Effect of active immunization against GnRH on testosterone concentration, libido and sperm quality in mature AI boars

Active immunization with a novel recombinant GnRH vaccine inhibits reproductive function in male goats

Gonadotropin-releasing hormone (GnRH) vaccines have been widely used to effectively inhibit gonadal development and reproductive function. To improve the immunogenicity of GnRH, we developed and evaluated the effects of GnRH6-kisspeptin-CRM197 immunization on the reproductive function in male goats. Thirty 3-month-old male goats (n = 30) were randomly assigned to control, surgical, and immunized groups. The immunized group received a 2 mL injection of the GnRH6-kisspeptin-CRM197 with a booster administered four weeks later. The control group was administered a white oil adjuvant. Blood samples were collected at regular intervals, and at week 20, the animals were euthanized for tissue collection. Serum antibody titers and testosterone levels were measured using ELISA and CLIA, respectively. Testicular parameters and histology were evaluated. The mRNA levels of reproductive-related genes in the HPG axis were measured using RT-qPCR. The results showed that the immunized goats had significantly increased serum GnRH and kisspeptin antibodies (P < 0.05) but decreased testosterone concentrations (P < 0.05) compared to the control group. Testicular size and histology were significantly affected in the immunized group, with notable reductions in testicular weight and dimensions (P < 0.01), and evidence of vacuolar degeneration and suppressed sperm production. The mRNA levels of FSHβ and LHβ in the pituitary, as well as FSHR, LHR, 3βHSD, and 17βHSD in the testis, were significantly lower in the immunized group compared to controls (P < 0.05). These findings suggest that GnRH6-kisspeptin-CRM197 is a safe antigen and a promising immunocastration vaccine with enhanced efficacy.

The Usefulness of Sexual Behaviour Assessment at the Beginning of Service to Predict the Suitability of Boars for Artificial Insemination

Simple Summary

Boars producing ejaculates of high quality and shortest duration are particularly valuable; this aspect can be the primary factor in inbreeding development and improvement of swine utilization. It is important to develop objective ways to describe the sexual activity of various breeds of boars and its application and effectiveness in conducting artificial insemination. The results of this study indicate that the time from entering the arena until achieving an erection, which is assessed at the beginning of a boar’s breeding utilization, may be used to predict a boar’s future libido. There was an association between the level of libido and ejaculate characteristics. Boars requiring the most time to begin ejaculation produce ejaculates with a higher sperm concentration and number.

Abstract

Parameters of sexual activity were determined in 49 young boars used for artificial insemination, four times at three-month intervals. The parameters included the time from entering the arena until mounting the phantom; the time from mounting the phantom until achieving erection; the time from achieving full erection until the start of ejaculation; duration of ejaculation; and the number of times the boar mounted the phantom. Characteristics of the ejaculates were also assessed. The libido parameter associated with the greatest efficacy of artificial insemination was the effectiveness of artificial insemination service, the time from entering the arena until the start of ejaculation. The significance of this trait for predicting ejaculation performance was analysed. The libido characteristics were classified into three categories: boars with a short reaction time to the phantom, boars with an intermediate reaction time, and boars with a long reaction time. For these groups, the characteristics of ejaculates collected at the start of the period during which ejaculates were collected and after three, six and nine months were determined. The sexual experience of boars was not associated with the expression of sexual behaviour because young boars during their first three months of ejaculate collections required less time to initiate ejaculation. The ejaculates with the greatest utility were obtained after six months of service. These ejaculates had the largest volume (255.22 mL), and the most insemination doses could be prepared from these ejaculates. On average, more than 23 insemination doses were prepared from ejaculates collected after six months of semen collections, which is about four doses more than from ejaculates collected at the start of artificial insemination service (p < 0.01).The time from entering the arena to beginning ejaculation can be used to predict a boar’s future libido. A relationship was shown between the level of libido and ejaculate characteristics. The ejaculates of the boars which needed the longest time to begin ejaculation at the start of semen collections had the greatest sperm concentration and number. In group 3, the boars’ejaculates contained about 6–9 × 10⁹ more sperm than the ejaculates of boars from group 1. After six months of the experimental period, the difference was nearly 15 × 10⁹ sperm (p < 0.05), and after nine months, it exceeded 22 × 10⁹ sperm (p < 0.01).

EFFECTS OF A GNRH VACCINE (IMPROVAC®) ON PATAGONIAN (OTARIA BYRONIA) AND CALIFORNIA SEA LIONS (ZALOPHUS CALIFORNIANUS)

Improvac^® is a gonadotropin-releasing hormone vaccine developed to reduce "boar taint" in the meat of male domestic pig. The use of Improvac for contraception of zoo and free-living animals has been increasing in recent years. This study reports the use, efficacy, and side effects of Improvac on five male sea lions. Administration of two injections of 600 µg of Improvac (gonadotropin releasing factor analogue-protein conjugate) 4-5 wk apart were delivered to two Patagonian and three California sea lions to reduce testosterone-related aggression, anorexia, and lethargy that occur during the breeding season. Behavior and physical changes were recorded for all individuals, and blood samples were taken from one Patagonian sea lion to measure plasma testosterone concentrations over time. Observations revealed a descension of the testes into the scrotum, orchitis, lameness, anorexia, and lethargy in all individuals for the first 3-5 d after the first administration of the vaccine. Plasma testosterone concentrations rose after the first dose of the vaccine and remained elevated for 1 mo, decreasing after the second injection to undetectable levels. Improvac administration can cause a peak of testosterone and breeding behavior just after the first inoculation, as previously described in swine and elephants, but has not been documented in pinnipeds. None of the treated animals in this study showed breeding behaviors during their normal breeding season (July-September).

Improvac induces immunocastration by affecting testosterone levels and disrupting spermatogenesis in male broiler chickens

Immunocastration (vaccination against Gonadotropin-releasing hormone (GnRH)) has been regarded as a friendly substitution to physical castration in animals. To date, a few studies have reported the use of Improvac for immunocastration in boar and one study in broiler chickens; however, there is an apparent dearth of scientific evidence regarding the application of Improvac for immunocastration in birds. In the present study, we evaluated the effects of Improvac-based immunocastration on testosterone levels and spermatogenesis in broiler chickens and the effects of Improvac on the expression of genes related to testosterone biosynthesis and metabolism as well as spermatogenesis. The birds were randomly divided into 4 groups (n = 30 each): Control group (non-immunized), Early group (immunized with Improvac at week 3), Late group (immunized with Improvac at week 6), and Early + Late group (immunized with Improvac at weeks 3 and 6). Immunization with Improvac significantly improved the average daily gain compared to the Control group. Of note, following Improvac vaccination, the reproductive efficiency was significantly decreased in male broiler chickens. Furthermore, parameters such as the serum testosterone concentration, spermatogenesis, and the expression levels of genes related to testosterone metabolism (Cyp17A1, Cyp19, HSD3B1, and HSD17B3) and spermatogenesis (Cyclin A1 and Cyclin A2) were significantly reduced in the immunized groups compared to the Control group. Taken together, these findings reveal that immunization against GnRH can be achieved, at least partially, in male broiler chickens. The results of our study also support the hypothesis of using Improvac as an alternative solution to caponization, with considerably improved animal welfare.

Sustainability of Pork Production with Immunocastration in Europe

Immunocastration, a technique to replace surgical castration of piglets, consists of two consecutive vaccinations to induce antibodies which transiently suppress testicular functions and avoid boar taint. It is a method to ensure both a high product quality and a high level of animal welfare. The impact of immunocastration on the three pillars of sustainability has been studied extensively. While all aspects of sustainability have been studied separately, however, a contemporary global overview of different aspects is missing. In immunocastrates, performance results are better than in barrows, but worse than in boars. The environmental impact of pork production with immunocastrates is lower than with barrows, but higher than with boars. The level of aggression is considerably lower in immunocastrates compared to boars. Societal concerns are mainly related to food safety, and are not supported by scientific evidence. After second vaccination, immunocastrates switch from a boar- to a barrow-like status. Therefore, the timing of second vaccination is a fine-tuning tool to balance advantages of boars with environmental and economic benefits against increased risk of welfare problems and boar taint. Nevertheless, both synergic and conflicting relationships between the pillars of sustainability must be communicated along the value chain to produce tailored pork products.

A role for selective contraception of individuals in conservation

Contraception has an established role in managing overabundant populations and preventing undesirable breeding in zoos. We propose that it can also be used strategically and selectively in conservation to increase the genetic and behavioral quality of the animals. In captive breeding programs, it is becoming increasingly important to maximize the retention of genetic diversity by managing the reproductive contribution of each individual and preventing genetically suboptimal breeding through the use of selective contraception. Reproductive suppression of selected individuals in conservation programs has further benefits of allowing animals to be housed as a group in extensive enclosures without interfering with breeding recommendations, which reduces adaptation to captivity and facilitates the expression of wild behaviors and social structures. Before selective contraception can be incorporated into a breeding program, the most suitable method of fertility control must be selected, and this can be influenced by factors such as species life history, age, ease of treatment, potential for reversibility, and desired management outcome for the individual or population. Contraception should then be implemented in the population following a step-by-step process. In this way, it can provide crucial, flexible control over breeding to promote the physical and genetic health and sustainability of a conservation dependent species held in captivity. For Tasmanian devils (Sarcophilus harrisii), black-flanked rock wallabies (Petrogale lateralis), and burrowing bettongs (Bettongia lesueur), contraception can benefit their conservation by maximizing genetic diversity and behavioral integrity in the captive breeding program, or, in the case of the wallabies and bettongs, by reducing populations to a sustainable size when they become locally overabundant. In these examples, contraceptive duration relative to reproductive life, reversibility, and predictability of the contraceptive agent being used are important to ensure the potential for individuals to reproduce following cessation of contraception, as exemplified by the wallabies when their population crashed and needed females to resume breeding.

Effect of active immunization using a novel GnRH vaccine on reproductive function in rats

To investigate the effect of gonadotropin-releasing hormone 2-multiple antigen peptide (GnRH2-MAP) on reproductive function. In our study, 20-day-old male rats (n = 90) were randomly allocated to one of three treatment groups: GnRH2-MAP immunization, GnRH2 immunization, and non-immunized control groups. The immunized animals were administered three doses of GnRH2-MAP or GnRH2 vaccines from 0 to 6 weeks at 2-week intervals. The control group only received oil adjuvant. Blood and right testis samples were collected, and the left testis was weighed and its volume was measured at 0, 2, 4, 6, 8, 10 and 12 weeks after the first immunization. The serum antibody titer and testosterone concentration were determined by ELISA, and the right testis samples were collected for histological analysis. The results revealed that the serum of vaccinated rats elicited a significantly higher antibody titer and a lower T concentration compared with the control group two weeks after the first immunization (P < 0.05), but the highest antibody titer and lowest T concentration were found in animals treated with GnRH2-MAP (P < 0.05). The second immunization resulted in a significant decrease in testicular weight and volume (P < 0.05) in both immunized groups compared to the control, but these values were significantly lower in the GnRH2-MAP group than in the GnRH2 group. Furthermore, seminiferous tubules revealed more significant atrophy in the GnRH2-MAP group than in the GnRH2 group, and no sperm were observed in rats of the GnRH2-MAP group. Thus, GnRH2-MAP may be an effective antigen and a potential immunocastration vaccine with higher effectiveness.

Effects of Active Immunization Against Akirin2 on Muscle Fiber-type Composition in Pigs

The objective of this study was to investigate effects of active immunization against Akirin2 on muscle fiber-type composition in pigs. Here we showed that the titer of Akirin2 antibody in pigs immunized with porcine Akirin2 (pAkirin2) was significantly increased. Active immunization against pAkirin2 decreased succinic dehydrogenase and malate dehydrogenase activities and increased lactate dehydrogenase activity in the longissimus dorsi muscle of pigs. Active immunization against pAkirin2 significantly decreased MyHC I and MyHC IIa mRNA expressions and MyHC I protein expression and increased mRNA expressions of MyHC IIb as well as protein expressions of MyHC IIb and fast-MyHC. mRNA expressions of nuclear factors of activated T cells c1 (NFATc1), transcriptional coactivator PPARγ coactivator-1α, myocyte enhancer factor 2C, and modulatory calcineurin interacting protein 1 exon 4 isform were also notably decreased by active immunization against pAkirin2. Together, our data imply that active immunization against pAkirin2 may result in a slow to fast fiber-type shift in pigs, and which may be mediated by suppression of the calcineurin/NFATc1 signaling pathway.