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

The transcriptome pattern of liver, spleen and hypothalamus provides insights into genetic and biological changes in roosters in response to castration

Chicken is widely accepted by consumers because of its delicate taste and abundant animal protein. The rooster after castration (capon) is believed to show better flavor, however, the molecular changes of the underpinned metabolism after castration is not yet understood. In this study, we aimed to figure out the alternation of meat quality and underpinned molecular mechanism via transcriptomic profiling of liver, spleen and hypothalamus as targeted organs in response to the castration. We identified differential expressed genes and their enriched functions and pathways in these organs between capon and rooster samples through RNA-seq analysis. In the liver, the lipid metabolism with targeted FABP1gene was found significantly enriched, which may be as one of the factors contributing to increased fat deposition and thus better meat flavor in capons than roosters, as predicted by the significantly lower shear force in capons than in roosters in meat quality experiments. However, the ability to xenobiotic detoxification and excretion, vitamin metabolism, and antioxidative effect of hemoglobin evidenced of the capon may be compromised by the alternation of SULT, AOX1, CYP3A5, HBA1, HBBA, and HBAD. Besides, in both the spleen and hypothalamus, PTAFR, HPX, CTLA4, LAG3, ANPEP, CD24, ITGA2B, ITGB3, CD2, CD7, and BLB2 may play an important role in the immune system including function of platelet and T cell, development of monocyte/macrophage and B cell in capons as compared to roosters. In conclusion, our study sheds lights into the possible molecular mechanism of better meat flavor, fatty deposit, oxidative detoxification and immune response difference between capons and roosters.

A selected population study reveals the biochemical mechanism of intramuscular fat deposition in chicken meat

BACKGROUND

Increasing intramuscular fat (IMF) is an important strategy to improve meat quality, but the regulation mechanism of IMF deposition needs to be systematically clarified.

RESULTS

A total of 520 chickens from a selected line with improved IMF content and a control line were used to investigate the biochemical mechanism of IMF deposition in chickens. The results showed that the increased IMF would improve the flavor and tenderness quality of chicken meat. IMF content was mainly determined both by measuring triglyceride (TG) and phospholipid (PLIP) in muscle tissue, but only TG content was found to be decisive for IMF deposition. Furthermore, the increase in major fatty acid (FA) components in IMF is mainly derived from TGs (including C16:0, C16:1, C18:1n9c, and C18:2n6c, etc.), and the inhibition of certain very-long-chain FAs would help to IMF/TG deposition.

CONCLUSIONS

Our study elucidated the underlying biochemical mechanism of IMF deposition in chicken: Prevalent accumulation of long-chain FAs and inhibitions of medium-chain FAs and very long chain FA would jointly result in the increase of TGs with the FA biosynthesis and cellular uptake ways. Our findings will guide the production of high-quality chicken meat.

Feed Restriction Improves Lipid Metabolism by Changing the Structure of the Cecal Microbial Community and Enhances the Meat Quality and Flavor of Bearded Chickens

Excessive fat deposition in full-fed Bearded chickens does not only reduce carcass yield but also causes consumer rejection of meat. Feed restriction (FR) is an effective method to save on feed cost, reduce carcass fat deposition, and improve meat quality. A total of 560 150-d Bearded chickens were randomly divided into seven groups (each with eight replicates of ten birds) for 40 days. The control group was fed with the basal diet ad libitum (CON), and the other six groups were fed with 90% of the feed intake (90% FI), 80% FI, 70% FI, 90% metabolizable energy (90% ME), 80% ME, and 70% ME of the CON, respectively. Compared to the CON group, FR increased meat yield, but the total weight of the Bearded chickens was slighter; 80% FI and 70% ME improved the relative lipid metabolism indices of chickens, especially the levels of triglycerides and total cholesterol in the plasma and liver (p < 0.05), and decreased calpastatin activity in the breast muscle (p < 0.05). Additionally, 16S rRNA sequencing of cecal microbial community indicated that an increase in the abundance of Hydrogenoanaerobacterium and Bacteroides plebeius was observed in the 80% FI group (p < 0.05), and an enrichment in Olsenella, Catabacter, and Lachnospiraceae were observed in the 70% ME group (p < 0.05) compared to the CON group. Moreover, compared to the CON group, the L * value of the breast muscle significantly decreased, and a * value significantly increased in the 80% FI group (p < 0.05). Notably, the concentrations of threonine, lysine, aspartic acid, glutamic acid, proline, and arginine and the activity of calpain in breast muscle increased in the 80% FI group more than in the CON group (p < 0.05), while valine, isoleucine, leucine, phenylalanine, lysine, alanine, tyrosine and proline decreased in ME restriction groups (p < 0.05). Taken together, our results indicated that 80% FI could improve lipid metabolism by changing the structure of the cecal microbial community, and the meat quality and flavor of the Bearded chickens in 80% FI group was improved with a promoted meat color score, flavor substances, and the calproteinase system.

Ovary removal modifies liver message RNA profiles in single Comb White Leghorn chickens

Ovaries produce sex hormones, and ovariectomized animals are often used as models for ovarian dysfunction. The liver is a vital organ involved in metabolism and immunity. In the present study, we conducted experiments to investigate the effects of ovariectomy on transcription and metabolic processes in the liver in chicken. Eight Single Comb White Leghorn (SCWL) female chickens were ovariectomized at 17 wk of age, and 8 intact SCWL females served as controls. At 100 wk of age, all chickens were euthanized. High-throughput transcriptome sequencing was performed on liver RNA obtained from ovariectomized and intact females. A total of 267 differentially expressed genes (DEG) were identified in our study. After analysis using DAVID functional annotation tool, one significant Kyoto Encyclopedia of Genes and Genomes pathway, the phosphatidylinositol signaling pathway, was clustered. Gene Ontology enrichment analysis yielded 46 significant Gene Ontology terms. Among terms describing biological processes, the glycerolipid metabolic and lipid localization processes were dominant. The anabolic genes, PEPCK and GK5, and the catabolic genes, VTG1; VTG2; PLD5; DGKQ; DGKE; and FABP3, were detected in ovariectomized chickens. Differentially expressed genes such as ENSGALG00000000162, IL-1Β, SVOPL, and CA12 implied that livers in ovariectomized chickens were subjected to strong inflammatory reactions, whereas defenses against endogenous materials were compromised. A comprehensive view of gene expression in the liver of ovariectomized chickens would advance our understanding of lipid metabolism, glycometabolism, and their relationships to pathologies induced by absence of the ovary. The identified DEG indicated that ovariectomy disturbed lipid metabolism in the liver and was accompanied by an increase in hepatic gluconeogenesis and reductions in phosphatidic acid synthesis and lipid carrier capacity.

Identification of the Differentially Expressed Genes of Muscle Growth and Intramuscular Fat Metabolism in the Development Stage of Yellow Broilers

High-quality chicken meat is an important source of animal protein for humans. Gene expression profiles in breast muscle tissue were determined, aiming to explore the common regulatory genes relevant to muscle and intramuscular fat (IMF) during the developmental stage in chickens. Results show that breast muscle weight (BMW), breast meat percentage (BMP, %), and IMF (%) continuously increased with development. A total of 256 common differentially expressed genes (DEGs) during the developmental stage were screened. Among them, some genes related to muscle fiber hypertrophy were upregulated (e.g., CSRP3, LMOD2, MUSTN1, MYBPC1), but others (e.g., ACTC1, MYL1, MYL4) were downregulated from Week 3 to Week 18. During this period, expression of some DEGs related to the cells cycle (e.g., CCNB3, CCNE2, CDC20, MCM2) changed in a way that genetically suggests possible inhibitory regulation on cells number. In addition, DEGs associated with energy metabolism (e.g., ACOT9, CETP, LPIN1, DGAT2, RBP7, FBP1, PHKA1) were found to regulate IMF deposition. Our data identified and provide new insights into the common regulatory genes related to muscle growth, cell proliferation, and energy metabolism at the developmental stage in chickens.

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.

Influence of storage and packaging method on chicken breast meat chemical composition and fat oxidation

The aim of this study was to determine the influence of storage conditions and packaging methods on chicken breast meat chemical composition and fat oxidation. In this study, chicken breasts available in retail sale were used for evaluation. The meat packed by three different methods (air packaging-AP, modified atmosphere packaging-MAP, and vacuum packaging-VP) was stored in a cooling room or a commercial display case for 9 D and tested for basic chemical composition, lipid oxidation (TBARS), and fatty acid composition. Meat in MAP during storage in the cooling room was characterized by higher (P ≤ 0.05) TBARS values as compared to meat packaged in AP and VP, respectively. The highest share in the fatty acid profile in chicken breasts was demonstrated by monounsaturated fatty acid, including cis C18:1 (n9 + n11) acid in the range from 31.86 to 34.66%. A high share of polyunsaturated acids was observed, including linoleic (C18:2 cis, cis) acid from 24.50 to 31.22% of all fatty acids. The simple relationship between the changes in the profile of fatty acids in meat packaged using different methods and in storage time was not determined, likely due to the variability of the composition of fatty acids in chicken breasts depending on the sample and the general low level of fat found in the meat.

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.

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.

Expression and effect of Calpain9 gene genetic polymorphism on slaughter indicators and intramuscular fat content in chickens

Calpain 9 (CAPN9) is expressed in the stomach and small intestine. CAPN9 has regulatory roles in hypertension, heart disease, gastric mucosal defense, and kidney disease. The involvement of CAPN9 has not been reported in the development of chickens. CAPN9 mRNA was found in adipose and muscle tissue in this study. Two linkage single nucleotide polymorphisms (SNP; G7518A and C7542G) in intron 4 were screened from 160 birds of the D2 chicken line. The 2 mutation sites were associated with carcass weight, evisceration weight, abdominal fat weight (AFW), abdominal fat percentage (AFP), and breast muscle percentage (all P < 0.05). Intramuscular fat (IMF) content was not significantly different in the 3 genotypes. But, the AA(7518)/GG(7542) genotype had the highest IMF content, highest breast muscle weight, and lower AFW and AFP. Moreover, the mRNA level of CAPN9 in abdominal fat tissue was significantly different (P < 0.05 or P < 0.01) between any 2 genotypes, consistent with AFW and AFP. In summary, the expression of CAPN9 in adipose and breast muscle tissue is reported for the first time. CAPN9 affected production performance of chickens. As a marker, the linkage G7518A and C7542G polymorphisms in intron 4 of CAPN9 could affect the production traits by regulating mRNA expression. The findings concerning the marker enrich the theoretical foundation for molecular breeding of high-quality broilers.

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.

Meat quality of poulards obtained from three conserved breeds of hens

The aim of the study was to determine the effect of genotype (breed/line) and spaying of pullets on body weight, estradiol level, carcass and meat quality. Subjects were Rhode Island Red (R-11), Yellowleg Partridge (Ż-33) and Sussex hens (S-66), 100 birds per line, which were divided into 2 groups, each having 50 pullets and 50 poulards. Spaying was performed at 10 wk of age, under local anesthesia by a veterinarian. The present study showed that blood estradiol levels in poulards were much lower than in pullets regardless of genotype. Poulards showed higher body weight and their carcasses higher lightness and yellowness. In the sensory evaluation, poulard breast meat was more tasty and leg meat also more juicy and tender compared to pullet meat. Among the three conserved breeds, Rhode Island Red (R-11) and Yellowleg Partridge (Ż-33) hens are the best starting material for poulard production. Their carcasses showed good muscling and intense yellowness desirable to the consumers. R-11 birds achieved highest body weight. Spaying of pullets had no significant effect on the profile of fatty acids, but greater and statistically significant differences in this regard were found between hen lines. Compared to S-66 birds, breast muscles of R-11 and Ż-33 birds contained more polyunsaturated fatty acids (PUFA). The breast and leg muscles of these birds had a lower content of saturated fatty acids (SFA ).