Transfer of vitrified blastocysts from one or two superovulated Large White Hyperprolific donors to Meishan recipients: reproductive parameters at Day 30 of pregnancy.

The present study was designed to determine the effect of pooling embryos from two donors on the reproductive success of transfer of vitrified/warmed porcine blastocysts. Intact blastocysts were collected from superovulated Large White Hyperprolific gilts (n = 24) on Days 5-5.5 after artificial insemination. Embryos were recovered by flushing the uterine horns, and unhatched blastocysts were selected. Vitrification and warming were performed as described by Berthelot et al. [Cryobiology 41(2000) 116]. To evaluate in vitro development, 37 vitrified/warmed blastocysts were cultured, non-vitrified embryos (n = 48) were used as controls. Embryo transfers were conducted in asynchronous (-24 h) Meishan gilts (n = 20). Twenty vitrified/warmed blastocysts were surgically transferred into one uterine horn. Ten recipients received embryos from one donor (Group 1) and the other 10 transfers were performed with mixed embryos from two donors (Group 2). Pregnancy was assessed ultrasonographically at Day 25 after estrus and recipients were slaughtered at Day 30 after transfer. In vitro survival rate of the vitrified/warmed blastocysts was lower (P < 0.01) than that from control embryos (73.0% versus 93.7%). The pregnancy rate for Group 1 (70%) was not different (P > 0.05) than that from Group 2 (90%). No significant differences were detected between Groups 1 and 2 for in vivo embryo development (number fetuses/transferred embryos in pregnant recipients) or in vivo embryo survival (number viable fetuses/transferred embryos in pregnant recipients). However, the in vivo efficiency (number viable fetuses/total transferred embryos) was higher (P < 0.05) when transfers were performed with embryos from two donors (19.5% versus 30.5%). These results indicate that pooling embryos from two donors increases the in vivo efficiency after transfer of vitrified/warmed porcine blastocysts.

Determination by echography of uterine changes around puberty in gilts and evaluation of a diagnosis of puberty.

Three experiments were carried out to evaluate the use of ultrasonography in assessing the onset of puberty in gilts. In experiment 1, gilts (n = 17) were scanned 3 times per week beginning at 133 and continuing until 187 days of age. The ultrasonic appearance of the uterus was described, quantified and compared with the reproductive status observed at slaughter. The quantification of the pictures showed a different correlation in time for infantile, impubertal, prepubertal and pubertal stages. For pubertal females, "uterine area" increased at around 180 days of age, well-defined sections of the uterine horns appeared 3 +/- 0.5 days before puberty. In infantile and impubertal gilts during the same period of age, uterine images remained dark and homogeneous; no significant change in the "uterine area" was observed. This difference in images allowed an evaluation of the diagnosis of puberty. In experiment 2, the gilts (n = 123) were scanned, the result was verified at slaughter the day after by examination of the genital tract. The uterine weight of the gilts that had reached a prepubertal or pubertal stage was significantly greater (P = 0.0001) than that in impubertal gilts. The sensitivity and the specificity of the diagnosis were 91.9% and 96.5% respectively. Experiment 3 was performed on a farm and echographic examinations were carried out one and five days after gilts (n = 117) arrived at the piggery. Oestrus detection or blood sampling for progesterone determinations were used as tools to determine the reproductive status. The sensitivity and the specificity of the diagnosis were 98.9% and 100% respectively. This diagnosis of puberty is thus accurate.