Comparing ethylene glycol with glycerol for cryopreservation of buffalo bull semen in egg-yolk containing extenders A.A. Swelum*, H.A. Mansour, A.A. Elsayed, H.A. Amer Department of Theriogenology, Faculty of Veterinary Medicine, Zagazig University, Egypt Received 19 February 2011; received in revised form 3 April 2011; accepted 19 April 2011 Abstract The objective of this work was to evaluate the possibility of substituting glycerol for ethylene glycol when cryopreserving buffalo semen. Semen of eight buffalo bulls was mixed, pooled, and frozen in one of these four diluents: centrifuged Tris egg yolk glycerol; centrifuged Tris egg yolk ethylene glycol; centrifuged Milk egg yolk glycerol; or centrifuged Milk egg yolk ethylene glycol. Semen quality parameters assessed after thawing were motility, survivability, livability, sperm abnormality, acrosome integrity, and plasma membrane integrity. Conception rate and pregnancy rate were calculated after insemination of 104 buffaloes by straws of different groups (26 female/extender). Improvement in livability, sperm abnormality, acrosome integrity, plasma membrane integrity, conception rate, and pregnancy rate were seen when using ethylene glycol to replace glycerol when freezing buffalo bull semen in centrifuged TRIS egg yolk 61.15  0.73, 24.85  0.41, 69.10  0.81, 71.75  0.72, 46.2%, and 46.2%, respectively, followed by centrifuged milk egg yolk extenders. © 2011 Elsevier Inc. All rights reserved. 1. Introduction The buffalo is remarkable for its feed conversion ability [1]. The buffalo carcass can yield palatable meat with less fat, less bone, and a higher proportion of muscle than the cattle carcass [2,3]. Moreover, buffalo milk is commercially more viable than cow milk for the manufacture of fat-based and solid non-fat-based milk products, such as butter, ghee, and milk powders [4]. The lower cholesterol value [5] and higher levels of various bioprotective factors, such as immunoglobu- lins, lactoferrin, lysozyme, and lactoperoxidase, as well as bifidogenic factors, render buffalo milk healthier than cow milk [6]. The buffalo population in Egypt is about 3 million head, a slightly higher number than cattle. Over 90% of the population are reared in small herds (1–3 animals), and the buffalo is considered the best milk producing animal in the country [7]. Despite its importance for the production of milk, meat, and leather, it has not received sufficient attention regarding the improvement of breeding practices [8]. Artificial insemination (AI) has made a significant contribution to genetic improvement in cattle and has the potential to do the same in buffaloes. AI is the first biotechnology applied to improve reproduction and ge- netics of farm animals. AI remains the main vehicle for the rapid dissemination of valuable genes and the method of choice to improve the genetic quality of livestock [9]. It is generally accepted that a substantial number (50%) of sperm are damaged during cryopreservation [10]. Intracellular ice crystallization during cryopreser- vation is the main cause of damage to the cells [11]. Therefore, the composition of extender and suitable cryoprotectants are important factors for successful se- men cryopreservation [12,13]. While the use of cryo- * Corresponding author: Tel.: 2 011 764 1176. E-mail address: aymanswelum@yahoo.com (A.A. Swelum). Available online at www.sciencedirect.com Theriogenology 76 (2011) 833– 842 www.theriojournal.com 0093-691X/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.theriogenology.2011.04.015