Homologous chromosome pairing and recombination are essential components of meiosis and sexual reproduction. The reshuffling of genetic material through breakage and reunion of chromatids ensure proper segregation of homologous chromosomes in reduction division and genetic diversity in the progeny. The advent of somatic cell nuclear transfer (SCNT) as a reproductive biotechnology for use in livestock industry has made it easy to bypass these vital steps. However, few studies have been carried out on the impact of SCNT on the reproductive characteristics of cloned animals and, none to date, on the meiotic processes in animals, which were created by circumventing meiosis. In an attempt to assess the impact of cloning by SCNT on the meiotic processes, we undertook an immunocytological comparison of recombination in normal and clone bulls using antibodies raised against the synaptonemal complex protein 3 (SCP3) to label the lateral elements and the mismatch repair protein 1 (MLH1) foci on bivalents as indicators of recombination events. Our studies involving five normal bulls of proven fertility, two SCNT-derived bulls, and four mature offspring of SCNT bulls showed that the mean number of crossing over per spermatocyte for normal bulls (42 ± 4 SD; ranging from 33 to 56), was not significantly different from that of SCNT-derived bulls (43 ± 5 SD; ranging from 35 to 56), and the offspring of SCNT-derived bulls (43 ± 5 SD; ranging from 37 to 58). It would appear that circumventing meiosis to produce these animals does not influence the meiotic processes revealed by MLH1 foci detected in spermatocytes.

Chromosome abnormalities are well known for their negative impact on the reproductive performance of carriers. Such abnormalities could have severe effect on animal industries which rely heavily on efficient reproduction. We conducted a cytogenetic survey of breeder pigs from 4 different Canadian farms to investigate the frequency of chromosome abnormalities and to assess their reproductive impact on pig populations. Our study revealed that 50% of the ‘hypoprolific’ boars and 2.5% of the young boars raised for service in artificial insemination were carriers of chromosome anomalies while no chromosome defect was noted in any of the ‘proven’ breeder boars. G-banding technique to determine the type of abnormalities detected 3 previously unreported translocations involving chromosomes 1 and 6, chromosomes 10 and 13 and chromosomes 9 and 14. The reciprocal nature of these translocations was confirmed either using fluorescent in situ hybridization (FISH) technique or immunostaining for synaptonemal complex delineation and were named rcp(1;6)(p22,q12), rcp(10;13), and rcp(9;14) (p24;q27), respectively. Prolificacy of 1/6 and 10/13 translocation carriers was noted to be reduced by more than 40% compared to their normal counterparts while it was reduced by 26% in carriers of the 9/14 translocation. Carriers of 1/6 and 9/14 translocations displayed a higher repeat breeding tendency, compared to their herd average (5 and 16%, respectively). While for the 9/14 translocation the prevalence of stillbirths was lower than that in their herd [8.7 vs. 10.4% (p < 0.001)]. The present results, albeit based on a relatively small number of pigs, indicate that the prevalence of chromosome abnormalities could be much higher in Canadian pigs compared to that reported in European pigs and underline the urgent need to initiate cytogenetic screening programs as one of the effective ways to reduce reproductive problems in Canadian pig populations.

The aim of this study was to assess the ultrasonographic characteristics of ovulatory follicles in cyclic Western White Face ewes (December) that had received intravaginal sponges containing medroxyprogesterone acetate (MAP; 60 mg) for 12 days, with or without an injection of 500 IU of equine chorionic gonadotropin (eCG) at sponge removal. We hypothesized that quantitative echotextural attributes of the follicles in ewes treated only with MAP would differ from those in MAP/eCG-treated ewes, reflecting the increased antral follicular growth and secretory function under eCG influence. Digital images of ovulatory follicles obtained at 0 and 24 h after MAP sponge removal and at 24 h before ovulation in the eCG-treated (five ewes, 13 follicles) and control (six ewes, 9 follicles) animals, were subjected to computerized analyses. The mean diameter of ovulatory follicles increased (p < 0.001) 24 h after eCG treatment. The mean pixel intensity and heterogeneity of the follicular antrum (p < 0.001), as well as mean pixel intensity of the follicular wall and perifollicular ovarian stroma (p < 0.05), were greater in eCG-treated animals compared with control ewes 24 h after sponge removal and at 24 h before ovulation. Mean serum concentrations of oestradiol-17beta tended to increase (p = 0.06) 24 h after eCG treatment and the eCG-treated ewes exceeded (p < 0.05) control animals in progesterone concentrations from days 9-15 after ovulation. Our results support the hypothesis that large antral follicles in eCG-treated ewes exhibit distinctive echotextural characteristics. Follicular image attributes in eCG-treated ewes appear to be indicative of the changes in follicular morphology and secretory activity caused by the administration of the exogenous gonadotropin, which has both FSH- and LH-like activities.

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