Effect of altering dose of PG600 on reproductive performance responses in prepubertal gilts and weaned sows

Differential Expression/Regulation of Progesterone Receptor in Reproductive Tissues (Ovary and Uterus) Induced by Human Chorionic Gonadotropin and Equine Chorionic Gonadotropin Treatments in Sows

We studied sows (Landrace × Yorkshire line, DanBred Hybrid) to evaluate the possible changes in progesterone receptor (PR) expression in the uterus and ovary caused by different non-hypophyseal gonadotropins treatments: equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG). Varying concentrations of eCG and hCG were evaluated (Groups 1, 2, 3, 4). PR expression was determined by immunohistochemistry, and labelling intensity was determined by the HScore method. In the ovary, PR expression in the granulosa cells of follicles did not differ significantly between Groups 1 and 2 (p < 0.05) but differed significantly from that in Groups 3 and 4 (p < 0.05), which in turn did not differ from each other. This PR expression pattern was similar across groups in the internal and external theca cells. Conversely, in the uterus, PR expression in the lining epithelium was lower in Group 4 than that in Group 1 (p < 0.05). Increased expression was observed in the endometrial lamina propria in all groups 2 and 4 compared to that in the control group (p < 0.05). Decreased expression was observed in the glandular epithelium and myometrium in Group 4 compared to that in Group 1 (p < 0.05). In the ovary, PR expression in the granulosa and outer and inner theca of the follicles was not significantly different (p < 0.05) between Groups 1 and 2 or Groups 3 and 4; however, the expression in these pairs of groups differed from each other. Thus, changes in PR expression may depend on the concentrations and proportions of exogenous hormones used in the treatments, indicating an alteration in the reproductive process.

Pregnancy Establishment and Diagnosis in Livestock

This comprehensive review explores the complex processes of reproduction, pregnancy establishment, and pregnancy diagnostic methods in cattle, sheep, goats, swine, horses, and camelids. It provides an overview of the history of pregnancy detection and an in-depth exploration of the physiology of pregnancy in livestock. The detection of conceptus tissue and fluids, conceptus-produced hormones, and maternal responses to conceptus signals, crucial for pregnancy diagnosis, are also discussed in detail, as are emerging methods for pregnancy diagnosis in livestock species. Overall, this review emphasizes the direct impact of pregnancy diagnosis and efficient pregnancy management for profitability of livestock enterprises.

Follicle development in pigs: State of the art

Understanding the factors and pathways involved with recruitment, atresia, and selection of follicles in the pig, may provide insight into approaches to limit fertility failures. Antral follicles depend upon FSH to the 2-3 mm stage, become codependent upon LH at 4-5 mm, and rely on LH when >5 mm. Within the follicle, gonadotropin binding, steroids, growth factors, and inhibin interact to determine the fate of the follicle. Continuous recruitment appears likely for follicles, and once >1 mm, they may have a limited period for survival, before selection or atresia. If true, then the number of healthy follicles that can respond to a hormone signal for selection, could vary by size and development stage. Which follicles are selected may depend upon their age, numbers of capillaries, granulosa and thecal cells, and FSH and LH receptors. This might also suggest that factors such as management, nutrition, and stress in prior weeks, could affect different cohorts of follicles to determine which of those from the ovarian population will be selected.

Mechanisms of Oogenesis-Related Long Non-coding RNAs in Porcine Ovaries Treated With Recombinant Pig Follicle-Stimulating Hormone

Reproductive efficiency is of significant importance in pork production for it has a great impact on economic success. Ovulation rate is an early component of reproduction efficiency of pigs, and it contributes to the upper limit of litter size. In this study, we used the newly developed recombinant pig follicle stimulating hormone (rpFSH) instead of traditional PMSG to increase ovulation rate of pigs in order to achieve higher litter size, for it was better at stimulating ovulation, and showed more cheaper and greener. However, relatively little is known about the underlying genetic bases and molecular mechanisms. Consequently, an experiment was carried out in ovaries of replacement gilts to screen the key genes and lncRNAs that affect the fecundity of pigs by RNA-seq technology. Twenty gilts were divided into two groups, including 10 rpFSH treatment pigs and 10 control animals. After slaughtering and collecting the phenotypic data, ovaries of five pigs in each group were selected for RNA-seq. Total RNA was extracted to construct the library and then sequence on an Illumina Hiseq 4000 system. A comprehensive analysis of mRNAs and long non-coding RNAs (lncRNAs) from 10 samples was performed with bioinformatics. The phenotypic data showed that rpFSH treatment groups had the higher (P < 0.01) ovarian weight and more mature follicles. The RNA-seq results showed that a total of 43,499 mRNAs and 21,703 lncRNAs were identified, including 21,300 novel lncRNAs and 403 known lncRNAs, of which 585 mRNAs and 398 lncRNAs (P < 0.05) were significantly differentially expressed (DE) between the two groups of rpFSH treatment group and controlled group. GO and KEGG annotation analysis indicated that the target genes of DE lncRNAs and DE mRNAs were related to prolactin receptor activity, mitophagy by induced vacuole formation, and meiotic spindle. Moreover, we found that NR5A2 (nuclear receptor subfamily 5, group A, member 2), a target gene of lncRNA MSTRG.3902.1, was involved in regulating follicular development, ovulation, and estrogen production. Our study provided a catalog of lncRNAs and mRNAs associated with ovulation of rpFSH treatment, and they deserve further study to deepen the understanding of biological processes in the regulation of ovaries of rpFSH treatment pigs.

Investigation into the variation in follicular and endocrine responses of prepubertal gilts treated with exogenous gonadotropins

The gonadotropin compound, PG600, is used to induce estrus in prepubertal gilts, but responses can be variable. This study was conducted to evaluate PG600 effects on follicles, estrus, ovulation and estrogen production. Prepubertal gilts (n = 50) were treated with PG600. Gilts were evaluated for estrus while daily boar exposure was occurring. A sub-population of gilts (n = 12) were slaughtered on Day 3 to assess cytochrome P450 aromatase (CYP19) immunohistochemical staining in ovarian antral follicles. Ovaries of the remaining gilts (n = 38) were evaluated on Day 3 using ultrasonography and blood samples were collected for quantifying estradiol-17β. On Day 3 following administration of PG600, 94.0 % of gilts had large follicles, but only 76.3 % had expressed behavioral estrus by Day 6. Furthermore, 92.1 % of gilts had ovulations, with 16.6 corpora lutea/gilt. There was no association of number of large follicles on Day 0 or 3 with occurrence of estrus or ovulation (P >  0.05). Estradiol-17β concentrations on Day 3 did not differ (P >  0.05) in anestrus compared to estrual gilts and varied in gilts with large antral follicles. Immuno-detection of CYP19 on Day 3 was greater (P <  0.01) in large and medium compared to small follicles, (64.3 %, 34.2 % and 14.7 %, respectively). Results validate there is a dissociation of large follicle development with estrogen production on Day 3 in gonadotropin-treated gilts. These results indicate failure to express estrus may be due to follicle variation in estrogen production or response to estrogen feedback at the hypothalamus.

Ovulatory Response of Weaned Sows to an Altered Ratio of Exogenous Gonadotrophins

Simple Summary

Efficient pork production relies on a consistent supply of market pigs. To achieve breeding targets, gonadotrophins can be administered at weaning to stimulate estrus onset. The present study examined the impact of supplemental human chorionic gonadotrophin activity (i.e., hCG), during a follicular phase induced by a standard gonotrophin protocol (i.e., PG600), in both ovarian follicular development and fertility in multiparous sows. The results confirmed that supplemental hCG at 24 h after PG600 increased follicle growth and reduced the interval to ovulation, but also increased the incidence of follicle cysts and reduced pregnancy success.

Abstract

At weaning, 33 mixed parity Hypor sows received either an injection of 400 IU equine chorionic gonadotrophin and 200 IU human chorionic gonadotrophin (hCG) (PG600; n = 13), PG600 with an additional 200 IU hCG 24 h later (Gn800; n = 11), or served as non-injected controls (n = 9). All gonadotrophin treated sows received an injection of 750 IU hCG at 80 h after weaning to induce ovulation (designated as time 0 h). At 0, 24, 36, 40, 44, 48, and 60 h, all sows were subject to transrectal ultrasonography to determine numbers and sizes of large (>6 mm) follicles and time of ovulation. The interval from injection of 750 IU hCG to ovulation was shorter in Gn800 compared to PG600 sows (p = 0.02), and more Gn800 sows had ≥9 preovulatory follicles compared to PG600 and controls (p = 0.02 and 0.003, respectively). Follicular cysts were evident in both PG600 and Gn800 sows.

PHYSIOLOGY AND ENDOCRINOLOGY SYMPOSIUM: Factors influencing follicle development in gilts and sows and management strategies used to regulate growth for control of estrus and ovulation1

Factors that affect follicle health and growth can influence estrus, ovulation, conception, and litter size. Since the majority of the breeding herd is composed of sows, production schedules are established based on synchronized follicle growth following weaning. Insemination of sows over a 3- to 4-d period after weaning facilitates farrowing over fewer days and helps improve the uniformity of pigs at weaning. Synchronized inseminations of the group are reduced when disturbance to the follicular phase results in delayed estrus. The failure of >15 follicles to uniformly progress beyond the 6.0 mm size within 4 d during the follicular phase is associated with delayed estrus and ovulation, reduced ovulation rate, and reduced farrowing rate. In sows, the follicular phase is initiated at weaning by removal of the suckling inhibition, whereas in cycling gilts, luteolysis and clearance of progesterone begins the process. The timing and patterns of follicle-stimulating hormone and luteinizing hormone stimulation to the ovary determine follicle health and selection for ovulation. Interestingly, abnormal wean-to-estrus intervals in sows and deviations from a 19- to 22-d estrous cycle in gilts are associated with reduced fertility. However, in both cases, it is not entirely clear whether the abnormal intervals are a direct result of problems occurring prior to or only during the follicular phase. In prepubertal gilts, the signal for initiating the follicular phase remains elusive, but could reside in differential sensitivity and response to hormone signals at the level of the ovary and brain. Although the mechanisms are not clear, factors such as boar exposure, stress, feed intake, growth rate, and birthweight have been shown to stimulate an early follicular phase. In contrast, inhibitors to follicle growth have been associated with season, heat stress, photoperiod, negative energy balance, poor body condition, slow growth, fewer parities, and short lactation length. Hormonal aids for inducing and delaying the follicular phase, as well as for inducing ovulation are available to aid in synchronized breeding schedules.

Differential gene expression of Eph-ephrin A1 and LEPR-LEP with high or low number of embryos in pigs during implantation

The objective of this study was to ascertain whether mRNA and protein expressions of implantation-related genes (erythropoietin-producing hepatocellular receptor-ligand A1, Eph-ephrin A1 and leptin receptor-leptin, LEPR-LEP) differed between pigs with high and low number of embryos, and whether these differences in gene expression might affect embryo implantation. Experimental pig groups (n = 24) for high and low number of embryos were prepared by altering the number of eggs ovulated in pre-pubertal gilts treated with 1.5 × (High) or 1.0 × (Low) PG600 ([400 IU PMSG + 200 IU hCG]/dose, AKZO-NOBEL). Gilts expressing oestrus were artificially inseminated twice and maintained in breeding and gestation until the reproductive tract was collected on day 22 of pregnancy. At slaughter, the reproductive tracts from each pregnant gilt from each treatment were immediately processed to collect samples for RNA and protein analysis. Within each gilt, three conceptus points were sampled, one from each horn and then a random conceptus within the tract. At each conceptus point, endometrial attachment site, chorion-allantois and embryo were collected and immediately frozen in liquid nitrogen. Number of corpus luteum (CL) (35.4 vs. 12.6) and total embryo number (18.8 vs. 10.2) were greater in the high-embryo compared to the low-embryo group, respectively (p < .05). Real-time qPCR results showed that Eph-ephrin A1 mRNA expression was less in the high-embryo (p < .05) compared to the low-embryo group. In addition, Western blotting analysis indicated that Eph-ephrin A1 and LEP protein expression at endometrial attachment site in high-embryo was less (p < .05) compared to low-embryo group. It was also noted that mRNA expression of Eph-ephrin A1 and LEPR-LEP was greater in pregnant than non-pregnant gilts (p < .05). Moreover, mRNA expression of Eph-ephrin A1 (p < .05) and LEPR-LEP was greatest at endometrial attachment site among all three tissues. There was a positive correlation between expressions of Eph-ephrin A1, LEPR-LEP and embryo length with the correlation coefficient 0.31-0.59. For Eph-ephrin A1, the highest correlation coefficient appeared between Eph A1 expression and normal embryo number, between ephrin A1 expression and embryo length. For LEPR-LEP, the highest correlation coefficient appeared between LEPR-LEP expression and ovary weight (0.79 for both, p < .05), followed by embryo length and weight. The results of this study suggest that low expression of Eph-ephrin A1 and LEPR-LEP is somehow related to increased embryo number during implantation and that endometrial attachment site might be the main target tissue of these gene products. Yet, the increased expression of Eph-ephrin A1 and LEPR-LEP appeared associated with increased embryo growth (length and weight) and ovary weight, Eph-ephrin A1 and LEPR-LEP might play roles in the regulation of embryo implantation in pigs.

Ovarian reaction and estrus manifestation in delayed puberty gilts after treatment with equine chorionic gonadotropin

BACKGROUND

Prolonged pre-insemination anestrus (i.e. delayed puberty) is a major contributing factor for culling up to 30% of the replacement gilts at large breeding farm units in Vojvodina. It is imperative to determine if these gilts are acyclic (prepubertal) or cyclic, but just fail to exhibit behavioural estrus. Recent investigations demonstrate that treatment with equine chorionic gonadotropin (eCG) can increase the diestrous phase duration in sexually mature gilts. Based on these finding, the aim of the present studies was to determine the reproductive status of delayed puberty gilts following injection with eCG.

METHODS

Two experiments were conducted on a swine breeding farm in Vojvodina. In Exp. 1, 20 prepubertal (acyclic) gilts, and 120 sexually mature (cyclic) gilts were injected with a single injection of 400  IU eCG + 200 IU human chorionic gonadotropin (hCG) or with 1000  IU eCG (cyclic gilts), at d5, d11 or d17 after spontaneous estrus detection, to determine their ovarian reaction and induced estrus manifestation. In Exp. 2, sixty delayed puberty gilts (estrus not detected until 8 month of age, av. 258 days) were culled from breeding herd and slaughtered to determine their reproductive status based on ovarian anatomical features. The second group of gilts (n = 60) was treated with a single 1000  IU eCG injection to determine their reproductive status, based on the interval between eCG injection to estrus detection and duration. The data were analyzed by descriptive statistics, t-test, analysis of variance and Duncan's test in the software package Statistics 10th.

RESULTS

Ovulations were induced in 90% of acyclic (sexually immature) and, on average, 93.3% of cyclic (sexually mature) gilts after the eCG injection. On average, 4 days after the eCG injection, estrus was detected in 85% of the treated acyclic (sexually immature) gilts and in 95% (19/20) of the cyclic (sexually mature) gilts, treated with eCG on day 17 after spontaneous estrus detection. The interval from eCG to induced estrus detection was prolonged (av. 25 days) in 95% (19/20) of the sexually mature gilts treated with eCG on day 5 and in 90% (18/20) of gilts treated on day 11 after spontaneous estrus detection (Exp. 1). Forty anestrous gilts reached cyclic pubertal ovarian activity. Estrus manifestation was detected in 56 gilts (93.3% of the total 60 treated prolonged anestrous gilts, av. 259 days of age), after a single 1000  IU eCG injection. Thirty-four gilts (60.7% of the total gilts in estrus) with prolonged eCG to estrus interval (av. 24.7 days) were considered spontaneously cyclic (sexually mature), but behaviourally anestrous before treatment. The remaining 22 (39.3% of the total gilts in estrus) were considered truly sexually immature (acyclic) before the treatment or were eCG injected in the late luteal or proestrous phase of spontaneous estrous cycle (Exp. 2).

CONCLUSIONS

In 66.7% of the delayed puberty gilts, pre-ovulatory follicles (PoF), corpora hemorrhagica (CH), corpora lutea (CL), or corpora albicantia (CA) were found on the ovaries upon post mortem examination. These gilts were considered as sexually mature before slaughtering. In 60.7% of the delayed puberty gilts, behavioural estrus was detected an average of 24.7 days following eCG injections. These gilts were considered as eCG treated during the luteal phase (diestrus) of the spontaneous estrus cycle. Both findings suggest that delayed puberty gilts actually reached cyclic pubertal ovarian activity (sexual maturity) before culling from the breeding herd.

Effect of gonadotropin treatment on estrus, ovulation, and litter size in weaned and anestrous sows

In the first of 2 experiments, we evaluated the effects on anestrous sows of pretreatment with FSH to stimulate the growth of small follicles, followed by eCG to stimulate the growth of medium follicles, estrus, and ovulation. In Exp. 2, we examined the effect of sows receiving 400 IU of eCG plus 200 IU of hCG (PG 600, Intervet/Schering Plough Animal Health, Boxmeer, the Netherlands) at weaning and then different doses and timing of supplemental hCG. In Exp. 1, a total of 87 multiparous Hypor sows deemed anestrus 7 d after weaning were assigned to intramuscular (i.m.) injection of 1) PG 600, 2) eCG (600 IU), 3) pretreatment with 87.5 IU of FSH on d 7 and 8 plus eCG on d 9, or were 4) noninjected controls. Sows had daily boar contact for 15 d after weaning for estrus detection. Blood samples were obtained on d 9 and 19 and assayed for progesterone to determine ovulation status. The weaning-to-estrus interval, number of sows in estrus and ovulating, farrowing rate, and litter size were not different (P > 0.1) in treated groups compared with controls. In Exp. 2, a total of 247 Hypor sows were assigned at weaning by parity (1 and 2 or > or = 3) to receive 1) an i.m. injection of PG 600, 2) PG 600 supplemented with 100 IU of hCG injected either concurrently or after 24 h, 3) 200 IU of hCG after 24 h, or 4) no injection (controls). Sows were exposed to boars daily for 7 d. After treatment of parity 1 and 2 sows, all gonadotropin-treated groups had an increased (P < 0.05) number of sows in estrus compared with the control group; weaning-to-estrus interval, farrowing rates, and litter size were unaffected (P > 0.1). After treatment of parity > or = 3 sows, there was no treatment effect on the estrous response and weaning-to-estrus interval; compared with control and PG 600-treated sows, farrowing rate was decreased (P < 0.05) for sows receiving 200 IU of hCG after 24 h. There was no effect (P > 0.1) of treatment on litter size. We conclude that gonadotropins can be used to increase estrus response in weaned sows, but that hCG treatment subsequent to PG 600 may be detrimental to sow fertility in parity > or = 3 sows.

Effect of hCG treatment on the oestrous and ovulation responses to FSH in prepubertal gilts

To ensure sufficient numbers of pregnant females, particularly at hotter times of the year, hormonal induction of gilt oestrus may be necessary. However, the gilt oestrus and ovulation responses to gonadotrophin treatment have often proven unpredictable. The objective of this study was to examine possible reasons for this unpredictability. Prepubertal gilts (approximately 150 days of age, n = 63) were assigned to one of three treatments: injection of 300 IU hCG (n = 15); pre-treatment with 100 mg FSH in polyvinylpyrrolidinone administered as 2 x 50 mg injections 24 h apart, followed by 600 IU eCG at 24 h after the second FSH injection (n = 23); or FSH pre-treatment as above followed by 300 IU hCG at 24 h after the second FSH injection (n = 25). To facilitate oestrus detection, gilts were exposed to a mature boar for 15 min daily for 7 days. Blood samples were obtained on the day of eCG or hCG injection and again 10 days later and gilt ovulation responses determined based on elevated progesterone concentrations. The oestrus responses by 7 days were 6.7%, 17.5% and 64.0% for gilts treated with hCG, FSH + eCG and FSH + hCG, respectively (p < 0.001). The oestrous gilt receiving hCG alone and one oestrous FSH + hCG gilt did not ovulate, all other oestrous gilts ovulated. A further two anoestrous FSH + eCG-treated gilts ovulated. These data suggest that FSH pre-treatment facilitated the development of ovarian follicles to the point where they became responsive to hCG, but had little effect on the response to eCG.

Induction of estrus in pubertal miniature gilts

Genetic engineering of miniature pigs has facilitated the development of numerous biomedical applications, such as xenotransplantation and animal models for human diseases. Manipulation of the estrus is one of the essential techniques for the generation of transgenic offspring. The purpose of the present study was to establish a useful method for induction of the estrus in miniature gilts. A total of 38 pubertal miniature gilts derived from 4 different strains were treated with exogenous gonadotropins. Estrus and ovulatory response were examined after treatment with pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) as 200 IU PMSG and 100 IU hCG, 300 IU PMSG and 150 IU hCG, or 1,500 IU PMSG only, followed by 100, 150 or 750 IU hCG 72 h later, respectively. The optimal protocol was determined to be the combination treatment of 200 IU PMSG and 100 IU hCG followed by 100 IU hCG. The administration of 200 IU PMSG and 100 IU hCG was effective in inducing estrus regardless of the strain, although there was a strain difference in the ovulatory response. These results indicate that treatment with a low-dose combination of PMSG and hCG provides one of the simplest methods for induction of estrus and ovulation in pubertal miniature pigs.

Synchronization and superovulation of mature cycling gilts for the collection of pronuclear stage embryos

An efficient protocol was developed to synchronize and superovulate mature pigs for the collection of pronuclear stage embryos suitable for DNA microinjection. A timed and coordinated regimen of Lutalyse, PG600 and Chorulon along with daily checking for estrus allowed synchronization of groups of gilts having estrous cycles at regular intervals. Pigs 10-16 days after the beginning of standing estrus have been successfully synchronized into estrus using this protocol. A standard dose of each drug was used independent of size or age of the animal. One protocol averaged 38.9 ovulations and 31.1 one-cell embryos recovered per animal.