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

Integrative analysis of the transcriptome, proteomics and metabolomics reveals key genes involved in the regulation of breast muscle metabolites in capons

Castration is widely used in poultry and livestock to enhance fat metabolism and improve the flavor, tenderness and juiciness of meat. However, the genetic regulatory mechanism underlying castration consequences have not been clarified. To investigate the key metabolites affecting the quality of capons and the key regulatory mechanisms, Qingyuan partridge roosters were subjected to castration. Metabolic profiling was used to detect differential metabolites in the breast muscle of both capon and control groups. Additionally, an integrative analysis of transcriptomics and proteomics was conducted to explore the genetic regulation mechanisms influencing meat quality. The results indicated that the muscle fiber density and shear force of capons was lower than that of normal chickens, and the fat percentage of capon group (CAM) was higher than control group (COM). The expression of the metabolite inostine-5'-monophosphate (IMP) was lower in capons, and lipid metabolites (PC (10:0/10:0), PC (6:0/13:1), LPC 22:6, LPC 18:2, LPE 18:1, LPE 20:4) were higher in capons. Metabolic pathways were found to be a common signaling pathway in all omics. Glutamate-ammonia ligase (GLUL), acetyl-CoA carboxylase beta (ACACB), 1-acylglycerol-3-phosphate O-acyltransferase 2 (AGPAT2), 4-hydroxy-2-oxoglutarate aldolase 1 (HOGA1) and glutathione S-transferase alpha 2 (GSTA2) regulate the expression of citric acid, arachidonic acid, palmitic acid, isocitric acid, and betaine. These findings highlight the key mechanisms contributing to the meat quality differences between capons and normal 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.

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.

The sex impact on the technological and chemical characteristics of meat derived from the Polish native chicken breed

The aim of the study was to evaluate the birds' sex as well as the caponisation influence on the technological traits of obtained meat, fatty acids profile as well as main chemical compounds distribution. In this study, 40 hens, roosters and green-legged partridge capons each were used (4 replications each). At 24 weeks of age, 2 birds from each replication subgroup were selected and slaughtered. During dissection analysis, pectoral and femoral muscles were sampled. Acidity, colour, tenderness, water holding capacity, drip and cooking loss were determined in the obtained material. The fatty acid profile of the meat was also determined, as well as the distribution of components in the pressed meat samples using FTIR spectroscopy. Statistically significant differences in the colour lightness index (L*) of the breast muscles were recorded, with cockerel meat being the darkest and capon meat the lightest. The greatest natural water loss was recorded in the hens' pectoral muscle; cooking loss was also the greatest in these samples. Roosters showed significantly the lowest content of monounsaturated fatty acids, at the same time the highest proportion of the n3 fatty acids group was found in capons. Irrespective of muscle, meat from roosters showed the highest susceptibility to oxidation (PI index). The variation in the chemical composition of the meat was confirmed by FTIR mapping.

Physicochemical characteristics of meat from capons derived from the crossing of conserved breed hens and meat roosters

The study aimed to determine the effect of castration on physicochemical properties of meat from capons derived from the crossing of Rhode Island Red (R-11) hens and meat roosters. Subjects were 100 crossbred cockerels, which were randomly assigned to 2 groups of 50 each. Group I (control) consisted of intact cockerels and birds from group II were subjected to castration. The castration was performed at 7 wk of age under local anesthesia by a veterinarian. All birds were fed ad libitum with the same feed mixtures and placed on litter under optimal environmental conditions at a stocking density of 5 birds/m². At the end of fattening (20 wk of age), 10 birds whose body weight was similar to group average, were selected from each group for slaughter. After slaughter, the birds were analyzed for dressing percentage and physicochemical parameters of breast and leg muscles, which were subjected to sensory evaluation. The results demonstrated that compared to intact cockerels, capons were characterized by significantly higher body weight, dressing percentage and carcass muscle content. Both the breast and leg muscles of the capons showed better physicochemical parameters and higher sensory score. It is therefore concluded that the birds derived from the crossing of Rhode Island Red (R-11) hens and meat roosters are good material for capon production, their meat is a product of distinctly higher quality.

Identification of Candidate Genes for Meat Color of Chicken by Combing Selection Signature Analyses and Differentially Expressed Genes

Meat color, an important index of chicken quality, is highly related to heme pigment, glycolysis, and intramuscular fat metabolisms. The objective of this study is to obtain candidate genes associated with meat color in chickens based on the comparison of fast-growing, white-feathered chickens (Line B) and slow-growing, yellow-feathered chickens (Jingxing Yellow), which have significant differences in meat color. The differentially expressed genes (DEGs) between Line B and Jingxing Yellow were identified in beast muscle. The fixation index (F_ST) method was used to detect signatures of positive selection between the two breeds. Screening of 1109 genes by the F_ST and 1317 candidate DEGs identified by RNA-seq. After gene ontology analysis along with the Kyoto Encyclopedia of Genes and Genomes, 16 genes associated with glycolysis, fatty acid metabolism, protein metabolism, and heme content were identified as candidate genes that regulate the color of chicken breast meat, especially TBXAS1 (redness), GDPD5 (yellowness), SLC2A6 (lightness), and MMP27 (lightness). These findings should be helpful for further elucidating the molecular mechanisms and developing molecular markers to facilitate the selection of chicken meat color.

Genome-Wide Association Study Using Whole-Genome Sequencing Identifies a Genomic Region on Chromosome 6 Associated With Comb Traits in Nandan-Yao Chicken

Comb traits have potential economic value in the breeding of indigenous chickens in China. Identifying and understanding relevant molecular markers for comb traits can be beneficial for genetic improvement. The purpose of this study was to utilize genome-wide association studies (GWAS) to detect promising loci and candidate genes related to comb traits, namely, comb thickness (CT), comb weight (CW), comb height, comb length (CL), and comb area. Genome-wide single-nucleotide polymorphisms (SNPs) and small insertions/deletions (INDELs) in 300 Nandan-Yao chickens were detected using whole-genome sequencing. In total, we identified 134 SNPs and 25 INDELs that were strongly associated with the five comb traits. A remarkable region spanning from 29.6 to 31.4 Mb on chromosome 6 was found to be significantly associated with comb traits in both SNP- and INDEL-based GWAS. In this region, two lead SNPs (6:30,354,876 for CW and CT and 6:30,264,318 for CL) and one lead INDEL (a deletion from 30,376,404 to 30,376,405 bp for CL and CT) were identified. Additionally, two genes were identified as potential candidates for comb development. The nearby gene fibroblast growth factor receptor 2 (FGFR2)-associated with epithelial cell migration and proliferation-and the gene cytochrome b5 reductase 2 (CYB5R2)-identified on chromosome 5 from INDEL-based GWAS-are significantly correlated with collagen maturation. The findings of this study could provide promising genes and biomarkers to accelerate genetic improvement of comb development based on molecular marker-assisted breeding in Nandan-Yao chickens.

Effects of Caponization on Growth Performance and Meat Physicochemical Properties of Crossbred Chickens

The aim of the study was to determine the effect of caponizing on body weight and physicochemical properties of meat of the capons – hybrids obtained from the crossing of hens of the Yellowleg Partridge (Ż-33) breed with meat roosters. The study covered 80 hybrid roosters, which were randomly assigned to two groups of 40 animals each (8 boxes of 10 birds in each group). Group I (control) consisted of uncastrated roosters while group II included birds, which were castrated at 8 weeks of age under local anaesthesia by a vet. Birds were fed ad libitum with the same standard diets and kept on litter under optimal environmental conditions with a stocking density of 7 animals/ m2. At the end of fattening, i.e. in the 20th week of life, 8 birds with a body weight close to the group average were selected from each group for slaughter. After slaughter, the effectiveness of the procedure was checked (lack of testicles), then the slaughter performance of birds, physicochemical parameters of the pectoral and leg muscles were determined, and sensory evaluation was performed. The procedure of castration of hybrid roosters had a positive effect on body weight, feed conversion ratio and carcass traits. The pectoral and leg muscles of the capons were characterized by better water absorption, tenderness and sensory evaluation compared to roosters. Among the assessed groups of birds there was also a variation in the colouring of whole carcasses and muscles, which were lighter (L*), more yellow (b*) and less red (a*) in caponized birds. In addition, the castration procedure had a positive effect on the total protein content in both the pectoral and leg muscles, which in turn, with a higher raw fat content, were distinguished by a favourable ratio of n-6/n-3 polyunsaturated fatty acids (PUFA). Based on the results, it can be concluded that the hybrids obtained from the crossbreeding of the Yellowleg Partridge (Ż-33) and Ross 308 meat roosters are good choice for capon production. They can complement poultry meat production with a niche product for consumers looking for products of exceptional quality.

Improvac immunocastration affects the development of thigh muscles but not pectoral muscles in male chickens

Improvac has been tentatively used to immune-castrate roosters. The aim of this study was to investigate whether Improvac affected skeletal muscle development in chickens. The muscle fiber type and size and the expression levels of genes related to muscle development in pectoral and thigh muscles were examined at 5, 9, and 14 wk of age in the control, early, late, and early + late Improvac-treated groups. Immunocastration with Improvac affected the development of thigh muscles and the expression of MYH1B, MSTN, and SM. The cross-sectional area in the early group was significantly larger than in the control group at the 14th week (P < 0.01). At the fifth week, the expression levels of MYH1B, MYOD, and MSTN in the early group were significantly higher than those in the control group (P < 0.05), and at the ninth week, the expression level of SM1 in the control group was significantly lower than that in early and late groups (P < 0.05). Immunocastration did not affect pectoral muscle development or the expression of genes related to muscle development.

Effects of dietary perilla seed oil supplementation on lipid metabolism, meat quality, and fatty acid profiles in Yellow-feathered chickens

This study evaluated the effect of the dietary replacement of 1% lard (CT) with 1% perilla oil (PO), 0.9% perilla oil + 0.1% anise oil (PA), or 0.9% perilla oil + 0.1% ginger oil (PG) on indices of lipid metabolism, antioxidant capacity, meat quality, and fatty acid profiles from Yellow-feathered chickens at day 63. Compared with the CT chickens, those given perilla oil had decreased (P < 0.05) plasma lipid levels including triglycerides (TG), total cholesterol (TCH), and low-density lipoprotein cholesterol (LDL-C). Hepatic TG, TCH levels, and fatty acid synthase activity were also decreased (P < 0.05) in chickens fed diets containing perilla oil. Abdominal fat percentage was significantly decreased in birds fed the PG compared to CT diets. Birds fed the PA or PG diets had increased (P < 0.05) hepatic total SOD, glutathione peroxidase, and glutathione-S-transferase than in chickens given PO alone. In addition, the content of reduced glutathione (GSH) in breast muscle was lower (P < 0.05) in birds fed PO compared with those given PG, and the reverse was true for content of malondialdehyde. Compared with the CT diet, the PO diet decreased breast muscle shear values and increased yellowness (b*) of breast muscle (P < 0.05). Birds fed the PA or PG diets had meat with better overall acceptability than those fed the CT diet. Chickens fed perilla oil diets exhibited higher contents of α-linolenic acid (C18:3n-3), DHA (22:6n-3), polyunsaturated fatty acids, and n-3 fatty acids, together with a lower content of myristic acid (C14:0), palmitic acid (C16:0), stearic acid (C18:0), total saturated fatty acids, and n-6/n-3 ratio compared to controls (P < 0.05). These findings indicate that perilla oil has the potential to decrease lipid-related indices and improve fatty acid profiles of breast meat in chickens without adverse effect on antioxidant status or meat quality; this was even better when perilla oil was given together with anise oil or ginger oil.

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.

Suitability of layer-type male chicks for capon production

The aim of this study was to determine the effect of age and caponization on the growth performance and carcass quality characteristics of Leghorn cockerels. The experiment was conducted on 224 Leghorn cockerels. At 8 wk of age, 112 birds were surgically castrated by a qualified veterinarian in accordance with Commission Regulation (EC) No. 543/2008. The birds were divided into 2 sex categories (with 8 replications per group and 14 birds per replication). The birds were raised to 28 wk of age, and were fed commercial diets ad libitum. From 12 wk of age, at 4-wk intervals, 8 intact cockerels and 8 capons (1 bird per replication) were selected randomly and slaughtered. Caponization had a beneficial influence on the feed conversion ratio (FCR). FCR (kg/kg) based on body weight (BW) gain, carcass weight gain, and edible weight gain was lower in capons from 24 wk of age (P < 0.05), and FCR based on lean weight gain was lower in capons from 21 wk of age (P < 0.05). The content of edible components expressed as a percentage of the total BW of cockerels and capons was similar in the corresponding age groups. Caponization had no effect on the total lean meat content of the carcass (P = 0.744), but differences were found between the weights of breast muscles and leg muscles. In week 24 and 28, the weight of breast muscles was higher in capons than in cockerels (P < 0.05). Cockerels had higher leg muscle weight than capons, and significant differences were noted in week 16 and in 28 (P < 0.05).

The Effect of Slaughter Age and the Diet in the Final Growth Phase of Poulards on Productivity and Meat Quality

The aim of the studies was to evaluate the effect of the diet in the final growth phase and slaughter age of poulards on productivity, dressing percentage, carcass colour and physicochemical properties of meat. The studies were conducted on 78 hybrids obtained by crossing Ross 308 broiler roosters with Rhode Island Red (R-11) dual-purpose laying hens (♂Ross 308 × ♀R-11). Birds were assigned to 3 groups: control group (K) fed starter, grower and finisher diets without addition of dairy products, experimental group S offered a finisher diet supplemented with 4% whey, and experimental group M receiving 4% milk powder supplement in the final growth phase. Spaying procedure was carried out at 8 weeks of age. Poulards were slaughtered at 18 and 20 weeks of age. The studies showed that by using hybrids of dual-purpose hens with broiler roosters for production of poulards, rearing period could be shortened to 18 weeks, and the obtained meat had comparable or even better quality traits compared with poulards slaughtered at 20 weeks of age. Supplementation of poulard diet with 4% whey or milk powder in the final growth phase had a beneficial effect mostly on improvement of sensory properties of meat. There were not many significant differences in meat quality between poulards fed the diet supplemented with milk and whey but instead there were differences between these groups and the control group fed the diet without these additives.

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 caponisation and age on the histology of the internal organs of Leghorn cockerels

1. Poultry researchers seek the most efficient bird line to produce capons (castrated cockerels). The previous studies did not include results from histopathological analyses of internal organs after caponisation. No data have been published on whether adipose tissue accumulates in internal organs or if caponisation changes the structure of the lymphoid organs and the accumulation of lymphoid cells. 2. The aim of this study was to analyse the occurrence of histopathological lesions in internal organs from Leghorn (layer-type) capons and cockerels at different times of fattening. 3. Two hundred, one-day-old Leghorn cockerels were used in this experiment. At 8 weeks of age, the birds were randomly divided into a control group (100 uncastrated cockerels) and a second group consisting of 100 castrated birds. At 12, 16, 20, 24 and 28 weeks of age, six cockerels and six capons were slaughtered. Samples of all internal organs from six cockerels and six capons at each slaughter age were evaluated. 4. The main histopathological differences between capons and cockerels were related to the accumulation of adipose tissue, with higher values noted in capons, especially in the gizzard and the caecum submucosa and fatty degeneration in liver hepatocytes. 5. Additionally, differences were observed more often in cockerels than in capons with regard to depletion of lymphoid cells in lymphoid organs, including the thymus and bursa of Fabricius in 28-week-old birds and the spleen in 24-week-old birds. 6. These studies prove that caponisation causes the accumulation of fat in internal organs and changes the structure of lymphoid organs. 7. Age influences the occurrence of desirable lesions, such as the accumulation of adipose tissue within the examined organs, and older capons (24 and 28 weeks old) are better sources of high quality, potentially edible tissues.

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.

Identification of molecular pathways and candidate genes associated with cocks' comb size trait by genome-wide transcriptome analysis

The comb of the male is an important secondary sexual characteristic. Although quantitative trait loci (QTLs) related to comb size have been identified, molecular mechanisms underlying this trait remain mostly unknown. In this study, RNA sequencing (RNA-seq) was employed to compare whole transcriptomic differences between two groups of Partridge Shank chickens that are divergent in comb sizes. A total of 563 differentially expressed genes (DEGs) were identified, including 277 up-regulated and 286 down-regulated DEGs. According to the animal QTL database, eight DEGs including BMP2 and CHADL matching the reported QTLs were associated with the comb size. Functional annotation analysis revealed that DEGs were involved in cell communication and calcium signaling. Protein-protein interaction network analysis showed that STK32A, PIK3R1, EDN1, HSPA5, and HSPA8 have an impact on comb growth. Moreover, potential alternative splicing events and single nucleotide polymorphisms were also identified. Our data provide a source for identifying genes and pathways with functions critical to comb size and accelerate studies involving molecular mechanisms of this sexual ornament.

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.

The analysis of meat and bone traits of Plymouth Rock cockerels and capons (P55) at different age

The aim of the study was the comparison of Plymouth Rock cockerels and capons and the evaluation of the influence of their age on slaughter yield, meat quality, and bone traits. The studies were conducted on cockerels and capons from P55 strain (Plymouth Rock). At 16, 18, and 20 wk of rearing, a dissection of whole carcasses of cockerels and capons was conducted, and breast and leg muscles were evaluated in terms of the physical and chemical traits, as well as the chemical composition. Also, traits of femur and tibia bones were studied. It was indicated that capons were characterized by a higher body weight (BW) before slaughter and higher weight of the eviscerated carcass than cockerels at consecutive dates of slaughter. Based on BW, the slaughter yield and muscle content of carcasses, it was found that the most optimal slaughter time in Plymouth Rock cockerels is at 18 wk and capons at 20 wk. It was observed that caponization had a significant effect on the chemical composition of breast muscles with respect to water and protein content. Along with bird age, collagen content in muscles decreased; however, significant differences were observed only in capons. At consecutive dates of evaluating cockerels, resistance and toughness of their femur and tibia bones increased significantly. Significant changes in the physical characteristics of bones were also found.

Long-bone properties and development are affected by caponisation and breed in Polish fowls

1. The aim of the study was to investigate the effects of caponisation on bone development of males of two native breeds in Poland. 2. The weight, length and cross-sectional area of tibiae and femora were measured, densitometric measurements and tests of strength were determined and dimensions were calculated. 3. Breed and caponisation did not influence bone weight and length. Higher mechanical strength of the femur was found in entire males, mainly in the Polbar breed. Tibial strength was reduced in capons of the Green Partridge breed. Maximum elastic strength was greater in the Polbar, irrespective of caponisation. Bone cross-sectional area was influenced by breed, while caponisation reduced femoral bone mineral density in both breeds. 4. Caponisation thus increased growth rate but had adverse effects on bone development. 5. Caponisation had fewer negative effects in the Polbar than in the Greenleg Partridge.

Effects of the origin and caponisation on carcass and meat traits in cockerels and capons aged 18 weeks

The aim of the present research was to evaluate the effect of the origin and caponisation on selected slaughter traits and quality indicators of meat in cockerels and capons of strains N88 (New Hampshire), R55 (Rhode Island Red), S11 (Sussex), and P55 (Plymouth Rock). The slaughter yield, breast muscle weight, percentage share of muscles in total in the carcasses, and fatness in general did not differ between the cockerels and capons within the evaluated strains. The trait that mostly distinguished cockerels from capons of strain N88 was the weight of leg muscles. Similarly, the fat content of carcasses expressed with the weight and percentage share of the skin with subcutaneous fat and abdominal fat did not differ between the evaluated groups of cockerels and capons. However, the weight of the leg muscles varied depending on the origin of cockerels and capons. As for the physiochemical properties of meat as well as its chemical composition, no significant differences were recorded in 18-week-old birds. The only obvious effect of the origin and caponisation was found on varied contents of fat in breast muscles in cockerels of strains N88 and P55, and capons of strain P55.

Effects of ovariectomy on body measurements, carcass composition, and meat quality of Huainan chickens

This study investigated the effects of ovariectomy on body measurements, carcass composition, meat quality, and steroid hormone concentrations of Huainan female chickens. The left ovaries of healthy Huainan chickens were surgically or sham removed at 7 weeks of age. Two slaughters were performed at 14 and 23 weeks of age. In each slaughter, 15 control, sham-operated, and ovariectomised chickens were used, respectively. The ovariectomised group had higher (P < 0.05) body length, keel length, body depth, and weight gain than the other two groups at 14 weeks of age. Ovariectomy increased bodyweight at 14 and 23 weeks of age. However, dressing percentage, breast muscle yield, and leg muscle yield were not affected by ovariectomy. Compared with intact and sham-operated chickens, ovariectomised chickens had higher shear force values at 23 weeks of age and higher redness values (a*) at 14 and 23 weeks of age in breast meat. Moreover, ovariectomy decreased and increased serum concentrations of oestradiol and testosterone, respectively. Therefore, ovariectomy increased bodyweight, altered breast meat quality by increasing redness values, and increased body size and growth rates during the early stage, with no effects on carcass composition yield in female chickens.

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.

Effect of caponization on performance and quality characteristics of long bones in Polbar chickens

The effect of caponization on the mechanical properties of Polbar chicken bones was the subject of investigation. The biomechanical strength of bones and the risk of their deformation or fracture were determined on the basis of their geometric, structural, material, and densitometric properties. Eight-week-old cockerels of Polbar breed were surgically castrated and then fattened until the 24th week of life. It was observed that caponization did not influence the weight and length of either of the long bones. It did however significantly reduce their ash content and the Ca and P contents in their femur, and P content in their tibia. Dual energy x-ray absorptiometry densitometry revealed that bone mineral content of the mid-diaphyseal part of both bones were reduced. Similarly, the bone tissue density of bones decreased. Caponization influenced the bone's geometric structure increasing the internal and external diameters of the bones. The bone cross-sectional area was greater in capons, and, consequently, the cross-sectional moment of inertia and the radius of gyration significantly increased. However, the relative wall thickness and cortical index were not altered. The three-point bending tests revealed the negative effect of caponization on the mechanical endurance of bones. Yield strength, Young modulus, and yield stress, characterizing the strength of the bone's material, decreased in capons. That suggests a higher risk of permanent deformation as capon bones become less elastic. Concluding, caponization negatively influenced the quality characteristics of Polbar chicken long bones.

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.

The analysis of meat traits of Sussex cockerels and capons (S11) at different ages

The aim of the study was to compare Sussex cockerels and capons as well as to estimate the influence of age on slaughter yield and meat quality. The tests were performed on cockerels and capons from strain S11 (Sussex). At 16, 18, and 20 wk of age, a dissection of the entire carcass was conducted. The breast and leg muscles were tested for physio-chemical traits, as well as chemical parameters. It was noted that, due to significant differences in BW of the eviscerated carcasses between wk 18 and 20 of slaughter, the best time to cease rearing S11 cockerels could be wk 20. However, for S11 capons, the optimal time for slaughter appeared to be wk 18 (no significant differences in BW and carcass weight or musculature between wk 18 and 20). The trait which did not differ between cockerels and capons slaughtered at different ages was slaughter yield. Fatness of the cockerels increased with age whilst the weight of capons' skin with subcutaneous fat was the same at wk 18 and 20 of evaluation. With increasing age, pH indicators of cockerels and capons' breast muscles were increasing; the water holding capacity of capons' breast muscles were also increasing. Both cockerels and capons showed darker color of breast muscle at wk 20 compared to wk 16 of evaluation. Redness of the breast muscle in the following periods of evaluation did not show significant differences, although with age, the yellowness of the cockerels and capons' breast muscle increased significantly. Among cockerels and capons, the water content in the breast and leg muscles were decreasing with age whilst the protein content was increasing. A significant growing tendency of the percentage of fat share in the breast and leg muscles with age was noted in the capon group. Conclusions for breeding practice are as follows: due to meat and quality traits, Sussex cockerels and capons can be used until wk 18 or 20 of life.