Group | Treatment | n | Presumed pregnant (D22) |
Calving | Pregnancy losses |
AI | control P4 suppl. |
11 10 |
9(81.8%) 7(70.0%) |
7(63.6%) 5(50.0%) |
2(22.2%) 2(28.6%) |
AI+ET | control P4 suppl. |
9 9 |
8(88.9%) 8(88.9%) |
1(11.1%) 5(55.6%) |
7(87.5%)a 3(37.5%)c |
2 ET | control P4 suppl. |
11 10 |
8(72.7%) 7(70.0%) |
4(36.4%) 5(50.0%) |
4(50.0%)b 2(28.6%)d |
Prostaglandins (PG) have been reported to be involved in all stages of sperm maturation, from spermatogenesis to the acrosomal reaction. They may also stimulate or inhibit sperm motility. Previous studies dealing with the role of prostaglandins on in vitro fertilisation of bovine oocytes for embryo production, were performed after the process of sperm capacitation being already initiated. The aim of this study was to evaluate the role of prostaglandins during swim-up and fertilisation procedures. In experiment I (9 trials), the following treatments were added to the swim-up medium: Control; Indomethacin (Indo, 2.8 x 10-5 M); Indo+PGF2alpha (1.4 x 10-7 M); Indo+PGE1 (1.4 x 10-7 M). The same treatments were added to the fertilisation medium (TALP + heparin + PHE), but PGF2alpha and PGE1 run together with control and Indo treatments in experiments II (10 trials) and III (9 trials), respectively. Bovine thawed semen was processed by swim-up in calcium free TALP medium with caffein for 1 h. A final sperm concentration of 1x106 spz/mL was used for insemination. After 22 h of incubation, COC were transferred to an embryo co-culture system using granulosa cells (TCM 199 + 10% oestrous superovulated cow serum). Embryos were evaluated for cleavage 48 h after insemination.
Treatments | Matured oocytes (n) | Cleavage rate (%) |
Experiment I (Swim-up): | ||
1. Control | 417 | 54.0a |
2. Indomethacin | 438 | 45.0b |
3. Indo+PGF2alpha | 440 | 38.4c |
4. Indo+PGE1 | 432 | 51.2a |
Experiment II (Fertilisation): | ||
1. Control | 323 | 67.8a |
2. Indomethacin | 302 | 53.0b |
3. Indo+PGF2alpha | 289 | 56.4b |
Experiment III (Fertilisation): | ||
1. Control | 318 | 55.3a |
2. Indomethacin | 321 | 47.7b |
3. Indo+PGE1 | 320 | 51.6ab |
Results show that prostaglandin synthesis inhibition significantly reduced fertilisation rates in all experiments. PGF2alpha showed an even greater reduction in fertilisation rates than indomethacin when added to swim-up medium. PGE1 was able to completely reverse the negative effect of indomethacin in swim-up medium. This reversal effect of PGE1 was only partially achieved when treatments were added to fertilisation medium. These results confirm that also in bovine, prostaglandins play an essential role during the capacitation and fertilisation mechanisms and further suggest that a very same prostaglandin may play different roles on each of these mechanisms with very important consequences to in vitro fertilisation rates.
Transfer of in vivo or in vitro produced (IVP) embryos to previously inseminated recipient cows is reported to result in high pregnancy and twinning rates. However , survival of IVP transferred embryos is greatly reduced after freezing. Data on survival rate of IVP frozen cattle embryos and their effect on pregnancy maintenance of previously inseminated recipient cows are presented in this paper. Beef suckler cows were treated for estrus synchronization with the Crestar@ (Intervet) method and a 500 UI eCG (Intergonan, Intervet) injection on the day of implant removal (left in situ 8-10 days) and then artificially inseminated. On D7 (D0 = estrus) cows were allocated at random to a control group (AI) or received an IVP frozen embryo in the uterine horn contralateral to the corpus luteum (AI+ET group ). This was done in 4 replicates. In replicates 3 and 4, half of the cows of the AI+ET group were P4 supplemented with a norgestomet implant between D7-21 (AI+ETsup group). Embryos were produced from in vitro matured, fertilized and co-cultured (granulosa cells) oocytes obtained from post-mortem recovered ovaries of dairy heifers and cows. Grade 1 blastocysts were frozen in 1.5 M ethylene-glycol plus 0.1 M sucrose in PBS+FCS, thawed in a 25°C water-bath, followed by direct transfer to recipients. Progesterone (P4) was measured in plasma samples on D0, D7 and D21. Pregnancy was diagnosed on D21 by plasma P4 and on D60 by echography. For data analysis (chi-square test) only cows responding to synchronization (showing estrus and P4D0 <= 0.5 ng/ml; P4D7 >= 1.0 ng/ml and a palpable corpus luteum) were considered. Data of the 4 replicates were analyzed together .
As shown in the table below. the number of females assumed pregnant on D21 (P4D0 <= 0.5 ng/m1, P4D7 >= 1.0 ng/ml and P4D21 > 2.0 ng/ml) was higher in the AI+ET groups than in the control group, but the difference was not significant (P > 0.05). On D60 pregnancy rates were not different, but calving rate of the AI+ET group was lower than in the other groups due to higher pregnancy losses (P < 0.01 ), specially between D60 and calving. Fourteen of the 17 IVP calves born were co-twins with AI calves. In the AI+ET group 60% of the losses were abortion of twins, which suggests that pregnancy maintenance of embryos resulting from AI may be negatively affected by the death of IVP frozen embryos.
Table. Effect of transfer of frozen IVP cattle embryos on pregnancy maintenance of inseminated recipients. Data = n (% ).
Group |
n |
Pregnant |
Calving |
Pregnancy |
IVP
Embryo |
|
|
|
D21 |
D60 |
|
losses |
survival |
AI |
92 |
64
(69.6) |
57
(62.0) |
54
(58.7) |
10
(15.6) a |
- |
AI+ET |
79 |
67
(84.8) |
48
(60.8) |
33
(41.8) |
34
(50.7) b |
11
(13.9) |
AI+ETsup |
34 |
29
(85.3) |
19
(55.9) |
19
(55.9) |
10
(34.5) ab |
6
(17.6) |