*Corresponding author email: smarko@vef.hr Symbiosis Group Symbiosis Group Symbiosis www.symbiosisonline.org www.symbiosisonlinepublishing.com Optimization of Sperm for In vitro Production of Bovine Embryos Marko Samardzija 1 *, Iva Getz 1 , Martina Lojkic 1 , Hrvoje Valpotic 1 , Drazen Djuricic 2 1 Faculty of Veterinary Medicine, Zagreb, Croatia 2 Veterinary Practice Djurdjevac, Djurdjevac, Croatia SOJ Veterinary Sciences Open Access Review Article of In vitro Production (IVP) of bovine embryos comprises In vitro Maturation (IVM), In vitro Fertilization (IVF) and In vitro Culture (IVC) until the stage of blastocyst [1]. The IVP enables the production of numerous offspring from genetically high- quality cows and thus it is in use in order to attain improvement of genetic selection in cattle breeding, as an alternative to the classical embryo transfer technique. The efficiency of IVP in a commercial system is measured by the number of pregnant cows following transfer so the selection of “good quality” embryos is a crucial step in influencing the outcome of this technology [2]. During mating, cervical mucus poses a barrier that only allows the migration of spermatozoa with normal morphology, progressive motility, and highly stable nucleus. Fresh ejaculates of bulls usually have more than 80% of progressively motile spermatozoa and 85% with morphologically normal shape. Frozen-thawed bull sperm has a lower percentage of progressive motility (30%-70%) [3]. The Aim of the cattle breeding industry is to identify genetically superior bulls and maximize the number of offsprings produced by selected bulls via Artificial Insemination (AI). The fertility of these bulls is important in achieving this aim. In the past, the laboratory evaluation of bull semen was based entirely on the subjective scoring of sperm motility under a light microscope and the measurement of sperm concentration. Occasionally, morphology was determined when certain pathologies were suspected. Use of these assessment procedures and a single protocol of freezing have led to the formation of very homogeneous sire populations in this respect. The sires still exhibit varying results with regard to field fertility. According to current knowledge, the assessment of ejaculate as a whole is erroneous [4]. It is necessary to separate the most viable spermatozoa from the bulk [5]. Hence, during optimization of frozen-thawed bull sperm for IVF special attention should be paid to the methods for selection of progressively motile spermatozoa [3]. With the use of such procedures, the sperm quality could be significantly improved by enhancing progressive motility and increasing the number of morphologically normal spermatozoa. Spermatozoa and leukocytes produce many oxygen radicals that alter the possibility of the sperm-oocyte fusion after repeated centrifugations, so the selection of sperm from other components with such procedures must be preferred [6]. This is the main Abstract The use of in vitro technique with domestic animal gametes and the methods of embryo manipulation of assisted reproduction is currently the most advanced method in cattle breeding with regard to scientific research and practice. The technology of In vitro Production (IVP) of bovine embryos comprises In vitro maturation, In vitro Fertilization (IVF) and In vitro culture until the stage of the blastocyst. During mating, cervical mucus poses a barrier that only allows the migration of spermatozoa with normal morphology, progressive motility, and highly stable nucleus. Fresh ejaculates of bulls usually have more than 80% of progressively motile spermatozoa and 85% with morphologically normal shape. Frozen-thawed bull sperm has a lower percentage of progressive motility (30%-70%) so special attention should be paid during optimization to the methods of sperm preparation for assisted reproduction such as IVP. With the use of such procedures, the sperm quality could be significantly improved by enhancing progressive motility and increasing the number of morphologically normal spermatozoa. Such selection of spermatozoa separates motile sperm from non-motile, removes seminal plasma, cryoprotective agents, other background materials and debris, and also at the same time initiates sperm capacitation. The efficacy of sperm preparation methods could be evaluated by using different sperm parameters such as: sperm motility, morphology, concentration, viability, membrane activity, acrosome status, reactive oxygen species formation, chromatin maturity and integrity, protamination degree and IVP rates. The aim of the current review is to consider and discuss scientific data regarding the necessity of bull sperm optimization for an IVF procedure in order to improve IVP efficiency of bovine embryos. It could be concluded that the use of different sperm optimization methods for IVF is essential in order to improve the quality of obtained sperm. However, it would be advisable to extend the comparison of sperm preparation methods by transfer of IVP embryos into recipient cows which will allow more reliable results of subsequent embryo development. Keywords: In vitro production; Optimization methods; Sperm; Bull Received: June 09, 2015; Accepted: July 13, 2015; Published: September 16, 2015 *Corresponding author: Marko Samardzija, Clinic for obstetrics and reproduction, Faculty of Veterinary Medicine, Heinzelova 55, 10000 Zagreb, Croatia, Tel: +385 1 2390 321; Fax: + 385 1 244 1390; E-mail: smarko@vef.hr Introduction The use of in vitro technique with domestic animal gametes and the methods of embryo manipulation for assisted reproduction is currently the most advanced method in cattle breeding with regard to scientific research and practice. The technology