330. SEASONAL EFFECTS ON OVARIAN DYNAMICS AND OOCYTE DEVELOPMENTAL COMPETENCE IN SOWS EXPERIENCING EARLY-PREGNANCY LOSS
M. Bertoldo A , P. K. Holyoake B , G. Evans A and C. G. Grupen AA Faculty of Veterinary Science, University of Sydney, Camden, Australia.
B Wagga Wagga Agricultural Institute, Industry and Investment NSW, Wagga Wagga, NSW, Australia.
Reproduction, Fertility and Development 22(9) 130-130 https://doi.org/10.1071/SRB10Abs330
Published: 6 September 2010
Abstract
Seasonal infertility in the domestic sow has a considerable economic impact on the pig industry. Reduced oocyte quality and increased wean-to-service interval (WSI) have been observed during the seasonal infertility period (1, 2). The aim of this study was to determine the relationship between season, WSI, ovarian dynamics and oocyte quality in sows experiencing early-pregnancy loss. Sows that experienced early-pregnancy loss were grouped according to their previous WSI (≤ 6 or > 6 d) and the presence (CL) or absence (NCL) of corpora lutea on their ovaries at the time of slaughter. Groups were WSI≤6d/CL, WSI≤6d/NCL, WSI>6d/CL and WSI>6d/NCL. Cumulus–oocyte complexes were recovered from antral follicles (3–8 mm) and subjected to parthenogenetic activation following in vitro maturation in summer (n = 742) and late-spring (n = 594). Data were analysed using a generalised linear mixed-model in GenStat release 10. The mean number of CL/sow was greater (11.57 ± 3.30) in late-spring compared to summer (9.26 ± 0.99; P < 0.05). There were no effects of WSI on oocyte developmental potential. A greater proportion of oocytes developed to the blastocyst stage in summer (55.94 ± 5.17%) compared to late-spring (31.18 ± 6.38%; P < 0.05). Blastocysts derived from oocytes collected in summer had a greater number of cells (46.60 ± 1.17) than blastocysts derived from oocytes collected in spring (43.2 ± 0.95; P < 0.05). Blastocysts derived from oocytes of CL ovaries had more cells (47.08 ± 1.13) than those derived from oocytes of NCL ovaries (42.91 ± 0.75; P < 0.05). It appears that sows experiencing early-pregnancy loss have inherently poor oocyte quality. The greater developmental potential of oocytes in summer suggests a proportion of sows culled for early-pregnancy loss in summer have good oocyte quality, but fail to conceive and/or initiate pregnancy due to other summer-autumn related factors, such as heat stress.
(1) Bertoldo et al., Reproduction, Fertility and Development, in press.
(2) Bertoldo et al., 2009. Theriogenolgy, 72: 393–400.
