Investigations into the control of litter size in swine: I. Comparative studies on in vitro development of Meishan and Yorkshire preimplantation embryos

Abstract

Three experiments were conducted to examine the in vitro development of preimplantation embryos from the prolific Chinese Meishan pig. Experiment 1 was conducted to assess whether Meishan embryos would develop in vitro and retain their viability, whereas Exp. 2 and 3 examined the developmental pattern of Meishan embryos. In all three experiments, Yorkshire embryos served as a contemporary comparison. Ovulation and embryo recovery rates were not different between Meishan and Yorkshire gilts. Meishan embryos cultured for 96 h were capable of establishing pregnancies. The number of cell nuclei present after 144 h of culture was lower (P < .01) for Meishan than for Yorkshire blastocysts. Meishan preimplantation embryos exhibited a slower (P < .02) in vitro rate of development from the four-cell to the compact morula stage than did Yorkshire embryos. Early blastocysts from Meishan gilts, although morphologically similar in size, contained fewer (P < .06) cells than did their counterpart Yorkshire embryos. These data demonstrate that Meishan embryos develop more slowly and contain fewer cells than do Yorkshire embryos. This differing developmental pattern of Meishan preimplantation embryos, if similar to that previously reported in miniature swine and mice, may relate to increased embryo survival.

Six placenta permeability-related genes: molecular characterization and expression analysis in pigs

“…In the study of Youngs et al (1993), the Meishan pig can farrow three to five more live pigs per litter than Western breeds Youngs et al, 1993). Wilson found that the Meishan placenta exhibits a marked and progressive increase in the density of blood vessels on the placental surface .…”

Placentation, maternal–fetal interface, and conceptus loss in swine

“…With fertilization rates close to 95% [5][6][7][8], the number early embryos can potentially reach around 20. However, by the time of farrowing, litter size is reduced down to 10 to 13 piglets/sow [9].…”

Comparisons of Culture of Chinese Meishan with Yorkshire Pig Embryosin vitro: Effects of Protein Supplementation and Development

“…Little research has been conducted on in vitro development of Meishan embryos. Youngs et al (1993) reported that Meishan embryos developed slower than embryos from Yorkshire females, zia uitro. Slower embryo development was associated with less estradiol-17p production from earlier maturing Meishan blastocysts which lengthened the optimal window of uterine receptivity allowing more later maturing Meishan than Yorkshire blastocysts to survive.…”