Direct transfer of a single frozen-thawed in vitro-produced embryo to avoid twin pregnancy in dairy cows.

Fertility of cow receiving fixed-time artificial insemination (FTAI) was compared with cow in which a single frozen-thawed in vitro-produced (IVP) embryo was fixed-time transferred (FTET) to avoid twin pregnancy. The study population was comprised of 596 lactating dairy cows synchronized for oestrus: 440 were fixed-time inseminated (AI cows), and 156 were given GnRH treatment at the time of embryo transfer (ET cows) 8 days post-oestrus. Of the 596 cows, 235 (39.4%) became pregnant: 175 (39.8%) AI cows and 60 (39.8%) ET cows. Twin pregnancy was recorded in 16% of the AI pregnant cows (28/175), whereas no ET cows had twins (0/60). Significant interaction (p < .01) was observed between breeding technique (FTAI vs FTET) and repeat (RB) or not repeat breeding (NRB) for the likelihood of pregnancy. This meant that using RB AI cows as reference, the odds ratio for pregnancy in RB ET cows was 2.2 (p = .04). In conclusion, transfer of a frozen IVP embryo proved useful to prevent the risk of twin pregnancy without affecting fertility.

Transfer of a single fresh in vitro-produced embryo may prevent twin pregnancy without compromising the fertility of the cow.

This study examines whether the transfer of a fresh in vitro-produced (IVP) embryo can avoid the risk of twin pregnancy without reducing the fertility of a cow. The study population was comprised of 416 lactating dairy cows synchronized for oestrus: 294 were fixed-time inseminated (AI cows), and 122 were given GnRH treatment at the time of embryo transfer (ET) an IVP embryo (ET cows). Of the 416 cows, 167 (40.1%) became pregnant. Twin pregnancy was recorded in 20.8% of the AI pregnant cows (21/101), whereas no ET cows had twins (0/66). Significant interaction (p < .01) was observed between breeding technique and the period of the year for the likelihood of pregnancy. This meant that using AI cows during the warm period (May-September) as reference, the odds ratio for pregnancy in ET cows during the warm period was 3.4 (p = .001). In conclusion, transfer of a single fresh IVP embryo proved useful to prevent the risk of twin pregnancy without affecting fertility.

Inducing ovulation with human chorionic gonadotrophin improves the pregnancy rate in lactating dairy cows receiving an in vitro-produced embryo.

While the global use of in vitro-produced embryos in dairy cattle is on the rise, several technical aspects of embryo transfer procedures have not yet been optimized. This study compares the effects of inducing ovulation using human chorionic gonadotropin (hCG) versus gonadotropin-releasing hormone (GnRH) at the end of a 5-day progesterone(P4)-based protocol for oestrous synchronization on the pregnancy rate of lactating dairy cow recipients of in vitro-produced embryos. Fresh embryos were transferred on Day-seven post-oestrus to ovulating cows receiving GnRH or hCG (groups GnRH and hCG, n = 60 each). Pregnancy was diagnosed by ultrasound on Day 28 post-oestrus. Forty-nine cows became pregnant: 16 in GnRH (26.7%) and 33 in hCG (55%). Taking GnRH-treated cows as reference, the odds ratio for pregnancy of hCG-treated cows was 3.3 (p = .002). In conclusion, hCG treatment given at the end of a 5-day P4-based protocol for oestrous synchronization improved the pregnancy rate in lactating dairy cows receiving an in vitro-produced embryo.

Effects of twin pregnancy prevention strategies such as GnRH dose and drainage of the smaller follicle on ovulation in dairy cows with two follicles of pre-ovulatory size in the same ovary.

We examined the effects of a single or 2.5-fold dose of dephereline [a gonadotropin-releasing hormone (GnRH) analogue] as well as the drainage of the smaller follicle at the time of insemination on ovulation in dairy cows with two follicles of pre-ovulatory size in the same ovary. The three study groups included 220 monovular cows (control), 110 non-drained cows with two follicles, and 110 cows with two follicles, of which one was drained. In each group, cows treated with a single dose or 2.5-fold dose of dephereline showed similar results following treatment. Ovulation failure of the non-drained follicle occurred in 29.1% of the drained cows, whereas ovulation occurred in 96% of the non-drained and control cows. Twin pregnancy was recorded in 19.4% of the pregnant non-drained cows with two follicles. In conclusion, the increased dephereline dose did not improve the ovulation rate in any group. Follicular drainage, however, prevented twin pregnancy in cows with two follicles, but also resulted in an increase in the non-drained follicle's rate of ovulation failure.

Improved embryo survival following follicular drainage of subordinate follicles for twin pregnancy prevention in bi-ovular dairy cows.

To prevent twin pregnancies in cattle, a simple transvaginal device can be used for follicular drainage. This study examines embryo survival following follicular drainage of the smaller pre-ovulatory follicle at timed artificial insemination (AI) in cows with a pre-ovulatory follicle in each ovary. The study groups established were a control group of 289 monovular cows, a non-drainage group of 114 bi-ovular cows and a follicular drainage group of 113 bi-ovular cows. All cows undergoing drainage developed a corpus luteum (CL) in the drained ovary. Pregnancy loss was recorded 56 days post-AI in 19.5% of the 149 cows that became pregnant. Pregnancy loss in the drainage group cows not suffering heat stress (3.8%) was significantly lower (P < 0.05) than in control non-heat stressed cows (20.9%) and heat-stressed non-drainage group cows (25%). Results indicate that CL induction by follicular drainage for twin pregnancy prevention may reduce the incidence of pregnancy loss.

Luteal activity following follicular drainage of subordinate follicles for twin pregnancy prevention in bi-ovular dairy cows.

Twin pregnancy is undesirable in dairy cattle. This study examines luteal activity following ultrasound-guided puncture and drainage of the smaller pre-ovulatory follicle at timed AI in cows with a pre-ovulatory follicle in each ovary. Luteal activity was determined through Doppler ultrasonography and plasma progesterone (P4) concentrations. The effects of GnRH treatment on Day 7 post-AI on subsequent luteal activity were also assessed. Two study groups were established: a control group of 29 cows and a follicular drainage (FD) group of 28 cows. After drainage, all cows developed a corpus luteum (CL) in the drained ovary. On Day 21 post-AI, drainage-induced CL and fellow CL were similar in terms of size and vascularization. According to a GLM repeated measures analysis of variance (P < 0.001), non-treated drained cows had lower P4 concentrations on Day 21 post-AI than non-treated non-drained cows, whereas GnRH treated cows, both drained and non-drained, showed the highest P4 concentrations at this time point. Twin pregnancy was recorded in 3 of the 8 pregnant control cows, whereas no twins were observed in the FD group. Our results indicate that luteal structures following follicular drainage were functional. As for the presence of an additional CL, this could suggest a reduced risk of pregnancy loss. In addition, luteal activity was significantly increased following GnRH treatment on Day 7 post-AI in drained cows.

The effects of a single or double GnRH dose on pregnancy survival in high producing dairy cows carrying singletons or twins.

Pregnancy loss during the late embryonic and early fetal periods influences dairy herd economy. The objectives of this study were to (1) investigate the effects of a single or double GnRH dose administered at the time of pregnancy diagnosis (28-34 days post-AI) on the pregnancy survival of cows in their third lactation or further carrying live singletons or unilateral twins, and (2) examine the impacts of GnRH treatment on subsequent twin reduction in twin pregnancies. Cows carrying singletons (n = 1,054) or unilateral twins (n = 379) were assigned at the time of pregnancy diagnosis to the following groups: control (no treatment), GnRH (100 µg GnRH), and 2GnRH (200 µg GnRH). Pregnancy loss was recorded in 180 of the 1,433 cows (12.6%) at 58-64 days post-AI. Based on the odds ratios, there was a significant (P < 0.0001) interaction between the treatment group and twin pregnancy. This interaction implies that control cows carrying twins were 3.2 times more likely to suffer pregnancy loss than the other cows, whereas the GnRH and 2GnRH treatment groups cows carrying singletons or twins had pregnancy loss rates similar to the control cows carrying singletons. Twin reduction was observed in 35 twin pregnancies (9.2%). Cows in the GnRH and 2 GnRH groups were seven times more likely to show twin reduction than control cows. Our results indicate that GnRH administered at the time of pregnancy diagnosis had no beneficial effects in cows carrying singletons. In contrast, for twin pregnancies, the treatment increased the rate of pregnancy survival and was accompanied by an increase in the twin reduction rate.

Effects of different five-day progesterone-based synchronization protocols on the estrous response and follicular/luteal dynamics in dairy cows.

This study compared the responses shown by lactating dairy cows to four different P4-based protocols for AI at estrus. Cows with no estrous signs 96 h after progesterone intravaginal device (PRID) removal were subjected to fixed-time AI (FTAI), and their data were also included in the study. In Experiment I, follicular/luteal and endometrial dynamics were assessed every 12 h from the beginning of treatment until AI. The estrous response was examined in Experiment II, and fertility was assessed in both experiments. The protocols consisted of a PRID fitted for five days, along with the administration of different combinations of gonadotropin releasing hormone (GnRH), equine chorionic gonadotropin and a single or double dose (24 h apart) of prostaglandin F2α. In Experiment I (40 cows), animals receiving GnRH at the start of treatment showed a significantly higher ovulation rate during the PRID insertion period while estrus was delayed. In Experiment II (351 cows), according to the odds ratios, cows showing luteal activity at the time of treatment were less likely to show estrus than cows with no signs of luteal activity. Treatment affected the estrous response and the interval from PRID removal to estrus but did not affect conception rates 28-34 days post AI. Primiparous cows displayed a better estrous response than multiparous cows. Our findings reveal acceptable results of 5-day P4-based protocols for AI at estrus in high-producing dairy cows. Time from treatment to estrus emerged as a good guide for FTAI after a 5-day P4-based synchronization protocol.

Effects of different five-day progesterone-based fixed-time AI protocols on follicular/luteal dynamics and fertility in dairy cows.

This study compares in two experiments the responses of lactating dairy cows to four different progesterone-based protocols for fixed-time artificial insemination (FTAI) in terms of their effects on follicular/luteal dynamics and fertility. The protocols consisted of a progesterone intravaginal device fitted for five days, along with the administration of different combinations of gonadotropin releasing hormone, equine chorionic gonadotropin and a single or double dose (24 h apart) of prostaglandin F2α. In Experiment I, the data were derived from 232 lactating cows. Binary logistic regression identified no effects of treatment on ovulation failure or multiple ovulation 10 days post artificial insemination (AI). Based on the odds ratio, the likelihood of ovulation failure was lower (by a factor of 0.1) in cows showing at least one corpus luteum (CL) upon treatment than in cows lacking a CL; repeat breeders (> 3 AI) and cows with multiple CLs at treatment showed lower (by a factor of 0.44) and higher (by a factor of 9.0) risks of multiple ovulation, respectively, than the remaining animals. In Experiment II, the data were derived from 5173 AIs. The independent variable treatment failed to affect the conception rate 28-34 days post AI, twin pregnancy or early fetal loss 58-64 days post AI. The results of this study demonstrate the efficacy of 5-day progesterone-based protocols for FTAI. All four protocols examined were able to induce ovulation in both cyclic and non-cyclic animals so that FTAI returned a similar pregnancy rate to spontaneous estrus. Our results suggest that the ovarian response and fertility resulting from each treatment are due more to the effect of ovarian structures at treatment than to the different combinations of hormones investigated.

A five-day progesterone plus eCG-based fixed-time AI protocol improves fertility over spontaneous estrus in high-producing dairy cows under heat stress.

This study compared the efficiency of a five-day or standard (nine-day) progesterone-based regimen combined with equine chorionic gonadotrophin (eCG) in a fixed-time AI (FTAI) protocol for dairy cows. The data examined were derived from 3577 inseminations conducted in three dairy herds. Animals with no estrus signs detected over 21 days were randomly assigned to a PRID-9 or PRID-5 group. Cows in each group received a progesterone intravaginal device (PRID) for 9 or 5 days, respectively, PGF(2α) and eCG on PRID removal, and GnRH 48 h later. Fixed-time AI was performed 12 h after the GnRH dose. Cows artificially inseminated following spontaneous estrus during the study period were considered as controls. Based on the odds ratio, the likelihoods of animals in PRID-9 in the warm (conception rate [CR] of 22.3%) and cool (32% CR) periods, and control animals in the warm period (26.6% CR) becoming pregnant were reduced (by factors of 0.6, 0.3 and 0.4, respectively) compared with the control animals in the cool period (CR of 43.7%). The risk of a twin pregnancy was higher (51.4%) for cystic PRID-9 cows (by a factor of 3.6) and lower (9.9%) for cyclic PRID-5 animals (by a factor of 0.4) compared with the PRID-9 cyclic cows. These findings indicate that the proposed protocol achieves similar results during the cool or warm season to those obtained when AI is conducted at spontaneous estrus during the cool season. In addition, PRID-5 reduced twin pregnancy compared with PRID-9.

A three-day PGF2α plus eCG-based fixed-time AI protocol improves fertility compared with spontaneous estrus in dairy cows with silent ovulation.

This study was designed to test the treatment with prostaglandin F2α (PGF2α) plus equine chorionic gonadotrophin (eCG) and GnRH 48 h later (PEG protocol) followed by fixed-time AI (FTAI) in dairy cows with silent ovulation (cows with a mature corpus luteum and no signs of estrus detected in the preceding 21 days). In Experiment I, ovulation following the PEG protocol monitored in 24 cows with silent ovulation was recorded in 83% of the cows 36 h after GnRH treatment. In Experiment II, control cows were artificially inseminated during spontaneous estrus (4615 AI), while cows in the PEG group (1266 AI) were subjected to FTAI 24 h after GnRH treatment. Binary logistic regression revealed a significant effect of the interactions of treatment by season, by parity or by repeat breeding syndrome (>3 AI) on the conception rate. The conception rate was negatively affected by the warm season and age in controls but not in treated cows, whereas repeat breeder cows in the control and PEG groups were less (by a factor of 0.7) or more (by a factor of 1.5) likely to become pregnant, respectively, than the remaining animals. Moreover, the likelihood of twin pregnancy was lower in multiparous PEG (by a factor of 0.4) cows than in the remaining cows. This protocol, besides overcoming the negative effects of heat stress and age on the conception rate, increased fertility in repeat breeder cows compared with spontaneous estrus. Moreover, this treatment regimen reduced the twin pregnancy rate in multiparous cows.