Serum progesterone concentrations, follicular development and time of ovulation using a new progesterone releasing device (DICO®) in sheep

Uterine tone influences fertility of Merino ewes following laparoscopic artificial insemination

Artificial insemination (AI) plays a critical role in facilitating rapid genetic and production gains within the sheep industry. However, variable rates of AI success remain a concern for the industry and a barrier to adoption. Furthermore, the degree to which female factors influence the success of intrauterine laparoscopic AI rather than natural mating remains unknown. As such, this study investigates the effect of several factors collected during the time of AI, on the success of intrauterine laparoscopic AI. Data was generously donated by artificial breeding companies and stud breeders during routine commercial AI operations. AI data was collected over 3 breeding seasons during commercial AI programs (N = 24 programs) using Merino ewes (N = 24,700). Sire ID (N = 253), time of AI following progesterone removal (approx. 43-59 h post removal), uterine tone and intra-abdominal fat (both scored 1-5) as well as age of the ewe were all recorded at the time of AI. Transcutaneous ultrasound subsequently determined pregnancy rate approximately 55 days post-AI. A multivariate regression analysis was performed and revealed pregnancy success to increase when semen was inseminated into a ewe with a uterine tone score of 4 or 5 (P < 0.001). The remaining factors fell short of significance within the multivariate model. An interclass coefficient variation matrix was also used to determine the proportion of variation contributed to AI success by random factors allocated in the model; site, sire, AI date and breeding season (45.99 %, 29.94 %, 15.15 % and 8.92 %, respectively). These results highlight the influence of uterine tone on ewe fertility following laparoscopic AI, but also that program location and the sire used can further modify this influence on pregnancy rate. These factors must now be considered in combination with semen factors per individual sire used during AI to ascertain the contribution of several factors to the success of laparoscopic AI in Australia.

Factors affecting the success of laparoscopic artificial insemination in sheep

Successful artificial breeding underpins rapid genetic and production gains in animal agriculture. In sheep, artificial insemination with frozen semen is performed via intrauterine laparoscopy as frozen-thawed spermatozoa do not traverse the cervix in sufficient numbers for high fertility and transcervical insemination is anatomically impossible in most ewes. Historically, laparoscopic artificial insemination has always been considered reasonably successful, but recent anecdotal reports of poor fertility place it at risk of warning adoption. Understanding the male, female and environmental factors that influence the fertility of sheep is warranted if the success of artificial insemination is to be improved and genetic progress maximised for the sheep industry. This review details the current practice of laparoscopic AI in sheep. It explores the effects of semen quantity and quality, the ewe, her preparation, and environmental conditions, on the fertility obtained following laparoscopic artificial insemination.

Effect of early administration of progesterone on the function of the corpus luteum of llamas

The aim of the present study was to evaluate if early administration of progesterone immediately after ovulation affects corpus luteum lifespan in llamas. Female llamas (n = 16) were induced to ovulate by Buserelin injection in the presence of an ovulatory follicle (Day 0). On Day 2, ovulation was confirmed and animals were randomly divided into two groups: treated animals (n = 8) received an intravaginal device containing 0.3 g of progesterone from Day 2 to Day 6 post-induction of ovulation and control group (n = 8) received a device with 0 g of progesterone. Blood samples were collected daily to determine plasma progesterone concentration and transrectal ultrasonographies were performed from Day 7 to Day 12 post-induction of ovulation. Mean maximum diameter of the corpus luteum was significantly lower and was reached before in the treated group than in the control group. The mean highest plasma progesterone concentration and the day that concentration was achieved were similar between groups. However, mean plasma progesterone concentration was significantly higher in the treated group than in the control group on Days 3 and 4 and lower on Days 8 and 9 post-induction of ovulation. The day that plasma progesterone concentration returns to 1 ng/ml differed between groups, occurring earlier in the treated group. In conclusion, the early increase of plasma progesterone concentration during the luteal phase, promoted the premature activation of the luteolytic process affecting corpus luteum function in llamas as it was previously reported in other species.

Recent advances in treatments for resynchronization of ovulation in small ruminants: a review

Hormonal methodologies to control small ruminants' estrous cycle are worldwide used and evolved, adjusting the application to the precise female physiological moments to enhance reproductive performance. The estrous cycle can be induced and/or synchronized, aiming for fixed-time artificial insemination, or based on estrus behavior signs for insemination, natural or guided mating. Successive protocols can be performed to resynchronize ovulation and increase reproductive outcomes in females that failed to conceive. These recently developed treatments aim to resynchronize the ovulation as earlier as non-pregnancy is detected. The present review aimed to summarize the recent advances and main findings regarding resynchronization protocols used in small ruminants. Lastly, we present future perspectives and new paths to be studied in the subject. The resynchronization treatment is still a growing field in small ruminant reproduction, nevertheless, some enhancements are found in the reproductive outcome, showing that such protocols can be successfully used in sheep and goat production.

Pharmacological approaches to induce follicular growth and ovulation for fixed-time artificial insemination treatment regimens in ewes

In Experiment I, during the non-breeding season, after intravaginal devices containing progesterone (P₄) were withdrawn (n = 28), estrous rates were greater with treatment with 400 IU eCG (P <  0.05) than with FSH (10 and 15 mg) and no treatment. During the breeding season (n = 147), estrous and pregnancy rates after fixed-time artificial inseminations (FTAI) were similar among groups: 300 IU eCG; 10 mg FSH; and control (P >  0.05). In Experiment II (non-breeding season), ewes of one group were treated with 300 IU eCG (n = 8) and of two groups were treated with 10 mg FSH. In one FSH group, 250 μg estradiol benzoate (EB) were administered after 24 h (n = 9); in the other, 4 μg GnRH were administered after 36 h (n = 10). Serum P₄ concentrations were greater in eCG-treated ewes (P < 0.05). Estrous rates were similar for the eCG- and FSH plus EB-treated ewes (P >  0.05). In Experiment III (breeding season), the treatments were: 300 IU eCG; 250 μg estradiol cypionate; 250 μg EB; or control (n = 22). Follicular growth was greater for eCG-treated ewes within 0-24 h and for control ewes within 48-72 h (P =  0.001). Although estrous and ovulation rates did not differ (P >  0.05), all eCG-treated ewes had ovulations. During the non-breeding season, FSH treatment promoted follicular growth but did not induce ovulations. For FTAI regimens, eCG was more effective than FSH plus GnRH and estradiol esters in inducing estrus and ovulation.

Seventy years of progestagen treatments for management of the sheep oestrous cycle: where we are and where we should go

Management of the ovine oestrous cycle is mainly based on the use of exogenous hormones to mimic or enhance (progesterone and its analogues) or manipulate (prostaglandin F2α and its analogues) the activity of the corpus luteum, combined with the application of other hormones mimicking the pituitary secretion of gonadotrophins (e.g. equine chorionic gonadotrophin). These protocols have been applied without major change for decades but, now, there are two reasons to reconsider them: (1) our greatly improved knowledge of the dynamics of ovarian physiology, following the application of transrectal ultrasonography, indicates that modification of the protocols may improve fertility yields and (2) increasing concerns about animal health and welfare, food safety and the environmental impact of the treatments, as evidenced by public opinion and therefore market forces. Here, we offer an overview of these issues, introduce an updated protocol and suggest ways for future improvements to the protocols.

Intravaginal administration of progesterone using a new technique for sustained drug release in goats

The objective of the present study was to develop and evaluate a sustained release vaginal progesterone (P₄) capsule containing a mixture of mucoadhesive polymer and silicone fluid. Goats were administered a gelatin capsule containing 0.4 g of P₄ mixed in silicone fluid and either a hydroxypropylmethylcellulose (HM) or polyaclil starch (PA) base. The mean plasma P₄ concentrations at 2 and 12 h after administration were significantly higher in goats treated with PA capsules than in those with HM capsules. The plasma P₄ concentrations in goats treated with HM capsules increased and remained above 1.0 ng/ml for 96 h after administration, whereas the plasma P₄ concentrations in goats treated with PA capsules remained above 1.0 ng/ml for only 24 h after administration. In the next experiment, an HM capsule was attached to a silicone device and inserted in the vagina for 10 days. The plasma P₄ concentration remained similar to that of the natural luteal phase for 9 days. These results suggest that a mixture of mucoadhesive polymer and silicone fluid has the potential to be applied clinically as a sustained release base for estrus synchronization or hormonal therapy.

Oocyte developmental competence is improved by relatively greater circulating progesterone concentrations during preovulatory follicular growth

This study evaluated the effect of progesterone priming during follicular growth on oocyte competence to undergo oocyte cleavage and embryo development in sheep. Two experiments were performed on a total of 195 females that either received or did not receive a progesterone treatment (CIDR-type device) during the first follicular wave, beginning soon after ovulation (i.e., Day 0 of the experiment). On Day 3, the follicular population and oocyte quality (Experiment 1 and 2) and the competence of oocytes for cleavage and embryo development (Experiment 2) were evaluated after laparoscopic ovum pickup (LOPU) and in vitro fertilization. In Experiment 1, in a 2 × 2 factorial study the progesterone priming treatment (treated or not) was or was not associated with a single dose of FSH in a slow-release hyaluronic acid preparation given on Day 0. The follicular population on Day 3 and the number and morphology of recovered cumulus oocyte complexes (COCs) were not affected by the progesterone treatment (P = NS) but were improved by the FSH administration (P <  0.05). An interaction between both treatments was observed (P <  0.05), with more desirable outcome with the females that received both the progesterone and the FSH treatments. In Experiment 2, half of the females received the exogenous progesterone priming, and all females received FSH on Day 0. After follicular aspiration on Day 3, the cleavage rate and the embryo development rate following in vitro fertilization and culture were greater in those females that received the progesterone treatment (P <  0.05). In conclusion, these studies provide evidence that progesterone treatment during follicular growth affects oocyte competence, with the greater progesterone concentrations enhancing the oocyte's capacity to undergo cleavage and embryo development.

Efficacy of using previously used controlled internal drug release (CIDR) insert on the reproductive performance, hormone profiles and economic measures of sheep

This study was conducted using 120 multiparous Awassi ewes during the breeding season to compare the effects of using previously used controlled internal drug release (CIDR) on the hormone profiles, reproductive performance and economic measures of ewes. Ewes were randomized to receive one of five previously used CIDR (previously used for 6, 12, 18, 24 or 30 days) or the new CIDR as a control for 6 days (CIDR6, CIDR12, CIDR18, CIDR24, CIDR30, and CIDR0 [control], respectively). Blood samples were collected on four occasions, at the time of CIDR insertion, after 3 days of insertion, and at the time of withdrawal and insemination. Serum estradiol (E2) and progesterone (P4) concentrations were measured. Timed insemination was performed 48 hr post-CIDR withdrawal. Pregnancy was diagnosed by ultrasonography 23 days after insemination and confirmed on day 35. The heat detection rate was significantly (p < 0.05) higher in the CIDR0 and CIDR6 groups than in the CIDR18 and CIDR30 groups. The total pregnancy rate and fecundity were significantly (p < 0.05) higher in the CIDR6 group than in other groups. P4 level was significantly (p < 0.05) higher in the CIDR0 group than in the CIDR30 group at the time of removal. At each time point, the E2 level was significantly (p < 0.05) higher in the CIDR6 group than at the other groups. The total variable cost, total cost, return and net profit were higher in the CIDR6 and CIDR0 groups than in the other groups. In conclusion, although previously used CIDRs are efficient at synchronizing oestrus in ewes, the duration of previously usage significantly affected the reproductive parameters and economic profit. CIDRs previously used for 6 days and new CIDRs provided the highest fertility and fecundity rates, besides return and net profit. Economically, it is not advisable to use CIDRs that previously used for 12 days or more.

Effect of a new device for sustained progesterone release on the progesterone concentration, ovarian follicular diameter, time of ovulation and pregnancy rate of ewes

This study evaluated the effectiveness of a new progesterone intravaginal device (DPR) in ewes through four experiments: Experiment 1 compared the circulating progesterone concentration of ovariectomized ewes that received either a new or a re-used DPR. Experiment 2 compared the progesterone concentration between DPR-estrous-synchronized ewes and naturally estrous-cycling ewes. Experiment 3 evaluated the effect of new and re-used DPRs on ovarian follicular dynamics and time of ovulation of estrous cycling ewes. Experiment 4 compared the pregnancy rate after the use of a DPR and Controlled Internal Drug Releasing Device (CIDR). The mean concentration of progesterone released by the DPR device during its first use (New Group: 5.1 ± 0.5 ng/ml) was greater than that during the second use (Re-used Group: 2.4 ± 0.3 ng/ml). There was no difference between the animals that received DPR devices for first and second use in terms of ovulatory follicle diameter, follicular wave emergence day for ovulatory follicle and period of ovulatory wave of ovarian follicular development. However, there was a significant difference between groups regarding the time between DPR device removal and first ovulation (New Group: 71.7 ± 2.5h and Re-Used Group: 63.9 ± 2.7h). Pregnancy rates were similar between ewes with DPR and CIDR devices. It was concluded that DPR is effective in increasing and maintaining progesterone concentrations, controlling follicular dynamics, promoting synchronized times of ovulation from healthy follicles, promoting development of a competent corpus luteum and when used results in pregnancy rates similar to that with use of the CIDR.

Follicular dynamics, interval to ovulation and fertility after AI in short-term progesterone and PGF2α oestrous synchronization protocol in sheep

The study was aimed to assess the influence that short-term progesterone treatments have on follicular dynamics, oestrus and ovulation in sheep. The treatment was tested thereafter in a field trial to assess its fertility after AI with fresh semen. In a first experiment, 12 ewes without CL were grouped to receive a new (n = 6) or used CIDR (n = 6) for 7 days and blood samples were obtained to follow plasma progesterone profiles. In a second experiment, 39 cycling ewes were synchronized by a 7-day P4+PGF2α protocol using a new (n = 20) or a 7-day used CIDR (n = 19). Half of both groups received 400 IU eCG and half remained untreated as controls. Ultrasound ovarian examination and oestrous detection were used to compare follicular dynamics, oestrus and ovulation in both groups. In a third experiment, 288 ewes in 3 farms were synchronized by the short-term P4+PGF2α+eCG protocol and ewes were AI with fresh semen 24 h after oestrous detection. Lambing performance was used to test the fertility of the treatment. In Experiment 1, ewes with new inserts presented higher P4 concentration than ewes with used inserts throughout the sampling period (p < 0.05) and exhibited a P4 peak at days 1-2 of the treatment that was not observed in ewes with used inserts. In Experiment 2, ewes treated with new and used inserts show similar ovarian and behavioral traits (p > 0.10). However, ewes treated with eCG show shorter interval to oestrus (p = 0.004) and tend to have larger mature CL (p = 0.06). In Experiment 3, oestrous presentation and lambing performance after AI with fresh semen was considered normal compared to published results. Results suggest that the oestrous synchronization protocol based on P4+PGF2α allows little control of follicular dynamics without compromising fertility after AI with fresh semen provided that eCG is added at the end of the treatment.

Re-use of intravaginal progesterone devices associated with the Short-term Protocol for timed artificial insemination in goats

Because intravaginal devices impregnated with 0.3 g of progesterone (i.e., CIDR-G) contain remaining hormone after their use in a Short-term Protocol (5 to 7 d of treatment), the reuse of these devices is proposed in goats. Two experiments were designed to study the effects of the reutilization of CIDR-G, establishing serum progesterone concentrations, follicular development, ovulatory response, and fertility. Experiment 1: Thirty dairy goats received a Short-term Protocol for 5 d using CIDR-G of first use (new devices, n = 10), second use (previously used for 5 d, n = 10), or third use (previously used twice for 5 d each time, n = 10). Goats were given (im) prostaglandin F(2α) (10 mg dinoprost) and eCG (300 IU) at device insertion and withdrawal, respectively. Serum progesterone concentrations induced by CIDR-G of first use were higher than CIDR-G of second or third use (P < 0.05); concentrations were consistently > 1 ng/mL in all females treated with reused devices. Estrus and ovulation were synchronized in 100% of goats (no differences among treatments). All females treated with new devices, but only 80% of females treated with re-used devices ovulated a new follicle that emerged after CIDR-G insertion (P = NS). Ovulation occurred between 60 and 70 h after device removal (no differences among groups). Experiment 2: In goats subjected to a Short-term Protocol followed by AI at 54 h after CIDR-G, pregnancy rates with CIDR-G of first, second, and third use were 75.3% (64/85), 67.4% (60/89), and 62.1% (54/87), respectively (devices of first versus third use, P < 0.05). In summary, intravaginal devices originally containing 0.3 g of progesterone appeared effective to synchronize estrus and ovulation after first, second and third use in the Short-term Protocol. Although the pregnancy rate with reused devices was acceptable (i.e., > 60%), it was significantly lower than that achieved with new devices and further studies to ensure adequate follicular turnover are required.