Effects of immunocastration performed at two live weights on the growth physiology, temperament and testicular development of feral beef bulls

Multiple-Pathway Synergy Alters Steroidogenesis and Spermatogenesis in Response to an Immunocastration Vaccine in Goat

BACKGROUND

Animal reproduction performance is crucial in husbandry. Immunocastrated animals serve as an ideal animal model for studying testicular function. During androgen suppression, the testis undergoes dramatic developmental and structural changes, including the inhibition of hormone secretion and spermatogenesis.

METHODS

To characterize this process, we investigated the effects of castration using a recombinant B2L and KISS1 DNA vaccine, and then identified functional genes in the testes of Yiling goats using RNA-seq and WGS. The experimental animals were divided into three groups: the PVAX-asd group (control), PBK-asd-immunized group, and surgically castrated group.

RESULTS

The results demonstrated that the administration of the recombinant PBK-asd vaccine in goats elicited a significant antibody response, and reduced serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH), resulting in smaller scrotal circumferences and decreased sexual desire compared to the control group. In addition, RNA transcriptome sequencing (RNA-seq) analysis of the testes revealed that the biological processes after immunocastration mainly focused on the regulation of cell matrix adhesion, histone acetylation, negative regulation of developmental processes, apoptosis, and activation of the complement system and the thrombin cascade reaction system. Then, we integrated the whole-genome sequencing and testis transcriptome, and identified several candidate genes (FGF9, FST, KIT, TH, TCP1, PLEKHA1, TMEM119, ESR1, TIPARP, LEP) that influence steroidogenesis secretion and spermatogenesis.

CONCLUSIONS

Multiple pathways and polygenic co-expression participate in the response to castration vaccines, altering hormone secretion and spermatogenesis. Taken together, our atlas of the immunocastration goat testis provides multiple insights into the developmental changes and key factors accompanying androgen suppression, and thus may contribute to understanding the genetic mechanism of testis function. Joint analysis of whole genome sequencing and RNA-seq enables reliable screening of candidate genes, benefiting future genome-assisted breeding of goats.

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.

Effectiveness of a New Recombinant antiGnRH Vaccine for Immunocastration in Bulls

Simple Summary

Castration of males is a common procedure in cattle production. Surgical procedures are most commonly used, but there is an increasing interest in non-invasive alternatives to avoid risk of infection, bleeding, pain, stress and to improve animal welfare. Immunization against gonadotropin-releasing hormone is currently being used in livestock, but there is only one commercially available vaccine for cattle and results regarding the number of doses needed to maintain castration are variable. The efficacy, safety, and production parameters of a new antigen for immunocastration in bulls was assessed. Results showed that two doses of the vaccine to 40 10-month-old bulls achieved testosterone suppression below productive performance. Live weight at slaughter and carcass yield was greater in immunized animals than in surgically castrated cattle. Castration effects of the vaccine were maintained until the end of the trial at 24 weeks.

Abstract

Castration by surgical techniques is common in livestock; however, post-surgery complications and concerns for animal wellbeing have created a need for new non-invasive alternatives. The objective of this study was to evaluate immunocastration in bulls using antigen GnRX G/Q; a recombinant peptide proved to be effective in laboratory and companion animals. A nine-month trial with 80 9-month-old Normand x Hereford bulls, kept in a pastured system, was conducted. The herd was divided in half with 40 bulls surgically castrated (SC) and 40 castrated by immunization against GnRH (IC). The antigen was injected on days 0 and 40 of the experiment. After the second dose, the IC group had elevated GnRH antibodies and decreased testosterone levels (below 5 ng/mL) that were maintained for 23 weeks. At slaughter on day 190, the immunocastrated group obtained a higher weight, hot carcass, and dressing percentage than the SC group. There was no difference in pH, color of meat, fat coverage, cooking loss, or tenderness between groups. The bulls showed no inflammatory reaction at the injection site or adverse side effects from the vaccine. Our results demonstrate that immunocastration with GnRX G/Q is an efficient and safe alternative to surgical castration in livestock. Additional work evaluating antigen effects over a longer period is needed to validate commercial viability.

A comparison of immunological, chemical and surgical castration of Nelore bulls

The objective was to compare effects of immunological, chemical and surgical castrations on testicular characteristics, scrotal surface temperatures, sperm quality, and serum testosterone concentrations in Bos indicus bulls. Eighty Nelore bulls (∼20 mo) were grazed on pasture, fed a supplement and slaughtered at ∼480 kg. Bulls were allocated into four groups (n = 20/group). The control group (CON) was non-castrated and there were three castration methods: immune (IMM - Bopriva®), injected on D-30, D30 and D60; chemical (CHE), an intratesticular injection of 40% CaCl₂ + 0.5% dimethylsulfoxide on D0; and surgical (SUR) on D0. The CHE group were surgically castrated on D60, due to testicular swelling and necrosis of scrotal skin. Most scrotal surface temperatures (infrared thermography) were significantly higher on D15 in CHE and SUR compared to CON, due to inflammation. All bulls were subjected to a breeding soundness evaluation on D-7 and slaughtered on D220. Scrotal circumference and testicular volume did not differ among groups (P > 0.05) at D0, but at D15, both end points were highest (P < 0.05) in the CHE group (due to swelling), although both end points were smaller for IMM versus CON (P < 0.05) at D60 and D150. Sperm motility in the IMM group was ∼50 and 10% of that in the CON group on D60 and D150, respectively. For the IMM group, serum testosterone concentrations were similar on D0 and D15 (but ∼50% of CHE or SUR on D0, attributed to the first treatment on D-30), and had decreased ∼70% on D60 and D150, whereas in the CHE and SUR groups, there were ∼80-90% decreases in testosterone after D0. In conclusion, immunological castration was a viable alternative to surgical castration, as it supressed testosterone production and spermatogenesis, with the benefits of being much less invasive, with better animal welfare and less stress.