused by reactive oxygen species. Despite the potent antioxidant power of astaxanthin, there are few studies using this molecule in cryopreservation of bovine semen and embryos. Therefore, the objectives of this proposal are to evaluate the supplementation of astaxanthin in commercial cryopreservation semen extenders based on egg yolk (Exp. 1) and liposomes (Exp. 2), as well as in commercial media for cryopreservation of bovine embryos produced in vitro, either by the slow freezing (Exp. 3) or vitrification (Exp. 4) techniques. In Experiments 1 and 2, six Nellore bulls will be used, which will have seven ejaculates (per animal) collected by electroejaculation at weekly intervals. Physical and morphological analyzes of the semen will be performed for dilution in medium containing egg yolk (Exp. 1) or liposomes (Exp. 2), according to the following treatments: G-AST: with addition of astaxanthin; G-DMSO: with addition of DMSO (toxicity control) and G-CONT: without addition of astaxanthin or DMSO (negative control). The semen will be frozen in straws and, after thawing, analysis of computerized sperm kinetics, plasmatic and acrosomal membrane integrity, mitochondrial membrane potential and oxidative stress will be performed. In Experiments 3 and 4 oocytes from slaughterhouse ovaries will be subjected to in vitro embryo production and will be cryopreserved by slow freezing technique (Exp. 3) or vitrification (Exp. 4), being distributed among the same treatments described for Exp. 1 and 2. Immediately after thawing/ warming, embryos will be evaluated for expansion and hatching, quantification of total and apoptotic cells, biochemical profile, and expression of genes related to oxidative stress and apoptosis pathways. It is expected that the use of astaxanthin directly in cryopreservation media results in less oxidative stress, improving sperm and embryo quality. (AU)

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