Association of soybean-based extenders with field fertility of stored ram (Ovis aries) semen: A randomized double-blind parallel group design

Two consecutive randomized double-blind field fertility experiments were conducted over a 4-month period and aimed at evaluating the association of two commercial soybean lecithin-based extenders (AndroMed [Minitub, Tiefenbach, Germany] and BioXcell [IMV Technologies, L'Aigle, France]) with pregnancy rates of chilled-stored (CS) and frozen-thawed (FT) ram semen. Semen samples with more than 2 x 10(9) sperm per mL and 70% progressive motile spermatozoa were collected via an artificial vagina from twelve proven fertile Chios rams, split-diluted with the above mentioned extenders, packaged in 0.25 mL straws and either stored at 5 +/- 1 degrees C for 30 to 36 hours or frozen and thawed. Non-lactating multiparous ewes were inseminated in progestagen-synchronized estrus either with CS (AndroMed: N = 212 and BioXcell: N = 206; intracervical AI) or with FT (AndroMed: N = 114 and BioXcell: N = 92; laparoscopic intrauterine AI) semen. Ovulation was confirmed in all ewes based on determination of blood plasma progesterone (>1 ng/mL) 8 days post AI. Ewes were screened for pregnancy diagnosis by transabdominal ultrasonography 65 days post AI. BioXcell was superior to AndroMed in preserving the fertilizing potential of CS (P 0.05). Ram-by-extender interactions were significant for pregnancy rates of CS and FT semen. Irrespective of extenders, overall pregnancy rates after intracervical and intrauterine AI were 75.1% and 62.2%, respectively (P < 0.001). In conclusion, BioXcell is a suitable extender for short- and long-term storage of ram semen. Selection of the ewes, farms, and extenders for intracervical AI programs can contribute to satisfactory fertility rates with semen preserved more than 24 hours at 5 degrees C. (c) 2013 Elsevier Inc. All rights reserved