الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
In the last decade, Assisted Reproductive Technologies (ART) such as in vitro maturation (IVM), in vitro fertilization (IVF), multiple ovulation and embryo transfer (MOET), have been applied to improve reproductive efficiency, and genetic potential (Shi et al., 2007). The in vitro production of embryos (IVP) is a promising approach to assisted reproductive technologies and could lead to genetic improvement in breeding schemes. Current (IVP) goals are to overcome some of the infertility disorders and generate cloned and/or transgenic animals. However, these processes still have low overall efficiency, which is somewhat due to the incomplete understanding of species-specific demands for in vitro oocyte maturation, fertilization, and embryo culture (Duque et al., 2002). Providing essential nutrients or survival factors to the maturation media has become a broadly applicable approach; this may have the advantages of enhancing in vitro oocyte competence and embryonic growth. In light of this, many approaches have been implemented to explore the impacts of different culture conditions enriched with antioxidants or vitamins on oocyte ripening and embryonic growth in different mammalian species (Saadeldin, et al., 2019). The low efficiency of in vitro embryo production could be attributed to the lack of knowledge on different nutritional requirements for oocyte maturation and embryo development, (ROS) generation, the difference in time of cytoplasmic and nuclear maturation, the inferior characters of frozen semen, apoptosis, and/or the alteration of transcription gene expression (Saadeldin, et al., 2019). Retinoic acid (RA), as a source of vitamin (A), plays a pivotal role in reproduction; its presence in excessive or insufficient amounts may result in Introduction 2 embryonic loss (Ward and Morriss-Kay, 1997). Retinoids collectively contain several features of vitamin (A) such as retinol; which is the main form of vitamin (A) and its derivatives (metabolites and analogues). Evidence from numerous reports in different mammalian species concluded that retinoids were involved in in vitro maturation, follicular growth, oocyte development, fertilization, and earlier embryonic growth. In cattle, the level of (RA) in the ovarian follicular fluid may be considered as an accepted marker for follicular health status, where high estradiol levels are greatly associated with healthy follicles, and the lowest levels indicate atretic follicles or follicle syndromes (Schweigert and Zucker, 1988). In addition, treatment with β-carotene (a precursor to vitamin (A) found in plants) or (RA) inhibited fetal reabsorption in rodents (Wellik and DeLuca, 1955) improved offspring output in rabbits (Besenfelder et al., 1993) and enhanced litter size in swine (Coffey and Britt, 1993). In ewes, the addition of retinol following natural mating was involved in superovulation and the enhanced competency of morula phase embryos (Eberhardt et al., 1999). However, in cattle, (RA) injection improved the quality of embryos gathered from superovulated individuals (Shaw et al., 1995). The biosynthesis and excretion of (RA) in the oviduct and uterus is controlled by the movement of the ovum or embryo inside the female genital tract (Kedishvili, 2013). This study aimed to evaluate the effect of addition different levels of retinol (0, 50, 100, 150, and 200 nM/ml) added to 1) maturation medium on cytoplasmic and nuclear maturation rates, fertilization rate, and embryo developmental competence (1st experiment), 2) fertilization medium on Introduction 3 fertilization rate and embryo developmental competence (2nd experiment), and 3) embryo culture medium on developmental competence of rabbit embryos (3rd experiment).