Mechanistic insight into the role of immunocastration on eliminating skatole in boars

Effects of dietary selenized glucose on intestinal microbiota and tryptophan metabolism in rats: Assessing skatole reduction potential

3-Methylindole (Skatole), a degradation product of tryptophan produced by intestinal microbial activity, significantly contributes to odor nuisance. Its adverse effects on animal welfare, human health, and environmental pollution have been noted. However, it is still unclear whether the intestinal microbiota mediates the impact of selenium (Se) on skatole production and what the underlying mechanisms remain elusive. A selenized glucose (SeGlu) derivative is a novel organic selenium compound. In this study, a diverse range of dietary SeGlu-treated levels, including SeGlu-deficient (CK), SeGlu-adequate (0.15 mg Se per L), and SeGlu-supranutritional (0.4 mg Se per L) conditions, were used to investigate the complex interaction of SeGlu on intestinal microbiome and serum metabolome changes in male Sprague-Dawley (SD) rats. The study showed that SeGlu supplementation enhanced the antioxidant ability in rats, significantly manifested in the increases of the activity of catalase (CAT) and glutathione peroxidase (GSH-Px), while no change in the level of malonaldehyde (MDA). Metagenomic sequencing analysis verified that the SeGlu treatment group significantly increased the abundance of beneficial microorganisms such as Clostridium, Ruminococcus, Faecalibacterium, Lactobacillus, and Alloprevotella while reducing the abundance of opportunistic pathogens such as Bacteroides and Alistipes significantly. Further metabolomic analysis revealed phenylalanine, tyrosine, and tryptophan biosynthesis changes in the SeGlu treatment group. Notably, the biosynthesis of indole, a critical pathway, was affected by SeGlu treatment, with several crucial enzymes implicated. Correlation analysis demonstrated strong associations between specific bacterial species - Treponema, Bacteroides, and Ruminococcus, and changes in indole and derivative concentrations. Moreover, the efficacy of SeGlu-treated fecal microbiota was confirmed through fecal microbiota transplantation, leading to a decrease in the concentration of skatole in rats. Collectively, the analysis of microbiota and metabolome response to diverse SeGlu levels suggests that SeGlu is a promising dietary additive in modulating intestinal microbiota and reducing odor nuisance in the livestock and poultry industry.

Testosterone regulates thymic remodeling by altering metabolic reprogramming in male rats

The thymus is an energy-consuming organ, and its metabolism changes with atrophy. Testosterone regulates thymus remodeling (atrophy and regeneration). However, the characteristics of the energy metabolism during testosterone-mediated thymic atrophy and regeneration remain unclear. In this study, we demonstrated that testosterone ablation (implemented by immunocastration and surgical castration) induced global metabolic changes in the thymus. Kyoto Encyclopedia of Genes and Genomes pathway enrichment for differential metabolites and metabolite set enrichment analysis for total metabolites revealed that testosterone ablation affected thymic glycolysis, glutamate metabolism, and fatty acid β-oxidation. Testosterone ablation-induced thymic regeneration was accompanied by attenuated glycolysis and glutamate metabolism and changed fatty acid composition and content. Testosterone supplementation in immunocastrated and surgically castrated rats enhanced glutaminolysis, reduced the level of unsaturated fatty acids, enhanced the β-oxidation of unsaturated fatty acids in the mitochondria, boosted the tricarboxylic acid (TCA) cycle, and accelerated thymic atrophy. Overall, these results imply that metabolic reprogramming is directly related to thymic remodeling.

GnRH-immunocastration: an alternative method for male animal surgical castration

Castration of male animals is intended to produce high-enhance quality of animal meat, prevent unpleasant taste, reduce aggressive behavior, and manage overbreeding. Over the years, Tranditional methods of mechanical and surgical castration have been employed over the years, but they fall short of meeting animal welfare requirements due to the associated risk of infection, pain, and stress. Immunocastration, specifically Gonadotropin-releasing hormone (GnRH)-immunocastration, targeting the hypothalamic-pituitary-testis (HPT) axis, has emerged as an animal-friendly alternative to surgical castration, effectively addressing these issues. This review seeks to systematically summarize the principles, development, current applications and challenges of GnRH-immunocastration, offering insights into its role in promoting animal welfare.

Active immunization against gonadotropin-releasing hormone affects thymic T cell production, migration, and colonization in male rat lymphoid tissue

Active immunization against gonadotropin-releasing hormone (GnRH) inhibits animal reproduction and has become a friendly alternative to surgical castration, which has been reported to affect the proportion of thymic T cell subpopulations. The effects of active immunization against GnRH on T cell migration from the thymus to the periphery and T cell distribution in lymphoid tissues remain unclear. Here, we showed that active immunization against GnRH increased thymic size and weight, enlarged the number of thymocytes, and enhanced CD4+ recent thymic emigrants (RTEs) and CD8+ RTEs migration to the blood and spleen. Active immunization against GnRH had no significant effect on naïve CD4+, naïve CD8+, CD4+ memory/activated, or CD8+ memory/activated T cells. In addition, active immunization against GnRH increased the proportion of CD3+ T cells in the spleen and lymph nodes. The percentages of CD3+CD4+ and CD3+CD8+ T cells in the blood, spleen, and lymph nodes were not significantly affected by GnRH immunization. Overall, these results enhance our understanding of thymic T cell production, migration, and colonization in rat lymphoid tissues affected by GnRH immunization.

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

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

Concentrations of Boar Taint Compounds Are Weakly Associated with Sexual Behavior of Young Boars

Strategies to control boar taint (BT) in meat relies on the reduction of skatole, indole, and androstenone concentration. This might have unfavorable effects on the libido of breeding boars. The association between BT compound concentration in backfat and libido was investigated in 391 commercial breeding boars. Six sexual behavior traits (SBT; sexual arousal, salivation, mounting performance, interest in the dummy sow, penis unsheathing, and overall libido score) were scored during the training of the boars with the dummy sow. Variation in SBT was analyzed by proportional-odds cumulative logistic models. Overall, indole, skatole, and androstenone concentrations were weakly associated with libido. Farm of origin, age at training or body weight, and BT compound levels were poor predictors of boar performance (the area under the ROC curve ranged from 0.60 to 0.69). This indicates that BT compound concentrations were weakly associated with libido, even though the probability of observing good SBT scores increased with high levels of androstenone, intermediate or low levels of skatole, and intermediate to high levels of indole. Hence, practices aiming at reducing androstenone, and controlling the concentrations of skatole and indole to intermediate levels are not expected to impair the libido of young boars.

Acute interstitial pneumonia and the biology of 3-methylindole in feedlot cattle

Acute interstitial pneumonia (AIP) of cattle has been recognized for many decades. While the pathogenesis and risk factors for this condition in pastured cattle are relatively well characterized, there remains a poor understanding of the disease as it occurs in intensively fed cattle such as in beef feedlots. Specifically, in pastured cattle, AIP results from excessive ruminal production of the pneumotoxicant 3-methylindole (3-MI). In feedlot cattle, the evidence to substantiate the role of 3-MI is comparatively deficient and further investigations into the cause, pathogenesis, and control are sorely needed. This review highlights our current understanding of AIP with a focus on the disease as it occurs in feedlot cattle. Additionally, it illustrates the need for further work in understanding the specific animal factors (e.g. the ruminal microbiome, and the role of concurrent diseases), management factors (e.g. animal stocking and vaccination protocols), and dietary factors (e.g. dietary supplements) that may impact the development of AIP and which are relatively unique to the feedlot setting. All stakeholders in the beef industry stand to benefit from a greater understanding of what remains a pressing yet poorly understood issue in beef production.

Effect of Castration Type and Diet on Growth Performance, Serum Sex Hormones and Metabolites, and Carcass Quality of Heavy Male Pigs

Simple Summary

Castration is indispensable in male pigs intended for the production of high-quality dry-cured ham; however, for welfare reasons, alternatives are being sought and, among them, immunocastration stands out. The literature shows that immunocastration might generate lower fat deposition than surgical castration, which is undesirable for the dry-curing process. Therefore, it would be interesting to confirm the impact of immunocastration in male pigs and to test feeding plans that benefit fatness. The aim of this trial was to assess the effect of type of castration (surgical vs. immunological) and diet (control vs. high energy vs. low crude protein and amino acids) on growth performance, serum sex hormones and metabolites, and carcass quality of male pigs destined for the Protected Designation of Origin Teruel ham. Although immunocastration improved productive performance, it reduced carcass fatness. Also, alternative diets to control improved the feed conversion ratio but did not influence carcass quality traits. In conclusion, under a quality point of view, surgical castration would be preferable over immunocastration for dry-cured ham production, and the use of moderately high-energy or low-crude-protein and -amino-acids diets from 80 to 137 kg of body weight would not provide improvements.

Abstract

A trial was carried out to study the effect of type of castration and diet on pigs destined for Teruel ham production, which is a Spanish protected designation of origin for dry-cured ham. A total of 144 Duroc × (Landrace × Large White) male pigs were used. Half of them were surgically castrated and the other half were immunocastrated with three doses at approximately 25, 58 and 79 kg of body weight. Furthermore, three diets (control vs. high energy vs. low crude protein-CP- and amino acids-AA) were tested from 80 to 137 kg of body weight. Growth performance, serum sex hormones and metabolites, and carcass quality were evaluated. Immunocastrated males grew faster and had better feed conversion ratio than surgically castrated males, but presented lower carcass fatness. Pigs fed the high-energy diet and the low-CP and -AA diet were more efficient at transforming feed into gain than those fed the control diet, but no effect was detected on carcass quality. In conclusion, surgically castrated males are preferable than immunocastrated males for Teruel dry-cured ham elaboration. Besides, a high-energy diet or a low-CP and -AA diet might improve productive performances, but does not provide any benefit in terms of carcass quality.

Influence of Immunocastration and Diet on Meat and Fat Quality of Heavy Female and Male Pigs

Two experiments were carried out; one with female pigs and the other with male pigs destined for Teruel dry-cured ham production, to evaluate the effect of immunocastration (entire gilts-EG vs. immunocastrated gilts-IG and surgically castrated males vs. immunocastrated males-IM) and diet (control vs. high energy vs. low crude protein and amino acids) on meat quality and fat composition. Fifteen meat samples and eight fat samples of each treatment were analyzed in both experiments. In the case of males, six fat samples per treatment were analyzed to determine boar taint. Immunocastration is a good strategy in gilts intended for dry-cured ham production because improves meat composition; however, in males, immunocastration impairs the results of pork chemical composition compared with surgical castration. The IG presented a lower polyunsaturated/saturated fatty acids ratio than EG, improving fat technological quality. Diets had little effect on pork or fat quality in gilts, but a high-energy level using oilseeds and a low-crude-protein and -amino-acids diet from 80 to 137 kg of body weight could be interesting in IM to maintain or increase fat consistency, respectively. Moreover, in general, immunocastration is effective in avoiding boar taint in males.

Effect of Dietary Supplementation with Dried Tuber of Jerusalem Artichoke on Skatole Level in Backfat and CYP2E1 mRNA Expression in Liver of Boars

The objective of this study was to investigate the effect of diets containing different levels of dried tuber of Jerusalem artichoke, Helianthus tuberosus, on skatole levels in backfat and on the CYP2E1 mRNA expression in the liver of commercial crossbred pigs. A total of 23 uncastrated male pigs from 10 litters of a commercial crossbred population of Large White × (Landrace × Large White), were used in this study. Boars were randomly divided into four different dietary treatment groups – a control group (K1; 5 boars; without supplementation of Jerusalem artichoke) and three experimental groups (6 boars each) that were fed with the diet containing different levels of dried Jerusalem artichoke (K2 – 4.1%; K3 – 8.2%; K4 – 12.2%) for 14 days before slaughter. Significant effects of diet on skatole levels were observed between the control group and the experimental groups (P = 0.0078). The lowest level of skatole was in the K3 group with 8.2% of Jerusalem artichoke. As for CYP2E1, a negative correlation was observed between the levels of skatole and CYP2E1 mRNA expression. Significant effect (P = 0.0055) was found in all experimental groups compared to the K1 group, and most pronounced in the K2 and K3 groups. The supplementation with Jerusalem artichoke resulted in lower level of skatole and higher CYP2E1 mRNA expression. The results suggest that affecting the expression of CYP2E1 by feed supplements could be an option to effectively reduce the levels of skatole in adipose tissue of entire male pigs.

FSH promotes fat accumulation by activating PPARγ signaling in surgically castrated, but not immunocastrated, male pigs

Follicle-stimulating hormone (FSH) was recently implicated as a novel regulator of fat accumulation. Surgical castration causes high FSH concentrations and increases fat accumulation, whereas immunocastration results in low FSH concentrations and less fat in immunocastrated boars versus barrows. However, detailed information regarding the role of FSH in regulation of fat accumulation in male pigs is unclear. First, expression of FSH receptor was confirmed (real-time quantitative PCR) in subcutaneous and visceral adipose tissues (SAT and VAT, respectively) of boars. Then, surgical castration (high FSH model) was compared to immunocastration (low FSH model) to investigate potential roles of FSH in adipogenesis and fat accumulation. High FSH concentrations after surgical castration activated PPARγ signaling by upregulating expression of CREB (P < 0.05), and then recruited an array of PPARγ target adipogenic genes, including transcription factor (C/EBPα), long-chain fatty acid uptake (LPL), fatty acid de novo synthesis (FASN, ACACA) and lipid droplet formation (PLIN1) in both SAT and VAT, promoting fat accumulation in barrows. In contrast, much lower serum FSH concentrations in immunocastrates attenuated (P < 0.05) expressions of PPARγ and PPARγ target genes in both SAT and VAT, resulting in less fat accumulation in immunocastrated boars versus barrows. We concluded that the substantially elevated FSH concentrations in barrows promoted fat accumulation by activating the PPARγ signaling pathway in adipose tissues, whereas immunocastrates accumulated less fat due to low FSH.

On the Road to End Pig Pain: Knowledge and Attitudes of Brazilian Citizens Regarding Castration

We explored the attitudes of Brazilians towards different methods to deal with boar taint in pork (surgical castration without pain control, SC; surgical castration with pain control, SC+PC; immunocastration, IC; raising entire males, EM). Two surveys (Sv1, n = 441 and Sv2, n = 768) containing closed and open questions were conducted. Nearly 70% of Sv1 and Sv2 participants were unaware that meat of entire males may have boar taint and that SC is widely used in pig production in Brazil. In Sv1, acceptability of SC+PC (63%) and IC (53%) was greater than of SC (15%). In Sv2, acceptability of IC (55%) and EM (52%) was greater than of SC (18%). Open-ended responses indicated that participants objected to inflicting pain to pigs to attain a production goal, and were concerned with organoleptic traits and risks of exogenous residues in pork. Participants' views regarding the potential increases in the cost of meat due to adoption of alternative methods varied; some argued that avoiding pain justifies an increase in the price of pork and others that this would impact especially lower income citizens. Our findings indicate that participants opposed surgical castration without pain control, and supported alternative methods. However, the concern with potential risks of presence of residues in meat, expressed by a few participants, may need to be addressed among consumers.

Pork Production with Entire Males: Directions for Control of Boar Taint

Simple Summary

Castration of male piglets has traditionally been carried out to control boar taint, but animal welfare concerns about surgical castration has brought this practice under scrutiny. In addition, castration decreases growth performance and increases the environmental impact of pork production, so alternatives to castration are needed to control boar taint. In this review, we summarize the current knowledge on boar taint metabolism and outline some key areas that require further study. We also describe some opportunities for controlling the boar taint problem and propose that by defining the differences in metabolic processes and the genetic variations that can lead to boar taint in individual pigs, we can design effective custom solutions for boar taint.

Abstract

Boar taint is caused by the accumulation of androstenone and skatole and other indoles in the fat; this is regulated by the balance between synthesis and degradation of these compounds and can be affected by a number of factors, including environment and management practices, sexual maturity, nutrition, and genetics. Boar taint can be controlled by immunocastration, but this practice has not been accepted in some countries. Genetics offers a long-term solution to the boar taint problem via selective breeding or genome editing. A number of short-term strategies to control boar taint have been proposed, but these can have inconsistent effects and there is too much variability between breeds and individuals to implement a blanket solution for boar taint. Therefore, we propose a precision livestock management approach to developing solutions for controlling taint. This involves determining the differences in metabolic processes and the genetic variations that cause boar taint in specific groups of pigs and using this information to design custom treatments based on the cause of boar taint. Genetic, proteomic or metabolomic profiling can then be used to identify and implement effective solutions for boar taint for specific populations of animals.