A single administration of a long-acting recombinant ovine FSH (roFSH) for cattle superovulation

Superovulating cattle with corifollitropin-alpha, a long-acting recombinant human FSH (rhFSH): Dose-response, half-life, effects on the ovaries, and embryo outcomes

The aim of this study was to evaluate the superestimulatory and superovulatory responses of cattle treated with corifollitropin-alpha, a long-acting human recombinant FSH (rhFSH). In the first and second experiments, we used Nelore (Bos indicus) heifers previously submitted to follicular wave suppression by active immunization against GnRH. In Experiment 1 (a dose-response study), heifers (n = 20) were randomly allocated into five groups, which received placebo (saline) or a single sc dose of 7.5, 15.0, 22.5 or 30.0 μg rhFSH. The heifers were subjected to daily ovarian scan and blood sampling during 11 days. We observed group, time, and group x time effects (P<0.0001) for both average follicle size and circulating FSH concentrations, with a strong correlation (R = 0.82, P<0.0001) between the area under curve (AUC) for both parameters. The peak concentration of FSH 24h after treatment and average follicle size at all timepoints, however, were similar (P>0.05) between groups 22.5 and 30.0 μg. In Experiment 2, heifers (n = 18) were allocated into three groups, which received (0h) either placebo (control), 25 μg rhFSH or 130 mg pFSH (Folltropin). There was no difference (P>0.05) in average follicle size at any moment, as well as in intrafollicular E2 at 120h or in plasma P4 seven days later between groups rhFSH and pFSH. In Experiment 3, cycling Nelore heifers (n = 20) were subjected to a wave synchronization protocol and superovulated (day 0) using a standard pFSH protocol (120 mg split in eight decreasing im doses) or with a single sc injection of 20 μg rhFSH. The number of follicles >7 mm on day 4 did not differ (P=0.4370). Heifers receiving rhFSH had greater average follicle size on day 4 (P=0.0005), ovulation rate (P<0.0001), and number of CL (P=0.0155), as well as a trend towards a greater number of ova (P=0.07) and viable embryos (P=0.0590). In Experiment 4, superovulation was induced with a single sc injection of 25 μg rhFSH in Girolando and Nelore cows and heifers (n = 20). None of the embryo yield endpoints differed between the two breeds (P>0.05). In conclusion, cattle superstimulation and superovulation can be successfully induced with a single dose of a long-acting rhFSH (corifollitropin-alpha).

Recent advancements to increase success in assisted reproductive technologies in cattle

Assisted reproductive technologies (ART) are fundamental for cattle breeding and sustainable food production. Together with genomic selection, these technologies contribute to reducing the generation interval and accelerating genetic progress. In this paper, we discuss advancements in technologies used in the fertility evaluation of breeding animals, and the collection, processing, and preservation of the gametes. It is of utmost importance for the breeding industry to select dams and sires of the next generation as young as possible, as is the efficient and timely collection of gametes. There is a need for reliable and easily applicable methods to evaluate sexual maturity and fertility. Although gametes processing and preservation have been improved in recent decades, challenges are still encountered. The targeted use of sexed semen and beef semen has obliterated the production of surplus replacement heifers and bull calves from dairy breeds, markedly improving animal welfare and ethical considerations in production practices. Parallel with new technologies, many well-established technologies remain relevant, although with evolving applications. In vitro production (IVP) has become the predominant method of embryo production. Although fundamental improvements in IVP procedures have been established, the quality of IVP embryos remains inferior to their in vivo counterparts. Improvements to facilitate oocyte maturation and development of new culture systems, e.g. microfluidics, are presented in this paper. New non-invasive and objective tools are needed to select embryos for transfer. Cryopreservation of semen and embryos plays a pivotal role in the distribution of genetics, and we discuss the challenges and opportunities in this field. Finally, machine learning (ML) is gaining ground in agriculture and ART. This paper delves into the utilization of emerging technologies in ART, along with the current status, key challenges, and future prospects of ML in both research and practical applications within ART.

Expression and functional characterization of chimeric recombinant bovine follicle-stimulating hormone produced in Leishmania tarentolae

Assisted reproductive techniques are routinely used in livestock species to increase and enhance productivity. Ovarian hyperstimulation is a process that currently relies on administering pituitary-derived follicle-stimulating hormone (FSH) or equine chorionic gonadotropin in combination with other hormones to promote the maturation of multiple follicles and thereby achieve superovulation. The use of partially purified preparations of FSH extracted from natural sources is associated with suboptimal and variable results. Recombinant FSH (rFSH) has been produced in a variety of heterologous organisms. However, attaining a bioactive rFSH of high quality and at low cost for use in livestock remains challenging. Here we report the production and characterization of a single chain bovine rFSH consisting of the β- and α-subunit fused by a polypeptide linker (scbFSH) using Leishmania tarentolae as heterologous expression system. This unicellular eukaryote is non-pathogenic to mammals, can be grown in bioreactors using simple and inexpensive semisynthetic media at 26°C and does not require CO2 or bovine serum supplementation. Stable cell lines expressing scbFSH in an inducible fashion were generated and characterized for their productivity. Different culture conditions and purification procedures were evaluated, and the recombinant product was biochemically and biologically characterized, including bioassays in an animal model. The results demonstrate that L. tarentolae is a suitable host for producing a homogeneous, glycosylated and biologically active form of scbFSH with a reasonable yield.

Evaluation of a long-acting recombinant bovine FSH for multiple ovulation and embryo transfer in dromedary camels

The present study was conducted to test a new super-agonist recombinant bovine FSH (rbFSH) to induce superovulation (SOV) in dromedary camels. In experiment I, a single IM injection of 40, 60, 80, 100, or 120 µg rbFSH was administered (4 donors per group) to determine the effective dose resulting in acceptable multiple ovulation and embryo yield. Administration of 40 µg was ineffective, while 100 and 120 µg were associated with increased numbers of developed follicles, corpora lutea, and recovered embryos compared to administration of 60 and 80 µg. In experiment II, donors were divided into treatment groups to compare rbFSH with two conventional protocols for SOV. Donors received a single dose of 2000 IU eCG in combination with 400 mg porcine follicle-stimulating hormone (pFSH; Folltropin-V®; Group 1, n = 29) or 500 µg of pFSH with 100 µg of pLH (Stimufol®; Group 2, n = 16). Group 3 (n = 19) received a single dose of 100 µg rbFSH. No difference was found in the size and number of follicles per donor. Response time, ovulation rate, and the number of corpora lutea and recovered embryos per donor were similar in all groups. The number of medium-sized and transparent embryos decreased while the number of small-sized and semi-transparent embryos increased in Group 3 (rbFSH) compared to the other two groups. The pregnancy rate of the recipients at 10 days post-ET, at two months of gestation, and the rate of early pregnancy loss (EPL) did not differ among the groups. In conclusion, a single IM administration of 100 µg rbFSH induces a successful superovulation in dromedary camels and has the advantage of reducing stress associated with multiple FSH administration of the conventional protocols.

Use of new recombinant proteins for ovarian stimulation in ruminants

Currently, gonadotropin products (follicle stimulating hormone, FSH, and luteinizing hormone, LH) used in animal reproduction are produced by extraction and purification from abattoir-derived pituitary glands. This method, relying on animal-derived materials, carries the potential risk of hormone contamination and pathogen transmission. Additionally, chorionic gonadotropins are extracted from the blood of pregnant mares (equine chorionic gonadotropin; eCG) or the urine of pregnant women (human chorionic gonadotropin; hCG). However, recent advancements have introduced recombinant gonadotropins for assisted animal reproduction therapies. The traditional use of FSH for superovulation has limitations, including labor requirements and variability in superovulation response, affecting the success of in vivo (SOV) and in vitro (OPU/IVEP) embryo production. FSH treatment for superstimulation before OPU can promote the growth of a homogenous follicular population and the recovery of competent oocytes suitable for IVEP procedures. At present, a single injection of a preparation of long-acting bovine recombinant FSH (rFSH) produced similar superovulation responses resulting in the production of good-quality in vivo and in vitro embryos. Furthermore, the treatment with eCG at FTAI protocol has demonstrated its efficacy in promoting follicular growth, ovulation, and P/AI, mainly in heifers and anestrous cows. Currently, treatment with recombinant glycoproteins with eCG-like activity (r-eCG) have shown promising results in increasing follicular growth, ovulation, and P/AI in cows submitted to P4/E2 -based protocols. Bovine somatotropin (bST) is a naturally occurring hormone found in cows. Recombinant bovine somatotropin (rbST), produced through genetic engineering techniques, has shown potential in enhancing reproductive outcomes in ruminants. Treatment with rbST has been found to improve P/IA, increase donor embryo production, and enhance P/ET in recipients. The use of recombinant hormones allows to produce non-animal-derived products, offering several advantages in assisted reproductive technologies for ruminants. This advancement opens up new possibilities for improving reproductive efficiency and success rates in the field of animal reproduction.

Effects of recombinant FSH (bscrFSH) and pituitary FSH (FSH-p) on embryo production in superovulated dairy heifers inseminated with unsorted and sex-sorted semen

Superovulation is a drug-based method used in cattle to stimulate the ovarian folliculogenesis and the number of oocytes and transferable embryos. The present study aimed to test the effects of recombinant FSH (bscrFSH) and pituitary FSH (FSH-p) on ovarian response and in vivo embryo production in superovulated dairy heifers inseminated with unsorted and sex-sorted semen. Forty healthy Holstein heifers subjected to a superovulation (SOV) protocol by using FSH-p or bscrFSH were divided randomly into four groups: a) FSH-p inseminated with unsorted semen (USP; n = 10), b) FSH-p inseminated with sex-sorted semen (SSP; n = 10), c) bscrFSH inseminated with unsorted semen (USR; n = 10), and d) bscrFSH inseminated with sex-sorted semen (SSR; n = 10). Ultrasonography was carried out on Day 8 (estrus) and Day 15 (embryo collection) to evaluate the ovarian structures [follicles (FL), corpora lutea (CL), and non-ovulated follicles (NOFL)]. Embryonic-derived parameters were scored on Day 15 [total structures collected (TS), unfertilised oocytes (UFOs), total embryos (TEs), transferable embryos (TFEs), freezable embryos (FEs), and degenerated embryos (DEs)]. No differences were observed regarding ovarian structures (FL and NOFL) irrespective of SOV protocol or group assessed (P > 0.05). CL increased in bscrFSH-derived SOV protocol (P < 0.05). On Day 15, the embryonic-derived parameters TEs, TFEs, and FEs decreased in SSP/SSR compared to USP/USR (P < 0.05). Differences were observed regarding UFOs, with a greater number in SSP and SSR (P = 0.01). In conclusion, the bscrFSH-derived SOV protocol showed improved results compared to FSH-p-derived SOV protocol regarding ovarian (CL) and embryo-derived (TFE) parameters irrespective of the type of semen used.

Superovulation of high-producing Holstein lactating dairy cows with human recombinant FSH and hMG

Superovulation of high-producing dairy cows is a challenging subject in dairy farms with respect to the cost, dose and type of gonadotropin. The objectives of this study were to compare three gonadotropin products: Folltropin-V® (highly purified FSH with porcine origin), Cinnal-f® (recombinant human FSH) and Menotropins® (hMG) for superovulation in high-producing Holstein lactating dairy cows and to investigate the pregnancy outcomes achieved following transferring embryos recovered from donors treated with different gonadotropins. Healthy high-producing Holstein lactating dairy cows (n = 30; milk production: 46.35 ± 8.78 kg; parity: 2-4; days in milk: 80-130 days) without any puerperal problems were selected as donors. On Day 10 after estrus (Day 0 of superovulation), donors (10 cows in each experimental groups) received Folltropin-V® (400 mg NIH, dissolved in 20 ml), Cinnal-f® (20 vials; each vial of 1 ml contains 75 IU Follitropin alfa) and Menotropins ® (20 ampules; each ampule of 1 ml contains 75 IU FSH and 75 IU LH), administered twice daily, in decreasing doses (4,4; 3,3; 2,2; 1,1 ml), over 4 days. On Day 2 of superovulation, donors received 3 doses of prostaglandin F₂α analogue, 6 h apart. They were inseminated twice with a frozen semen at 12 and 24 h after standing estrus. Concurrent with the second insemination, donors received 2500 IU hCG (Karma Pharmatech GmbH, Germany). On Day 7 after standing estrus, superovulatory responses (number of CLs, total ova/embryos and transferable embryos) were recorded and Code 1 embryos, recovered from each treated donors, were transferred to synchronized heifers. Pregnancy was detected on Day 30 and 60 after AI. Gestation length, the number and weight of live births were recorded. Data were analyzed using Proc GLM, Proc Mixed and Proc Genmod of SAS. The respective number of corpora lutea, total number of ova/embryos and transferable embryos were not different among donors received Cinnal-f (25.5 ± 3.01, 11.2 ± 2.77, 5.1 ± 0.86), Menotropins (24.0 ± 3.21, 9.0 ± 2.04, 6.3 ± 1.74) and Folltropin-V (20.3 ± 3.21, 8.9 ± 1.90, 5.1 ± 1.16; P > 0.05). Pregnancy rates on Day 30 was similar among treatment groups (P > 0.05). However, pregnancy rates on Day 60 and the number of calves born healthy was less in heifers that received embryos from Cinnal-f treated donors (P < 0.05). In conclusion, Cinnal-f and Menotropins could provide similar superovulatory response to Folltropin-V for superovulation of high-producing Holstein lactating dairy cows.

Towards Improving the Outcomes of Multiple Ovulation and Embryo Transfer in Sheep, with Particular Focus on Donor Superovulation

Considerable improvements in sheep multiple ovulation and embryo transfer (MOET)protocols have been made; however, unlike for cattle, MOET is poorly developed in sheep, and thus has not been broadly applicable as a routine procedure. The tightly folded nature of the ewe cervix, the inconsistent ovarian response to various superovulatory treatments, and the requirement of labor to handle animals, particularly during large-scale production, has limited the implementation of successful MOET in sheep. Moreover, several extrinsic factors (e.g., sources, the purity of gonadotrophins and their administration) and intrinsic factors (e.g., breed, age, nutrition, reproductive status) severely limit the practicability of MOET in sheep and other domestic animals. In this review, we summarize the effects of different superovulatory protocols, and their respective ovarian responses, in terms of ovulation rate, and embryo recovery and transfer. Furthermore, various strategies, such as inhibin immunization, conventional superovulation protocols, and melatonin implants for improving the ovarian response, are discussed in detail. Other reproductive techniques and their relative advantages and disadvantages, such as artificial insemination (AI), and donor embryo recovery and transfer to the recipient through different procedures, which must be taken into consideration for achieving satisfactory results during any MOET program in sheep, are also summarized in this article.

Effects of Extra-Long-Acting Recombinant Bovine FSH (bscrFSH) on Cattle Superovulation

Over the last few years, several commercial FSH products have been developed for cattle superovulation (SOV) purposes in Multiple Ovulation and Embryo Transfer (MOET) programs. The SOV response is highly variable among individuals and remains one of the main limiting factors in obtaining a profitable number of transferable embryos. In this study, follicle stimulating hormone (FSH) from different origins was included in two SOV protocols, (a) FSH from purified pig pituitary extract (NIH-FSH-p; two doses/day, 12 h apart, four consecutive days); and (b) extra-long-acting bovine recombinant FSH (bscrFSH; a single dose/day, four consecutive days), to test the effects of bscrFSH on the ovarian response, hormone profile levels, in vivo embryo production and the pluripotency gene expression of the obtained embryos. A total of 68 healthy primiparous red Angus cows (Bos taurus) were randomly distributed into two experimental groups (n = 34 each). Blood sample collection for progesterone (P4) and cortisol (C) level determination was performed together with ultrasonographic assessment for ovarian size, follicles (FL) and corpora lutea (CL) quantification in each SOV protocol (Day 0, 4, 8, and 15). Moreover, FSH profiles were monitorised throughout both protocols (Day 0, 4, 5, 6, 7, 8, 9, 10, and 15). In vivo embryo quantity and quality (total structures, morulae, blastocysts, viable, degenerated and blocked embryos) were recorded in each SOV protocol. Finally, embryo quality in both protocols was assessed by the analysis of the expression level of crucial genes for early embryo development (OCT4, IFNt, CDX2, BCL2, and BAX). P4 and cortisol concentration peaks in both SOV protocols were obtained on Day 15 and Day 8, respectively, which were statistically different compared to the other time-points (p < 0.05). Ovarian dimensions increased from Day 0 to Day 15 irrespective of the SOV protocol considered (p < 0.05). Significant changes in CL number were observed over time till Day 15 irrespective of the SOV protocol applied (p < 0.05), being non- significantly different between SOV protocols within each time-point (p > 0.05). The number of CL was higher on Day 15 in the bscrFSH group compared to the NIH-FSH-p group (p < 0.05). The number of embryonic structures recovered was higher in the bscrFSH group (p = 0.025), probably as a result of a tendency towards a greater number of follicles developed compared to the NIH-FSH-p group. IFNt and BAX were overexpressed in embryos from the bscrFSH group (p < 0.05), with a fold change of 16 and 1.3, respectively. However, no statistical differences were detected regarding the OCT4, CDX2, BCL2, and BCL2/BAX expression ratio (p > 0.05). In conclusion, including bscrFSH in SOV protocols could be an important alternative by reducing the number of applications and offering an improved ovarian response together with better embryo quality and superior performance in embryo production compared to NIH-FSH-p SOV protocols.

Immunization Against Inhibin Promotes Fertility in Cattle: A Meta-Analysis and Quality Assessment

Superovulation and embryo transfer techniques are important methods in cattle breeding. Combined with traditional superovulation protocols, immunization against inhibin can further improve follicular development and embryo yield. The aim of this study is to determine the efficacy of immunization against inhibin in improving the fertility of cattle through meta-analysis and to provide better clinical veterinary practice guidance. Three English databases (PubMed, EMBASE, Web of Science) were searched for research articles of immunizations against inhibin influence on cattle fertility. Literature screening, data extraction, and meta-analysis were conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. In addition, the Systematic Review Center for Laboratory animal Experimentation (SYRCLE) risk-of-bias (RoB) tool was used to assess the risk of bias of the included animal studies. Potentially relevant studies (317) were identified, and finally 14 eligible studies (all in English) were included. The results of meta-analysis revealed that immunization against inhibin has significant effects on improving the number of ovulations [mean difference (MD) = 0.44, 95% confidence interval (CI) = (0.31, 0.56)], embryos and unfertilized ova [MD = 4.51, 95% CI = (2.28, 6.74)], follicles of the three size categories, the incidence of multiple ovulations [OR = 22.50, 95% CI = (8.13, 62.27)], and the conception rate [OR = 2.36, 95% CI = (1.26, 4.40)]. Moreover, it improved the production of embryos [grades 1 embryos: MD = 3.84, (3.54, 4.15); grade 2 embryos: MD = -0.73, (-0.89, -0.57); grade 3 embryos: MD = -0.50, (-0.75, -0.25); degenerated embryos: MD = 1.16, (-0.51, 2.82); transferable embryos: MD = 2.67, (2.03, 3.31)] and the number of corpora lutea [MD = 1.25, 95% CI = (0.79, 1.71)]. In the above indicators, the differences between the two groups were statistically significant (all p < 0.0001). Additionally, according to the quality evaluation results, the risk of bias in the included studies is relatively high. The quality evaluation of the results of the included studies showed that the risk of bias mainly concentrated in the selective, performance, detection, and reporting of bias aspects.

Recombinant Technologies to Improve Ruminant Production Systems: The Past, Present and Future

The use of recombinant technologies has been proposed as an alternative to improve livestock production systems for more than 25 years. However, its effects on animal health and performance have not been described. Thus, understanding the use of recombinant technology could help to improve public acceptance. The objective of this review is to describe the effects of recombinant technologies and proteins on the performance, health status, and rumen fermentation of meat and milk ruminants. The heterologous expression and purification of proteins mainly include eukaryotic and prokaryotic systems like Escherichia coli and Pichia pastoris. Recombinant hormones have been commercially available since 1992, their effects remarkably improving both the reproductive and productive performance of animals. More recently the use of recombinant antigens and immune cells have proven to be effective in increasing meat and milk production in ruminant production systems. Likewise, the use of recombinant vaccines could help to reduce drug resistance developed by parasites and improve animal health. Recombinant enzymes and probiotics could help to enhance rumen fermentation and animal efficiency. Likewise, the use of recombinant technologies has been extended to the food industry as a strategy to enhance the organoleptic properties of animal-food sources, reduce food waste and mitigate the environmental impact. Despite these promising results, many of these recombinant technologies are still highly experimental. Thus, the feasibility of these technologies should be carefully addressed before implementation. Alternatively, the use of transgenic animals and the development of genome editing technology has expanded the frontiers in science and research. However, their use and implementation depend on complex policies and regulations that are still under development.

The incompletely fulfilled promise of embryo transfer in cattle-why aren't pregnancy rates greater and what can we do about it?

Typically, bovine embryos are transferred into recipient females about day 7 after estrus or anticipated ovulation, when the embryo has reached the blastocyst stage of development. All the biological and technical causes for failure of a female to produce a blastocyst 7 d after natural or artificial insemination (AI) are avoided when a blastocyst-stage embryo is transferred into the female. It is reasonable to expect, therefore, that pregnancy success would be higher for embryo transfer (ET) recipients than for inseminated females. This expectation is not usually met unless the recipient is exposed to heat stress or is classified as a repeat-breeder female. Rather, pregnancy success is generally similar for ET and AI. The implication is that either one or more of the technical aspects of ET have not yet been optimized or that underlying female fertility that causes an embryo to die before day 7 also causes it to die later in pregnancy. Improvements in pregnancy success after ET will depend upon making a better embryo, improving uterine receptivity, and forging new tools for production and transfer of embryos. Key to accelerating progress in improving pregnancy rates will be the identification of phenotypes or phenomes that allow the prediction of embryo competence for survival and maternal capacity to support embryonic development.