Ovarian responses and pregnancy rate with previously used intravaginal progesterone releasing devices for fixed-time artificial insemination in sheep

Impact of oestrus synchronization devices on ewes vaginal microbiota and artificial insemination outcome

Introduction

The low pregnancy rate by artificial insemination in sheep represents a fundamental challenge for breeding programs. In this species, oestrus synchronization is carried out by manipulating hormonal regimens through the insertion of progestogen intravaginal devices. This reproductive strategy may alter the vaginal microbiota affecting the artificial insemination outcome.

Methods

In this study, we analyzed the vaginal microbiome of 94 vaginal swabs collected from 47 ewes with alternative treatments applied to the progesterone-releasing intravaginal devices (probiotic, maltodextrin, antibiotic and control), in two sample periods (before placing and after removing the devices). To our knowledge, this is the first study using nanopore-based metagenome sequencing for vaginal microbiome characterization in livestock.

Results

Our results revealed a significant lower abundance of the genera Oenococcus (Firmicutes) and Neisseria (Proteobacteria) in pregnant compared to non-pregnant ewes. We also detected a significant lower abundance of Campylobacter in the group of samples treated with the probiotic.

Discussion

Although the use of probiotics represents a promising practice to improve insemination results, the election of the suitable species and concentration requires further investigation. In addition, the use of progestogen in the synchronization devices seemed to increase the alpha-diversity and decrease the abundance of harmful microorganisms belonging to Gammaproteobacteria and Fusobacteriia classes, suggesting a beneficial effect of their use.

Approaches of estrous synchronization in sheep: developments during the last two decades: a review

The objective of the current review was to summarize the protocols used for estrous synchronization in ewes during the last two decades. Progesterone (P4) is a major hormone used in most protocols. P4 in the form of a controlled internal drug releasing (CIDR) device, medroxyprogesterone acetate (MAP), and fluorogestone acetates (FGA) has been used for estrous synchronization. Also, gonadotropins such as equine chorionic gonadotropin (eCG) and gonadotropin-releasing hormone (GnRH) are often administered at the end of P4-based protocols to improve fertility. Moreover, the administration of prostaglandins (PG) and ram effects have been used for estrus induction and synchronization of ewes. The findings of previous studies indicate that the outcome of administering various synthetics P4 analogues (CIDR, MAP, and FGA) in ewes is comparable in terms of estrous synchronization/induction. The supplementation of P4-based protocols with eCG, however, improves the estrus response and pregnancy rate during breeding and non-breeding season. On the other hand, PG is effective for successful estrous synchronization during the breeding season only. Often, two injections of PG are administered either 11 or 14 days apart along with P4-based protocols to lyse ovine corpus luteum (CL) when it is receptive to PG i.e., 3 days post-ovulation. Alternatively, the "ram effect" has been shown to improve the efficacy of P4-based protocols and can be used as an alternative to eCG in ewes. The current review describes the methods of synchronization and their outcomes during breeding and a non-breeding season in ewes.

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.

The Effect of P4 + eCG Estrus Induction Protocol during the Deep and the Transition Anestrous Period on the Reproductive Performance of Crossbred Dairy Goats

Simple Summary

The effect of an ultra-short progesterone (P4) plus equine chorionic gonadotropin (eCG) based estrus induction protocol during deep seasonal anestrous, or the reproductive transition period upon reproductive performance in an arid environment (26° N) was assessed. Results confirm a multidimensional response of goats regarding the effectiveness of P4 + eCG estrus induction protocols, mainly modulated by a specific time within the anestrous season (June) or even by specific management or a particular environment at herd level (herd 1 in this study), although, it is quite remarkably non–dependent on the animal’s body weight or body condition score.

Abstract

Seasonal reproduction restricts the offering of goat commodities across the year. Therefore, it is crucial to improve diverse strategies to induce the reproductive response in goats during the anestrus stage. The effectiveness of a short P4 + eCG-based estrus induction protocol during both the deep anestrous (March) or the reproductive transition period (June) upon the reproductive performance of crossbred dairy goats was assessed. Adult, anestrous, 24–30-month- old dairy crossbred (Saanen–Alpine–Nubian × Criollo) goats (n = 123) from two commercial herds and 10 sexually active goat bucks were used. Before the trials, the anestrous status of goats was confirmed. Then, goats were randomly allocated into two different experiments. In Exp. 1, we tested the effect of different doses (D) of intramuscular progesterone (P4; 10 or 20 mg + eCG (100 UI)) and type of breeding (TB), natural mating (NM), or artificial insemination (AI), on two commercial goat herds (H1 & H2), in March (deep anestrous). In Exp. 2, we evaluated the effect of D (P4; 10 or 20 mg + 100 UI eCG) in goats subjected to NM, and either during deep anestrous (March; M) or transitional anestrous (June; J), in two commercial herds. After breeding, conception and pregnancy were diagnosed with ultrasound scanning. The response variables were estrus induction (EI; %), estrus latency (EL; h), ovulation (OVP; %), ovulation rate (OR; units), fertility (FERT; %), and pregnancy (PREG; %). No differences (p > 0.05) in live weight (LW) and body condition score (BCS) occurred between herds in both trials. In Exp. 1, EI, EL, OVP, OR, FERT, and PREG were affected (p < 0.05) by the H–TB–D interaction, whereas in H1 + P4–20 combination had the highest (p < 0.05) EI, EL, and OVP values. Irrespective of TB, H1 had the largest (p < 0.05) OR, independently of TB or D. Also, the lowest (p < 0.05) OVP occurred in the AI + P4–10 group, while the AI had the lowest (p < 0.05) FERT, irrespective of D. FERT and PREG were two-fold higher (p < 0.05) in NM compared with AI. In Exp. 2, EI, EL, OVP, OR, FERT, and PREG were affected (p < 0.05) by the H–M–D interaction. In general, H2 + P4–10 had the lowest (p < 0.05) reproductive outcomes in March, whereas H1 had the largest (p < 0.05) values in either month. No differences (p > 0.05) between P4 doses occurred for EI, OVP, OR, FERT, and PREG. Yet, the largest (p < 0.05) EL occurred with P4–20 in June. No correlations (p > 0.05) occurred between LW and all the reproductive variables. BCS was positively correlated (p < 0.05) with EI (0.34), OVP (0.44), OR (0.58), and PREG (0.20). Also, positive correlations (p < 0.05) occurred between EI with EL (0.83), OVP (0.80), OR (0.64), and PREG (0.56); EL with OVP (0.58), OR (0.44), and PREG (0.42); OVP with OR (0.79) and PREG (0.70), as well as OR and PREG (0.63). Results of these studies confirm a multidimensional response regarding the effectiveness of P4 + eCG for estrus induction in goats mainly modulated by a specific time within the anestrous season, or even by specific management or a particular environment at the herd level (H1), although quite remarkably independent of the animal’s LW or BCS at herd level. Moreover, the best reproductive outcomes occurred with NM in June. The most reproductive variables were similar using either 10 or 20 mg P4 + 100 IU eCG, giving the possibility to lessen the scale in the use of exogenous hormones while obtaining acceptable out of season reproductive response.

Addition of eCG to a 14 d prostaglandin treatment regimen in sheep FTAI programs

In the present study, there was evaluation of the alternative of adding eCG as part of a long-interval prostaglandin-F_2α (PG) treatment on the reproductive efficiency of Merino sheep during the breeding season. A total of 210 ewes and 182 ewe lambs were randomly assigned to three experimental groups to induce the timing of estrus among ewes in a: Long-interval PG, group being synchronized using two doses of PG 14 days apart; Long-interval PG + eCG group being synchronized using the same treatment regimen as Group PG with the addition of 200 IU eCG to the regimen, administered concomitantly with the second PG administration; and MAP + eCG group being synchronized with intravaginal progestin sponges for 14 days plus 200 IU eCG, administered at the time of sponge removal. The percentage pregnancy rate in ewes of the MAP + eCG group was greater than the ewes of the Long-interval PG and Long-interval PG + eCG groups (76.4 % compared with 52.0 % and 62.5 %, respectively; P < 0.05). The prolificacy rate was greater in the ewes of the Long-interval PG+eCG group compared with the other groups (114 % compared with 100 % and 103 %, respectively; P < 0.05). When considering the fecundity rate, ewes of the Long-interval PG+eCG and MAP+eCG groups had greater values than ewes of the Long-interval PG group (71.2 % and 78.8 % compared with 52.0 %, respectively; P < 0.05). The Long-interval PG+eCG is an alternative to the conventional progestin sponge plus eCG treatment regimen with there being a greater fecundity rate when this regimen is used compared with the Long-term PG and similar to MAP-eCG treatment regimens.

Influence of the Ovine Genital Tract Microbiota on the Species Artificial Insemination Outcome. A Pilot Study in Commercial Sheep Farms

To date, there is a lack of research into the vaginal and sperm microbiome and its bearing on artificial insemination (AI) success in the ovine species. Using hypervariable regions V3-V4 of the 16S rRNA, we describe, for the first time, the combined effect of the ovine microbiome of both females (50 ewes belonging to five herds) and males (five AI rams from an AI center) on AI outcome. Differences in microbiota abundance between pregnant and non-pregnant ewes and between ewes carrying progesterone-releasing intravaginal devices (PRID) with or without antibiotic were tested at different taxonomic levels. The antibiotic treatment applied with the PRID only altered Streptobacillus genus abundance, which was significantly lower in ewes carrying PRID with antibiotic. Mageebacillus, Histophilus, Actinobacilllus and Sneathia genera were significantly less abundant in pregnant ewes. In addition, these genera were more abundant in two farms with higher AI failure. Species of these genera such as Actinobacillus seminis and Histophilus somni have been associated with reproductive disorders in the ovine species. These genera were not present in the sperm samples of AI rams, but were found in the foreskin samples of rams belonging to herd 2 (with high AI failure rate) indicating that their presence in ewes' vagina could be due to prior transmission by natural mating with rams reared in the herd.

The reused progesterone device has the same effect on short or long estrus synchronization protocols in tropical sheep

This study aimed to evaluate the effect of progesterone (P4) device reutilization in long and short protocols for transcervical timed artificial insemination (TAI) in Santa Inês ewes. A total of 275 multiparous lactating ewes were blocked according to body weight (BW, 49.1 ± 7.3 means ± SE), body condition score (BCS, 2.9 ± 0.4; scale of 1-5), and days postpartum (50 ± 8.2 days), and allocated to one of the treatments. The treatments were arranged in a factorial design, in which the factor 1 was the P4 device type (new or a device of 0.3 g of P4 previously used by 11 days), and the factor 2 was the short or long TAI protocol (P4 device remained by 7 or 11 days, respectively). At device removal, all ewes received 300 IU eCG and 6.70 mg of Dinoprost tromethamine. After TAI protocol, ewes remained with ram by 21 days. There was no interaction between factors in any variables. Ewes that received a new P4 device delayed (P = 0.05) to show estrus compared with ewes receiving a previously used P4 device, but it did not affect pregnancy rate. The long protocol tended to increase pregnancy rate compared with short protocol (33% vs. 24%, respectively; P = 0.07). However, the pregnancy rate at the end of reproductive period was similar in both groups (about 84%). Thus, the use of long protocols tended to improve reproductive performance, and the reused P4 device did not affect pregnancy rate.

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.

CHARACTERIZATION AND CELULAR PROLIFERATION OF OVARIAN STRUCTURES OF EWES BY THE TECHNIQUE OF AGNOR: OVARIAN MORFOMETRY AND CORRELATIONS

The AgNOR staining technique for nucleolar organizer regions (NORs) is characterized by marking proteins related to ribossomal ribonucleic acid evaluating celular proliferation. The objective was to study the ovarian morphometry and the value of AgNOR thecnique application to evaluate the proliferation of healthy cels from ovarian structures in crossbred ewe. 102 pairs of ovaries were collected and from the largest follicle of each ovary was measured its diameter. From the largest corpus luteum (CL) was measured the diameter and width, classifying the CL in: included, protruberant, massive and cavity, followed by AgNOR staining. The significance level was 5%. It had difference (p<0.05) for the diameter of the largest follicle between right (RO): 4.2±2,3mm and left (LO): 3.6±2,2mm sides. There was a correlation (p<0.01) between the NORs of internal theca (IT) and external theca (ET): RO (0.46) and LO (0.61); NORs of granulosa and IT: RO (0.54) and LO (0.59); and NORs of granulosa and ET: RO (0.34) and LO (0.38). Was conclude that the NORs quantification was appropriate to study the determination of the potential for ovarian structures proliferation, which was similar for right and left sides.

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.

Re-used progesterone devices efficiently synchronise oestrus and ovulation after autoclaving process in Toggenburg goats during the breeding season

This study compared new and previously used (and autoclaved) progesterone devices for synchronisation of oestrus during the breeding season in Toggenburg goats. Nulliparous (n = 17) or lactating (n = 50) received new intravaginal devices containing 0.3 g progesterone (CONTROL), or similar devices previously used for either 6 (USED6) or 12 (USED12) days and subsequently autoclaved. All goats received 5 mg dinoprost at device insertion and 200 IU equine chorionic gonadotropin 5 days later and all devices were removed after 6 days. After device removal, females were mated by fertile bucks. Ovarian ultrasonography was performed every 12 h after device removal until ovulation detection. Blood samples were collected for determination of plasma progesterone concentration in different moments and intervals (from 7 days before device insertion to 3 days after its removal). There was no difference (P > 0.05) among groups CONTROL, USED6 or USED12 for: oestrus response [75% (18/24), 77% (17/22) or 71% (15/21), respectively]; duration of oestrus (30.7 ± 3.4, 31.8 ± 1.7 or 32.8 ± 3.4 h), percentage of ovulating goats [67% (6/9), 78% (7/9) or 56% (5/9)], ovulation rate (1.3 ± 0.2, 1.4 ± 0.2 or 1.8 ± 0.4 units of corpora lutea), average follicle diameter (6.2 ± 0.1, 6.7 ± 0.1 or 6.8 ± 0.3 mm) and pregnancy rate [54% (13/24), 50% (11/22) or 48% (10/21)]. Plasma progesterone concentrations were not different (P > 0.05) for does among treatments and between nulliparous and lactating females. In conclusion, autoclaved, previously used intravaginal progesterone devices are effective in synchronising oestrus and ovulation in cyclic goats during the breeding season.

Effects of progestagen exposure duration on estrus synchronization and conception rates of crossbreed ewes undergoing fixed time artificial insemination

Synchronization of estrus and ovulation are of paramount importance in modern livestock improvement programs. These methods are critical for assisted reproduction technologies, including artificial insemination and embryo transfer, that can increase productivity. In the current study, subcutaneous implants containing norgestomet were placed for long (14 days), medium (9 days), and short (5 days) periods of time in 70 crossbred ewes undergoing fixed-time artificial insemination. The resulting effects on estrus synchronization and conception rates were subsequently evaluated. Among the synchronized ewes, 85.7% (60/70) underwent estrus over a period of 72 h after progestagen treatment ceased. The shortest mean interval between withdrawal of the device and onset of estrus (34.2 ± 8.9 h) was observed in the G14 days of P4 group (p < 0.05). The conception rate of the G14 days of P4 group was statistically higher than that of the other groups (83.3% vs. 60.9% vs. 47.8%; p < 0.05). In conclusion, 14 days of norgestomet treatment produced higher conception rates and a greater number of pregnancies at the beginning of the breeding season.