S. Di Francesco

The influence of gamete co-incubation length on the in vitro fertility and sex ratio of bovine bulls with different penetration speed.

The objectives of this work were to evaluate whether the sperm penetration speed is correlated to the in vitro fertility and whether adapting the gamete co-incubation length to the kinetics of the bull improves in vitro fertility and affects the sex ratio. In vitro matured oocytes were co-incubated with spermatozoa from four different bulls (A-D). At various post-insemination (p.i.) times (4, 8, 12, 16 and 20 h), samples of oocytes were fixed and stained with DAPI for nuclei examination, while the remaining ones were transferred into culture to evaluate embryo development. The blastocysts produced were sexed by PCR. Two bulls (A and B) had faster kinetics than the others (C and D), as shown by the higher penetration rates recorded at 4 h p.i. (43%, 30%, 11% and 6%, respectively for bulls A, B, C and D; p<0.01). The differences in the kinetics among bulls did not reflect their in vitro fertility. The incidence of polyspermy was higher for faster penetrating bulls (36%, 24%, 16% and 4%, respectively for bulls A, B, C and D; p<0.01) and at longer co-incubation times (0%, 16%, 19%, 30% and 34%, respectively at 4, 8, 12, 16 and 20 h p.i.; p<0.01). The fertilizing ability of individual bulls may be improved by adapting the co-incubation length to their penetration speed. A sperm-oocyte co-incubation length of 8 h ensured the greatest blastocyst yields for the two faster penetrating bulls. On the contrary, 16 h co-incubation was required to increase (p<0.01) cleavage rate of the two slower bulls. Bulls with a faster kinetics did not alter the embryo sex ratio towards males. The female/male (F/M) ratios recorded were 2.1, 1.4, 1.2, 1.3 and 1.6, respectively at 4, 8, 12, 16 and 20 h p.i.

Influence of temperature and time during ovary transportation on in vitro embryo production efficiency in the buffalo species (Bubalus bubalis)

Abstract The aim of this study was to evaluate the influence of temperature during ovary collection/transportation and that of the time interval between ovary collection and processing in the laboratory, on in vitro embryo production efficiency in buffalo species. A retrospective analysis of data collected over the last 4 years in our lab was carried out on 3461 oocytes, recovered over 120 replicates. No differences in oocytes developmental competence were observed in relation to the time interval between ovary collection and processing in the laboratory (3-6 h). On the contrary, a correlation was found between oocyte developmental competence, evaluated in terms of cleavage and blastocyst rate, and temperature during ovary collection/transportation. In particular, lowering temperature during ovary transportation significantly improved both cleavage (74.6 % vs 65.8 and 63.1 % for temperature ranges of 25-30°C, 30-34°C and 34-37°C, respectively ; P<0.05) and blastocyst rates (30.9 % vs 21.8 and 22.7 % for temperature ranges of 25-30°C, 30-34°C and 34-37°C, respectively ; P<0.05). It was concluded that extending the time interval between ovary collection and processing to 6 h is not detrimental for buffalo oocyte developmental competence. Furthermore, lowering temperature during ovary collection and transportation increases the in vitro embryo production efficiency in buffalo species.