TY - JOUR
T1 - The difference in embryo quality between Belclare and Suffolk ewes is not due to differences in oocyte quality
AU - Fair, S.
AU - Hanrahan, J. P.
AU - Ward, F.
AU - O'Meara, C. M.
AU - Duffy, P.
AU - Donovan, A.
AU - Lonergan, P.
AU - Evans, A. C.O.
PY - 2006/7/15
Y1 - 2006/7/15
N2 - We have previously reported that the percentage of fertilized oocytes which reached the blastocyst stage by Day 6 after AI with frozen-thawed semen was higher for Belclare (94%) than Suffolk (59%) ewes. This may reflect differences in the timing of fertilization (Experiment 1) or differences in oocyte quality (Experiments 2 and 3). In Experiment 1, oocytes recovered from slaughterhouse ovaries were matured in vitro for 18, 20, 24, 28 or 30 h prior to fertilization and were then cultured in vitro. In Experiment 2, Belclare (n = 69) and Suffolk (n = 71) ewes were laparoscopically inseminated using frozen-thawed semen. Presumptive zygotes were recovered between 23 and 47 h post-insemination and cultured in vitro (grouped by breed). In Experiment 3, immature oocytes from Suffolk and Belclare ewes, were matured, fertilized and cultured in vitro (grouped by breed). Cleavage rate and blastocyst development was assessed. There was no effect of time of fertilization on cleavage rate, however, a lower proportion of cleaved oocytes reached the blastocyst stage after insemination at 30 h compared to 24 h (P < 0.001). Ewe breed did not affect cleavage rate of oocytes matured and fertilized in vivo (41 ± 9.6 and 47 ± 10.1) or in vitro (47 ± 9.4 and 52 ± 9.4) for Belclare and Suffolk ewes, respectively (P > 0.05; %±S.E.). Likewise, ewe breed had no effect on the percentage (±S.E.) of cleaved oocytes developing to the blastocyst stage for in vivo (29 ± 7.2 and 25 ± 7.9) or in vitro matured and fertilized oocytes (29 ± 6.1 and 36 ± 5.9) from Belclare and Suffolk ewes, respectively (P > 0.05). Based on this study oocyte quality does not differ between the breeds and in addition a 4 h difference in the timing of fertilization, reflective of the breed difference in the timing of the LH surge in vivo, would not affect early embryo development.
AB - We have previously reported that the percentage of fertilized oocytes which reached the blastocyst stage by Day 6 after AI with frozen-thawed semen was higher for Belclare (94%) than Suffolk (59%) ewes. This may reflect differences in the timing of fertilization (Experiment 1) or differences in oocyte quality (Experiments 2 and 3). In Experiment 1, oocytes recovered from slaughterhouse ovaries were matured in vitro for 18, 20, 24, 28 or 30 h prior to fertilization and were then cultured in vitro. In Experiment 2, Belclare (n = 69) and Suffolk (n = 71) ewes were laparoscopically inseminated using frozen-thawed semen. Presumptive zygotes were recovered between 23 and 47 h post-insemination and cultured in vitro (grouped by breed). In Experiment 3, immature oocytes from Suffolk and Belclare ewes, were matured, fertilized and cultured in vitro (grouped by breed). Cleavage rate and blastocyst development was assessed. There was no effect of time of fertilization on cleavage rate, however, a lower proportion of cleaved oocytes reached the blastocyst stage after insemination at 30 h compared to 24 h (P < 0.001). Ewe breed did not affect cleavage rate of oocytes matured and fertilized in vivo (41 ± 9.6 and 47 ± 10.1) or in vitro (47 ± 9.4 and 52 ± 9.4) for Belclare and Suffolk ewes, respectively (P > 0.05; %±S.E.). Likewise, ewe breed had no effect on the percentage (±S.E.) of cleaved oocytes developing to the blastocyst stage for in vivo (29 ± 7.2 and 25 ± 7.9) or in vitro matured and fertilized oocytes (29 ± 6.1 and 36 ± 5.9) from Belclare and Suffolk ewes, respectively (P > 0.05). Based on this study oocyte quality does not differ between the breeds and in addition a 4 h difference in the timing of fertilization, reflective of the breed difference in the timing of the LH surge in vivo, would not affect early embryo development.
KW - Artificial insemination
KW - Embryo quality
KW - Ewe breed
KW - Oocyte quality
KW - Sheep
UR - http://www.scopus.com/inward/record.url?scp=33745437881&partnerID=8YFLogxK
U2 - 10.1016/j.theriogenology.2005.11.001
DO - 10.1016/j.theriogenology.2005.11.001
M3 - Article
C2 - 16332386
AN - SCOPUS:33745437881
SN - 0093-691X
VL - 66
SP - 191
EP - 197
JO - Theriogenology
JF - Theriogenology
IS - 2
ER -