Boar Taint Research Articles

230 The relationship between hormone status and the metabolism of androstenone and skatole in isolated porcine hepatocytes

Abstract Surgical castration is a significant welfare concern within the swine industry; however, it is currently the most effective method to prevent boar taint, which is a meat quality issue that develops in entire male pigs due to the accumulation of androstenone and skatole in the fat. Metabolism of the boar taint compounds occurs within the liver and promotes their excretion, ultimately reducing the extent of their accumulation in the fat. Previous research has demonstrated that plasma concentrations of estrone sulfate (E1S), which are indicative of steroid hormone status in the boar, are highly variable between individual animals of similar live body weights at slaughter. Testicular steroids are known to influence the activity and expression of some enzymes regulating the metabolism of skatole, but the effect of hormone concentrations on the entire expression profile of enzymes responsible for boar taint metabolism has not been characterized. Therefore, the objective of this study was to relate plasma E1S concentrations at slaughter to expression levels of genes regulating the metabolism of androstenone and skatole and their respective metabolite profiles in isolated hepatocytes, to further characterize the relationship between hormone status and boar taint metabolism. Blood and liver samples were collected from 5-mo-old crossbred [(Yorkshire x Landrace) x Duroc] boars (n = 8)] at slaughter. Plasma E1S concentrations were quantified using a radioimmunoassay and gene expression in the liver was evaluated by RT-qPCR. Hepatocytes were also isolated and incubated with androstenone or skatole, with metabolite concentrations in the incubation media quantified by high-performance liquid chromatography. Statistical analysis was performed using Pearson correlation. Plasma E1S concentrations at slaughter ranged from 2.2-108.5 ng/mL and were positively correlated with overall skatole metabolism (r = 0.77, P = 0.0265), the production of the Phase I skatole metabolites 3-methyloxindole (3MOI; r = 0.80, P = 0.0183), and 3-hydroxy-3-methyloxindole (HMOI; r = 0.73, P = 0.0413), as well as expression levels of CYP2C33 (r = 0.88, P = 0.0042), CYP2C49 (r = 0.78, P = 0.0221), and CYB5R1 (r = 0.80, P = 0.0165), which regulate skatole metabolism. A strong positive relationship was also identified between overall skatole metabolism and the production of 3MOI (r = 0.96, P = 0.0001) and HMOI (r = 0.93, P = 0.001). Androstenone metabolism primarily resulted in the production of Phase II glucuronide metabolites, but the levels produced were not related to E1S concentrations or gene expression levels. Taken together, these results demonstrate that plasma E1S concentrations are related to the rate of skatole, but not androstenone, metabolism in mature boars. Additional research is required to assess the potential of E1S concentrations as a biomarker for the rate of skatole metabolism in vivo and establish thresholds that could be used to identify boars with high and low rates of metabolism. This may provide an opportunity to develop targeted treatments for boar taint based on the metabolic status of the animal.

469 Reducing crude protein levels with amino acid supplementation in the finishing diets of heavy Duroc sire line pigs: Effects on carcass and meat traits in males and females

Abstract Nutrition represents 70% of pig production costs, particularly protein; therefore, decreasing protein costs is of capital importance. Reducing crude protein (CP) contents to levels below recommended whilst supplementing with amino acids (AAs) is an interesting strategy to reduce costs without decreasing production performances. It has been conducted essentially in lean genotypes during the growth stage. Few studies address heavy genotypes or sex differences during the finishing period. Our objective is to study carcass and meat (loin) traits of heavy [Duroc X (Landrace X Large-White)] male and female pigs during the finishing stage under a 2% CP reduction with crystalline AA supplementation, hypothesizing that both sexes will be affected equally. In total, 60 males and 60 females, 9 wk old animals were used and allotted in split-sex pens (6 pigs/pen) with water and dry feed ad libitum. At 15 wk of age, when pigs weighed an average of 68 kg, two isoenergetic diets with different CP levels were provided (145 and 125 g CP/kg, control and low-CP) during the last 42 d of fattening. In the low-CP diet, crystalline AAs were added. On last day of the trial, animals weighed 116.5 kg on average and were slaughtered. Hot carcass weights and yields, ham fat thickness, lean meat percentage and boar taint by human nose scoring were determined. Loin samples (one per pen) were used to determine thawing losses, pH, color, Texture Profile Analysis (TPA: hardness, cohesiveness, springiness) and chemical composition (moisture, ash, protein, collagen, fat, and saturated fat). Data were analyzed using the simple least squares models that included dietary treatment and sex and their interaction as fixed effects with the pen as the experimental unit. Carcass weights were greater in control males than in females (91.2 vs 85.7 kg; P < 0.05). No effect of sex or diet was detected on carcass yields, lean contents or ham subcutaneous fat thickness. There was a great impact of sex for loin subcutaneous fat thickness, with males having 7 to 8% greater values in both dietary treatments (P = 0.011). Low-CP females had a greater percentage of carcasses of greater lean content compared with the three other groups (P < 0.05). Boar taint, carcass pH, color traits, chemical analysis and TPA did not differ across diets. A strong dietary influence was noticeable with animals of both sexes in the Low-CP diets having greater fat and saturated fat contents than animals in the control groups (P = 0.02). In conclusion, the 20g/kg CP reduction supplemented with AAs can efficiently be used in heavy Duroc sire line genotype during the finishing phase without leading to major impairments in carcass or meat traits, regardless of sex.

505 Utilizing porcine hepatocyte cultures to test the effect of short chain fatty acids on androstenone metabolism

Abstract Boar taint is an off-putting odor found in the meat of entire male pigs due to the accumulation of androstenone and skatole in the fat. Development of boar taint is dependent on the balance between the rate of synthesis and metabolism of these compounds. Prior studies have shown that feed ingredients high in fermentable carbohydrates, including chicory root, sugar beet pulp, and Jerusalem artichoke decreased the synthesis of skatole in the hindgut and altered the metabolism in the liver, resulting in a skatole concentrations comparable with castrated males. However, the mechanism of how these dietary fermentable carbohydrates affect liver metabolism is not well understood. Metabolism of boar taint compounds takes place in a two-phase process, regulated by various enzymes and cytochrome families. Short-chain fatty acids (SCFAs) are produced from the microbial fermentation of fiber and have been shown to have regulatory effects on histone deacetylases and gene expression in humans, providing a potential mechanism in which feed high in dietary fiber reduces boar taint. The purpose of this study was to assess if SCFA directly affect the metabolism of androstenone in liver hepatocytes. Primary hepatocytes were isolated from the liver of 6 [(Yorkshire x Landrace) x Duroc] boars weighing around 90 kg. Cells were treated in triplicate with acetate, butyrate, propionate, and various combinations for 24 h to alter gene expression. Two sets of wells acted as a control, not being treated with SCFAs. The cells were then incubated with androstenone for 3 h, and media was extracted, and metabolite production was analyzed using high-performance liquid chromatography. The effects of treatments were using a one-way ANOVA with a Dunnet’s adjustment for multiple comparisons to a control. Results showed the combined acetate, butyrate, and propionate treatment had the greatest effect on androstenone glucuronide production when compared with the control, resulting in significant increases (P < 0.05) ranging from 82 ± 1.6% to 1 ± 2.4% in individual boars. Other treatments had a similar effect, significantly increasing the production of androstenone glucuronide but to a lesser degree. Butyrate increased production ranging from 40 ± 2.2% to 5±1.5% (P < 0.05), propionate from 38 ± 3.6% to 3 ± 2.6% (P < 0.05), acetate and butyrate from 61±3.9% to 1 ± 2.8% (P < 0.05), acetate and propionate from 70±3.5% to 5±1.7% (P < 0.05), and butyrate and propionate from 82 ± 2.5% to 4 ± 1.1% (P < 0.05) when compared with the control. In conclusion, this trial provided evidence that SCFAs produced by the microbial fermentation of fiber can significantly increase hepatic androstenone metabolism in some animals, with a wide range in these effects among individual boars. Future research will involve assessing the effects of SCFAs on hepatic skatole metabolism.

PSVIII-13 A comparison of biochar and activated charcoal as feed additives to prevent boar taint

PSVIII-13 A comparison of biochar and activated charcoal as feed additives to prevent boar taint

Organic rearing of non-castrated male pigs: welfare indicators, carcass traits, pork quality and boar taint in Duroc and Pietrain crossbreds

The main principles of organic farming as presented by the European organisation for organic food and farming are health, ecology, fairness and care, but the intrinsic quality of products is also important for consumers. Pig genotype was tested as a lever to improve animal welfare and pork quality (meat tenderness, processing ability) of organic, non-castrated males while controlling the risk for boar taint. Non-castrated Large White × Duroc (D, n = 47) or Large White × Pietrain NN (P, n = 34) males were involved in two batches, each including one group of pigs per genotype. Each group was reared in a pen from the same building on deep straw bedding (1.3 m2/pig), with a feeding zone (0.2 m2/pig) and an outdoor area (1.0 m2/pig), from 28 kg BW until slaughter at ca. 125 kg BW. All pigs received ad libitum the same growing and finishing diets, and hay. Overall, health and welfare indicators showed few problems, but the proportions of pigs with skin scratches, and tail lesions at the end of the finishing period, were lower in D than in P pigs (P < 0.05). Growth rate and final BW did not differ between genotypes. The D pigs had lower carcass lean meat content (P < 0.001) and relative proportions of ham and loin (P ≤ 0.01), and higher proportions of belly and backfat (P ≤ 0.001) than P pigs. Compared to P, loin (Longissimus muscle) of D pigs was less light and exudative and had higher chroma (P < 0.05), but pH 24 h and glycolytic potential did not differ. Loin meat of D pigs had higher intramuscular fat content (P < 0.001) and tended to have a lower shear force (P = 0.09), but cooking loss did not differ. In the ham muscles, D pigs had higher chroma than P pigs in the Gluteus medius, whereas pH 24 h did not differ in the Gluteus medius and Semimembranosus. D pigs had higher backfat concentrations of androstenone (P < 0.001), and skatole and indole (P < 0.05) than P pigs, suggesting a higher risk of rejection by consumers due to boar taint. However, only one D carcass was detected as tainted by human nose test. Altogether, organic farming of non-castrated Duroc crossbred males appears to be favourable for animal welfare, technological and several sensory pork properties provided that the risk of undesirable odours is limited through management practices.

90. Carcass characteristics and boar taint in entire male pigs from organic farms

90. Carcass characteristics and boar taint in entire male pigs from organic farms

88. Effect of adding lucerne to the diet and additional straw bedding on the welfare of pigs and the risk of boar taint in organic farming

88. Effect of adding lucerne to the diet and additional straw bedding on the welfare of pigs and the risk of boar taint in organic farming

4. Genetic study of the use of a human nose panel as phenotypes to detect boar taint

4. Genetic study of the use of a human nose panel as phenotypes to detect boar taint

Development of a highly reproducible GC-HRMS method for determination of Skatole in pig tissues

This study presents a sensitive and reproducible mass spectrometry method for quantifying skatole in porcine adipose tissue, muscle, and serum samples applicable for abattoirs and laboratories. Leveraging gas chromatography-high-resolution Orbitrap microscopy and microwave-assisted liquefication of the adipose tissue, the method demonstrates robust performance across key parameters. Impressive linearity (R2) values of 0.9999 and 0.9996 for adipose tissue and serum, respectively. Notably, the method exhibits a low Limit of Detection (LoD) of 0.5 ppb for adipose tissue and 0.9 ppb for serum, with corresponding Limits of Quantification (LoQ) at 1.65 ppb and 3.04 ppb, respectively. The method showed significant reproducibility of 5.9% and repeatability (RSD%) of 8.78% for adipose tissue and 4.08% for serum, with recovery rates of 90% and 87%, respectively. This streamlined method offers promising, effective quantification of boar taint compounds, emphasizing its sensitivity and reproducibility.

Hepatic Gene Expression and Metabolite Profiles of Androstenone and Skatole Relative to Plasma Estrone Sulfate Levels in Boars.

Testicular steroids can alter the activity and expression of enzymes within the liver and may influence the metabolism of skatole and androstenone, which are responsible for boar taint. Plasma levels of estrone sulfate (E1S) are indicative of the steroidogenic capacity of the boar and are variable between animals of similar live weights at slaughter. This study aimed to characterize the relationship between steroidogenic capacity and the metabolism of boar taint compounds by relating plasma E1S levels at slaughter weight to the expression levels of genes regulating the metabolism of androstenone and skatole, along with their respective metabolite profiles. RT-qPCR was used to evaluate gene expression in the liver. Hepatocytes were also isolated and treated with androstenone or skatole, with metabolite levels in the incubation media quantified by high-performance liquid chromatography. Plasma E1S levels ranged from 2.2-108.5 ng/mL and were positively correlated with overall skatole metabolism (p = 0.038), the production of metabolites 3-methyloxindole (p = 0.026) and 3-hydroxy-3-methyloxindole (p = 0.036), and expression levels of key genes involved in skatole metabolism, specifically CYP2C33 (p = 0.0042), CYP2C49 (p = 0.022), and CYB5R1 (p = 0.017). There was no association between androstenone metabolism and plasma E1S concentrations; however, there was evidence of possible co-regulation amongst genes involved in the metabolism of androstenone, skatole, and estrogens. These findings indicate that steroidogenic capacity is related to the rate of skatole, but not androstenone metabolism, in slaughter-weight boars.

Enhanced HPLC Method for Boar Taint Quantification.

Boar taint is an unpleasant odour found in the carcasses of entire male pigs, resulting from androstenone and skatole accumulation during pubertal development, and impacting pork quality. This study proposes the validation of an adapted chromatographic method for quantifying skatole and androstenone in the pigs' liquid fat using fluorescence detection. A good chromatographic separation was achieved, with skatole (SKA) and androstenone (AND) elution at 4.4 and 9.9 min., respectively. An external calibration method was applied, with calibration curves correlation coefficient of 0.9999 for both analytes. Detection limit values were 1.53 and 16.02 ng/g for SKA and AND, respectively. SKA recovery was 99.72±2.34 % (2.34 % RSD) and 102.84±1.62 % (1.57 % RSD) for AND. Results showed good precision values (repeatability <2.46 % RSD for SKA, <6.85 % RSD for AND; intermediate precision <2.87 % RSD for SKA, <6.98 % RSD for AND). The method's robustness was tested and the values were within the reference ranges. The validation results proved that the adaptation of an existing method resulted in good assessments of robustness, reliability and accuracy.

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.

The Effect of the Boar Taint Masking Strategy (Adding Dried Origanum vulgare or Allium sativum) on Sensory Characteristics.

With increasing efforts to ban surgical castration, it is important to find ways to mask the level of boar taint in meat. The aim of this study was to test the possibility of masking boar taint or skatole levels by adding dried Origanum vulgare or Allium sativum and to evaluate consumer sensory preferences towards the skatole concentration in different carcass parts (longissimus lumborum; semimembranosus; neck chop and subcutaneous fat) and the masking strategy (addition of Allium sativum or Origanum vulgare). In the first experiment, the effect of the masking strategy was evaluated at three different skatole concentrations (0.069, 0.269 and 0.463 µg/g). The results showed that the samples with low and medium skatole levels were significantly different between the control group and the groups treated with Origanum vulgare or Allium sativum. In both cases, the addition of Allium sativum and Origanum vulgare had a positive effect on the parameters of abnormal odour and pleasantness of odour (p < 0.05). According to the results of the second experiment, meat samples from leaner parts, such as the neck chop semimembranosus and longissimus lumborum, not treated with Allium sativum and Origanum vulgare for masking, were significantly (p < 0.05) worse in terms of the occurrence of boar taint or abnormal odour than the masked samples. No significant differences were found between the two masking methods.

PSII-2 Effect of piglet processing and castration on growth performance in feeder pigs

Abstract Early in life castration in swine is a common practice to improve muscle and fat deposition and avoid “boar taint”, which is caused by production of androsterone and skatole within the intact male. The objective of this study was to evaluate the effect of performing piglet processing and castration on the same day compared with a 2-d protocol processing on d 1 and castrating on d 7. To determine the effect of processing protocol on subsequent growth in piglets, 42 piglets were randomly assigned at birth to one of two processing protocols: d 3 processing (“early”) or d 1 and d 7 processing (late). For both castration dates, males were castrated using the open method of castration. A sterile scalpel blade was used to make two vertical cuts posterior to each testicle before complete removal of each testicle. Both male and female piglets were assigned to a processing protocol, but only male piglets underwent castration as a sterility procedure. Females on the same processing protocol were subject to similar processing methods and vaccinations but were not sterilized. Body weights were collected on all piglets at d 1, 3, 7, 14, 21, 28 (weaning), and 56. For males, vocalization during the castration procedure was also recorded and analyzed along with growth and performance measures. At weaning (d 28), the early castrated barrows group weighed significantly more than the late castrated barrows; however, there were no significant differences in the body weight at weaning for the early group (males + females) as a whole compared with the late group (males + females) as a whole. This indicates that while males benefited from an early castration and were able to gain more body weight during the pre-weaning phase when processing occurred on d 3 rather than on d 1 and 7, females undergoing two processing dates gained less body weight between birth and weaning.

23 The effects of dietary net energy level on grow-finish performance and carcass characteristics of intact male market pigs managed with Improvest

Abstract Improvest is a gonadotropin releasing factor (GnRF) analogue-diphtheria toxoid conjugate product approved for temporary suppression of testicular function and reduction of boar taint in intact male pigs (Zoetis Canada Inc.). Objectives for this study were to determine the effects of dietary net energy (NE) level during the grow-finish period on live performance and carcass characteristics of intact male pigs managed with Improvest/immunological castration (IC) when compared with physically castrated (PC) male pigs. The 101-d study began when 1,008 pigs (504 intact male pigs and 504 PC male pigs; 10 wk old) were allocated by body weight to 48 pens with 21 intact males or 21 PC males per pen. Three dietary NE treatments were fed to pigs using five dietary phases to provide an average of 2,212 kcal/kg (Low NE), 2,337 kcal/kg (Medium NE), or 2,462 kcal/kg (High NE). Dietary programs were formulated according to standardized ileal digestible lysine requirements of IC males or PC males. The experiment was designed and analyzed as a 2 × 3 factorial with main effects of Improvest management and NE. For the overall study period, there were no significant interactions between Improvest management and NE (P ≥ 0.19) for average daily feed intake (ADFI), average daily gain (ADG), or gain to feed ratio (G:F; Table). There were also no significant interactions between Improvest management and NE (P ≥ 0.06) for carcass characteristics. Immunologically castrated male pigs consumed less feed (5.3% less ADFI; P &amp;lt; 0.01), grew faster (5.1% greater ADG; P &amp;lt; 0.01), and were more efficient (11.2% greater G:F; P &amp;lt; 0.01) compared with PC male pigs. Hot carcass weight (HCW) did not differ (P = 0.16) between IC males and PC males (attributed to 1.6 percentage unit less dressing percentage for IC males; P &amp;lt; 0.01); however, IC males were leaner (0.9 mm less backfat and 0.65% greater predicted lean yield; P &amp;lt; 0.01) compared with PC males. For the overall study period, pigs fed Low NE and Medium NE diets consumed more feed than pigs fed High NE diets, and pigs fed Low NE diets grew slower than pigs fed Medium NE and High NE diets. This resulted in pigs fed Low NE diets having 4.4% less G:F than pigs fed Medium NE and 8.6% less G:F than pigs fed High NE diets (P &amp;lt; 0.01). Pigs fed Low NE had 3.0 kg lighter (P &amp;lt; 0.01) HCW compared with Medium NE, while High NE had intermediate HCW that did not differ from the other two treatments. Overall, typical Improvest response levels were sustained for each of the NE treatments in this study; however, consideration should be provided to the known production impacts of low NE diets when male market pigs are managed with Improvest.

Spiced-marinating injection brine effect on the entire pork quality

Searching for new alternatives to commercialize pork from entire male pigs that could be affected by a boar taint sensory defect would be adequate. In this study, two different marinade mixtures (additives, salt, white wine plus different spices for mixture 1 and 2) were injected into pork loin pieces from castrated (C1 and C2) and entire male pigs (E1 and E2) with a high boar taint level (5.51 µg.g−1 AND and 0.73 µg.g−1 SKA) to evaluate their effect on the physicochemical and sensory quality of pork, and to assess their boar taint masking properties. To achieve this, physicochemical and sensory analyses with trained panellists were carried out. Marinated meat showed some differences in colour and a reduction in cooking losses. Mixture 2 achieved the best boar taint masking effect, due to spices content mainly nutmeg and ginger, and other ingredients such as white wine. In conclusion, marinating pork from entire male pigs can contribute to achieving an acceptable quality standard.

Heavy Pigs Reared for Italian Dry-Cured Products: Does Immunocastration Influence the Fatty Acid Profile of Loins and Backfat?

The Italian pig sector requires heavy pigs (raised for at least nine months and slaughtered at >160 kg). In order to avoid boar taint and lower the impact on welfare, immunocastration provides an alternative to surgical castration. This study investigated the effects of immunocastration compared to surgical castration on the chemical composition and fatty acid profile of loins (longissimus dorsi muscle) and adipose tissue in Italian heavy pigs raised for dry-cured ham. Twenty-four male pigs were subjected to surgical castration (n = 12) or immunocastration (n = 12). Carcass parameters were monitored at slaughter, and samples of longissimus dorsi muscle and subcutaneous fat were analysed. This study showed no significant differences in carcass characteristics and proximate composition of fresh meat. However, variations were observed in the fatty acid profiles of meat and adipose tissue between groups. Notably, saturated fatty acids, particularly stearic acid (18:0), were higher in the intramuscular fat (IMF) of the immunocastrated pigs compared to the surgically castrated pigs. Conversely, monounsaturated fatty acids, predominantly oleic acid (18:1n-9), were higher in the IMF from the surgically castrated pigs compared to the immunocastrated pigs. While immunocastration may offer benefits in terms of animal growth and carcass composition, it could lead to unfavourable lipid changes in fresh loin meat for Italian heavy pigs.

Effect of SNPs in the Promoter Region on the Expression of Cytochrome P450 2E1 (CYP2E1) in Pig Liver.

Boar taint, an unfavorable odor in the meat of intact male pigs, is caused primarily by the accumulation of two compounds: androstenone and skatole. This multifactorial trait is regulated by numerous dietary, management and genetic factors. At the mechanistic level, there are many genes known to be involved in boar taint metabolism. Cytochrome P450 2E1 (CYP2E1) impacts boar taint through the phase I metabolism of skatole. The aim of this study was to identify single-nucleotide polymorphisms (SNPs) within the CYP2E1 gene promoter and explore their relationship with the expression of CYP2E1 mRNA and protein. Sequencing of the promoter region using pools of genomic DNA identified seven promoter region SNPs at -159, -586, -1693, -1806, -2322, -2369 and -2514 bp upstream of the ATG start site. Genomic DNA was obtained from 65 boars from the three major swine breeds: Duroc, Landrace and Yorkshire, and individual animals were genotyped for the identified SNPs. RNA was isolated from liver tissue and quantitative PCR was performed to measure CYP2E1 gene expression, while levels of CYP2E1 protein in liver were measured by Western blotting. Significant within-breed variation in CYP2E1 protein and mRNA expression was observed, indicating significant differences in gene expression among individuals. However, levels of CYP2E1 mRNA and protein were not significantly correlated. Two SNPs within the promoter were significantly associated with CYP2E1 mRNA expression, but not with protein expression. This study provides evidence of additional mutations affecting the gene expression of CYP2E1 and suggests that factors that affect the differences in translation of CYP2E1 mRNA may also be important in affecting skatole metabolism.

Differential Regulation of Male-Hormones-Related Enhancers Revealed by Chromatin Accessibility and Transcriptional Profiles in Pig Liver.

Surgical castration can effectively avoid boar taint and improve pork quality by removing the synthesis of androstenone in the testis, thereby reducing its deposition in adipose tissue. The expression of genes involved in testis-derived hormone metabolism was altered following surgical castration, but the upstream regulatory factors and underlying mechanism remain unclear. In this study, we systematically profiled chromatin accessibility and transcriptional dynamics in liver tissue of castrated and intact full-sibling Yorkshire pigs. First, we identified 897 differentially expressed genes and 6864 differential accessible regions (DARs) using RNA- and ATAC-seq. By integrating the RNA- and ATAC-seq results, 227 genes were identified, and a significant positive correlation was revealed between differential gene expression and the ATAC-seq signal. We constructed a transcription factor regulatory network after motif analysis of DARs and identified a candidate transcription factor (TF) SP1 that targeted the HSD3B1 gene, which was responsible for the metabolism of androstenone. Subsequently, we annotated DARs by incorporating H3K27ac ChIP-seq data, marking 2234 typical enhancers and 245 super enhancers involved in the regulation of all testis-derived hormones. Among these, four typical enhancers associated with HSD3B1 were identified. Furthermore, an in-depth investigation was conducted on the androstenone-related enhancers, and an androstenone-related mutation was identified in a newfound candidatetypical enhancer (andEN) with dual-luciferase assays. These findings provide further insights into how enhancers function as links between phenotypic and non-coding area variations. The discovery of upstream TF and enhancers of HSD3B1 contributes to understanding the regulatory networks of androstenone metabolism and provides an important foundation for improving pork quality.

An overlooked compound contributing to boar taint and consumer rejection of meat products: 2-Aminoacetophenone

Mainly skatole and androstenone have so far been considered causative for boar taint. Using a mixed methods approach it is shown herein that 2-aminoacetophenone (AAP) affects human perception of pork, too. We explored the importance of AAP in four trials: (1) chemical analyses of 221 fat samples from boar carcasses revealed that AAP occurs, on average, in similar quantities as skatole while the levels of androstenone being four-fold. (2) ranking tests with mixtures of androstenone and/or skatole with AAP presented on smell strips to trained sensory assessors showed that AAP amplifies boar odour. In order to study AAP's importance in meat products, four experimental variants of Lyon type sausage were then produced: a control, a product with added skatole (0.075 μg/g fat tissue), with added AAP (0.075 μg/g fat tissue), and with addition of both compounds. (3) results of a consumer discrimination test panel (n = 71) showed that, when added to a sausage system, APP causes a sensory difference of similar size as skatole while the methodology chosen affects the effect size: tetrad tests proved to be more sensitive than duo trio difference tests, in the tetrad test a sensory difference expressed as d’ (d-prime) of 1.0 was reached. (4) a hedonic consumer test (n = 121) finally revealed that APP decreased consumer liking of the APP-spiked sausage - even to a stronger extent than skatole. APP caused significant drops in smell, taste, mouth-feel, after-taste and overall liking in Lyoner.Overall the findings suggest that, in the context of pork meat, AAP is of similar olfactory importance as skatole.