Individual return to Leydig cell function after GnRH-immunization of boars

Male Reproductive Organ Weight: Criteria for Detection of Androstenone-Positive Carcasses in Immunocastrated and Entire Male Pigs

Immunocastration and rearing of entire males (EMs) are sustainable alternatives to surgical castration. However, these animal carcasses have variable risk of boar taint and should be identified at the slaughter line. We aimed to identify a simple and reliable indicator of androstenone-related boar taint by evaluating pelvic urogenital tract weight as a marker of boar-taint animals at the slaughter line. The pelvic urogenital tract, testes, and accessory sex glands of EMs and immunocastrates (ICs) were collected, dissected, and weighed, before colorimetric measurements of testicular tissue. Additionally, GnRH antibody titers and testosterone, androstenone, and skatole levels were determined. Our results showed that 81.8% of EMs had androstenone levels above the risk threshold (>0.5 µg/g fat; EM/A^high subgroup), whereas in ICs, the C/A^high subgroup with androstenone >0.5 µg/g fat accounted for only 4.3%. Androstenone levels correlated negatively with GnRH antibody titers and positively with testosterone levels and reproductive organ weights. Identification of ICs with androstenone levels above the threshold (IC/A^high subgroup) may be achieved via testes or pelvic urogenital tract weight measurements. However, in EMs, the latter is a more reliable parameter. A principal component analysis based on these variables and hierarchical clustering also distinguished the A^high from the A^low subgroup, irrespective of IC/EM. The findings highlight the possible use of pelvic urogenital tract weight along with testes weight as a simple, reliable, and efficient morphometric indicator for identifying androstenone-positive carcasses of different sex categories.

Single or repeated immunization against GnRH fails to completely abolish spermatogenesis in dwarf bucks (Capra hircus)

In both captive wildlife and production animals is important to develop strategies for population control. Immunization against GnRH is an easy and inexpensive immunocastration method that reduces the concentration of testosterone and decreases sperm quality. However, its effectiveness depends on the species and repetition of the treatment. This study aimed to compare the effectiveness of a single treatment (initial immunization plus a booster with Improvac) vs repeated treatment (six doses of Improvac) to inhibit testicular function and maintain the contraceptive status during long periods in bucks. Three Dwarf bucks (Capra hircus) received two doses of Improvac, the first on Week 0, and the booster 4 weeks later (single immunization, group SI) while three Dwarf bucks received one dose of Improvac every 6 months during 3 consecutive years (repeated immunization, group RI). The other three Dwarf bucks remained untreated (control bucks, group CON). Bucks from RI had a greater decrease in scrotal circumference, testosterone concentration, male odor intensity, and sperm quality than SI bucks. However, there were no differences between SI and CON bucks in any of the variables studied. Overall, repeated treatment of Improvac decreased the testicular function of Dwarf bucks, although did not produce complete infertility. However, the repetition of the treatment produced more intensive negative effects, indicating that the strength of the effects of Improvac is rapidly lost in bucks.

Does Immunocastration Affect Behaviour and Body Lesions in Heavy Pigs?

Simple Summary

Castration of piglets is routinely practiced to prevent the presence of boar taint. In Europe, around 61% of pigs are surgically castrated, 54% of which do not receive any pain-relief therapy. The increasing public awareness towards animal welfare and the ethical characteristics of animal-derived products has led to the necessity of finding more animal-friendly alternatives. Among them, immunocastration, a process of active immunisation leading to the suppression of testicular function, has shown promising results in light pig production, both in terms of animal welfare and productivity. Besides, no study has yet investigated animal welfare in immunocastrated males intended for Italian heavy pig production. This study aimed at evaluating the effect of immunocastration on the welfare of heavy pigs by monitoring behaviour and body lesions in immunocastrated and surgically castrated pigs. Salivary testosterone levels and productive traits were also evaluated. Our results confirmed that immunocastration is a suitable alternative to surgical castration with profitable productive performance, whereas the higher activity of animals and the higher presence of body lesions before the effective immunisation caused an impairment of animal welfare, which should be further investigated as a critical aspect in heavy pig production.

Abstract

Immunocastration has been pointed out as an alternative to surgical castration; though, most of the scientific studies were performed in light pig production. This study aimed to evaluate the effect of immunocastration on animal welfare in heavy pig production through the evaluation of behaviour and body lesions. A total of 188 commercial-hybrid pigs were randomly allocated into two treatment groups: surgical castration (SC) and immunocastration with Improvac^® (IC). Data on behaviour, body lesions, and salivary testosterone levels were collected the day before each vaccination at 15, 22, 32, and 36 weeks of age. IC and SC pigs were slaughtered at 40 and 41 weeks of age, respectively; productive and carcass traits data were also collected. Considering productive performance, our results confirmed that IC pigs grew faster and presented a higher weight at slaughter. A critical period for pig welfare was observed before 32 weeks: testosterone concentration and body lesion score were significantly higher in IC pigs compared to SC pigs; active behaviours were significantly more frequent in IC at 15 weeks. Immunocastration may represent a suitable alternative to surgical castration with profitable productive performances, whereas the impairment of welfare during the period before the effective vaccination should be further investigated as a potential critical aspect in heavy pig production.

Immunocastration in adult boars as a model for late-onset hypogonadism

Background

While immunocastration has been studied in male pre‐pubertal pigs, data on older, sexually mature animals are limited. To understand the physiological effects of androgen deprivation in the late sexual development phase, we compared mature immunocastrated boars (n = 19; average age = 480 days) to young male immunocastrated pigs (n = 6; average age = 183 days) and young entire males (n = 6; average age = 186 days) as positive and negative controls, respectively.

Objectives

We hypothesized that the timing of gonadotropin‐releasing hormone suppression (early or late sexual development phases) influences the extent of reproductive function inhibition, histological structure of testicular tissue, and expression levels of selected genes related to steroid metabolism.

Materials and methods

Antibody titer, hormonal status, and histomorphometric analysis of testicular tissue were subjected to principal component analysis followed by hierarchical clustering to evaluate the immunocastration effectiveness in mature boars.

Results

Hierarchical clustering differentiated mature immunocastrated boars clustered with young immunocastrated pigs from those clustered with entire males. Although all mature immunocastrated boars responded to vaccination, as evidenced by the increased gonadotropin‐releasing hormone antibody titers (p < 0.001), decreased serum luteinizing hormone concentrations (p = 0.002), and changes in testicular tissue vascularization (lighter and less red testicular parenchyma; p ≤ 0.001), the responses were variable. Sharp decreases in testes index (p < 0.001), Leydig cell volume density (p < 0.001), Leydig cell nucleus‐to‐cytoplasm ratio (p < 0.001), and testosterone concentration (p < 0.001) were observed in mature immunocastrated boars clustered with young immunocastrated pigs compared with those that clustered with entire males. Additionally, mature immunocastrated boars clustered with young immunocastrated pigs showed lower hydroxysteroid 17‐beta dehydrogenase 7 expression than entire males (p < 0.05). The young immunocastrated pigs group showed higher follicle‐stimulating hormone receptors than the entire males and mature immunocastrated boars, lower steroidogenic acute regulatory protein expression levels compared with entire males, and mature immunocastrated boars clustered with entire males (p < 0.01).

Conclusion

The two‐dose vaccination regime resulted in progressive but variable regression of testicular function in adult (post‐pubertal) pigs; however, it was insufficient to induce a complete immunocastration response in all animals.

Immunocontraception of male and female giraffes using the GnRH vaccine Improvac®

The aim of this study was to develop protocols for contraception in both sexes of giraffes (Giraffa camelopardalis) by using the GnRH vaccine Improvac®. We evaluated the success of immunization by analyzing fecal reproductive hormone metabolites in female (n = 20) and male (n = 9) giraffes. Endocrine analysis provided the basis for the successful immunization protocol, as well as for assessing long-term effects. Reliable reduction of fecal steroid metabolites to baseline levels in female giraffes was achieved with three, and in males with four or five injections at 4-week intervals. Effective booster injections were administered at 2-month intervals in the first year of treatment and at three to 4-month intervals in the following years. In addition to endocrine analysis, we determined vaccination efficacy in bulls by assessing testicular atrophy. Long-term (>2 years) use in females was often accompanied by prolonged periods of persistent corpus luteum activity, although normal cycles were not observed. Problems might occur with reversibility, because in a few males and females, even after more than 2 years since treatment had been stopped, fecal hormone metabolites have not returned to pretreatment levels. The results are somewhat ambiguous, as reproduction can be suppressed by use of Improvac®, but the question of reversibility remains unsolved.

Effect of Immunocastration and Diet on Growth Performance, Serum Metabolites and Sex Hormones, Reproductive Organ Development and Carcass Quality of Heavy Gilts

It is desirable to increase fatness in gilts destined for Teruel dry-cured ham production. A total of 192 Duroc × (Landrace × Large White) gilts of 40.3 ± 4.80 kg body weight (BW) were used to assess the impact of immunocastration and feeding on growth performance, serum metabolites and sex hormones, reproductive organ development, and carcass quality. Six treatments were arranged factorially (2 × 3) with two types of gilt (entire gilts (EG) vs. immunocastrated gilts (IG)) and three experimental diets (control vs. high energy vs. low crude protein and amino acids) provided from 76 to 134 kg BW (n = 4 per treatment, being the replicate the pen with eight pigs). Immunocastration was carried out at 58 and 77 kg BW. The IG grew faster and showed lighter reproductive tracts and greater fatness than EG. The experimental feeds had limited effect on carcass quality, but the high-energy diet improved gain-to-feed ratio and the low-protein and -amino-acids diet did not impair growth performance. In conclusion, immunocastration was a better strategy than the tested diets to increase the fatness of gilts intended for Teruel dry-cured ham, although increasing energy or decreasing crude protein and amino acid levels in the diet could be beneficial strategies for pig farmers.

Effect of terminal sire line and timing second vaccination on effectiveness of immunocastration, performance, and carcass and meat quality

Performance (from 10 weeks until slaughter), carcass and meat quality, and effectiveness of immunocastration was compared in crossbred offspring of stress positive (BP+) and negative (BP-) Belgian Piétrain and Canadian Duroc (CD) given the second vaccination of Improvac® at different times (4, 6, 8 weeks before slaughter). CD offspring had a significantly higher daily gain (DG) and feed intake (DFI), and lower predicted lean meat percentage (LMP) and dressing yield compared to BP+ and BP-, while feed conversion ratio (FCR) did not differ. CD offspring had significantly lower drip loss and higher pH_i, intramuscular fat content than BP+ and BP- (except for pH_i). No significant effect of vaccination time on DG nor FCR was observed. Predicted LMP tended to increase as time-post injection decreased, while meat quality was minor affected. Earlier vaccination had no effect on the effectiveness of immunocastration based on testosterone and GnRH-binding.

Early Immunocastration of Pigs: From Farming to Meat Quality

The study aimed to test a very early immunization of pigs to prevent boar taint with regard to its practicability and influence on production performance, its reliability in ensuring good meat and fat quality, and animal welfare. Immunization was already conducted at piglet production stage and could be easily integrated into routine vaccination (week 3) and weaning practices (week 7). The fattening and slaughter performance of the animals was not affected by the immunization regime and was within the usual range. In addition, there were no abnormalities in animal behavior and the prevalence of injuries caused by aggressive interactions. All animals were classified as infertile on the basis of the histological examination of the testicles. However, the testosterone levels measured at slaughter were significantly higher in animals of the early immunization regime than in animals subjected to the standard immunization regime. Androstenone and skatole levels as the main components of boar taint were, on average, higher and varied to a greater extent in early immunized animals. Furthermore, the comparison of the immunization scheme did not result in significant differences for meat quality and for fatty acid composition.

Welfare Aspects of Raising Entire Male Pigs and Immunocastrates

Simple Summary

Surgical castration of male piglets without pain treatment and anaesthesia is not only a welfare problem but also violates the integrity of the animals. The favoured alternatives of raising entire male pigs (EM) with or without immunocastration (vaccination against boar taint) may, however, impose additional welfare problems under the current housing and management conditions. This focused review is intended to summarise the current state of scientific knowledge and practical reports on critical welfare issues and risk factors. Raising EM with or without subsequent immunocastration could be a welfare conform, future-oriented alternative to conventional surgical castration of pigs, provided that they are kept in a healthy and socially stable environment with sufficient physical resources, as safeguarded by measures of enhanced animal care and management control.

Abstract

For a long time, scientists assumed that newborns have a severely limited sense of pain (if any). However, this assumption is wrong and led to a “start of the exit” from piglet surgical castration. Some of the currently discussed or already implemented alternatives such as general or local anaesthesia during surgical castration raise additional welfare concerns as well as legal problems and/or are hardly applicable. The favoured long-term, welfare-friendly “gold standard” is to raise entire male pigs (EM). However, this may also impose certain welfare problems under the current conventional housing and management conditions. The specific types of behaviour displayed by EM such as mounting and aggressive behaviours but also increased exploration, which are partially linked to sexual maturation, increase the risk for injuries. The current status of knowledge (scientific literature and farmer experiences) on housing of EM suggests that environmental enrichment, space, group-stability, social constellation, feeding (diet and feeder space), health and climate control are critical factors to be considered for future housing systems. From an animal welfare point of view, an intermediate variant to be favoured to reduce problematic behaviour could be to slaughter EM before reaching puberty or to immunize boars early on to suppress testicular function. Immunization against endogenous GnRH can reduce EM-specific problems after the 2nd vaccination.

Immuno-castration of female and male pigs with anti-gonadotrophin releasing hormone vaccine: Morphometric, histopathological and functional studies of the reproductive system

Immuno-castration is increasingly recommended in pigs due to welfare reasons; however, there are few studies in females compared to males. This aim of this study was to investigate the effects of immuno-castration in female and male pigs. The weight, the morphometric and microscopic characteristics of the reproductive organs, and the hormone concentrations were studied in 12 immunocastrated females (IF) and 12 immunocastrated males (IM) and compared with control animals (C). At slaughter, IF tended to have greater body weights than CF (P =  0.051), whereas in IM and CM pigs there were not body weight differences (P =  0.140). The weight of the reproductive tract and size of all individual organs were less in IF compared with CF. Results from histological assessments indicated IF had more atretic follicles and a thinner endometrial mucosa than control females. Hormone concentrations were not different between CF and IF (P >  0.050). As a result of immuno-castration, there was impaired spermatogenesis in most males. Results from microscopic evaluations indicated there was a marked decrease of spermatogonial cells and size of Leydig cells in the testicles. Accessory gland structures were affected in CM and IM with there being differences in gross and microscopic characteristics. Testosterone concentrations, unlike estradiol, were different in IM compared to CM (P <  0.001). These results provide evidence that immuno-castration with the anti-gonadotrophin releasing hormone vaccine is effective in female and male pigs and induces morphological and endocrine changes incompatible with fertility.

Chronic use of a GnRH agonist (deslorelin) or immunization against GnRH: effects on testicular function and sperm quality of bucks

Chronic use of GnRH agonists and immunization against GnRH have been used as reversible contraceptive methods. The aim of this study was to compare the effectiveness of both treatments to inhibit reproductive function of adult bucks, in terms of strength and duration of the effects. We used 9 control untreated bucks (CON), 7 bucks treated chronically with a GnRH agonist (subcutaneous implants with 7.4 mg of deslorelin, Suprelorin, Virbac) (AGO), and another 7 bucks were immunized against GnRH (dose of 2 mL of Improvac-Zoetis with 300 μg of a synthetic incomplete analog of natural GnRH; 300 mg of diethylaminoethyl-dextran; and 2.0 mg of chlorocresol) (IMM). Testicular and sperm evaluations, testosterone concentrations, and male odor were determined from 4 wk before applying the treatments until 17 mo of their application. Scrotal circumference of CON (21.0 ± 0.1 cm) and IMM (21.2 ± 0.2 cm) was greater than that of AGO bucks (19.9 ± 0.2 cm) (P < 0.05 for each), without difference between CON and IMM bucks. Pixels' color intensity of testicular ultrasound images was not affected by treatment (general mean ± SEM: 116.0 ± 1.8). Testosterone concentration was greater in CON than AGO and IMM in months 3 and 4, greater in CON and IMM than AGO bucks in months 15 and 16, and greater in IMM than CON and AGO bucks in month 17 (P < 0.05 for all comparisons). Male odor was greater in CON (1.5 ± 0.0) than IMM bucks (1.3 ± 0.0) and greater in IMM than AGO (1.1 ± 0.0) bucks (P < 0.05 for each). Treatment negatively affected all the sperm variables: the total number of sperm in the ejaculate, sperm motility, sperm with normal morphology and sperm with integral membrane function. It was concluded that both treatments were effective in inhibiting the reproductive axis; however, neither of them produced azoospermia or decreased testosterone concentrations to undetectable levels. With both treatments, there were individual males exhibiting characteristics of fertility in all periods of the study. However, chronic use of a GnRH agonist seemed to be the most effective treatment in terms of duration and strength.

Influences of Immunocastration on Endocrine Parameters, Growth Performance and Carcass Quality, as Well as on Boar Taint and Penile Injuries

Simple Summary

Surgical castration of male pigs is associated with pain. Improvac^®, a GnRH vaccine induces an endogenous immune reaction that leads transiently to a decrease in testicular steroid synthesis after second vaccination. Investigating consequences of different vaccination schemes revealed that GnRH vaccination reliably prevents boar taint, if the manufacturers’ recommendations are applied. It had beneficial effects on animal welfare as it reduced penile injuries. Animals showed improved feed efficiency, leaner carcasses, and lower PUFA (polyunsaturated fatty acids) percentages than surgically castrated animals. Thus, immunocastration offers a reliable and animal friendly alternative to surgical castration.

Abstract

Castration of male pigs without anesthesia is a significant welfare issue. Improvac^®, a GnRH vaccine induces an endogenous immune response leading to a decrease in testicular steroids. Consequences of different vaccination schemes on testicular function and carcass quality were evaluated in immunocastrated boars (IC), surgical castrates (SC), and entire males (EM). Therefore, 128 male piglets were assigned to five treatment-groups and a long term follow-up group. IC groups received two vaccinations (V1, V2) with Improvac^® at 8 and 12, 12 and 16, or 12 and 18 weeks. Testosterone-concentrations decreased significantly two weeks after V2 in feces and dropped in serum from V2 to slaughter (S) except IC-8/12 without differing significantly. GnRH-binding results indicated the highest values for IC-12/18 animals. While IC-12/16 and IC-12/18 animals showed boar taint compounds below the threshold levels, two IC-8/12 animals had concentrations above the threshold level. Feed-efficiency was higher in EM than in SC with IC in between. In IC compared to EM, a decreasing amount of polyunsaturated-fatty-acids was obvious and GnRH-vaccination reduced penile injuries. The examined vaccination protocols reduce penile injuries, improve feed efficiency and carcass quality, and reliably prevents boar taint, if manufacturer’s recommendations concerning vaccination schedules are applied. Therefore immunocastration offers a reliable, animal friendly alternative to surgical castration.

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.

Effects of an anti-gonadotrophin releasing hormone vaccine on the morphology, structure and function of bull testes

Castration reduces aggressive and sexual behaviour and provides better carcass quality in bull calves. Vaccination against gonadotrophin-releasing hormone (GnRH) is used as an alternative to surgical castration for the purposes of reducing pain and distress in the animals. Currently, no anti-GnRH vaccine has been authorized for use in cattle in the European Union. The aim of the present study was to assess the effect of an anti-GnRH swine-specific vaccine (Improvac®, Zoetis, USA) on the morphology, structure and function of bull testes. Animals were vaccinated at days 1, 21 and 104 of the experimental period and were classified based on their live weight into the following two groups: LIGHT (172.9 ± 30.00 kg) and HEAVY (323.8 ± 37.79 kg). The scrotal circumference was measured on day 1 and prior to slaughter (day 164). At slaughter, the sperm motility and concentration in the caudae epididymis were assessed. Testes were weighed, measured and examined using ultrasound, and then tissue samples were collected and fixed in formalin. Histological and immunohistochemical studies were performed on the testes to measure the diameter of the seminiferous tubules and assess the testicular cell populations. The results revealed that suppression of testicular development was associated with the use of the Improvac® vaccine, which resulted in a smaller size of the testes and impaired spermatid production. However, the effect of Improvac® was more pronounced and consistent in calves vaccinated at a low live weight than at a heavy live weight, which suggested that vaccination is more effective when calves are vaccinated before or early during puberty. However, testes from calves vaccinated at a low live weight were more prone to the development of intraluminal concretions in the seminiferous tubules.

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.

Penile Injuries in Immunocastrated and Entire Male Pigs of One Fattening Farm

Penile injuries in boars have been discussed as a relevant welfare problem in pork production with entire males (EM). The incidence of penile injuries with immunocastrated boars has not been described so far. Thus, it was the aim of this study to systematically compare frequency and severity of penile injuries in EM and IC. Incidence and size of penile injuries (wounds, scars, hematomas) were evaluated in 192 IC and 215 EM from one farm after slaughter (120 kg live weight; four batches (BA) in at least weekly intervals over five weeks). 75.8% EM and 48.4% IC showed injuries at the pars libra of the penis. Scars were observed in 71.2% EM and 44.8% IC. Scars/animal were significantly influenced by treatment (IC vs. EM), B and treatment x B and increased with age in EM (BA1: 2.61 ± 3.05; BA4: 3.59 ± 3.47), but not in IC (BA1: 2.00 ± 3.02; BA4: 1.22 ± 1.91). Wounds were obvious in 17.2% EM and 8.3% IC. Wounds/animal were only influenced significantly by treatment and were lower in IC than in EM. Thus, it is concluded that immunocastration reduces the frequency and severity of penile injuries in IC when compared to EM of same age and weight.

Age at castration (surgical or immunological) impacts carcass characteristics and meat quality of male pigs

In order to accurately estimate body composition at slaughter and to meet specific market targets, the influence of age at time of castration (surgical or immunological) on body composition and boar taint indicators must be determined for male pigs. In all, 48 males were randomly assigned to one of four management regimens: (1) entire male pigs (EM), (2) EM surgically castrated at ~40 kg BW and 10 weeks of age (late castrates; LC), (3) conventional, early surgical castrates (within 4 days of birth; EC) and (4) EM immunized with a gonadotropin-releasing hormone (GnRH) analog (primary dose at 30 kg BW and 8 weeks of age; booster dose at 70 kg and 14 weeks of age; IM). Pigs were fed corn and soybean meal-based diets that were not limiting in essential nutrients. Back fat was sampled on days -3, 8, 18 and 42, relative to administering the booster dose of GnRH analog at day 0, to determine androstenone concentrations (n=8 or 9/group). Fat androstenone concentrations in IM were lower than EM between days 8 and 42 after administering the booster dose (173 v. 863 ng/g, respectively; P<0.01), and were not different from surgically castrated males (EC and LC) after day 18. Slaughter occurred at ~115 kg BW, 42 days (6 weeks) after administering the booster dose for IM, and 10 and 20 weeks after surgical castration for LC and EC, respectively (n=8 or 9/group). At slaughter, live BW, liver weight as a percent of live BW, dissectible bone as a percent of cold carcass side, body protein and water contents and whole-body protein deposition decreased with time after surgical castration (linear; P<0.05), whereas dressing percentage, dissectible fat, probe fat depth and body fat content increased with time after surgical castration (linear; P<0.05). The IM had intermediate dressing percentage and dissected fat to EM and EC, whereas liver weight as a percent of live BW and body protein and lipid contents were not different from EM. Whole-body lipid deposition tended to be greater in IM than in EM between 14 and 20 weeks of age (373 v. 286 g/d; P=0.051). In conclusion, castration of male pigs after 6 weeks of age has a lasting effect on physical and chemical body composition. The relationship between time after castration and body composition may be developed to predict carcass composition and can be used to determine the ideal immunization schedule aimed at specific markets in the future.

Immunization of dogs with recombinant GnRH-1 suppresses the development of reproductive function

This study was designed to evaluate the effect of active immunization using recombinant GnRH-I protein on reproductive function in dogs. Six male and six female dogs were randomly assigned to either a control group or an immunization group (n = 3 males or 3 females/group). Dogs (aged 16 weeks) were immunized against GnRH-I with a maltose-binding protein-gonadotropin-releasing hormone I hexamer generated by recombinant DNA technology. Blood samples were taken at 4-week intervals after immunization. The serum concentrations of testosterone and estradiol and anti-GnRH-I antibodies were determined by RIA and ELISA, respectively. The results showed that active immunization with recombinant GnRH-I increased the serum levels of anti-GnRH antibodies (P < 0.05) and reduced the serum concentrations of testosterone (P < 0.05) and estradiol (P < 0.05) as compared with the controls. At 28 weeks of age, testes and ovaries were taken surgically for morphologic evaluation. Histologic studies performed on testicular and ovarian tissues revealed clear signs of atrophy in the recombinant GnRH-I-immunized dogs and a significant reduction (P < 0.05) in the weights and sizes of paired testes and ovaries in the treated dogs. Microscopically, spermatogonia were visible, but no spermatids and spermatozoa were detected in the seminiferous tubules. Neither early antral nor antral follicles were found in the immunized group. These results demonstrate that recombinant GnRH-I is an effective immunogen in dogs.

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

Background

The aim of the present study was to investigate the efficacy of the Improvac on testosterone concentration in blood serum, sexual behavior and sperm quality in matured AI boars. A total of nine Danish Landrace AI boars were included in the analysis.

Methods

The trial period lasted for 15 weeks and was divided into four periods: Control period: three weeks before vaccination; Period I – four weeks after first vaccination; Period II – four weeks after second vaccination, Period III – four weeks after third vaccination. Blood and sperm samples were collected at weekly intervals. Freshly collected sperm samples were analyzed.

Results

Testosterone concentration correlated with libido (r = 0.531; p < 0.001), volume of ejaculate (r = 0.324; p < 0.001) and the percentage of morphologically normal spermatozoa (r = 0.207; p < 0.05). Testosterone concentration rised significantly (p < 0.05) in 5–6 week of trial, e. i. after the first dose of Improvac and after this peak the level of testosterone further progressively decreased (p < 0.05).

Conclusions

Results from this study indicate that active immunization of sexually matured boars against GnRH has negative impact on testosterone concentration, sexual behavior, volume of ejaculate and total number of normal spermatozoa in ejaculate.

Early immunocastration of male pigs with Improvac(®) - effect on boar taint, hormones and reproductive organs

The aim of this study was to investigate the effect of a vaccine against gonadotropin-releasing hormone (GnRH), Improvac(®) (Pfizer Ltd), administered at a pre- or early pubertal stage on boar taint, hormonal status and reproductive organs. Crossbred male pigs (Swedish Yorkshire dams×Swedish Landrace sires or Swedish Yorkshire sires, n=192) were at birth randomly allocated to four groups: one group of pigs surgically castrated without anaesthesia before age 1 week, a second group of early vaccinated pigs given Improvac at ages 10 and 14 weeks, a third group of standard vaccinated pigs given Improvac at ages 16 and 20 weeks, and a fourth group of entire male pigs. Following the second vaccine injection, antibody titres increased rapidly, accompanied by a rapid decrease in testosterone and a slower decrease of skatole in plasma to the same low levels as for surgically castrated pigs. At slaughter, the levels of androstenone and skatole in adipose tissue were low in surgically castrated and vaccinated pigs, whereas entire male pigs had elevated levels (p<0.001). Similarly, oestradiol was at low levels for surgically castrated and vaccinated pigs, whereas entire male pigs had elevated levels (p<0.001). IGF-1 was lowest for surgically castrated pigs and highest for entire male pigs, with vaccinated pigs at an intermediate level (p<0.001). At slaughter, reproductive organs were small in pigs vaccinated with Improvac, and smaller in pigs vaccinated early (p<0.001). Under our experimental conditions, early vaccination with Improvac can be used as an alternative to the recommended schedule with maintained control of boar taint and testicular secretory activity.

Is there a role for immunocontraception?

The world's population is continuing to grow at an alarming rate and yet no novel methods of contraception have been introduced since 1960s. The paucity of our current contraceptive armoury is indicated by the 46 million abortions that are performed each year, largely in developing countries where population growth is greatest. Thus, whatever new forms of fertility control we develop for the next millennium, the particular needs of developing countries should be borne in mind. Contraceptive vaccines have the potential to provide safe, effective, prolonged, reversible protection against pregnancy in a form that can be easily administered in the Third World. In this review we consider the contraceptive targets that might be pursued, how vaccines might be engineered and the problems generated by inter-individual variations in antibody titre. We conclude that the specifications for a safe, effective, reversible vaccine are more likely to be met in animals than man.

Effects of long-term treatment with the GnrH agonist deslorelin (Suprelorin) on sexual function in boars

Immunization against GnRH has been proven effective for boar taint removal, and long-term treatment with GnRH analogues has been shown to suppress GnRH dependent reproductive processes in several species. This study was conducted to treat boars (n = 5) with Suprelorin, i.e., an implant that contains 4.7 mg of the long-acting GnRH analogue deslorelin, and to test the effects on sexual function. Insertion of the implant occurred at the age of 5 weeks and animals were observed until market age at 26-27 weeks. Surgically castrated (n = 4) and intact boars (n = 3) served as controls. Testes growth was markedly reduced and steroidogenesis (testosterone, estrone, estrone sulphate, estradiol 17beta) as well as spermatogenesis suppressed in 4 of 5 GnRH treated boars, respectively. The remaining fifth boar resumed testes growth after week 17 of age and had high hormone concentrations when tested at weeks 26 and 27. Restoration of spermatogenesis was observed at 34 weeks of age. There were no effects of treatment on general health, nor were there local inflammatory reactions. Results indicate that suppression of sexual functions in boars due to long-term treatment with the GnRH agonist deslorelin through an implant such as Suprelorin is possible and can last for several months up to market age; thus it has potential as an alternative to other methods used for boar taint removal. Because the maximum duration of suppression seems to vary between boars, further studies are necessary to refine the treatment.

Development of combined vaccines for rabies and immunocontraception

Rabies prevention and appropriate population management of free-ranging animals have an important role to play in the eventual elimination of rabies in dogs. An effective sterilant based on rabies vaccines has the potential to create a supportive measure of public acceptability and to reduce associated clinic visit costs. We inserted the coding sequence of gonadotropin-releasing hormone (GnRH) into different locations within the rabies virus ERA glycoprotein (G) gene, and demonstrated that the amino terminus (N), antigenic site IIa, and the junction between the ecto- and cytoplasmic domains (C) of the G were suitable sites for GnRH insertion. The rescued recombinant rabies viruses ERA-N-GnRH and ERA-C-GnRH grew as well as the parental ERA virus, reaching 1x10(9)ffu/ml in cell culture. Insertion and expression of the GnRH were stable in the viruses after multiple passages in vitro. To increase immunogenicity of the GnRH peptide, two copies of GnRH, aligned in tandem, were fused to the N terminus of the G. The recombinant rabies virus ERA-N-2GnRH was recovered and grown to high titers in cell culture. All GnRH-carrying rabies viruses induced antibodies against GnRH in immunized mice and protected 100% of the animals after rabies virus challenge. The recombinant viruses reacted strongly with the serum from a GonaCon-immunized animal. The GnRH-carrying rabies viruses have significant potential in rabies and animal population control.