COMPARISON OF BACTERIOLOGICAL QUALITIES OF VARIOUS EGG-YOLK SOURCES AND THE IN-VITRO AND IN-VIVO FERTILIZING POTENTIAL OF BOVINE SEMEN FROZEN IN EGG-YOLK OR LECITHIN BASED DILUENTS

The addition of components of animal origin (egg yolk, milk) to most c ommercial diluents used to freeze bull semen represents a potential ri sk of contamination of the doses with bacteria or mycoplasma. A series of quantitative and qualitative analyses were performed to detect mic robiological contamination observed in Biociphos plus (a new lecithin- glycerol based freezing salt buffer), in an egg yolk diluent (Triladyl ) or in an egg yolk+milk-based (Laiciphos) diluent of bull semen. The 2 diluents containing animal products showed moderate (10 to 60 CFU/mL ) contamination (17/17 samples) with bacteria or mycoplasma, or both, while no contamination was observed in the 6 examined batches of Bioci phos plus. Biociphos plus was also compared with another commercial di luent (Laiciphos) for use in freezing bull semen intended for in vitro and/or in vivo fertilization. Mo difference (P>0.05) could be detecte d between the 2 diluents for in vitro fertility rates (percentage of c leaved zygotes: 85.7% and 88.0%, respectively, for Laiciphos and Bioci phos plus). Similarly, 2 series of comparisons conducted in dairy cows artificially inseminated with semen frozen in either Biociphos plus o r Laiciphos showed no difference in fertilizing capacity (tested at 60 to 90 d; P>0.05) irrespective of the age of the bulls (Trial 1, bulls aged 14 to 15 mo; Trial 2, bulls aged 2 to 5 yr, field trials). It is concluded that, in addition to maintaining the fertilizing capacity o f bull semen at levels comparable to those observed with standard free zing diluent, Biociphos plus also prevents microbiological contaminati on by bacteria or mycoplasma, both of which are generally present in t he various commercially available sources of egg yolk. (C) 1998 by Els evier Science Inc.