Active Immunization against Gonadotrophin-releasing Hormone in Chinese Male Pigs

We have investigated, under the normal conditions of local Chinese pig farming, castration of young male pigs by vaccination with a newly developed vaccine against gonadotrophin releasing hormone (GnRH). Because of the very early onset of puberty, long fattening period and relatively harsh circumstances in Chinese pig production, an investigation of the endocrine response of Chinese breeds to this type of vaccination was of particular interest. Fifteen crossbred boars (Yorkshire × Yanan) from three different litters were randomly assigned to three groups of five animals each. The first group was immunized at 13 weeks of age with a GnRH tandem dimer OVA‐conjugate in Specol and received a booster immunization 8 weeks later. The second group was injected with Specol alone and served as untreated controls. The remaining group was surgically castrated at the time of weaning (at 6 weeks of age). Pigs were fed ad libitum from weaning onwards. All animals were slaughtered at 31 weeks of age. Immunized boars had undetectable or low serum testosterone (0.09 ± 0.12 ng/ml), low fat androstenone (0.05 ± 0.01 μg/g) levels and very low testes weights (19.1 ± 4.3 g). Intact controls had much higher serum levels of testosterone (9.76 ± 4.81 ng/ml), fat androstenone levels (2.26 ± 0.87 μg/g) and testes weights (114.3 ± 29.41 g) at slaughter. Both the immunized and castrated group grew significantly faster than intact boars (p < 0.01). Average daily gains in immunized, castrated and intact animals were 0.69 ± 0.08, 0.63 ± 0.05 and 0.42 ± 0.07 kg (mean ± SD), respectively. The present data demonstrate for the first time that the newly developed anti‐GnRH vaccine works very well under practical Chinese pig farming conditions, and can be an attractive alternative to surgical castration.     

Vaccination of boars with a GnRH vaccine (Improvac) eliminates boar taint and increases growth performance.

Peri- and postpubertal boars accumulate substances (e.g., androstenone and skatole) in their fatty tissue that are responsible for boar taint in pork. The objective of this study was to assess the efficacy of a GnRH vaccine, Improvac, in eliminating boar taint. Three hundred male (200 intact boars, 100 barrows) crossbred (Large White x Landrace) pigs were used in a 2 x 3 factorially arranged experiment. The respective factors were sex group (barrows, boars treated with placebo, or boars treated with Improvac) and slaughter age (23 or 26 wk). Vaccines were administered 8 and 4 wk before slaughter. All Improvac-treated pigs exhibited anti-GnRH titers. Testes and bulbo-urethral gland weights in treated pigs were reduced by approximately 50% (P < 0.001) and serum testosterone levels were below 2 ng/mL in the majority of treated boars (94 and 92% across both age groups at 2 and 4 wk, respectively). Boar taint, as assessed by the concentration of androstenone and skatole in s.c. fat, was suppressed to low or undetectable levels in 100% of Improvac-treated boars. No Improvac-treated pigs had significant concentrations of either androstenone (> 1.0 microg/g) or skatole (> 0.20 microg/g). In contrast, 49.5% of placebo-treated controls had significant androstenone and 10.8% had significant skatole levels, resulting in 10% of the control boars with high concentrations of both compounds. The mean concentrations of taint compounds in the Improvac-treated pigs were not significantly different from those in barrows. Improvac-treated boars grew more rapidly (P = 0.051 and < 0.001 for pigs slaughtered at 23 and 26 wk of age, respectively) than control boars over the 4 wk after the secondary vaccination, possibly because of reduced sexual and aggressive activities. Compared with barrows, Improvac-treated boars were leaner and had superior feed conversion efficiency. The vaccine was well tolerated by the pigs, and no observable site reactions could be detected at the time of slaughter. Vaccination of boars with Improvac allows production of heavy boars with improved meat quality through prevention and control of boar taint.     

Effect of a Gonadotropin-releasing Hormone Vaccine (ImprovacTM) on Steroid Hormones, Boar Taint Compounds and Performance in Entire Male Pigs

The objective of this study, comprising two trials, was to evaluate the effect of a gonadotropin‐releasing hormone (GnRH‐vaccine Improvac^TM; Pfizer Ltd) in a sample of the Swedish pig population. The pigs (n = 120) were assigned to three groups: control (entire male pigs), surgical castration and immunization against GnRH. Surgically castrated pigs did not express detectable levels of either testosterone or estrone sulphate (E1S) in plasma, or androstenone in fat and had lower skatole and indole levels in fat than entire male pigs. Immunization significantly reduced testes weight and bulbourethral gland length, plasma levels of the testicular hormones testosterone and E1S, and fat levels of androstenone, skatole and indole. Skatole levels in plasma were significantly lower than in entire male pigs in the second trial, but not in the first due to overall low skatole levels. All immunized pigs and surgically castrated pigs expressed skatole concentrations in fat below the level of 0.2 μg/g, above which meat is regarded as tainted. In contrast, eight entire male pigs exceeded this level. Indole levels in plasma from immunized pigs were lower than those from entire male pigs. Surgical castration caused lower daily weight gain in the suckling period compared with piglets raised intact, whereas in the post‐weaning period no difference was observed. Immunization resulted in higher feed intake and daily weight gain after the second injection. The estimated lean meat content was improved in comparison with the castrated pigs, but was lower than for entire male pigs. Dressing percentage was lower in immunized pigs than in surgically castrated and entire male pigs. The frequency of skin damage did not differ between immunized and entire male pigs or between immunized and surgically castrated pigs.     

Effect of live weight and dietary supplement of raw potato starch on the levels of skatole, androstenone, testosterone and oestrone sulphate in entire male pigs

This study evaluated the effect of supplement of raw potato starch (RPS) on the levels of skatole, androstenone, testosterone and oestrone sulphate in plasma from entire male pigs. The study also evaluated relationships between plasma levels of skatole and testicular steroids at three different live weights (LW) of approximately 90, 100 and 115 kg. A total of 111 entire male pigs of a crossbred (Yorkshire dams×Swedish Landrace sires) were used. Animals were raised either in mixed pens, with females and males, or single-sex pens. Each pen contained seven or nine pigs. The most fast-growing three pigs from the pens with nine pigs were slaughtered when they reached 90 kg LW, and the remaining pigs were slaughtered at 115 kg LW. All pigs were fed the same commercial diet until the average pen weight reached 100 kg. Then, 33 out of 80 remaining pigs received RPS, 0.6 kg per pig and day, for 2 weeks prior to slaughter. Blood samples were taken from the pigs at three occasions: first, the day prior to first slaughter occasion, low-weight group; second, the day prior to change in diet, middle-weight group; and third, the day prior to second slaughter occasion, high-weight group. Plasma was analysed for the levels of skatole, androstenone, testosterone and oestrone sulphate. Fat samples were taken at slaughter and analysed for the levels of skatole and androstenone. The levels of skatole and testicular steroids in plasma were significantly higher in entire male pigs from the high-weight group fed no RPS compared to those from low- and middle-weight groups. The levels of the investigated compounds did not differ between low- and middle-weight groups (P>0.1). The diet with RPS induced a decline in skatole levels in plasma and fat (P<0.001), but not plasma levels of testicular steroids and fat levels of androstenone (P>0.05). Skatole levels were positively correlated to testosterone and oestrone sulphate levels in the middle- and high-weight pigs fed no RPS as well as to testosterone in the low-weight group. In the high-weight group fed RPS, skatole levels were not correlated to any of the analysed compounds. Approximately 26% of the entire male pigs (11 out of 43) from the high-weight group fed no RPS produced skatole levels in fat above 0.20 μg/g, whereas the pigs from the low- and high-weight group fed RPS did not produce skatole levels above 0.20 μg/g in fat. Androstenone levels in fat were high in all groups. In total 47% (52 out of 111) pigs expressed androstenone levels above the rejection levels in fat of 1.0 μg/g and 88% (98 out of 111) had androstenone levels above 0.5 μg/g. It was concluded that a lower slaughter weight and the supplement of raw potato starch to the diet could be used to reduce skatole levels in entire male pigs. Androstenone levels in fat, however, could not be reduced by either a lower weight at slaughter or dietary manipulation.     

Immunization against 5α-androstenone in boarsL'immunisation contre la 5-androsténone chez le verratImmunisierung gegen 5α-Androstenon in Ebern

The effects of specific immunization against 5α-androstenone have been examined in large, genetically homologous groups of boars reared either to bacon weight (90–95 kg live weight) or to heavy manufacturing weight (115–120 kg live weight). At the lighter weight, immunization significantly (P < 0.05) reduced the concentration of androstenone in the adipose tissue from a mean value of 1.77 (S.E. 0.2) μg g^?1 fat in untreated boars (n=39) to 1.10 (S.E. 0.18) μg g^?1 for animals (n=19) treated with 5α-androstene-3-BSA. In contrast, boars (n=20) treated with 5α-androstenone-11-BSA as immunogen accumulated androstenone to a level of 1.99 μg g^?1 fat (S.E. 0.38). At the heavier weight, immunization reduced the accumulation of androstenone in adipose tissue from a mean value of 1.81 μg g^?1 fat (S.E. 0.22) in untreated boars (n=76) to 1.17 μg g^?1 (S.E. 0.19) for animals (n=22) treated with androstene-3-BSA as immunogen. In contrast, boars (n=21) treated with androstenone-11-BSA as immunogen accumulated androstenone to a mean level of 1.74 μg g^?1 fat (S.E. 0.46). No detrimental side-effects were observed in the immunized animals and the advantages of male-type performance and carcass composition were fully preserved.     

Effect of hCG Stimulation on Plasma Androstenone Concentrations and Cytochrome b5 Levels in Testicular Tissue

The effect of Human chorionic gonadotropin (hCG) stimulation on the concentrations of free and conjugated androstenone in plasma was studied in 34 crossbred entire male pigs (Landrace x Swedish Yorkshire). Seventeen pigs were treated with hCG 4 days prior to slaughter and the remaining pigs were treated with sterile saline and served as controls. Blood samples were taken prior to hCG or saline injection and on the day before slaughter and analysed for concentrations of free and conjugated androstenone. Testicular tissue samples were taken at slaughter and analysed for the levels of cytochrome b5 (cyb5) protein. Here we have demonstrated for the first time that hCG stimulation causes an increase in the plasma levels of both free and conjugated androstenone. Not all animals responded in the same way to hCG treatment regarding levels of free and conjugated androstenone demonstrating that individual animals can have differences in their capacity to produce free and conjugated androstenone. We suggest that hCG treatment is a good way to determine the potential for androstenone conjugation when androstenone synthesis in the testis is high. The levels of cyb5 protein in the testis were slightly related (r=0.41, p < 0.10) to free androstenone levels in the pigs after hCG administration, although levels of cyb5 protein were not affected by hCG treatment.     

GnRH类似物疫苗免疫去势效果的影响因素

利用GnRH类似物疫苗主动免疫动物机体可达到与手术去势类似的效果,同时避免了手术去势对动物机体产生的影响。抗原、佐剂、免疫次数、免疫剂量以及免疫时间都会对其免疫效果产生影响。采用GnRH类似物疫苗免疫动物通常需要有力的佐剂以及多次加强免疫来克服个体反应的差异性。     

Effect of information provisioning on attitude toward surgical castration of male piglets and alternative strategies for avoiding boar taint

Pork consumers know little about boar taint and the methods used to avoid it. As such, relevant information is necessary to assist consumers to judge the acceptability of different strategies to avoid boar taint. The effect of basic (T1) or extensive (T2) written information or T2 with supplementary audio–visual information (AV) on the opinion concerning immunocastration (IC), raising entire male pigs (EM) and surgical castration with anaesthesia (SA) as compared to castration without anaesthesia (SC) was investigated in a student population. Overall, IC was significantly preferred over SC. The information condition influenced the preference for IC and EM as compared to SC. Participants exposed to AV were more positive to IC than participants exposed to T1 and T2, and more positive to EM than participants exposed to T2. The impact of information condition was not affected by gender, farming experience, knowledge about the boar taint issue or personal relevance of pig welfare. Potential effects of providing background information and media campaigns on public surveys ought to be considered. Supplementary audio–visual information increased the impact of information provisioning.     

Evaluation of medetomidine, ketamine and buprenorphine for neutering feral cats

A combination of medetomidine (M, 100 μg/kg), ketamine (K, 10 mg/kg) and buprenorphine (B, 10 μg/kg), administered by intramuscular injection, was evaluated for spaying and castration (neutering) of feral cats (n = 101). Eleven animals (11%) required supplemental anesthesia (isoflurane by mask) to maintain an adequate plane of surgical anesthesia. Atipamezole (A, 125 μg/kg) was administered subcutaneously at the completion of surgery. All cats recovered from surgery and were released the following day. A hemoglobin saturation (SpO(2)) value of < 95% was recorded at least once during anesthesia in all cats. This MKB combination can be used in a feral cat sterilization clinic, but isoflurane supplementation may be necessary. Further research is indicated to determine the clinical significance of the low SpO(2) values associated with this anesthetic regimen.     

The function of the pituitary-testicular axis in dogs prior to and following surgical or chemical castration with the GnRH-agonist deslorelin

Chemical castration, that is the reduction of circulating testosterone concentrations to castrate levels by administration of a GnRH-agonist implant, is a popular alternative to surgical castration in male dogs. Detailed information concerning the pituitary-testicular axis following administration of a GnRH-agonist implant is still scarce. Therefore, GnRH-stimulation tests were performed in male dogs, prior to and after surgical and chemical castration. This approach also allowed us to determine plasma concentrations of testosterone and oestradiol in intact male dogs for future reference and to directly compare the effects of surgical and chemical castration on the pituitary-testicular axis. In intact male dogs (n = 42) of different breeds GnRH administration induced increased plasma LH, FSH, oestradiol and testosterone concentrations. After surgical castration basal and GnRH-induced plasma FSH and LH concentrations increased pronouncedly. Additionally, basal and GnRH-induced plasma oestradiol and testosterone concentrations decreased after surgical castration. After chemical castration, with a slow-release implant containing the GnRH-agonist deslorelin, plasma LH and FSH concentrations were lower than prior to castration and lower compared with the same interval after surgical castration. Consequently, plasma oestradiol and testosterone concentrations were lowered to values similar to those after surgical castration. GnRH administration to the chemically castrated male dogs induced a significant increase in the plasma concentrations of LH, but not of FSH. In conclusion, after administration of the deslorelin implant, the plasma concentrations of oestradiol and testosterone did not differ significantly from the surgically castrated animals. After GnRH-stimulation, none of the dogs went to pre-treatment testosterone levels. However, at the moment of assessment at 4,4 months (mean 133 days ± SEM 4 days), the pituitary gonadotrophs were responsive to GnRH in implanted dogs. The increase of LH, but not of FSH, following GnRH administration indicates a differential regulation of the release of these gonadotrophins, which needs to be considered when GnRH-stimulation tests are performed in implanted dogs.     

Evaluation of the efficacy of immunocastration vaccine composed of gonadotrophin-releasing hormone conjugated with Salmonella typhimurium flagellin in rats

Immunocastration is an alternative method to replace surgical castration that is commonly performed in domestic and pet animals. In this study, a new immunocastration vaccine was developed, and its efficacy was evaluated in male rats. Six tandem copies of gonadotrophin-releasing hormone (GnRH) peptide were genetically fused to Salmonella typhimurium flagellin fljB (STF2) that is a ligand of toll-like receptor 5 (TLR5). The recombinant STF2-GnRH protein expressed in Escherichia coli was used as the immunocastration vaccine. Sixteen male rats were equally assigned to four groups. Excluding the control rats, three groups were immunized with 100, 200 and 400 μg of the STF2-GnRH vaccine, respectively. All of the immunized rats developed significantly higher titres of antibodies to GnRH than the control rats. The size and weight of both testes and epididymides from the immunized rats were significantly smaller than those of the control rats. Testicular tissues in the immunized rats demonstrated atrophy of seminiferous tubules and decreased numbers of both spermatogonia and spermatocytes. These data indicate that the newly developed STF2-GnRH vaccine has a potent immunogenicity to GnRH and efficiently suppresses the development of testes in rats.     

Social effects and boar taint: significance for production of slaughter boars (Sus scrofa)

A study was conducted to elucidate the effects of social factors on the concentrations of boar taint substances, androstenone and skatole, in boars. The factors included dominance (social rank) and the effects of strongly tainted animals on other members of the group. Four successive replicates of 100 pigs (50 boars + 50 gilts) with an average live weight of 24 kg were randomly allocated to 10 pens of 10. Data for this study were collected during the period of 67 to 114 kg of live weight and included the repetitive recording of agonistic behavior during competitive feeding; blood sampling for determination of plasma androstenone, skatole and testosterone in boars; feces sampling for determination of skatole content; and collection of bulbourethral glands in boars, and uteri plus ovaries in gilts at slaughter, for the assessment of sexual maturity. Results show an influence of social rank on plasma concentrations of androstenone (P = .0001) and testosterone (P = .0001), the weight of the bulbourethral glands (P = .0001), and plasma skatole (P = .02). Pens were classified according to the pig with the highest concentration of androstenone in the pen into high, medium, and low maximum pens. In pens with high maximum concentrations of androstenone, the second-highest androstenone concentration (P = .0001), and the average concentration (P = .0003) in the pen were higher than those in pens with medium or low maximum concentrations of androstenone. Mean aggression level was also higher (P = .02), but pens with high maximum aggression level did not have higher mean androstenone concentration. Rank effect on androstenone was more important than aggression effect. Neither maximum androstenone concentration nor maximum aggression level in a pen was related to the pen mean stage of sexual maturity in either sex. No influences of rank, aggression, or aggression received were found on the feces skatole level, and no pheromonal communicative function was demonstrated for skatole. High androstenone concentrations did not have a suppressive effect on androstenone concentrations in other males of the group; on the contrary, the levels were increased. This may be due to a stimulating effect of androstenone and, possibly, mating activity. Consequently, in the production of boars for slaughter, strongly tainted animals should be avoided or removed and mating activity minimized. This could be facilitated by, for instance, slaughtering before sexual maturity or separate rearing of the sexes.     

The effect of early postnatal treatment with a gonadotropin-releasing hormone agonist on the developmental profiles of testicular steroid hormones in the intact male pig

Three studies examined the effects of early postnatal treatment with a GnRH agonist on plasma concentrations of testosterone, dehydroepian-drosterone sulfate, 16-androstene steroids in fat and salivary glands, androstenone in fat and plasma, and testicular development of intact male pigs. The first study involved 45 7-d-old pigs assigned to three treatment groups: 1) boars administered 100 microg/kg of Lupron depot, 2) boars administered 200 microg/kg of Lupron depot, and 3) control boars receiving a saline carrier. The second study involved 20 7-d-old pigs assigned to two treatments: daily injection of 200 microL of 0.5 mg/mL Lupron from d 7 to 35 and controls treated with saline. The third study involved a total of 100 animals assigned to 10 groups of 10 based on their age at slaughter. These groups were subdivided into one of two treatments: 1) boars injected with 200 microL of 0.5 mg/mL of Lupron from d 3 to 35 and 2) control boars injected with saline. Testicular steroid hormone concentrations in plasma decreased (P < 0.01) within 7 d of GnRH agonist treatment. Following cessation of treatment, steroid levels increased to control levels and remained constant until the final rise at 5 mo. Plasma testosterone levels in the 100 microg/kg depot treatment group were higher (P < 0.05) than that of the 200 microg/kg and control group at 164 d of age. There were no differences between treatments (P > 0.05) in testicular steroid hormone levels at the end of study 2 or 3. There were no differences (P > 0.05) in concentrations of 16-androstene steroids in salivary glands between any of the treatment groups at market weight in studies 1 and 2. Fat androstenone levels measured in the third study ranged between 0.6 microg/g and 4.2 microg/g at 7 to 28 d of age. Treatment with GnRH agonist decreased plasma steroid levels and testicular development; however, by d 60 testicular size and weight were at control levels and remained similar until 180 d of age. The results of these studies indicate that daily administration of a GnRH agonist significantly decreased testicular development and steroidogenesis only during treatment, but testis growth and steroidogenesis had returned to control levels by 60 d of age in male pigs. Suppression of the early postnatal rise in testicular steroid hormones did not affect growth performance or steroid hormone levels at 5 to 6 mo of age.     

Physical,chemical and sensorial parameters for lambs of different groups,slaughtered at different weights

The object of this experiment was to study physicochemical and sensorial traits in the 11th and 13th ribs of 24 Santa Ines (SI), 24 1/2 Ile de France?×?1/2 Santa Inês (ILE?×?SI) and 8 1/2 Texel?×?1/2 Santa Inês (TE?×?SI), slaughtered at different weights (30, 35, 40 and 45 kg, respectively). Subjective measurements (marbling, colour and texture) were carried out on the Longissimus dorsi, as well as initial pH (0 h) and final pH (24 h) after slaughter. The experiment was in a 3?×?4 factorial design and analysed using general linear model and correlation procedures in SAS®. Breed group did not influence colour (3.32), shear force (3.57 kg-force (kgf)) or loss in cooking (24.05%) of the L. dorsi, but slaughter weight affected these, with stronger colour, tougher meat and greater loss in cooking as slaughter weight increased. For sensorial analysis, the L. dorsi were cut, identified and evaluated by 30 untrained judges using a linear scale. Significant differences were detected in preference (6.61 points), tenderness (6.32 points), succulence (6.33 points) and flavour (7.08 points) of the meat from different breed groups and slaughter weights. For preference, all meats were well accepted although the crossbred animals slaughtered at 45 kg were less acceptable.     

Effects of slaughter time post-second injection on carcass cutting yields and bacon characteristics of immunologically castrated male pigs

Body weights of finishing pigs can be variable within a finishing barn near the time of slaughter; therefore, it is common to market pigs over a period of time. This allows lighter pigs more time to gain BW and approach a desired end point. Use of immunological castration late in life to control boar taint, as an alternative to physical castration early in life, increases cutting yields of finishing male pigs compared with physical castrates. Because of common marketing strategies, it is important for advantages in cutting yields to span a broad spectrum of slaughter ages and BW. The primary objectives in this study were to evaluate carcass cutting yields, pork quality, belly quality, and bacon processing characteristics of immunologically castrated (IC) male pigs fed a moderate level of distillers dried grains with solubles and slaughtered at either 4 wk (early slaughter group) or 6 wk (late slaughter group) post-second injection. A total of 156 male pigs (physical castrates or IC males) were selected from a population of 1,200 finishing pigs. Data were analyzed with the MIXED procedure of SAS as a split-split plot design. Body weights of IC males were 3.60 kg heavier (P = 0.03) than physical castrates when slaughtered at 4 wk post-second injection and 7.52 kg heavier (P < 0.0001) than physical castrates when slaughtered at 6 wk post-second injection. Because of a lack of interaction (P > 0.05) between sex and time of slaughter post-second injection, some response variables were pooled. Hot carcass weights were not different (P = 0.57) between physical castrates (91.98 kg) and IC males (92.52 kg). There was a 2.77 percentage unit decrease (P < 0.001) in dressing percentage of IC males (71.78%) compared with physical castrates (74.55%). Lean cutting yields of IC males were 2.62 percentage units greater (P < 0.0001) than physical castrates and carcass cutting yields were 2.27 percentage units greater (P < 0.0001) for IC males when compared with physical castrates. There were no differences between IC males and physical castrates for shear force (P = 0.09), ultimate pH (P = 0.57), objective color (P ≥ 0.31), subjective color score (P = 0.64), or drip loss (P = 0.30). Bellies from IC males were thinner (P = 0.01) and had narrower belly flops (P < 0.0001) than bellies from physical castrates. There were no differences (P = 0.74) in cured belly cooked yield between IC males and physical castrates. Overall, immunological castration improved cutting yields, did not affect pork quality, made fresh bellies thinner, and did not affect cured belly characteristics when pigs were fed a moderate level of distillers dried grains with solubles during the finishing phase of production.     

Expression of 3beta-hydroxysteroid dehydrogenase, cytochrome P450-c17, and sulfotransferase 2B1 proteins in liver and testis of pigs of two breeds: relationship with adipose tissue androstenone concentration

An excessive accumulation of androstenone in pig adipose tissue is a major contributor to the phenomenon of boar taint. Androstenone deposition is dependent on the rate of androstenone biosynthesis in testis and androstenone degradation in liver. The aim of the current study was to examine the possibility of the existence of breed-specific mechanisms controlling androstenone accumulation in pig adipose tissue. The specific objective was to investigate the expression of some of the key enzymes involved in testicular and hepatic androstenone metabolism in pigs of 2 breeds by using animals with high and low androstenone concentrations within each breed. The study was conducted with Norwegian Landrace (N. Landrace) and Duroc boars. The mean androstenone values for the low- and high-androstenone groups were 0.1 +/- 0.01 microg/g and 7.58 +/- 0.68 microg/g for N. Landrace boars, and 0.22 +/- 0.04 microg/g and 13.55 +/- 1.14 microg/g for Duroc boars. The enzymes investigated were 3beta-hydroxysteroid dehydrogenase (3beta-HSD), cytochrome P450-c17, and sulfotransferase 2B1 (SULT2B1). Expression of cytochrome P450-c17 in liver and testis did not differ between animals with high and low androstenone concentrations in either the N. Landrace or Duroc breed. Expression of hepatic 3beta-HSD, which catalyzes the first stage of androstenone degradation, was decreased in high-androstenone N. Landrace boars (P < 0.01), but not in high-androstenone Duroc boars. In contrast, the expression of hepatic SULT2B1, which catalyzes the second stage of steroid catabolism, was decreased in high-androstenone Duroc animals (P < 0.05), but not in high-androstenone N. Landrace animals. Sulfotransferase 2B1 was also inhibited in testis of high-androstenone pigs of both breeds compared with low-androstenone animals. We report breed differences in expression of the androstenone-metabolizing enzymes 3beta-HSD and SULT2B1 in the liver of high- and low-androstenone pigs. It is suggested that accumulation of androstenone in adipose tissue of N. Landrace boars might be related to a low rate of hepatic androstenone degradation in metabolic stage I, whereas the high androstenone concentration in Duroc boars might be related to a low rate of androstenone metabolism in metabolic stage II.     

Performance of male pigs immunized against GnRH is related to the time of onset of biological response

In this study, the performance of male pigs immunized against GnRH was determined in relation to the onset of their biological response to the immunization. Pigs were immunized at 9 and 17 wk of age and were housed in a pen together with both a surgically castrated and an intact boar littermate. Feed intake was restricted to 2.8 to 3.2 times maintenance requirement for energy. Animals were weighed weekly and slaughtered at 108 kg BW. Depending on the time of onset of the response after immunization in terms of biological effects, immunized pigs were retrospectively grouped into two categories. One category consisted of the immunized pigs, which had undetectable or low levels of LH and testosterone at the time of booster immunization-known as "early" responding immunocastrates (E-IM, n = 8), whereas the "late" responding immunocastrates (L-IM, n = 7) had substantial LH and testosterone levels at that time. This dichotomy of the response to immunization also was reflected in testis weight, with 17 g and 40 g for E-IM and L-IM pigs, respectively. At slaughter, testis size and weight were reduced (P < 0.001) in the immunocastrated pigs as compared to the intact boars. Androstenone concentrations in backfat of all immunocastrated pigs were undetectable. Growth performance (i.e., ADG and feed efficiency [FE, g gain/kg feed]), was better in boars and L-IM pigs than in surgical castrates and E-IM pigs (P < 0.05). Average daily gain and FE did not differ between E-IM pigs and the surgical castrates, but intact boars performed better than L-IM (P < 0.02). There were no significant differences in carcass quality (backfat thickness and meat percentage) between boars and surgical castrates at slaughter. However, for both characteristics L-IM pigs and intact boars performed better (P < 0.03) than E-IM pigs. Thus, growth performance in L-IM is better than in either E-IM or surgical castrates.     

Effects of increasing lysine on carcass composition and cutting yields of immunologically castrated male pigs

The objective of this experiment was to determine if increasing lysine in the diets of immunologically castrated (IC) male pigs would increase percentage fat free lean and carcass cutting yields when compared with physical castrates. The anti-gonadotropin-releasing factor (GnRF) immunological product (Improvest, Pfizer Animal Health) is used worldwide to immunologically castrate entire male pigs to control boar taint and take advantage of the inherent ability of the entire male to deposit more muscle, less fat, and grow more efficiently than physically castrated males. The immunization process essentially allows the pig to grow as an entire male pig for most of its life and then removes any boar odor (boar taint) before slaughter. Reported lean meat advantages may also provide economic benefits to the domestic meat industry. Approximately 1,200 male pigs [physical castrates, IC males, and entire males] were each assigned to 1 of 4 diet programs which differed in lysine content. In each case, lysine was fed in a conventional step-down program that culminated with the following concentrations in the late finishing diet: physical castrates fed low lysine (0.7%), IC fed low lysine (0.7%), IC fed low/medium lysine (0.8%), IC fed medium/high lysine (0.9%), IC fed high lysine (1.0%), and entire males fed high lysine (1.0%). At 25 wk of age (5 wk post-second injection), pigs were individually weighed and the 2 pigs (n=96) in each pen closest to the median pig BW were selected and slaughtered. The right side of each carcass was dissected into soft tissue, skin, and bone. Proximate composition was determined on the soft tissue to determine percentage fat-free lean. The left side of each carcass was weighed and initially fabricated into ham, loin, belly, and whole shoulder. Each primal piece was weighed again and further fabricated into respective subprimal cuts. Immunological castration did not change (P>0.05) shear force values or ultimate pH when compared with either physical castrates or entire males. Marbling appeared to decrease as dietary lysine was increased among IC males. As expected, IC males had a greater (P<0.05) percentage fat-free lean than physical castrates but less (P<0.05) than entire males. Immunologically castrated males fed diets with medium/high and high lysine had greater (P<0.05) lean cutting yields and carcass cutting yields than physical castrates. Lean cutting yield and carcass cutting yields appeared to increase as dietary lysine was increased among IC males. Overall, immunological castration improved carcass cutability, increased percentage fat free lean, and had no effect on pork quality when compared with physical castrates.     

Reducing the length of time between slaughter and the secondary gonadotropin-releasing factor immunization improves growth performance and clears boar taint compounds in male finishing pigs

The objective of this study was to evaluate whether altering the timing of the secondary anti-gonadotropin-releasing factor (GnRF) immunization closer to slaughter in male finishing pigs would reduce the increase in P2 fat depth (6.5 cm from the midline over the last rib), while still limiting the incidence of boar taint. Entire male pigs are immunized against GnRF to reduce the concentration of testicular steroids that in turn limits the incidence of boar taint. Additionally, testicle measurements and color measurements were taken to examine whether they could be used to differentiate nonimmunized entire males from immunized male pigs. A total of 175 Large White × Landrace entire male pigs aged 16 wk (59 kg of BW) were used in a completely randomized design with 5 treatment groups based on the time that pigs received the secondary immunization before slaughter. Pigs were housed in groups of 7 and randomly allocated to 1 of 5 treatments with 5 replicates per treatment. The treatment groups were as follows: no secondary immunization before slaughter, and the secondary immunization given at 2, 3, 4, or 6 wk before slaughter. The P2 fat depth levels were reduced (P = 0.054) with the secondary immunization closer to slaughter (11.7, 11.3, 12.8, 12.6, and 13.7 mm for no secondary immunization, secondary immunization at 2, 3, 4, and 6 wk before slaughter, respectively). Androstenone concentration did not exceed the generally accepted industry sensory threshold of 1.0 μg/g of fat, and both androstenone concentration in the adipose tissue and testosterone concentrations in the blood were suppressed (P < 0.001) in all immunized pigs regardless of timing of the secondary immunization compared with pigs that did not receive the secondary immunization. Skatole concentration of all pigs in the experiment did not exceed the generally accepted industry sensory threshold of 0.2 μg/g. Testes weight was reduced (P < 0.001) with increased time between slaughter and the secondary immunization. Immunized pigs, regardless of time before slaughter, had greater L* (lightness) and b* (yellowness) color of the testicle surface (P < 0.001 and P = 0.020, respectively), and less a* (redness) color compared with entire males (P < 0.001). The study provides further evidence of the efficacy of the anti-GnRF immunization and indicates that the secondary immunization can be moved closer to slaughter, while still limiting the incidence of boar taint. Testicle measurements and color measurements together could provide a method of discrimination between carcasses from immunized entire males clear of boar taint and tainted carcasses.