Effect of caponization and testosterone implantation on hepatic lipids and lipogenic enzymes in male chickens

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.

Effects of Caponization on Growth Performance and Carcass Composition of Yangzhou Ganders

Simple Summary

Goose meat is recognized as one of the healthiest foods. Goose capons are specially bred and consumed in several parts of China for their high-quality meat. However, the effects of caponization on goose growth and carcass traits have remained uninvestigated, and its molecular mechanisms remain unclear. In this research, caponization lowered testosterone and increased the total cholesterol and triglyceride concentrations in serum. Caponization increased live weights by promoting food intake and abdominal fat deposition, and improved meat quality by increasing intermuscular fat. Changes in the expression of these genes indicate that caponization increases the live weight mainly by increasing fat deposition rather than muscle growth. These results expand our understanding of the mechanisms of caponization on growth performance and fat deposition in ganders.

Abstract

In this study, we determined the effects of caponization on the growth performance and carcass traits of Yangzhou ganders. Fifty sham operated geese (the control group) and 80 caponized geese (the caponized group) were selected at 150 days of age and reared until 240 days of age. At 210 days of age, 30 geese from the caponized group were selected and fed with testosterone propionate (testosterone group). The results showed that caponization lowered testosterone and increased the total cholesterol and triglyceride concentrations in serum, live weights, average 15 day gains, and feed intake. Abdominal fat and intramuscular fat were significantly higher in the caponized geese than in the control at 240 days. Gene expression analysis showed that caponization promoted abdominal fat deposition and intermuscular fat content by upregulating the expression of adipogenic genes in the liver, adipose tissue, and muscle tissue. The high expression of SOCS3 in the hypothalamus, liver, and muscle of caponized geese suggests that caponization may lead to negative feedback regulation and leptin resistance. Changes in the expression of these genes, along with the downregulation of PAX3 in the breast muscle and MYOG in the leg muscles, indicate that caponization increases the live weight mainly by increasing fat deposition rather than muscle growth. These results expand our understanding of the mechanisms of caponization on growth performance and fat deposition in ganders.

Effects of dietary nicotinic acid supplementation on meat quality, carcass characteristics, lipid metabolism, and tibia parameters of Wulong geese

The purpose of this study was to evaluate the effects of nicotinic acid (NA) supplementation on the meat quality, carcass characteristics, lipid metabolism, and tibia parameters in Wulong geese. A total of 360 twenty-nine-day-old Wulong geese were randomly divided into 6 treatments, and each treatment included 6 pens with 10 birds per pen. Birds were fed a basal diet supplemented with 0, 20, 40, 60, 80, or 100 mg/kg NA for 12 wk. Dietary NA supplementation linearly decreased L* value and increased pH and water-holding capacity in the breast muscle (P < 0.05). Increasing NA levels linearly and quadratically decreased shear force of breast muscle (P < 0.001). Dietary NA supplementation linearly reduced the thickness of subcutaneous fat plus the skin and percentage of abdominal fat, and enhanced the width of intermuscular fat band (P < 0.001). Dietary NA addition linearly and quadratically increased intramuscular fat (IMF) content (P ≤ 0.001). Increasing NA levels decreased serum total cholesterol and low-density lipoprotein cholesterol levels and increased serum lipase activity and hepatic mRNA expression of lipoprotein lipase in a linear manner (P < 0.05). There were linear and quadratic effects in serum triglycerides and high-density lipoprotein cholesterol (HDL-C) levels and malate dehydrogenase activity with the NA addition (P < 0.05). Feeding the NA-supplemented-diets linearly increased tibia length, circumference, fat-free dry weight, and ash content (P < 0.001). There were linear and quadratic increases in Ca and P contents with the NA supplementation (P < 0.05). According to the quadratic regression analyses fitted to shear force, IMF content, serum triglycerides and HDL-C levels, and tibial Ca and P contents, the optimal dietary NA supplementation was 80 to 90 mg/kg. In conclusion, NA addition enhanced meat quality and IMF content, regulated lipid metabolism, and increased tibia quality of Wulong geese. The dosage of 80 mg/kg NA in Wulong geese aged 5 to 16 wk was recommended.

Nocturnal One-Hour Lighting Stimulates Gonadal Development and Lowers Fat Deposition in Male Mule Ducks

In this study, the effects of a nocturnal light pulse on body weight, organ mass, gonadal function, and plasma levels of metabolites were determined in male mule ducks. In total, 32 15-week-old mule ducks were randomly allocated to either Group C (control group) or L+ (lighting group). Group C was exposed to the natural photoperiod, whereas Group L+ was provided with a 1-h lighting over 20:00-21:00 every day, in addition to the natural photoperiod. At the end of the 42-day experiment, Group L+ had significantly lower relative weights (% of live weight) of the digestive tract and abdominal fat and higher relative weights of the breast meat and testes than Group C. Moreover, Group L+ had significantly higher plasma testosterone and lower plasma glucose levels. However, no between-group differences were observed in the triacylglycerol and uric acid levels. Histological examination demonstrated that the seminiferous tubule diameter was larger in Group L+ than in Group C. Moreover, the meiosis stage in spermatogenesis had begun in Group L+ but not in Group C. In conclusion, the supplemented 1-h lighting at 20:00 stimulated gonadal development and function and reduced fat deposition.

Effect of immunocastration and caponization on fatty acid composition of male chicken meat

Recently, immunocastration with Improvac (ImmC). has been tested in broilers and a considerable reduction in serum testosterone concentration (reduced by 79% compared to roosters) was observed. The aim of this study was to evaluate the effect of immunocastration on meat fatty acid (FA) composition and its comparison with caponized and intact males (roosters). The study was conducted with 3 experimental groups: control group (roosters), the group of birds submitted to surgical caponization (SurgC), and the group of birds submitted to immunocastration with Improvac. The comparison of breast meat partial FA sums of castrated (SurgC and ImmC) with control birds (roosters) revealed that castrated birds showed significantly higher content of n-3 polyunsaturated fatty acids (n-3 PUFA) than control birds (1.76 vs. 1.46 g/100 g of total FA; superiority of 20.2%), which has contributed to the occurrence of significant differences on both the n-6/n-3 ratio and the atherogenicity index (AI). In contrast, on leg meat portion, castrated birds displayed higher contents of both total saturated and monounsaturated fatty acids (SFA and MUFA, with 2.2 and 4.1% more, respectively) and lower total n-6 PUFA content (8.3% less) than was observed in control birds, which contributed to significant differences in the AI index. On the other hand, the comparison of breast meat portion from SurgC with ImmC showed that immunocastration contributed to lower total SFA and higher total n-6 PUFA, which have contributed to significant differences on both Polyunsaturated/Saturated (P/S) and n-6/n-3 ratios. Whereas, on leg meat portion no significant differences were observed on partial sums and a single difference was observed on the thrombogenicity index. Immunocastration of broilers has contributed to minor changes in the FA profile, but has improved the overall lipid quality indexes in both breast and leg meat portions. Therefore, immunocastration could be applied as an alternative method to caponization without negative consequences in meat FA profile.

Reproductive Endocrinology of Nonalcoholic Fatty Liver Disease

The liver and the reproductive system interact in a multifaceted bidirectional fashion. Sex steroid signaling influences hepatic endobiotic and xenobiotic metabolism and contributes to the pathogenesis of functional and structural disorders of the liver. In turn, liver function affects the reproductive axis via modulating sex steroid metabolism and transport to tissues via sex hormone-binding globulin (SHBG). The liver senses the body's metabolic status and adapts its energy homeostasis in a sex-dependent fashion, a dimorphism signaled by the sex steroid milieu and possibly related to the metabolic costs of reproduction. Sex steroids impact the pathogenesis of nonalcoholic fatty liver disease, including development of hepatic steatosis, fibrosis, and carcinogenesis. Preclinical studies in male rodents demonstrate that androgens protect against hepatic steatosis and insulin resistance both via androgen receptor signaling and, following aromatization to estradiol, estrogen receptor signaling, through regulating genes involved in hepatic lipogenesis and glucose metabolism. In female rodents in contrast to males, androgens promote hepatic steatosis and dysglycemia, whereas estradiol is similarly protective against liver disease. In men, hepatic steatosis is associated with modest reductions in circulating testosterone, in part consequent to a reduction in circulating SHBG. Testosterone treatment has not been demonstrated to improve hepatic steatosis in randomized controlled clinical trials. Consistent with sex-dimorphic preclinical findings, androgens promote hepatic steatosis and dysglycemia in women, whereas endogenous estradiol appears protective in both men and women. In both sexes, androgens promote hepatic fibrosis and the development of hepatocellular carcinoma, whereas estradiol is protective.

Decreased testosterone levels after caponization leads to abdominal fat deposition in chickens

BACKGROUND

Caponization results in reduced androgen levels, which leads to abdominal fat accumulation in capons. In this study, we sought to understand the molecular mechanisms behind this fat accumulation.

RESULTS

Abdominal fat (AF) content increased significantly (P < 0.05) and serum and AF testosterone levels decreased significantly (P < 0.05 or P < 0.01) after caponization. In AF tissue, 90 differentially expressed genes related to lipid metabolism were screened by gene expression profiling in caponized and sham-treated chickens. Among these, six representative genes were significantly up-regulated (APOA1, SCD, FABP7, RXRG, and FADS2) or down-regulated (FABP3) (P < 0.05 or P < 0.01) and were strongly associated with the PPAR pathway. In addition, cell junction pathways were also enriched. In vitro, Fat content was significantly lower in cells treated with testosterone compared with control cells (P < 0.01), and mRNA levels of RXRG, FABP7, and FABP3 changed accordingly, confirming the effect of testosterone on fat deposition.

CONCLUSIONS

The results of this study indicate that testosterone reduction likely regulates gene expression through PPAR and cell junction pathways resulting in increased fat accumulation. These results provide increase our understanding of the biological mechanisms by which caponization induces greater fat accumulation.

Testosterone protects high-fat/low-carbohydrate diet-induced nonalcoholic fatty liver disease in castrated male rats mainly via modulating endoplasmic reticulum stress

We previously showed that testosterone (T) deficiency enhanced high-fat/low-carbohydrate diet (HFD)-induced hepatic steatosis in rats independent of insulin resistance and that T replacement reduced hepatic macrovesicular fat accumulation and inflammation. The present report explores the mechanism of T's protective effects on HFD-induced steatohepatitis. Adult male rats were randomized into four treatment groups for 15 wk: intact rats on regular chow diet or HFD, and castrated rats on HFD with or without T replacement. Fatty acid β-oxidation and de novo synthesis were not changed by castration and T replacement, but expression of lipid export proteins ApoB100 and microsomal triglyceride transfer protein (MTP) was suppressed by HFD in both intact and castrated rats but restored by T replacement. Macrovesicular lipid droplet-related proteins perilipin 1 and fat-specific protein 27 were increased by HFD in castrated rats and suppressed by T replacement. Higher activation/expression of ER stress proteins (PERK, IRE-1α, JNK, NF-κB, and CHOP) was demonstrated in castrated rats fed HFD compared with intact animals, and T replacement suppressed these changes. We conclude that 1) HFD leads to ApoB100/MTP suppression reducing export of lipids; 2) castration promotes progression to steatohepatitis through activation of the ER stress pathway and enhancement of macrovesicular droplet protein expression; and 3) testosterone suppresses ER stress, inhibits the formation of macrovesicular lipid droplets, promotes lipid export, and ameliorates steatohepatitis induced by HFD and castration.

The effect of age and castration on the growth rate, blood lipid profile, liver histology and feed conversion in Green-legged Partridge cockerels and capons

The surgical castration of male chickens induces hormonal changes, which permanently influence metabolic processes in birds. The aim of this study was to determine the effect of age and castration on the growth rate, feed conversion, lipid profile and histopathological changes in the livers of cockerels and capons. The experimental materials comprised male chickens of the Green-legged Partridge breed (old traditional Polish chicken breed), raised to 28 weeks of age. At 8 weeks of age, 100 birds were castrated. Caponization had a significant effect on the plasma concentrations of total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol and triacylglycerols (P<0.05). Fatty degeneration and lymphoid cell infiltration were observed more frequently in the livers of capons than cockerels. Capon carcasses were characterized by increased deposition of abdominal and subcutaneous fat (P<0.05). Total meat weight in the carcasses of cockerels and capons was similar, but the proportions of muscles were different. From 20 weeks of age, the weight of breast muscles was higher, and the weight of leg muscles was lower in capons than in cockerels (P<0.05). Capons were characterized by higher liver weight, higher gizzard weight and lower heart weight than cockerels (P<0.05). The feed conversion ratio (kg/kg BW) was similar in intact cockerels and capons. The values of carcass quality parameters and feed conversion ratio as well as histopathological changes in the liver indicate that Green-legged Partridge capons should be slaughtered at 20 to 24 weeks of age.

Testosterone replacement ameliorates nonalcoholic fatty liver disease in castrated male rats

Nonalcoholic fatty liver disease is common in developed countries and is associated with obesity, metabolic syndrome, and type 2 diabetes. T deficiency is a risk factor for developing these metabolic deficiencies, but its role in hepatic steatosis has not been well studied. We investigated the effects of T on the pathogenesis of hepatic steatosis in rats fed a high-fat diet (HFD). Adult male rats were randomly placed into four groups and treated for 15 weeks: intact rats on regular chow diet (RCD), intact rats on liquid HFD (I+HFD), castrated rats on HFD (C+HFD), and castrated rats with T replacement on HFD (C+HFD+T). Fat contributed 71% energy to the HFD but only 16% of energy to the RCD. Serum T level was undetectable in castrated rats, and T replacement led to 2-fold higher mean serum T levels than in intact rats. C+HFD rats gained less weight but had higher percentage body fat than C+HFD+T. Severe micro- and macrovesicular fat accumulated in hepatocytes with multiple inflammatory foci in the livers of C+HFD. I+HFD and C+HFD+T hepatocytes demonstrated only mild to moderate microvesicular steatosis. T replacement attenuated HFD-induced hepatocyte apoptosis in castrated rats. Serum glucose and insulin levels were not increased with HFD in any group. Immunoblots showed that insulin-regulated proteins were not changed in any group. This study demonstrates that T deficiency may contribute to the severity of hepatic steatosis and T may play a protective role in hepatic steatosis and nonalcoholic fatty liver disease development without insulin resistance.

Gender, caponization and exogenous estrogen effects on lipids, bone and blood characteristics in Taiwan country chickens

This study investigated gender, caponization and exogenous estrogen effects on lipids, bone and blood characteristics in Taiwan country chickens. Thirty male chickens were caponized at 8 weeks (capons); 15 capons were injected with estrogen (5 mg/bird estradiol 3-benzoate) every 2 weeks from 8 to 28 weeks, and 15 sham-operated male (shams) chickens and 15 females were selected for this trial. The results showed that the shams had lower relative abdominal and chest subcutaneous fat than females (P < 0.05). The estrogen-treated capons had greater relative abdominal and chest subcutaneous fat than shams and capons (P < 0.05), which might result from higher blood very low-density lipoproteins and triacylglycerol concentrations (P < 0.05). Caponization could dramatically increase relative abdominal fat (506%; P < 0.05). The shams had higher tibia weight and biomechanical properties, such as maximum bone strength and bending moment values than the capons (P < 0.05). Tibia biomechanical properties were reduced by estrogen treatment (P < 0.05). The females obtained the lowest biomechanical value in all treatments (P < 0.05). Histological examination revealed cavity formation in the cortical bone of estrogen-treated capons and female chickens, which suggested that estrogen reduced bone biomechanical properties by destroying its structural integrity.

Androgen inhibits abdominal fat accumulation and negatively regulates the PCK1 gene in male chickens

Capons are male chickens whose testes have been surgically incised. Capons show a significant increase in fat accumulation compared to intact male chickens. However, while caponization leads to a significant reduction in androgen levels in roosters, little is known about the molecular mechanisms through which androgen status affects lipogenesis in avian species. Therefore, investigation of the influence of androgens on fat accumulation in the chicken will provide insights into this process. In this study, Affymetrix microarray technology was used to analyze the gene expression profiles of livers from capons and intact male chickens because the liver is the major site of lipogenesis in avian species. Through gene ontology, we found that genes involved in hepatic lipogenic biosynthesis were the most highly enriched. Interestingly, among the upregulated genes, the cytosolic form of the phosphoenolpyruvate carboxykinase (PCK1) gene showed the greatest fold change. Additionally, in conjunction with quantitative real-time PCR data, our results suggested that androgen status negatively regulated the PCK1 gene in male chickens.

In ovo leptin administration affects hepatic lipid metabolism and microRNA expression in newly hatched broiler chickens

BACKGROUND

A leptin-like immunoreactive substance has been found in chicken eggs and has been implicated in serving as a maternal signal to program offspring growth and metabolism. In the present study, we investigated the effects of in ovo leptin administration on hatch weight, serum and hepatic concentrations of metabolites and hormones, as well as on the expression of genes involved in hepatic lipid metabolism and the predicted microRNAs (miRNAs) targeting the affected genes. To this end we injected fertile eggs with either 0.5 μg of recombinant murine leptin or vehicle (PBS) before incubation.

RESULTS

Prenatally leptin-exposed chicks showed lower hatch weight, but higher liver weight relative to the body weight, compared to the control group. In ovo leptin treatment increased the hepatic content and serum concentration of leptin in newly hatched chickens. The hepatic contents of triglycerides (TG) and total cholesterol (Tch) were decreased, whereas the serum levels of TG, Tch and apolipoprotein B (ApoB) were increased. The hepatic mRNA expression of sterol regulator element binding protein 1 (SREBP-1c), SREBP-2, hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) and cholesterol 7α-hydroxylase 1 (CYP7A1) was significantly up-regulated, as was the protein content of both SREBP-1c and SREBP-2 in hepatic nuclear extracts of leptin-treated chickens. Moreover, out of 12 miRNAs targeting SREBP-1c and/or HMGCR, five were significantly up-regulated in liver of leptin-treated chicks, including gga-miR-200b and gga-miR-429, which target both SREBP-1c and HMGCR.

CONCLUSIONS

These results suggest that leptin in ovo decreases hatch weight, and modifies hepatic leptin secretion and lipid metabolism in newly hatched broiler chickens, possibly via microRNA-mediated gene regulation.

Effects of caponization on fat metabolism-related biochemical characteristics of broilers

A two-trial experiment was conducted to evaluate the effects of caponization on fat metabolism-related biochemical characteristics of broilers. Male Redbro broilers were purchased, caponized at 3 weeks and reared until either the 18th (Trial 1) or the 24th (Trial 2) week. In Trial 1, five slaughters were performed at 6, 9, 12, 15 and 18 weeks of age while in Trial 2 one slaughter at the end of the experiment (24 weeks). In each slaughter, the abdominal adipose tissue cellularity, the NADP dehydrogenase activity in the liver and some serum lipoproteins concentrations were assessed. Caponization had a marked effect on the adipocyte volume and NADP-malate dehydrogenase activity in the liver at 24 weeks but it did not affect adipocyte number or the activity of NADP-isocitrate dehydrogenase activity at any age (p < 0.05). Regarding the lipoproteins, cholesterol and HDL-cholesterol were elevated in capon serum at 18 weeks of age while no difference was detected in the triglyceride concentration at any age. In conclusion, a relationship between fat deposition at the phenotypic level and the level of lipogenic enzymes and lipoproteins capons was established but not as pronounced as expected as some parameters displayed a constant increasing pattern while others did not.

Influence of partial and complete caponization on chicken meat quality

Caponization is a surgical technique adopted to alter the sexual maturation of male chickens with the aim of improving the quality characteristics of carcass and meat. Under commercial conditions within each flock, about 10% of the birds usually result with incomplete caponization and are called slips. A trial was conducted to compare quality traits of breast and thigh meat from capons (n = 12), slips (n = 12), and cocks (unoperated birds; n = 12) (Hubbard x Golden Comet) reared together and processed at 180 d old under commercial conditions. Capons exhibited the highest (P < 0.01) values of breast and thigh meat lightness and yellowness as well as the lowest values of redness (P < 0.01) compared with cocks and slips. These variations in meat color were related to a lower concentration of heme pigments in both breast and thigh meat from capons. Capons and slips presented lower Allo-Kramer shear values of cooked breast meat (P < 0.05) in comparison with cocks. As for chemical composition, capons showed a higher content of total lipid, cholesterol, and ash both in breast and thigh meat. Total saturated, monounsaturated, and polyunsaturated fatty acids were not strongly affected by caponization. However, capons exhibited a significantly higher (P < 0.01) content of linoleic and linolenic acids as well as a lower content of arachidonic, eicosapentaenoic, docosapentaenoic, and docosahexaenoic acids in respect to slips and cocks. Overall, this study indicated that caponization can affect the main meat quality traits with special regards to appearance (color), texture, and composition. Finally, it was found that slips present intermediate meat quality characteristics between capons and cocks.