Caponization and testosterone implantation effects on blood lipid and lipoprotein profile in male chickens

The effect of caponization on tibia bone histomorphometric properties of crossbred roosters

The negative effect of caponization on the structural, geometric and mechanical parameters of femur and tibia has been shown in a few studies. Nevertheless, its influence on tibia bone microarchitecture is still largely unknown. Therefore, this study aimed to assess the effect of castration on the microstructural parameters of the trabecular and compact bone of tibia bone in crossbred chickens. The experiment involved 96 roosters derived from crossing Yellowleg Partridge hens ([Formula: see text]-33) and Rhode Island Red cockerels (R-11) fattened until the 16th, 20th and 24th week of life. Animals were randomly divided into 2 groups of 48 each. Group I (control) consisted of intact roosters and group II (experimental) consisted of birds subjected to caponization at the 8th week of age. The castration surgery had no influence on some properties within compact bone such as osteon diameter On.Dm, osteon perimeter On.Pm, osteon area On.Ar, osteocyte lacunar number Ot.Lc.N, osteon bone area On.B.Ar, osteon wall thickness On.W.Th as well as thick-mature collagen content in all analyzed age groups of animals. Nevertheless, our results demonstrate that castration caused a decrease of Haversian canal area Hc.Ar, osteocyte lacunar area Ot.Lc.Ar and osteocyte lacunar porosity Ot.Lc.Po among the 16-week-old birds, decrease of Haversian canal perimeter Hc.Pm and increase of fraction of bone area On.B.Ar/On.Ar among 16- and 24-week-old individuals and also an increase of osteocyte lacunar density Ot.Lc.Dn in the osteons of the oldest roosters. Additionally, some microstructural parameters of trabecular bone show the negative effect of caponization. The youngest 16-week-old capons were characterized by thinnin the trabecular in the epiphysis part of tibia. Moreover, in the case of 24-week-old, there is an increase in the trabecular separation Tb.Sp with simultaneous decrease of trabecular number Tb.N compared to roosters, which may suggest the increase of the bone resorption among the oldest individuals. The increased bone turnover in the epiphysis part of the tibia bone also indicates changes in the collagen fibers distribution, where among 20-week-old animals there is a decrease in the content of immature thin collagen fibers with simultaneous increase in the content of mature thick collagen fibers. Furthermore, among the oldest 24-week-old individuals we can observe the increased thick-to-thin collagen ratio, which may be a sign of slowing down in bone formation.

The effect of caponization on bone homeostasis of crossbred roosters. I. Analysis of tibia bone mineralization, densitometric, osteometric, geometric and biomechanical properties

The presented study focuses on assessing the effect of caponization on the densitometric, osteometric, geometric and biomechanical parameters of tibial bones in crossbred chickens. The study was carried out on 96 hybrids between Yellowleg Partridge hens (Ż-33) and Rhode Island Red cockerels (R-11) aged 16 weeks, 20 weeks and 24 weeks. Birds were randomly assigned to 2 groups-the control group (n = 48; which consisted of intact roosters) and the experimental group (n = 48, which consisted of individuals subjected to caponization at the age of 8 weeks). The caponization had no effect on the densitometric, osteometric and geometric parameters (except the horizontal internal diameter of 16-week-old individuals) of tibia bone, as well as the content of calcium (Ca), phosphorus (P) and the Ca/P ratio in the bone mineral fraction in all analyzed age groups of animals. However, it contributes to a lower percentage of ash in the bones of capons at 20 and 24 weeks of age compared to cockerels. On the contrary, some mechanical and material parameters show the negative effect of caponization. Ultimate load and bending moment decreased in capons in all of the analyzed age groups of animals and yield load, stiffness and ultimate stress also decreased but only in the group of 20-week-old and 24-week-old individuals. This can contribute to the weakening of the capon bones, and in the perspective of prolonged maintenance to their deformation and even fracture.

Effects of testis testosterone deficiency on gene expression in the adrenal gland and skeletal muscle of ducks

1. Testosterone has an anabolic effect on skeletal muscle. The testes produce most of the testosterone in vivo, while the adrenal glands contribute smaller amounts. When testis testosterone is deficient the adrenal gland increases steroid hormone synthesis, which is referred to as compensatory testicular adaptation (CTA).2. To reveal the effects of testis testosterone deficiency on adrenal steroid hormones synthesis and skeletal muscle development, gene expression related to adrenal steroid hormones synthesis and skeletal muscle development were determined by RNA-seq.3. The results showed that castrating male ducks had significant effects on their body weight but no significant impact on cross-sectional area (CSA) or density of pectoral muscle fibres. In skeletal muscle protein metabolism, expression levels of the catabolic gene atrogin1/MAFbx and the anabolic gene eEF2 were significantly higher, with concomitant increases after castration. The adrenal glands' alteration of the steroid hormone 11β-hydroxylase (CYP11B1) was significantly lower following castration.4. Expression pattern analysis showed that the adrenal glands' glucocorticoid receptor (NR3C1/GR) had a potential regulatory relationship with the skeletal muscle-related genes (Pax7, mTOR, FBXO32, FOXO3, and FOXO4).5. The data showed that castration affected muscle protein metabolism, adrenal steroid and testosterone synthesis. In addition, it was speculated that, after castration, steroid hormones produced by the adrenal gland could have a compensatory effect, which might mediate the changes in skeletal muscle protein metabolism and development.

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.

Untargeted LC-MS-based metabonomic analysis of the effect of photoperiod on the testes of broiler roosters

Photoperiod is an important factor that stimulates the reproductive performance of broiler breeder roosters. However, the mechanism by which photoperiod affects the reproductive performance of broiler breeder roosters has not been fully studied. To study the effects of different photoperiods on the reproductive performance of broiler breeder roosters, 120 Arbor Acres broiler breeder roosters aged 20 weeks were randomly assigned to three groups (n = 40), and the three groups were treated with different photoperiod regimes: control (CTR; 12.5 h of light and 11.5 h of dark, 12.5 L: 11.5 D), short day (SD; 16 L: 8 D) and long day (LD; 8 L: 16 D). Serum and testes were collected after 4 weeks of feeding, and testosterone-related indices were detected. We found that testosterone synthesis in the testes of broiler roosters was boosted with prolonged of photoperiod. Subsequently, metabonomics was used to identify the differential endogenous metabolites that may affect the function of the testes in breeder roosters. We found compared with other groups, the concentrations of creatine, uridine monophosphate, phosphoribosyl pyrophosphate, dCMP, α-D-glucose and citric acid in the SD group decreased significantly (p < 0.05), and glyoxylic acid, D-ribose 5-phosphate, deoxyuridine and orotic acid in the SD group increased significantly (p < 0.05), while the CTR group and LD group showed no significant difference (p > 0.05). The concentrations of linoleic acid and α-linolenic acid in the LD group were increased significantly (p < 0.05) than those in the CTR and SD groups. Compared with the CTR group, the concentrations of histamine in the SD and LD groups were significant increased (p < 0.05). The 13 of the different metabolites could be used as candidate biomarkers for different photoperiods affecting testosterone synthesis, may be used to molecular breeding of high reproductive performance broiler roosters.

Effect of Caponisation on Bone Development in Native Male Chickens

The aim of the study was to determine the effect of caponisation on the morphometric traits and mechanical parameters of tibial and femoral bones in Greenleg Partridge cocks. The experiment involved 200 cocks. At the age of 8 weeks, 100 birds were subjected to surgical castration. At week 24, the birds were slaughtered and tibial and femoral bones were collected from 10 non-caponised cocks and 10 capons. The caponisation surgery had no effect on the weight and length of any of the long bones but resulted in reduction (P≤0.05) of the ash content in both bones and Ca in the femur. It also influenced the geometric structure of the bones, i.e. there was an increase (P≤0.05) in the second moment of inertia in the tibial bone and the cross-sectional area and mean relative wall thickness in the femoral bone of the capons. The three-point bending test revealed a negative effect of caponisation on the mechanical strength of the bone. Values characterising the highest bone material strength, i.e. yielding load (femur), maximum force moment (tibia) and yielding deformation, bending point resistance, and load-to-deformation (both bones), declined in the capons. The investigations demonstrated a negative effect of caponisation on the quality of long bones. The tibial bone seems to be slightly more sensitive to the caponisation effects than the femoral bone. It can be assumed based on the analysis of biomechanical traits that the bones of capons are more susceptible to deformations or fractures due to their modified geometry and mechanical brittleness.

Three-Point Scale of Lipid Concentration and Localization in Muscle Tissue of Birds Using Oil Red O Staining

Research on skeletal muscles includes chemical, sensorial, histopathological, microbiological analysis, and the influence of observed data on meat quality. The aim of this paper was to establish a point scale for analysing the fat concentration in breast and thigh muscles of birds during histological examination. The need for a point scale showing lipid localization arises during the experiment, including the castration of the bird. During necropsy, pectoral and thigh muscles were put into 30% saccharose solution with the addition of sodium azide. Then, frozen samples were cut into 8 µm sections and stained with Oil Red O (Bio-Optica, Milan, Italy) to detect lipids. Four main locations were evaluated: the area around vessels, perimysium between fascicles, endomysium between fascicles, and sarcoplasm of the fibres. Each location was separately evaluated for pectoral and thigh muscles. The percentage of tissue occupied by lipids in different locations was detected using Panoramic Viewer software (3DHISTECH, Budapest, Hungary). The results from the point scale analysis, similar in pectoral and thigh muscles, confirmed data from the chemical analysis. Significant differences were observed in all examined periods in chemical analysis (P<0.05) and were visible in the point scale with a higher number of birds with higher lipid concentration in all examined locations. Our scale analysis of lipid concentration, confirmed by chemical analysis, is an objective tool and can be used separately in muscle tissues in experiments where there is the need for lipid visualization. An established three-point scale can be a tool in poultry muscle tissue evaluation because not only accumulation but also lipid location is crucial in determining the usefulness of meat in culinary processing.

Effects of caponization and age on the histology, lipid localization, and fiber diameter in muscles from Leghorn cockerels

Poultry researchers seek general and native lines of birds for capon production. The primary aim is to find high-quality meat with valuable sensory attributes. Castration decreases androgen levels and changes lipid metabolism, resulting in the accumulation of abdominal, subcutaneous, and intramuscular fat, which changes the flavor, texture, and tenderness of the meat. Histological analysis of selected skeletal muscles from Leghorn capons and cockerels was the main aim of the present study, along with examination of lipid localization in muscle tissue. We also assessed fiber type and diameter in the pectoral muscles (pectoralis major). The experiment was performed on 200 Leghorn cockerels; testes were removed at 8 wk of age. At 12, 16, 20, 24, and 28 wk of age, 6 cockerels and 6 capons were slaughtered, and samples from the pectoral and thigh muscles were evaluated. Differences in the focal necrosis of the fibers with infiltration of lymphoid cells (P < 0.05) were observed in thigh muscles, with higher numbers in cockerels than in capons. All examined locations in the pectoral and thigh muscles of capons (around the blood vessels, in the perimysium, in the endomysium, and in the sarcoplasm) showed higher concentrations of lipids compared to levels in cockerels. The analysis of fiber type in pectoralis major muscles revealed that all fibers were type IIB. The diameters of the fibers of the pectoral muscles were different (P < 0.05) at 28 wk of age, and the diameters of the giant fibers were different (P < 0.05) at 16 wk of age. The high concentration of lipids in the skeletal muscles of Leghorn capons is remarkable. Thus, ethical reasons as well as economic reasons should be considered when one-day-old cockerels are eliminated.

Effects of caponization and age on the histology, lipid localization, and fiber diameter in muscles from Greenleg Partridge cockerels

The preference of modern consumers for high-quality meat has forced breeders to use native breeds to produce capons. Caponization, both chemical and surgical, leads to androgen deficiency and changes in lipid metabolism and results in the accumulation of abdominal, subcutaneous, and intramuscular lipids, which change the sensory values of the meat. The aim of this study was to histologically evaluate selected skeletal muscles from Greenleg Partridge capons and cockerels. We examined lipid localization in the muscular tissue and also assessed both fiber type and fiber diameter in the pectoral muscles. The experiment was performed on 200 Greenleg Partridge cockerels and testes were removed at 8 wk of age. At 12, 16, 20, 24, and 28 wk of age, 6 cockerels and 6 capons were slaughtered, and samples from the pectoral and thigh muscles were evaluated. Our histopathological evaluation revealed only minimal changes, and no significant differences between capons and cockerels were observed. The pectoral and thigh muscles of the capons had higher concentrations of lipids around the blood vessels, in the perimysium, in the endomysium, and in the sarcoplasm. The analysis of fiber type in the Pectoralis major muscles revealed that the fibers were all the IIB type. The diameters of the fibers of the pectoral muscles were significantly different (P < 0.05) at 20, 24, and 28 wk of age, and diameters of the giant fibers were significantly different (P < 0.05) at 24 and 28 wk of age. High concentrations of lipids in the meat of the capons is undesirable due to health-related reasons. However, the ability of adipose tissue to improve the sensory values of meat will always be a major quality of native/traditional products.

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.

Effects of caponization and ovariectomy on objective indices related to meat quality in chickens

Capons and ovariectomized chickens are birds that have been gonadectomized to improve the meat quality. This study investigated the effects of caponization and ovariectomy on physical, chemical, and fatty acid and amino acid profiles of meat from Beijing-You chickens (a Chinese local breed) at market age (17 wk). All birds (20 capons, 20 ovariectomized, and 40 controls) were reared under the same conditions. Breast muscle fiber diameter and area were significantly smaller and the fiber density was higher in capons and ovariectomized chickens than in controls (P < 0.05). Compared with controls, caponization and ovariectomy significantly decreased breast muscle shear values and redness (a*), as well as increased yellowness (b*), hue (H*), and chroma (C*) (P < 0.05). There was significantly more intramuscular fat (IMF) in capons than in controls (P < 0.05), and there was a tendency for more inosine-5΄-monophosphate (IMP) in capons than in controls (P = 0.10). The levels of IMF and IMP in ovariectomized chickens were significantly higher than those in controls (P < 0.05). Capons and ovariectomized chickens exhibited a significantly higher content of palmitic acid (C16:0), palmitoleic acid (C16:1) and oleic acid (C18:1), together with a lower content of stearic acid (C18:0), arachidonic acid (C20:4), and lignoceric acid (C24:0) compared to controls (P < 0.05). The total saturated, monounsaturated, and polyunsaturated fatty acids as well as amino acid composition were not affected by gonadectomy (P > 0.05). Overall, this study indicates that both caponization and ovariectomy likely improve the meat quality of the breast muscle based on the objective indices of IMF, appearance (color), texture, and minor change of the fatty acid profile; ovariectomy improves flavor-related indices.

Differences in textural properties of cooked caponized and broiler chicken breast meat

This study was aimed at evaluating textural properties of cooked chicken breast meats obtained from 3 production systems (conventional raising, feed modification, and caponization) and determining the relationship between instrumental parameters and sensory attributes associated with the texture of capon meat. Texture of cooked breast meats was determined using 3 instrumental methods: Warner-Bratzler Shear (WBS), texture profile analysis (TPA), and uniaxial compression (UC), and sensory analysis by trained panelists. The results indicated that cooked caponized meat showed the lowest values of WBS force, shear energy, hardness, Young's modulus of UC, and the 2 sensory attributes (firmness and number of chews) (P < 0.05). In contrast, springiness and juiciness were the highest in the caponized meat (P < 0.05), suggesting that capon meat was more tender and juicier than the others. Feed-modified chicken samples showed intermediate textural characteristics between the samples of capon and conventionally raised broiler. Pearson's correlation revealed that WBS force, shear energy, Young's modulus of UC, gumminess, and springiness were strongly correlated with 3 sensory attributes (firmness, number of chews, and juiciness). Partial least squares regression (PLSR) demonstrated that 72% of all sensory attributes for the first 2 PLSR components were explained by 36% of the instrumental parameters and the production systems. Loading and score plot illustrated that conventional raising contributed to a high degree of firmness and number of chews, and positively correlated with shear energy, WBS force, gumminess, hardness, and Young's modulus. Contrarily, caponization was negatively correlated with those sensory attributes. The univariate analysis indicated that firmness and number of chews were positively correlated with all instrumental parameters, except springiness. Juiciness was positively correlated with springiness but negatively correlated with the others. The study suggested that the cooked meat of capons could be differentiated from those of broilers raised conventionally and with feed-modified diets based on textural properties. Based on the optimized simulating equation, texture of caponized breast could be explained by WBS force, shear energy, Young's modulus, and gumminess.

The seasonal glucocorticoid response of male Rufous-winged Sparrows to acute stress correlates with changes in plasma uric acid, but neither glucose nor testosterone

We sought to clarify functional relationships between baseline and acute stress-induced changes in plasma levels of the stress hormone corticosterone (CORT) and the reproductive hormone testosterone (T), and those of two main metabolites, uric acid (UA) and glucose (GLU). Acute stress in vertebrates generally stimulates the secretion of glucocorticoids, which in birds is primarily CORT. This stimulation is thought to promote behavioral and metabolic changes, including increased glycemia. However, limited information in free-ranging birds supports the view that acutely elevated plasma CORT stimulates glycemia. Acute stress also often decreases the secretion of reproductive hormones (e.g., T in males), but the role of CORT in this decrease and the contribution of T to the regulation of plasma GLU remain poorly understood. We measured initial (pre-stress) and acute stress-induced plasma CORT and T as well as GLU in adult male Rufous-winged Sparrows, Peucaea carpalis, sampled during the pre-breeding, breeding, post-breeding molt, and non-breeding stages. Stress increased plasma CORT and the magnitude of this increase did not differ across life history stages. The stress-induced elevation of plasma CORT was consistently associated with decreased plasma UA, suggesting a role for CORT in the regulation of plasma UA during stress. During stress plasma GLU either increased (pre-breeding), did not change (breeding), or decreased (molt and non-breeding), and plasma T either decreased (pre-breeding and breeding) or did not change (molt and non-breeding). These data provide only partial support to the hypothesis that CORT secretion during acute stress exerts a hyperglycemic action or is responsible for the observed decrease in plasma T taking place at certain life history stages. They also do not support the hypothesis that rapid changes in plasma T influence glycemia.

Physicochemical composition and sensory quality evaluation of capon and rooster meat

The aim of the present study was to evaluate the effect of caponization on the physicochemical and sensory characteristics of rooster and capon meat (2 Portuguese autochthonous chicken breeds of roosters:Amarela and Pedrês), raised under the same production. The birds were castrated at 9 wk of age and bred until 140 d of age. Forty Amarela (20 roosters and 20 capons-castrated male) and 40 Pedrês Portuguesa (20 roosters and 20 capons) breed chickens, 5 free-range chickens, and 5 broilers were used. From the breast, leg, and wing muscles, physicochemical parameters such as pH, water activity (aw), physical color, moisture content, ash, CP, pigments, collagen, and total fat and fatty acids profile, were analyzed according to standard procedures. Caponization did not affect pH, aw, lightness (L*), yellowness (b*), ash, protein, collagen, saturated fatty acids (SFA), polyunsaturated fatty acids (PUFA), and the ratio of unsaturated fatty acids (UFA)/SFA. Results show that caponization decreased (P≤0.05) moisture content and increased (P≤0.05) pigments and intramuscular fat content. Capons showed higher (P≤0.001) redness (a*) and chroma (C*), and lower (P≤0.001) hue (H*) compared to roosters. Caponization increased (P≤0.05) monounsaturated fatty acids content and PUFA/SFA. The main fatty acids found were oleic (C18:1), palmitic (C16:0), and linoleic (C18:2). Capons had greater (P≤ 0.05) C18:1 content but lower (P≤0.01) butyric acid (C4:0), caprylic acid (C8:0), stearic acid (C18:0), and (P≤0.05) arachidonic acid (C20.4) content than roosters. The objective of sensory analysis was making the comparison of the Amarela and Pedrêsmeat with a free-range chicken and a broiler. Panelists classified the capon meat (Amarela and Pedrês) as juicier and less tough and fibrous than rooster meat. Broilers were in general juicier, tenderer, and less fibrous than the other chickens in this study. The results of sensory evaluation complement those obtained in physicochemical analysis, suggesting that caponization promotes an overall improvement in meat quality.

Effect of caponisation on physicochemical and sensory characteristics of chickens

The meat fats content associated to nutritional and sensory characteristics are the most important concerns of consumers. To study the effect of caponisation on the meat quality of two different breed chickens, slaughtered at 18 weeks of age, raised under the same conditions, the physicochemical and sensory characteristics of capons (castrated males at 8 weeks of age) and roosters��� meat of native Amarela Portuguesa and native Pedr��s Portuguesa breeds were evaluated. Forty Amarela (20 roosters and 20 capons), 40 Pedr��s (20 roosters and 20 capons) chickens, and also, six free-range chicken and six broilers were evaluated. The pH, water-holding capacity, Warner-Bratzler shear force, moisture content, ash, myoglobin, collagen, CP, total fat and fatty acids profile were evaluated in breast and leg meat, according to standard procedures. Leg meat capon showed greater intramuscular fat content (P���0.05), monounsaturated fatty acids (MUFA) and CP (P���0.001) than leg roosters. Caponisation increased the content of myoglobin and MUFA (P���0.05) and reduced the moisture content in the leg (P���0.05). The main fatty acids found were oleic acid (C18:1), palmitic acid (C16:0) and linoleic acid (C18:2). The greatest value of C18:1 was observed in capon���s breast (P���0.01). Sensory analysis was made to compare the Amarela and Pedr��s meat with a free-range chicken and a broiler. The sensory taste panel classified the capon���s meat (Amarela and Pedr��s) as juicier, less fibrous and tougher than rooster���s meat. The broiler was in general juicier, tenderer and less fibrous than the other birds. The results of sensory analysis complement those obtained in physicochemical analysis, suggesting that caponisation promotes an overall improvement in meat quality.

Effect of age and caponization on blood parameters and bone development of male native chickens in taiwan

An experiment was carried out to determine the effect of age and caponization on the development blood and bone characteristics development in male country chickens in Taiwan. A total of two hundred 8-wk-old LRI native chicken cockerels, Taishi meat No.13 from LRI-COA, were used as experimental animals. Cockerels were surgically caponized at 8 wks of age. Twelve birds in each group were bled and dressed from 8 wks to 35 wks of age at 1 to 5 wk intervals. The results indicated that the plasma testosterone concentration was significantly (p<0.05) lower in capons after 12 wks of age (caponized treatment after 4 wks) than that of the intact males. The relative tibia weight, bone breaking strength, cortical thickness, bone ash, bone calcium, bone phosphorus and bone magnesium contents were significantly (p<0.05) higher in intact males, while capons had higher (p<0.05) plasma ionized calcium, inorganic phosphorus and alkaline phosphatase concentration. The plasma testosterone concentration, relative tibia weight, tibia length, breaking strength, cortical thickness, bone ash, calcium, and phosphorus contents of intact males chickens increased significantly (p<0.05) with the advance of age. In addition, the relative tibia weight of capons peaked at 18 wks of age, and declined at 35 wks of age. The bone ash, calcium and phosphorus content increased most after 14 wks of age in male native chickens in Taiwan. Also, tibia length and cortical thickness peaked at 22 wks of age. However, the peak of bone strength was found at 26 wks of age. These findings support the assertion that androgens can directly influence bone composition fluxes in male chickens. Caponization caused a significant increase in bone loss at 4 wks post treatment, which reflected bone cell damage, and demonstrated reductions in the relative tibia weight, breaking strength, cortical thickness, bone ash, calcium, phosphorus and magnesium contents, and increases in plasma ionized calcium, inorganic phosphorus and alkaline phosphatase concentration.

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.

Effects of caponization on growth performance, carcass composition and meat quality of males of a layer line

The present experiment was conducted in order to evaluate the effects of caponization on growth, carcass composition and meat quality of males of a layer line reared until the 34th week of age. Two hundred and fifty males of a layer line were purchased and randomly divided in two equal groups: intact males and capons. Caponization was conducted at 45 days of age. Three slaughters were performed at the ages of 26, 30 and 34 weeks of age. Caponization did not affect feed intake and final live weight. Capons had a heavier breast and lighter leg than intact males. Lipid accumulation was enhanced by the caponization and fat was stored mainly at the fat pad and the skin of the commercial parts excluding the drumstick. The Pectoralis major muscle of capons had higher intramuscular fat content, lightness (L) and yellowness (b*) values and lower redness values (a*). In conclusion, caponization could be applied to a layer genotype in order to produce commercial chicken meat.

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.

Effects of caponisation on lipid and fatty acid composition of intramuscular and abdominal fat of medium-growth broilers

1. Capons and intact male broilers were used to investigate the effects of caponisation on intramuscular fat and abdominal adipose tissue lipid content and fatty acid profile. 2. Capons had significantly higher total lipid content (P<0·05). 3. Neutral lipids were the major fractions in intramuscular and abdominal fat but their proportions differed significantly among groups and tissues (P<0·05). 4. The predominant saturated, monounsaturated and polyunsaturated fatty acids in all samples were C16:0, C16:1 ω-9, C18:0, C18:1 ω-9, C18:1 ω-7, C18:2 ω-6 and C20:4 ω-6. 5. Caponisation resulted in a significant ω-6/ω-3, PUFA and PUFA/SFA ratio reduction as well as a significant increase in atherogenic and thrombogenic indices increase in intramuscular fat (P<0·05) without affecting their appropriate value for a healthy diet.

Effect of light intensity on broiler production, processing characteristics, and welfare

Manipulation of light intensity is an important management tool affecting broiler production and well being. Despite considerable research on light intensity, there is still a debate on the optimum level to be used for intensively housed broilers. Two trials were conducted with the objective of investigating the effect of light intensity, within the practical levels at confinement barns (1, 10, 20, and 40 lx), on production, processing characteristics, and welfare of broilers raised to 35 d of age. Each light intensity treatment was replicated in 2 environmentally controlled rooms in each trial with 950 Ross × Ross 308 chicks per room. Data were analyzed as a randomized complete block design with trial serving as a block. All chicks were exposed to 40 lx of light intensity and 23 h of light for the first 7 d followed by treatment light intensity and 17 h of day length thereafter. Body weight and feed consumption were determined at 7, 14, and 35 d of age. At the end of each trial, 60 birds per treatment were processed to determine the detailed meat yield. Skeletal and footpad and ocular health were monitored at 31 and 32 d of age, respectively. Body weight, feed consumption, feed:gain ratio, and mortality were unaffected by light intensity. Carcass, thigh, and drum yield as a percentage of live weight decreased linearly with increasing light intensity. The 1 lx treatment resulted in heavier wings as a percentage of live weight. Light intensity had no effect on skeletal health, but ulcerative footpad lesions decreased linearly with increasing light intensity. Birds exposed to the 1 lx treatment had heavier and larger eyes. In conclusion, light intensity did not affect broiler production and mortality but did affect carcass characteristics. The 1 lx light intensity treatment had a negative effect on broiler welfare as demonstrated by increased ulcerative footpad lesions and eye size.

Effects of caponization on growth performance, carcass composition, and meat quality of medium growth broilers

A 2-trial experiment was conducted to evaluate the effects of caponization on growth performance, carcass composition, and meat quality of medium growing broilers. Male chicks were caponized at 3 wk of age and reared until either 18 (trial 1) or 24 (trial 2) wk of age. In trial 1, the experimental groups included intact males, sham-operated chickens, and capons, whereas trial 2 comprised only intact males and capons. The concentration of testosterone was drastically reduced by caponization but remained detectable (trial 1). In both trials, BW was lower for capons during 4 to 9 or 10 wk of age when contrasted to intact males (P < 0.05). In trial 1, capons had heavier livers than intact males and sham-operated chickens. In addition, they had lighter hearts than sham-operated chicks (P < 0.05). In trial 2, capons displayed smaller drumstick and heart weights (P < 0.05). There was a tendency for increased fat pad weight in capons (P < 0.10). Caponization resulted in increased skin-fat weights of the thigh and the breast of 24 wk of age. This was also valid for carcass fat, when expressed as a percentage of the cold carcass weight, and intramuscular fat. Caponization had no effect on pH 24 h postmortem and cooking loss. Capons' breasts had lower shear values and displayed lighter, more yellow, and less red meat than that of intact males. Conclusively, caponization, without affecting growth performance, altered meat quality characteristics, resulting in special quality chicken meat.

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

This study was conducted to determine the role and effects of testosterone in lipogenesis by measuring and analyzing the lipid composition and lipogenic enzyme activity of livers from capons treated with various doses of exogenous testosterone implant. Healthy and uniform male Single Comb White Leghorn chickens were caponized at 12 wk of age. Sixteen-week-old capons were randomly selected for a 10-wk experiment. Fifteen intact males and 15 capons were used for trial 1. In trial 2, 10 sham-operated males and 40 capons were used. The capons were randomly divided into 4 independent treatments with sialistic implants of cholesterol (1.62 mm i.d., 3.6 mm o.d., 9.24 +/- 0.36 mg; CHOL), low testosterone (1 mm i.d., 3 mm o.d., 5.88 +/- 0.23 mg), medium testosterone (1.62 mm i.d., 3.16 mm o.d., 9.81 +/- 0.17 mg), or high testosterone (2 mm i.d., 4 mm o.d., 16.7 +/- 0.24 mg). In trial 1, the results showed that caponization increased total hepatic lipid and triacylglycerol contents and decreased the nonesterified fatty acid content (P < 0.05) compared with the intact male. Meanwhile, caponization increased nicotinamide adenine dinucleotide phosphate -malic dehydrogenase (MDH) activity and MDH mRNA content (P = 0.09) simultaneously. In trial 2, comparing treatments with the various implantation doses of testosterone, the liver triacylglycerol content of capons the medium-dose implantation was decreased as compared with those receiving CHOL (P < 0.05). The total lipid and phospholipid contents of liver were decreased in capons receiving the high-dose implantation (P < 0.05), whereas the relative weight and nonesterified fatty acid content were increased (P < 0.05) and reached the same level as those in the sham treatment (P > 0.05). With an increased implantation dose, MDH activity of capons receiving the medium dose or higher was not different from those receiving the CHOL and sham treatments (P > 0.05). The increase in MDH activity at the transcriptional and translational levels suggests that caponization may positively regulate hepatic lipogenesis. In contract, implantation of testosterone up to the threshold concentration depressed hepatic lipogensis and lipid accumulation.

Effects of Caponization and Different Exogenous Androgen on the Bone Characteristics of Male Chickens

The effects of caponization and androgen implantation on the bone characteristics of male chickens were evaluated. Healthy Single Comb White Leghorn cockerels were caponized or sham operated (sham) at 12 wk old. Sixteen birds from each group were selected for a 14-wk experiment in trial 1. Sixteen birds from the sham group and 64 from the caponized group (randomly allocated into 4 treatments) were implanted with 10.4 +/- 0.4 mg (1.62-mm i.d., 3.6-mm o.d.) of cholesterol, testosterone (TES), 5alpha-dihydrotestosterone (5alpha-DHT), or 19-nortestosterone (19-NorT) and were assigned to trial 2 for a 14-wk experiment. The results from trial 1 showed that caponization increased BW (P < 0.05) and decreased tibia stress, ash content, and P content with higher blood P concentration (P < 0.05) as compared with the sham group. In trial 2, the cholesterol implantation group showed the lowest tibia breaking strength, bending moment, stress, and ash content (P < 0.05). The 19-NorT implantation group showed decreased (P < 0.05) blood Ca and P concentration but increased tibia ash and P content, reaching the same level as the sham group (P > 0.05). The adverse effects of caponization on bone characteristics could be improved using androgen implantation. Among the implantation groups, the 19-NorT implantation group showed the best improvement in tibia breaking strength and bending moment, followed by the TES and 5alpha-DHT groups. The TES group showed the best improvement in tibia stress, followed by the 19-NorT and 5alpha-DHT groups.