Effect of a single or two doses of an anti-GnRH vaccine on testicle morpho-functional characteristics in Nelore bulls

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.

Effect of active immunization with recombinant GnRH6-kisspeptin fusion protein on reproductive function in male rats

Immunological castration can be an alternative to traditional surgical castration. The active immunization against GnRH or kisspeptin has a castrating effect. To date, the fusion protein vaccine of combination with GnRH and kisspeptin have not been studied. Thus, the present study will develop a GnRH6-kisspeptin vaccine by genetic engineering method and investigate its immunocastration effect in male rats. Twenty 20-day-old male rats were randomly divided into two groups: the control group (n=10) and the immunization group (n=10). The initial immunization took place at week 0 followed by three booster doses administered intervals. The control group received an equivalent dose of white oil adjuvant. Orbital blood samples were collected at various time points following the initial immunization, at 0, 2, 4, 6, 8, 10 and 12 weeks, respectively. The entire left testis was weighed and its volume measured at week 12. Samples from the right testis were obtained for histological analysis. Serum levels of GnRH and kisspeptin antibodies, as well as testosterone levels were determined using ELISA. The results showed that the serum levels of GnRH and kisspeptin antibody titres of the immunized rats were significantly higher compared to the control group (P<0.05). Additionally, the testosterone concentration was effectively reduced following the intensified immunization. The testes of the immunized group exhibited a reduction in size and a significant decrease in the number of spermatogonia in the testicular tissue compared to the control group (P<0.05). These data indicate that the recombinant GnRH6-kisspeptin protein effectively induced immunological castration in rats.

GnRH-immunocastration: an alternative method for male animal surgical castration

Castration of male animals is intended to produce high-enhance quality of animal meat, prevent unpleasant taste, reduce aggressive behavior, and manage overbreeding. Over the years, Tranditional methods of mechanical and surgical castration have been employed over the years, but they fall short of meeting animal welfare requirements due to the associated risk of infection, pain, and stress. Immunocastration, specifically Gonadotropin-releasing hormone (GnRH)-immunocastration, targeting the hypothalamic-pituitary-testis (HPT) axis, has emerged as an animal-friendly alternative to surgical castration, effectively addressing these issues. This review seeks to systematically summarize the principles, development, current applications and challenges of GnRH-immunocastration, offering insights into its role in promoting animal welfare.

Evaluation of the effects of the recommended oral dose of diflubenzuron on bovine sperm and oocyte quality using CASA and OPU-IVEP

Introduction

The aim of this study was to evaluate potential effects of diflubenzuron on the production and quality of gametes, and on in vitro embryo production (IVEP) outcomes, in cattle.

Methods

Two experiments were performed, the first to evaluate effects on semen, and the second on cumulus-oocyte complexes (COC) and on IVEP. Nelore (Bos taurus indicus) bulls (n = 14) or heifers (n = 16) were allocated into control (CG) or treatment (DIF) groups. All groups received a mineral mix supplement added (DIF) or not (CG) with diflubenzuron (30 mg/head/day), during 8 weeks. Animals were weighed and blood samples were collected throughout the experimental period. Every other week, bulls were subjected to semen collection and heifers to transvaginal ultrasound-guided follicle aspiration sessions. Semen underwent physical and morphological evaluation, and samples were stored for further computer-assisted sperm analysis. The COC recovered were evaluated according to morphology and those classified as viable were sent to an IVEP laboratory.

Results

Diflubenzuron had no effect (P > 0.05) on average body weight or in any blood hematological or biochemical endpoints, regardless of gender. In experiment 1, there was no difference (P > 0.05) between DIF and CG groups for sperm concentration, morphology, or kinetics. In experiment 2, there was also no effect of diflubenzuron on the number of total, viable, or grade I oocytes, as well as on cleavage or blastocyst rates (P > 0.05).

Discussion

In summary, the oral administration of diflubenzuron, within the recommended dose, has no short-term negative effects on sperm production and quality or on oocyte yield and developmental potential in vitro, in cattle.

Active immunization against GnRH as an alternative therapeutic approach for the management of Bos indicus oocyte donors diagnosed with chronic cystic ovarian disease

The aim of this study was to evaluate the effect of active immunization against GnRH in Nelore (Bos indicus) cows repeatedly used as oocyte donors that developed chronic cystic ovarian disease (COD). In the first experiment, ovarian and uterine features were first compared between COD cows (n = 15) and healthy cows (n = 22, cycling control group) from the same breed and herd. Cows with COD had a greater number of large (P < 0.0001) and medium follicles (P < 0.01) but lesser small follicles (P < 0.05) than cycling controls. Mucometra was diagnosed in 73.3% of COD cows, but in none of the controls. No difference in average thickness of the endometrium was detected between groups; however, endometrial thickness and mucometra score were negatively correlated (R = -0.73, P = 0.0029) in COD cows. In the second experiment, COD cows were randomly allocated into two experimental groups, which received two 1.0 mL SC injections of either an anti-GnRH vaccine (COD immunized group, n = 8) or saline (COD control group, n = 7), given 28 days apart. Cows were examined weekly by transrectal ultrasonography during nine consecutive weeks after the first injection to evaluate the number and distribution of follicles among size classes, endometrial thickness, and presence of clinical mucometra. Vaccination against GnRH resulted in a progressive suppression of follicle growth and a reduction in the average size of the largest follicle, as well as in the number of large follicles (P < 0.01) in COD immunized cows compared with COD controls from week 7 onwards. Conversely, the number of small follicles in the COD immunized group increased after week 5 and was greater (P = 0.0023) than controls on week 9. Endometrial thickness and mucometra score were not affected (P > 0.05) by immunization against GnRH. In the third experiment, the COD immunized cows with effective suppression of follicle growth four weeks after the 2nd injection (n = 6) were submitted to three consecutive ovum pick-up (OPU) sessions (weeks 10, 11, and 12) for in vitro embryo production (IVEP). Cumulus-oocyte complexes (COC) collected from slaughterhouse ovaries were used as controls for IVEP. COD cows with produced 25.0 ± 3.8 COC per OPU session with no apparent detrimental effect of anti-GnRH vaccine on oocyte developmental potential in vitro, i.e., we observed similar cleavage rate (P = 0.5914) and greater blastocyst rate (P = 0.0177) in immunized cows compared with COC from slaughterhouse controls. Finally, in the fourth experiment wave emergence and follicular dynamics after follicle ablation were compared between COD immunized cows with effective suppression of follicle growth and a subset (n = 6) of the cycling, control group. No follicles grew beyond 4 mm diameter after follicle ablation in the COD immunized group, whereas a normal follicular wave emergence occurred in cycling controls. Antral follicle count was similar between cycling controls and COD immunized groups at 24 h and 96 h post-follicle ablation (P > 0.05), but greater in cycling controls at 48 h and 72 h post-follicle ablation (P < 0.05). In summary, our results suggest that active immunization against GnRH is effective to induce the regression of follicular cysts as well as increase the number of small follicles growing on the ovaries, in oocyte donors diagnosed with chronic COD, with no apparent negative effect on oocyte developmental potential in vitro.