Livestock Production Science 64 (2000) 281–284
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Short communication
Effect of asynchronous non-surgical transfer of porcine embryos
on pregnancy rate and embryonic survival
*
W. Hazeleger , J.P.T.M. Noordhuizen, B. Kemp
Wageningen Institute of Animal Sciences, Department of Animal Husbandry, Wageningen Agricultural University, P.O. Box 338, 6700 AH Wageningen, The Netherlands
Received 24 November 1998; received in revised form 14 July 1999; accepted 7 September 1999
Abstract
Embryo survival was determined after non-surgical transfer to recipients with a variable synchrony of ovulation. Groups of 10 to 15 freshly weaned multiparous sows (donors and recipients) were checked and paired for time of ovulation, resulting in recipients ovulating from 24 h before to 36 h after the donors (‘asynchrony’ of 224 to 136 h). Embryos were collected from 34 donors at 120 h (range 108–132 h) after ovulation and 16.662.4 morulae and blastocysts were transferred to 31 recipients. Pregnant recipients were slaughtered on Day 35 (Day 05ovulation) to evaluate embryonic survival. Twelve recipients were pregnant at Day 21 and five were still pregnant at Day 35. One recipient was excluded due to cystic ovaries. An asynchrony of 118 to 136 h resulted in 1 / 12 recipients pregnant at Day 21 and no pregnancies at Day 35, while an asynchrony of 224 to 112 h resulted in 11 / 18 recipients pregnant at Day 21 and five still pregnant at Day 35 (P,0.05). The presence of $6 morulae within a litter never resulted in pregnancies at Day 21 (0 / 9), while with ,6 morulae, 12 / 21 recipients were pregnant at Day 21 (P,0.05), irrespective of the degree of asynchrony. The results seem to indicate that only blastocysts should be transferred successfully by a non-surgical procedure at 108 to 132 h after ovulation. Recipients should ovulate between 24 h before to 12 h after the donors. Transfers to recipients ovulating 18 to 36 h after the donors appear to lead to very low pregnancy rates. However, these conclusions need to be confirmed in a study with more animals. 2000 Elsevier Science B.V. All rights reserved.
Keywords: Pig; Non-surgical; Embryo transfer; Asynchrony; Ultrasonography
1. Introduction results of the current non-surgical procedures
(Reichenbach et al., 1993; Galvin et al., 1994; With the development of non-surgical embryo Hazeleger and Kemp, 1994; Li et al., 1996; Yone-transfer techniques in pigs, a revalidation of some mura et al., 1996) range from 9 to 60% farrowing transfer conditions might be needed, since they are rate and 3.1 to 6.7 piglets born. These results are less based on the use of surgical transfer. The average than the average results of surgical procedures with a farrowing rate of 58% and a litter size of 6.5
¨ ¨
(reviewed by Brussow and Konig, 1988).
*Corresponding author. Tel.: 131-318-483-661; fax: 1
31-Our previous research with non-surgical transfer
318-485-006.
of embryos to the uterine body indicated a higher
E-mail address: [email protected] (W.
Hazeleger) survival of blastocysts compared with morulae in
282 W. Hazeleger et al. / Livestock Production Science 64 (2000) 281 –284
synchronous transfers at Day 4 (Hazeleger and (Hazeleger and Kemp, 1994). Embryos were evalu-Kemp, 1994). It might be that blastocysts are in a ated and morphologically normal embryos (of at more appropriate stage for survival in the environ- least morulae stage) were collected and placed in ment of the uterine body or by the relative advanced transfer medium (Dulbecco’s PBS plus 10% lamb development of the blastocysts in comparison with serum, 398C) in 0.25-ml straws. After transport and the development of the uterus of the recipient. In washing in transfer medium at 398C, 15 to 20 previous research using surgical transfer, embryos morphologically normal embryos were transferred to with an advanced development showed a better a recipient, within 2–3 h after collection. To ensure a survival (Polge, 1982). It also seems plausible that, normal physiological variation in embryonic de-in non-surgical transfers, embryos may profit from velopment, embryos from one donor were transferred some asynchrony between the donor and recipient. to one recipient. However, when the number of Therefore, in this study, embryos recovered 120 h collected embryos was limited, a few embryos of (range 108–132 h) after ovulation were transferred to similar development from another donor were added recipients with a variable synchrony of ovulation, in (n57 recipients). The transferred embryos (in 0.1 order to find an optimal synchrony window for ml transfer medium) were deposited in the uterine non-surgical transfers. body or at the beginning of a uterine horn of a recipient. The recipients were placed in individual crates without restraint or sedation during transfer.
2. Materials and methods
2.3. Recipient data collection and analysis 2.1. Animals
The recipients were checked for oestrous symp-Groups of 10–15 commercial crossbred toms daily. From two weeks after transfer onwards, (Landrace3Yorkshire) multiparous sows arrived at the recipients were checked three times weekly with the experimental station at the day of weaning ultrasonography for pregnancy. Recipients with em-(approximately 3–4 weeks after farrowing). Thirty- bryonic fluid and CL around Day 21 after ovulation four donors and thirty-one recipients, which showed and not returning to oestrus before Day 24 were approximately simultaneous oestrus expression and considered as being pregnant on Day 21. On Day 35, ovulation, were selected and paired. Oestrus was the pregnant recipients were slaughtered to evaluate checked once daily by standing response to a boar. the survival of the transferred embryos. The number Donors were artificially inseminated at the first and of foetuses with a healthy appearance were counted. second day after onset of oestrus with a commercial Pregnancy rates were compared by Fisher’s exact
9
dose of 80 ml of semen (3310 cells). The time of test using the FREQ procedure of the SAS package
ovulation (5Day 0) of all animals was estimated by (SAS, 1990) between classes of synchrony intervals transrectal ultrasonography (Soede et al., 1992) (after post-priori assignment of splits of synchrony starting 12 h after the onset of oestrus, and repeated intervals between donors and recipients), between every 6 (n520 transfers) or 12 h (n511 transfers) litters of embryos with greater or less than six until ovulation had taken place. Asynchrony was morulae, between litters with or without added based on the difference in time between the ovula- embryos from other donors, and between embryos tion of recipients and donors. This resulted in younger or older then 120 h. All data are expressed recipients ovulating 24, 18, 12, 6 or 0 h before or 6, as mean6SD (and range).
12, 18, 24 or 36 h after the time of ovulation of donors.
3. Results
2.2. Embryo collection and transfer
3.1. Embryos transferred The donors were slaughtered between 108 and 132
W. Hazeleger et al. / Livestock Production Science 64 (2000) 281 –284 283
consisted of, on average, 3.565.5 (0–20) morulae, to small litters had no effect on the pregnancy rate at 6.166.3 (0–20) blastocysts, 6.566.3 (0–19) ex- Day 21 (4 / 7 pregnant with added embryos and 8 / 23 panded blastocysts and 0.561.4 (0–5) hatched blas- pregnant without added embryos; P.0.10). tocysts from 34 donors.
3.2. Pregnancy rate 4. Discussion
One of the recipients had cystic ovaries (detected Despite a low number of pregnant recipients, the on Day 21 after ovulation) and was excluded from results of this study indicate that an asynchrony analysis, because it is unknown if this disorder was a window of 224 to 112 h (recipients ovulating cause for not being pregnant or developed after not from 24 h before to 12 h after donors) might be being pregnant. Twelve of the remaining 30 recipi- optimal for non-surgical transfers. Although no ents (40%) were pregnant at Day 21 after ovulation. differences between synchronous and asynchronous Five of these recipients were still pregnant at slaugh- transfers were found by Yonemura et al. (1996), ter on Day 35 and the other seven recipients returned Galvin et al. (1994) reported 10 / 40 pregnancies in to oestrus between Days 24 and 35 after ovulation. synchronous (Day 4 embryos to Day 4 recipients) On average, 5.862.8 normal developing foetuses and 0 / 15 pregnancies in asynchronous (Day 5 (33619% as percentage of the transferred embryos) embryos to Day 4 recipients) transfers. The results of were found in the five pregnant recipients Galvin et al. (1994) and our results for non-surgical By categorising asynchrony periods in which transfers differ from previously published results for pregnancies were found, it appeared that an surgical transfers (Polge, 1982). In that report, the asynchrony window of 118 to 136 h (recipients results were optimal if the embryos (Day 3 to Day 9) ovulating long after the donors) resulted in only one were transferred to recipients which came in oestrus pregnancy at Day 21 (1 / 12; 8%) and no pregnancies 1 or 2 days after the donors. An explanation might at Day 35, while an asynchrony window of 224 to be that after surgical transfers the embryos might 112 h resulted in 11 pregnancies at Day 21 (11 / 18; benefit from such asynchrony due to anaesthesia or 61%) and five pregnancies at Day 35 (5 / 18; 28%; surgical trauma. Under sub-optimal conditions, after P,0.05). Within the synchrony range of 224 to surgical transfer of in vitro cultured embryos, better 112 h no differences in pregnancy rate could be results are also reported when the recipients ovulated
detected. later than the donors (Blum-Reckow and Holtz,
284 W. Hazeleger et al. / Livestock Production Science 64 (2000) 281 –284
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