Fat Androstenone Levels Research Articles

Assessing boar taint in Portuguese pork: A small-scale study of prevalence and classification via established detection thresholds

Aim of study: To assess the boar taint prevalence in the Portuguese pork industry through an observational study model by measuring skatole and androstenone levels in fat and to compare it with the estimated thresholds for these compounds among Portuguese consumers. Area of study: Portugal. Material and methods: Adipose tissue samples from 140 animals (102 entire males and 38 females) were collected in three Portuguese abattoirs for boar taint quantification. Cut-off limits were determined using best-estimate thresholds (BET) for skatole and androstenone. Main results: Boar taint quantification for the 140 animals revealed levels of 36.0±4.7 ng/g of skatole and 64.5±21.3 ng/g of androstenone, and values were significantly higher in males. Group BET values were 35.4 ng/g and 566.3 ng/g for skatole and androstenone, respectively. BET values were exceeded in 28.8% of the samples for skatole and 0.7% for androstenone. Research highlights: The investigation revealed a generally low level of boar taint in the samples of this small-scale study on skatole and androstenone prevalence in Portugal's pork supply chain. However, occasionally a significantly elevated boar taint levels suggest that relying solely on slaughtering sexually immature males might not fully resolve this issue.

Monitoring of behavior, sex hormones and boar taint compounds during the vaccination program for immunocastration in three sire lines

Immunocastration (vaccination against boar taint) is an alternative method to prevent boar taint without the need for surgical castration. This study investigates the evolution of boar taint compounds in serum and fat, serum steroid compounds as well as behavior in immunocastrated pigs from 3 sire lines: 15 stress positive Belgian Piétrain (BP), 20 stress negative French Piétrain (FP), and 20 stress negative Canadian Duroc (CD). Hormone and boar taint compounds in serum were determined at 4 time points; boar taint compounds in fat were determined at 3 time points. Behavior, skin lesions, animal and pen fouling were also recorded before the first vaccination (<V1), between the first and second vaccination (<V2), and after the second vaccination (>V2). Aggressiveness, eating and drinking and general activity behavior declined from <V1 to <V2 and > V2 for all sire lines. Pigs from BP were cleaner than FP and CD pigs. Even though immunocastration was effective in general (reduced testosterone, estradiol as well as androstenone in serum) for all sire lines, some individual pigs showed either androstenone or skatole levels in fat above cutoff values. While the immunocastration mechanism works as intended for androstenone, and also for skatole for the three sire lines, the risk of carcasses with boar taint compounds above cutoff levels (respectively 1.9 and 3.7%) still remains to some extent.

Sensory quality of meat from crossbred boars in relation to their age and slaughter weight

The aim of this study was to evaluate the effect of age of boars and their slaughter weights on the pleasantness and intensity of pork meat taste and odour. A total of 652 sensory evaluations of meat samples from sixteen crossbred entire male pigs aged 121 to 136 days with slaughter weight of 80–120 kg were performed by sensory profiling method. The age was a greater factor influencing the level of boar taint than the slaughter weight of animals. There were significant differences in the intensity of boar odour between categories of young animals (121 days) and old animals (135–136 days) (P = 0.0473) and between categories of adult animals (128 days) and old animals (P = 0.0194). Among the evaluated descriptors stronger correlations were calculated between olfactometric than between taste descriptors. Significant correlations were found between androstenone levels in subcutaneous fat and the results of sensory evaluation of muscle samples from the oldest animals aged 135–136 days.

Exploiting whole genome sequence data to fine map and characterize candidate genes within a quantitative trait loci region affecting androstenone on porcine chromosome 5.

SummaryMale piglets are routinely castrated to eliminate boar taint. However, this treatment is undesirable, and alternative approaches, including genetic strategies to reduce boar taint, are demanded. Androstenone is one of the causative agents of boar taint, and a QTL region affecting this pheromone has previously been reported on SSC5: 22.6–24.8 Mb in Duroc. The QTL region is one of the few reported for androstenone that does not simultaneously affect levels of other sex steroids. The main objective of this study was to fine map this QTL. Whole genome sequence data from 23 Norwegian Duroc boars were analyzed to detect new polymorphisms within the QTL region. A subset of 161 SNPs was genotyped in 834 Duroc sires and analyzed for association with androstenone in adipose tissue and testosterone, estrone sulphate and 17β‐estradiol in blood plasma. Our results revealed 100 SNPs significantly associated with androstenone levels in fat (P < 0.001) with 94 of the SNPs being in strong linkage disequilibrium in the region 23.03–24.27 Mb. This haplotype block contains at least four positional candidate genes (HSD17B6,SDR9C7,RDH16 and STAT6) involved in androstenone biosynthesis. No significant associations were found between any of the SNPs and levels of testosterone and estrogens, confirming previous findings. The amount of phenotypic variance explained by single SNPs within the haplotype block was as high as 5.4%. As the SNPs in this region significantly affect levels of androstenone without affecting levels of other sex steroids, they are especially interesting as genetic markers for selection against boar taint.

Urinary signature of pig carcasses with boar taint by liquid chromatography-high-resolution mass spectrometry

ABSTRACTBoar taint is an offensive odour that can occur while cooking pork or pork products and is identified in some uncastrated male pigs that have reached puberty. It is widely held that boar taint is the result of the accumulation in back fat of two malodorous compounds: androstenone and skatole. The purpose of this study is to assess a mass spectrometry-based metabolomics strategy to investigate the metabolic profile of urine samples from pig carcasses presenting low (untainted) and high (tainted) levels of androstenone and skatole in back fat. Urine samples were analysed by LC-ESI(+)-HRMS. Discrimination between tainted and untainted animals was observed by the application of multivariate statistical analysis, which allowed candidate urinary biomarkers to be highlighted. These urinary metabolites were positively correlated to androstenone and skatole levels in back fat. Therefore, the study suggests that the measurement of these urinary metabolites might provide information with regard to androstenone and skatole levels in live pigs.

Boar taint, meat quality and fail rate in entire male pigs and male pigs immunized against gonadotrophin releasing factor as related to body weight and feeding regime

The objective of this experiment was to compare the pork quality of entire male pigs and pigs immunized against GnRF (IC males) at both light (64.8kg) and heavy (106kg) liveweights and two feeding regimes (restricted at 2.5 times maintenance and ad libitum). There was no difference in objective measurements (P>0.05) or eating pork quality (P>0.1) between entire male and IC males. Fail rates were reduced by 9.1% and 12% for pork from IC males for quality grade (P=0.007) and re-purchase intention (P=0.001), respectively, compared to pork from entire males. Skatole (P=0.001) and androstenone (P<0.001) levels in belly fat were higher in entire male than IC male pigs. In addition, 37.5% of the light entire male pigs fed ad libitum showed skatole levels that exceeded the sensory threshold of 0.2μg/g. This work confirms that immunization against GnRF is effective in eliminating boar taint and reducing pork quality fail rates by approximately 10% compared to pork from entire males.

Transcript levels of genes implicated in steroidogenesis in the testes and fat tissue in relation to androstenone accumulation in fat of pubertal pigs

The present study was performed to measure messenger RNA levels of steroidogenic enzymes in testes and fat tissue and determine whether they are related to fat androstenone level. Real-time polymerase chain reaction experiments were performed on 26 testes and 12 adipose tissue samples from pubertal boars using 21 genes. The absence of significant correlations between fat androstenone and the transcriptional activity of the SRD5A2 and SRD5A3 genes but the high correlation coefficient with that of the SRD5A1 gene (r = 0.62, P < 0.05) suggests that the enzyme coded by SRD5A1 is mainly responsible for the last step of androstenone synthesis. The testicular transcriptional activities of CYP17, CYP11A1, CYP19A, AKR1C-pig6, SRD5A1, LHCGR, and AR were significantly correlated. Only transcriptional levels of CYP17, CYP11A1, CYP19A, SRD5A1, and AKR1C-pig6 were correlated with the fat concentration of androstenone (0.57 < r < 0.70, P < 0.05) confirming that the amount of androstenone stored in fat is related to the production in testes of androstenone and more generally to all sex steroids. Altogether, our data are in favor of a preponderant role of AKR1C-pig6 instead of HSD17B3 for testicular synthesis of steroids. Concerning fat tissue, our data do not support a significant de novo biosynthesis of steroids in porcine adipose tissues. The presence of transcripts coding for steroid enzymes, especially those of AKR1C-pig6, suggests that steroids can be transformed. None of transcript abundance was related to androstenone accumulation (P > 0.1). Therefore, steroids synthesized elsewhere can be transformed in fat tissue but synthesis of androstenone is unlikely.

Boar taint compound levels in back fat versus meat products: Do they correlate?

Surgical castration of male pigs will soon be abandoned, turning a major advantage of this practice, the elimination of boar taint, into the biggest challenge for pig industry when raising intact male pigs becomes common practice. To map the (economical) consequences in relation to boar-taint consumer acceptance, as well as offer a processing strategy for tainted carcasses to stockholders, the current study investigated not only back fat boar taint levels, but additionally generated information on the levels of boar taint compounds recovered after the production of commercially relevant meat products using UHPLC-HRMS laboratory analysis. Our results demonstrate that levels of androstenone, skatole and indole in back fat and meat products tend to correlate strongly, particularly in fatty meat products (generally r>0.80). Concentration values in the edible (lean) meat fraction were significantly lower compared to back fat and fat sampled from fresh or processed meat (p<0.05).

Skatole Metabolism in the Pigs with Reduced Testicular Oestrogen Synthesis

The objectives of the study were to investigate the involvement of oestrogens in the regulation of skatole levels in pigs. In total, 44 intact male pigs, siblings from 10 litters, were included in the study. Pigs were orally treated weekly with either 0.1 mg letrozole/kg body weight to reduce endogenous oestrogens or the canola oil vehicle. Fat and liver samples were collected at slaughter at 16, 20 and 40 weeks of age. Skatole and androstenone levels in fat and activities of hepatic cytochrome P4501A1, CYP1A2, CYP2A19 and CYP2E1 were analysed. Letrozole treatment did not significantly change either the levels of skatole or activities of skatole-metabolising enzymes, suggesting that oestrogens are not responsible for gender-related differences in skatole concentrations in porcine tissues.

Effects of hydroxy‐delta‐5‐steroid dehydrogenase, 3 beta‐ and steroid delta‐isomerase 1 polymorphisms on fat androstenone level and gene expression in Duroc pigs

A high level of androstenone in porcine adipose tissue is a major factor contributing to boar taint. Porcine hydroxy-delta-5-steroid dehydrogenase, 3 beta- and steroid delta-isomerase 1 (3β-HSD, also known as HSD3B1) plays a key role in the hepatic metabolism that catalyzes androstenone to β-androstenol. Therefore, 3β-HSD is a candidate gene for boar taint. This study aimed to investigate functional 3β-HSD polymorphisms in Duroc pigs. We found eight single nucleotide polymorphisms (SNPs) in the full-length porcine 3β-HSD. Four of the SNPs had restriction enzyme sites, and we genotyped them in 147 uncastrated male Duroc pigs using a polymerase chain reaction-restriction fragment length polymorphism method. Pigs with the GG genotype at the g.165262G>A locus (SNP5) had significantly lower androstenone levels than did those with other genotypes (P=0.030). SNP5 also was associated with differences in 3β-HSD mRNA levels: pigs with the GG genotype had higher levels than those with other genotypes (P=0.019). The SNP5 polymorphism could affect the hepatic catabolism of androstenone and consequently impact androstenone accumulation in the adipose tissue. Therefore, SNP5 in the 3β-HSD of Duroc pigs could be a useful selective marker for decreasing boar taint.

New investigations around CYP11A1 and its possible involvement in an androstenone QTL characterised in Large White pigs

BackgroundPreviously, in boars with extreme androstenone levels, differential expression of the CYP11A1 gene in the testes has been characterised. CYP11A1 is located in a region where a QTL influencing boar fat androstenone levels has been detected in a Large White pig population. Clarifying the role of CYP11A1 in boar taint is important because it catalyses the initial step of androstenone synthesis and also of steroid synthesis.ResultsA genome-wide association study located CYP11A1 at approximately 1300 kb upstream from SNP H3GA0021967, defining the centre of the region containing the QTL for androstenone variation. In this study, we partially sequenced the CYP11A1 gene and identified several new single nucleotide polymorphisms (SNP) within it. Characterisation of one animal, heterozygous for CYP11A1 testicular expression but homozygous for a haplotype of a large region containing CYP11A1, revealed that variation of CYP11A1 expression is probably regulated by a mutation located downstream from the SNP H3GA0021967. We analysed CYP11A1 expression in LW families according to haplotypes of the QTL region's centre. Effects of haplotypes on CYP11A1 expression and on androstenone accumulation were not concordant.ConclusionThis study shows that testicular expression of CYP11A1 is not solely responsible for the QTL influencing boar fat androstenone levels. As a conclusion, we propose to refute the hypothesis that a single mutation located near the centre of the QTL region could control androstenone accumulation in fat by regulating the CYP11A1 expression.

Expression levels of 25 genes in liver and testis located in a QTL region for androstenone on SSC7q1.2

A quantitative trait locus (QTL) for boar fat androstenone levels has been identified near the SSC7 centromere in a Large White × Meishan cross. Backcrosses were produced to isolate the Chinese haplotype in a European genetic background. The expression of 25 genes from the QTL region was studied in the testes and livers of 5-month-old backcross boars, with the aim of identifying the causal gene. Using Fluidigm, a new high-throughput technology, the expression of 25 genes was measured in a single real-time PCR experiment. This study found six significantly down-regulated genes (C6ORF106, C6ORF81, CLPS, SLC26A8, SRPK1 and MAPK14) in the testes of MS-LW backcross boars. However, according to current knowledge, none of the genes appear to be related to androstenone metabolism. In the livers, none of the genes were significantly up- or down-regulated, including TEAD3, which was previously designated as a possible candidate to explain this QTL.

Efficacy of non-nutritive sorbent materials as intestinal-binding agents for the control of boar taint

In many countries, male pigs are castrated to prevent boar taint, but this practice raises concerns about animal welfare and reduces the production efficiency of pork. The objective of this study was to develop dietary manipulations to prevent boar taint. We evaluated the effectiveness of adding activated carbon (AC) or Tween-60 (Tween; polyoxyethylene sorbitan monostearate) to pig finishing diets to reduce levels of androstenone (AND) and skatole in plasma and fat of entire male pigs. Boars (159 ± 2 days of age at the start of the experiment) were fed diets supplemented with either 5% AC or 5% Tween for 28 days followed by either 14 or 28 days of recovery. Plasma samples were collected at experimental days 0, 7, 14, 21, 28, 42 and 56, and backfat biopsies were taken at experimental days 0, 28, 42 and 56. Feeding AC significantly (P < 0.05) reduced the levels of AND in plasma by day 28 compared to day 0 and by day 42 in fat compared to day 0. AC treatment also decreased levels of oestrone sulphate (E1S) in plasma by day 7 compared to day 0. Treatment with Tween significantly decreased (P < 0.05) the levels of plasma AND by day 28 from levels at day 0. Tween treatment did not significantly affect levels of fat AND or plasma E1S compared to day 0; however, fat AND levels decreased between days 28 and 42 following treatment with Tween (P < 0.05). Levels of plasma E1S, plasma AND and fat AND for control boars remained constant throughout the experiment. Skatole plasma concentrations were very low and did not vary significantly (P > 0.05) from day 0 for any treatment, but fat skatole levels decreased by day 42 in the Tween treatment group. Importantly, there was no difference in growth rate between the control and experimental groups. We conclude that adding AC or Tween to finishing diets for boars can reduce the levels of plasma and fat AND, but further work is needed to confirm the effects of these treatments on reducing fat skatole levels.

Differences in testosterone, androstenone, and skatole levels in plasma and fat between pubertal purebred Duroc and Landrace boars in response to human chorionic gonadotrophin stimulation

The concentrations of the boar taint compounds androstenone and skatole in plasma and fat, together with those of testosterone in plasma, were investigated in pubertal purebred Duroc and Landrace boars following stimulation with human chorionic gonadotrophin (hCG). Higher initial levels of androstenone and testosterone were found in Duroc than Landrace boars. Duroc boars, which were approximately ten days older than the Landrace boars, also showed a more advanced stage of spermatogenesis than Landrace boars. While Landrace boars had the highest skatole levels. Following stimulation with hCG the relative increases in testosterone, androstenone, and skatole concentrations were highest in Landrace boars. The level of androstenone in fat three days after hCG stimulation exceeded 1 μg/g fat in all stimulated boars. The decreases in plasma levels of androstenone and testosterone on Days 2 and 3 after hCG stimulation were more pronounced in Landrace than Duroc boars. However, unlike the plasma androstenone and testosterone levels, the plasma concentrations of skatole did not decrease on Days 2 and 3 following stimulation, but remained elevated on Day 3. These results indicate that the lower levels of testicular steroids in Landrace boars compared with Duroc boars was not due to a lower production capacity, but more likely to a faster dissapearance of steroids in Landrace boars. In the present study, age, live weight, and testicular development did not significantly contribute to the variation in fat androstenone. The present data and previous reports on candidate genes related to androstenone biosynthesis and metabolism suggests that future selection against factors associated with boar taint remains a possible solution for the problem of boar taint in the swine industry.

Transcript profiling of candidate genes in testis of pigs exhibiting large differences in androstenone levels

BackgroundBoar taint is an unpleasant odor and flavor of the meat and occurs in a high proportion of uncastrated male pigs. Androstenone, a steroid produced in testis and acting as a sex pheromone regulating reproductive function in female pigs, is one of the main compounds responsible for boar taint. The primary goal of the present investigation was to determine the differential gene expression of selected candidate genes related to levels of androstenone in pigs.ResultsAltogether 2560 boars from the Norwegian Landrace and Duroc populations were included in this study. Testicle samples from the 192 boars with most extreme high or low levels of androstenone in fat were used for RNA extraction, and 15 candidate genes were selected and analyzed by real-competitive PCR analysis. The genes Cytochrome P450 c17 (CYP17A1), Steroidogenic acute regulatory protein (STAR), Aldo-keto reductase family 1 member C4 (AKR1C4), Short-chain dehydrogenase/reductase family member 4 (DHRS4), Ferritin light polypeptide (FTL), Sulfotransferase family 2A, dehydroepiandrosterone-preferring member 1 (SULT2A1), Cytochrome P450 subfamily XIA polypeptide 1 (CYP11A1), Cytochrome b5 (CYB5A), and 17-beta-Hydroxysteroid dehydrogenase IV (HSD17B4) were all found to be significantly (P < 0.05) up-regulated in high androstenone boars in both Duroc and Landrace. Furthermore, Cytochrome P450 c19A2 (CYP19A2) was down-regulated and progesterone receptor membrane component 1 (PGRMC1) was up-regulated in high-androstenone Duroc boars only, while CYP21 was significantly down-regulated (2.5) in high-androstenone Landrace only. The genes Nuclear Receptor co-activator 4 (NCOA4), Sphingomyrlin phosphodiesterase 1 (SMPD1) and 3β-hydroxysteroid dehydrogenase (HSD3B) were not significantly differentially expressed in any breeds. Additionally, association studies were performed for the genes with one or more detected SNPs. Association between SNP and androstenone level was observed in CYB5A only, suggesting cis-regulation of the differential transcription in this gene.ConclusionA large pig material of highly extreme androstenone levels is investigated. The current study contributes to the knowledge about which genes that is differentially expressed regard to the levels of androstenone in pigs. Results in this paper suggest that several genes are important in the regulation of androstenone level in boars and warrant further evaluation of the above mentioned candidate genes, including analyses in different breeds, identification of causal mutations and possible gene interactions.

Testicular germ cell development in relation to 5α-Androstenone levels in pubertal entire male pigs

Androstenone is a 16-androstene steroid pheromone produced in the Leydig cells in the testis, and considered to be one of the major compounds responsible for boar taint. In entire male pigs, progress of sexual maturation has been related to an increase in androstenone levels in fat. Onset of puberty and subsequent reproductive function involves genetic factors affected by the internal and external environment. In this study entire male cross-bred pigs were housed under two different light regimens in order to manipulate the onset of puberty. DNA flow cytometry (FCM) was used to study spermatogenesis and monitor the proportions of haploid (1n), diploid (2n), and tetraploid (4n) testicular cells, with conventional histological evaluation used as the reference technique. Agreement between these two methods was found to be good. The best fit model explained 34% of the variation in the androstenone concentrations. Sexual maturation in boars of 125-146 days of age, as assessed by DNA FCM, was not significantly associated with the variation in androstenone concentrations in adipose tissue when various independent variables (breed, age, light strategy, skatole concentrations in fat, and length of the bulbourethralis glands) were included in this model. These findings support the suggestion that selection against androstenone may be an option in the breeding of entire male pigs.

The effect of a c.‐8G&gt;T polymorphism on the expression of cytochrome b5A and boar taint in pigs

The level of cytochrome b5A (CYB5A) in pig testis is correlated with boar taint from androstenone and an AF016388:c.-8G>T polymorphism in CYB5A has been linked with low androstenone levels in the fat of pigs. In this study, we developed a polymerase chain reaction-based assay to genotype 1242 boars from eight lines for the c.-8G>T SNP. The c.-8T allele was found in all eight lines at a frequency ranging from 1.8% to 20.3% with an overall frequency of 8.6%. Significant deviations from Hardy-Weinberg equilibrium were found in the Hampshire, Landrace and Yorkshire breeds. The homozygous mutant c.-8TT occurred infrequently and was not found in some lines, but was consistently associated with low androstenone levels in fat. Both CYB5A mRNA and CYB5A protein levels were decreased in the c.-8TT genotype in a subset of Yorkshire boars, suggesting that low levels of CYB5A protein in the c.-8TT mutant were not due to inefficient translation of CYB5A mRNA. There were significant but modest marker effects on fat androstenone levels in Landrace, Yorkshire and a Large White/Duroc cross and fat skatole in Duroc and Sire Line breeds. There was no effect of CYB5A genotype on bulbourethral gland length, suggesting that this SNP will not affect reproductive traits. We conclude that the c.-8G>T SNP in the CYB5A gene has a significant but modest effect on boar taint in male pigs and could be useful in some breeds as part of a panel of SNP markers in a marker-assisted selection programme to produce low boar taint pigs.

Effect of polymorphism in the porcine cytochrome b5 (CYB5A) gene on androstenone and skatole concentrations and sexual development in Swedish pig populations

The present study investigated the presence of a single-nucleotide polymorphism (G > T) at base −8 upstream of ATG in 5′ untranslated region of cytochrome b5 (CYB5A) gene in Swedish pig populations and evaluated the significance of this polymorphism for androstenone and skatole levels, sexual development and performance parameters in pigs. Frequencies of the T allele were 6.7% for Swedish Yorkshire × Landrace crossbred pigs (n = 245), 6.5% for Swedish Yorkshire (n = 99) and 12.8% for Landrace breed (n = 74). No deviations from Hardy–Weinberg equilibrium were observed in the investigated populations. In Swedish Yorkshire × Landrace crossbred entire male pigs (n = 193), plasma samples were analysed for skatole, androstenone, testosterone and oestrone sulphate, and fat samples were analysed for androstenone, skatole and free oestrone. Additionally, testis weight and bulbourethral gland length for crossbred pigs were recorded. Plasma androstenone levels were significantly lower in the G/T genotype at 90 kg live weight compared with the wild G/G genotype at the same live weight (P = 0.006). In heavier pigs, plasma androstenone levels did not differ between genotypes (P = 0.382). Fat androstenone levels were not affected by CYB5A genotype (P = 0.252). Skatole levels in the G/T genotype at 115 kg live weight were lower compared with those in the G/G genotype in plasma (P = 0.048) and fat (P = 0.028), although no differences were observed in lighter pigs. Testis weight, bulbourethral gland length, testosterone and oestrone sulphate levels in plasma, and oestrone levels in fat were not affected by genotype. We concluded that the presence of the T allele in the CYB5A gene resulted in lower androstenone levels in plasma, and lower skatole levels in fat and plasma; this reduction, however, was dependent on the live weight of the animals. Reproductive hormones and growth rate did not differ between the pigs of different genotypes, whereas a higher lean meat content was found in the G/T genotype in comparison with the G/G genotype. The practical application of those results in Sweden is doubtful because of lack of the effect on androstenone in fat and the low frequency of the T allele in the studied Swedish pig populations.

Development and validation of a method for simultaneous analysis of the boar taint compounds indole, skatole and androstenone in pig fat using liquid chromatography–multiple mass spectrometry

Boar taint in entire male pigs remains a problem for fresh pork production. Since castration of pigs will be prohibited in the future on animal welfare reasons, attempts are made to detect boar taint pre and post mortem. Post mortem techniques focus on simultaneous quantification of the three boar taint substances by one simple and reliable method. In this study a liquid chromatographic multiple mass spectrometric (LC–MS n ) method has been developed and validated for the simultaneous determination of indole (2,3-benzopyrrole, ID), skatole (3-methylindole, SK) and androstenone (5α-androst-16-en-3-one, AEON) in pig fat samples. Sample preparation was kept as short as possible, since a single extraction method for structurally different indols and steroids was seeked after. Analytes were extracted from the fat matrix by methanol and clean-up consisted of freezing the extract in liquid nitrogen followed by a filtration step. The analytes were chromatographically separated on a Symmetry C 18 column. Recoveries for ID, SK and AEON, as calculated from fortified fat samples using 2-methylindole (2-MID) as internal standard, were 96, 91 and 104%, respectively. However, matrix interferences were encountered determining the androstenone levels in fat. Linearity, determined in fat samples, was in the range of 50–1600 μg kg −1 for the indolic compounds and 125–2000 μg kg −1 for the steroid AEON. The correlation coefficients ( R 2) of the calibration curves were 0.998 for ID, 0.997 for SK and 0.810 for AEON.

Long-term effect of vaccination against gonadotropin-releasing hormone, using Improvac™, on hormonal profile and behaviour of male pigs

The objective of this study was to evaluate the long-term effect of a gonadotropin-releasing hormone (GnRH) vaccine, Improvac (Pfizer Ltd.), on the levels of GnRH antibodies, testosterone, estrone sulphate (E1S) and androstenone, as well as skatole and indole in male pigs. Additionally, the long-term effect of immunocastration on social and sexual behaviour was studied. Male pigs were assigned to two treatment groups: a treatment group given two doses of Improvac ( n = 12) and a control group of entire male pigs ( n = 12). The pigs were kept either 16 or 22 weeks after vaccination. Blood samples were collected five or six times; prior to both first and second vaccination, then three or four times during the 16 or 22 week period after second vaccination. Immunocastration significantly reduced levels of testosterone and E1S in plasma, and levels of androstenone in fat ( P < 0.001 for all). Skatole and indole levels in plasma and fat were also lower in immunocastrated pigs than in entire male pigs. These effects lasted up to 22 weeks after the second vaccination. Testis weight and bulbourethral gland length were lower in immunocastrated pigs at slaughter and these pigs showed less social, manipulating and aggressive behaviour than entire male pigs. The immunocastrated pigs remained sexually inactive throughout the study. Our study represents a further step in the evaluation of the effectiveness of Improvac as an alternative to surgical castration of entire male pigs. It shows that Improvac may have an extended effect compared with that currently implied by the directions for use.