Effect of gelatin addition to freezing extender on rabbit semen parameters and reproductive performance

Abstract

An improvement in reproduction management has been associated to the wide use of artificial insemination in rabbits. The use of frozen semen in this species is greatly limited due to its low fertility rates. Moreover, in politocous species, prolificacy is a very important trait and it is particularly affected when semen is frozen. Since gelatine addition to fresh semen extenders improves and prolongs motility and viability sperm parameters, its use in semen freezing could enhance sperm efficiency after thawing. The aim of this study was to assess the effects of gelatine addition to freezing extender using a commercially available extender (MIII) and a tris-based extender (TGC). Four experimental extenders were used: TGC extender with gelatine, the same without gelatine and MIII extender with and without gelatine. In order to evaluate seminal parameters, motility was assessed using the Computer Assisted Sperm Analysis, while viability rate was calculated using flow cytometry. To evaluate in vivo frozen-thawed semen, 273 females were inseminated. No significant difference was found among the four freezing extenders when motility, viability fertility or prolificacy were considered. Motility rates ranged between 22.4% and 35.1%, while viability varied between 22.5 and 30.9%. Fertility rates oscillated from 80.8% to 86.2% and the total born ranged from 7.9 to 8.5. While in vitro results were lower than those obtained in other studies, in vivo results were quite favourable. In conclusion, gelatine addition did not improve sperm motility and viability after thawing nor fertility and prolificacy after insemination with frozen-thawed semen, using MIII or TCG extender.