Effect of light restriction on productive results and behavior of broiler chickens

The study aimed to evaluate the effect of light restriction (18L:6D vs. 14L:10D), genotype (A vs. B), and sex on performance, behavior, and meat quality, and the occurrence of wooden breast (WB) and white striping (WS) in broiler chickens. To this purpose 704 one-day-old chickens of 2 genotypes, half males and half females, were reared from hatching until slaughtering at 45 d of age in 32 collective pens (22 chickens per pen). Light restriction reduced growth rate and final live weight (LW), but improved feed conversion ratio (FCR) (P < 0.01) and reduced inactive behaviors of chickens (P < 0.001). Light restriction also reduced WS occurrence in breasts (89.5 to 64.6%; P < 0.001) and reduced meat shear force (2.64 to 2.20 kg/g; P < 0.05) and ether extract content (2.29 to 1.87%; P < 0.05). Regarding genotype, compared to genotype B, chickens of genotype A were heavier (3,242 g vs. 3,124 g; P < 0.01) with higher cold carcass weight and Pectoralis major muscle yield (12.9 vs. 12.0%; P < 0.001) and a higher FCR (1.63 vs. 1.61; P < 0.01). Finally, females had lower final LW (2,852 g vs. 3,513 g) and higher FCR (1.64 vs. 1.59) than males (P < 0.001), but a higher proportion of breast and P. major (P < 0.001), lower cooking losses (P < 0.001) and shear force (P < 0.01), and higher protein content (21.6 vs. 20.7%; P < 0.001). In conclusion, light restriction depressed growth, but was effective in decreasing WS occurrence and improved feed conversion. The decrease in inactive behaviors (sitting/laying) of light-restricted chickens can be positively considered in view of animal welfare.

Black soldier fly larvae used for environmental enrichment purposes: Can they affect the growth, slaughter performance, and blood chemistry of medium-growing chickens?

Introduction

This research has been aimed at evaluating the effects of live black soldier fly larvae (BSFL) (Hermetia illucens) on the growth, slaughtering performance, and blood parameters of medium-growing chickens.

Methods

A total of 240, 28-day-old, Label Rouge Naked Neck chickens were allotted to four experimental groups, according to the gender (males-females) and to the absence (control group, C) or presence (larvae group, L) of a dietary supplementation with 10% live BSFL, on the basis of the expected average daily feed intake (ADFI) (6 replicates/diet, 10 chickens/replicate). The birds were weighed weekly, and the feed consumption was recorded to calculate the average live weight, feed conversion ratio (FCR), average daily gain (ADG), and the ADFI. At 82 days of age, 2 birds/replicate (12 birds/diet) were selected and slaughtered. The blood samples were collected, and the carcass traits (carcass, breast, thigh, and organ weights and yields) were assessed.

Results and discussions

Overall, the administered live BSFL did not impair the growth and slaughtering performance, or the blood traits, while the C females showed a better FCR than the treated ones (P < 0.05). The live BSFL consumption time was longer for the females than for the males (P < 0.001). The weight of the immune organs (spleen and bursa of Fabricius) increased as the live BSFL supplementation increased (P < 0.05). Furthermore, the provision of live BSFL reduced the gamma glutamyl transferase (GGT, U/l) activity content in the blood (P < 0.05). Finally, both the leukocytes (%) and the monocytes (%) were more abundant in the C groups than in the larvae ones (P < 0.05 and P < 0.01, respectively). In short, the supplementation of live BSFL can be used successfully as an environmental enrichment, without affecting the growth performance of male birds. Furthermore, the immune organ activity could be enhanced by the provision of live BSFL.

Immunomodulatory Effects of Chicken Soups Prepared with the Native Cage-free Chickens and the Commercial Caged Broilers

The objective of this study was to compare the immunomodulatory effects of the chicken soups prepared with the native free-range chickens and the commercial caged broilers in the immunosuppressive mice. The immunosuppressive mice model was established by the intraperitoneal injection of 100 mg of cyclophosphamide (CTX) per kg body weight. The powders of Gushi Chicken Soup (GCS), Honglashan Chicken Soup (HCS), and Cobb Broiler Soup (CBS) were prepared by high-pressure stewing followed by spray drying. The chicken soups' nutrient content and the effects of three chicken soups on the body weight, organ index, blood index, and serum cytokine and immunoglobulin contents in the immunosuppressive mice were determined. The three chicken soups promoted the recovery of immunosuppressive mice, but the expression mechanisms were different. The GCS was more effective than the HCS and CBS in restoring blood index, promoting cytokine secretion, and increasing immunoglobulin content (P < 0.05). The HCS stimulated the Th1-type immune response and promoted immunoglobulin secretion (P < 0.05), while the CBS increased the production of CD4⁺ and promoted the T-cell functions better than other soups (P < 0.05). Although soups from the native free-range chickens and the commercial caged broilers showed distinctly different mechanisms in promoting immunity, both could be used as potential immunomodulators.

The Assessment of a Multifactorial Score for the Adaptability Evaluation of Six Poultry Genotypes to the Organic System

Simple Summary

The choice of a suitable poultry genotype for the organic system is still an open question. Currently, poultry genotypes are mainly classified on the basis of their daily weight gain (DWG). However, it is important to underline that the organic system is characterized by the presence of outdoor space; therefore, the grazing capacity of chicken and other intrinsic characteristics are crucial aspects. Indeed, although DWG is an important parameter, it is probably not the only factor that should be considered to determine the adaptability of poultry to this system, in which the genotype could also have an important role. Accordingly, this study defines an adaptability score (AS) using a multifactorial approach in order to consider simultaneously different variables such as behaviors, plumage conditions, and body lesions. Moreover, the specific effect of DWG and genotype on the AS were evaluated. This allowed us to conclude that the DWG and genotype are connected, but the chicken genotype is the driving force that should be considered in order to evaluate poultry’s adaptability to organic systems.

Abstract

This study aimed to develop an adaptability score (AS) for chicken strains, which includes behavioral, plumage conditions, and body lesion indicators through a multifactorial approach. A total of 600 male chickens from 6 poultry genotypes—Ranger Classic (R1), Ranger Gold (R2), Rowan Ranger (R3), Hubbard Red JA (A), CY Gen 5 × JA87 (CY), and M22 × JA87 (M)—were reared under organic conditions, fed ad libitum, and individually weighed weekly to calculate the daily weight gain (DWG). The behavioral observations consisted of the explorative attitude (EA), recorded at 21 days, and the behavioral patterns (BPs) recorded the week before the slaughter. The AS was established by a principal component analysis, and the AS of these genotypes was compared. Moreover, the effect of DWG and genotype on the AS was evaluated by univariable and multivariable regression models. Although the DWG and genotype were strictly dependent, genotype was the most important factor affecting the AS. In fact, its effect was significant both in univariable (p < 0.001) and multivariable models (p < 0.001). Conversely, the DWG was significant only in the univariable and lost significance when the effect of genotype was introduced in the model.

Techniques for in vivo assessment of myopathies in broiler chicken breasts using a biopsy as a support tool

An experiment was conducted to validate non-invasive evaluation techniques as in vivo evaluation tools for the myopathies wooden breast and white striping that affect broilers, using biopsy as a support tool. It evaluated 30 Cobb 500® broiler chickens in a completely randomized design consisting of two sexes (males and females) and 15 replications per treatment. At 14, 21, 35, 42 and 49 days, the surface temperature of the birds' breasts was recorded using infrared thermography, analysis of fillet depth, and echogenicity by ultrasound imaging. All broiler chickens were sent for biopsy at 21, 35 and 42 days to collect a fragment of the pectoral muscle for descriptive morphological analyses of histological lesions and muscle fibre morphometry. Males had higher echogenicity values at 14, 21 and 42 days. There was no influence of bird sex on the occurrence of the wooden breast and white striping myopathies at 49 days of age in broilers selected and submitted to the biopsy protocol. There was a general trend of decreasing surface temperature for both sexes according to their age. Muscles with less area occupied with fibres had a lower surface temperature. It was concluded that ultrasonography with a 3.5 MHz transducer detects muscle changes after 28 days of age, which is consistent with the myopathic lesions studied. Infrared thermography is a potential method for detecting changes in breast temperature indicating myopathic lesions. A biopsy can be used as an auxiliary tool in the study of myopathies in broiler chicken breasts.RESEARCH HIGHLIGHTS Detection of changes in the breast muscle after 28 days of age with ultrasonography.Changes in the surface temperature range of pectoral muscle with infrared thermography.Use of biopsy as a tool for early diagnostic evaluation in broiler myopathies.

Gastrointestinal Tract Morphometrics and Content of Commercial and Indigenous Chicken Breeds with Differing Ranging Profiles

Optimal development of the gut is important for nutrient absorption and for poultry to resist diseases. The aim of the study was to compare gastrointestinal tract morphometrics, small intestine microstructure, as well as the amount of pasture matter and feed ingested by the birds with outdoor access presenting either an outdoor-preferring, moderate-outdoor or indoor-preferring ranging profile. Sixty non-beak trimmed birds per strain: broiler hybrid Sasso and Polish indigenous green-legged partridge were housed from week 5 to 10 in groups of 10, under conditions of EU organic meat chicken production. Pens with outdoor ranges were video recorded, to obtain frequencies of the birds' range use. Statistical analysis was conducted applying generalized linear mixed models, applying the ranging profile as a fixed effect and pen as a random factor. The weight of the pasture matter in bird crops was the highest in moderate-outdoor profiled green-legged partridges, as compared to other ranging profiles (p = 0.04). In Sasso, villi in the small intestines were significantly higher in the outdoor-preferring compared to indoor-preferring profiled birds (p = 0.04), while their area was larger in the outdoor-preferring Sasso birds (p = 0.01). The level of development of the gastrointestinal tract and its content may be a potential indicator of the birds' ranging profile and forage consumption.

How the kinetic behavior of organic chickens affects productive performance and blood and meat oxidative status: a study of six poultry genotypes

The aim of this study was to analyze the relationship between the kinetic behavior, carcass characteristics, oxidative status (blood and meat), and meat fatty acid profiles of 6 organically reared slower growing chicken genotypes (SrG). One hundred male chickens of 6 SrG were used: Ranger Classic (RC), Ranger Gold (RG), Rowan Ranger (RR), RedJA (RJ), CY Gen 5 JA87 (CY), and M22 × JA87 (M). Twenty chickens/genotype were selected to analyze behavior, while, 15 individuals were slaughtered and different traits were analyzed in the blood and drumstick meat. The variables were grouped into different principal components: kinetic activity (PC1, with explorative attitude as the highest score), productive performance (PC2, carcass and head/feet yields), blood (PC3, carbonyls, and TBARS) and meat (PC6, thiols, and TBARS) markers, technological traits (PC4, pH, and color), proximate meat composition (PCA5, moisture, lipids, protein, and ash), fatty acid profile, and nutritional indexes (PC7, IP, and PUFAn-3). Uni- and bivariate analyses showed a strong positive association between kinetic behaviors and blood and meat oxidation and a medium positive association with fatty acid profile and nutritional indexes, whereas a negative association was found between productive performance loads and the technological traits of meat. Generalized linear models showed that all PCs were influenced by genotype. In particular, CY and M resulted as less active genotypes; conversely, RR showed more kinetic activity, whereas RJ, RG, and RC exhibited intermediate levels of activity. Cluster analysis of kinetic behavior and blood or meat oxidative status highlighted 2 groups: nonwalking (NW: CY and M) and walking (W: RC, RG, RR, and RJ) animals. However, in the W group, another was visualized, constituted by genotypes with high kinetic activity resulting in the worst oxidative balance (Walking not trained-genotypes, Wnt: RR and RJ). The present results confirmed that the kinetic behavior of SrG genotypes is negatively correlated with productive performance. Furthermore, a significant association between kinetic behavior and blood (positively correlated) or meat (negatively correlated) oxidative status was noted. Such differences are mainly due to the intrinsic response of the genotypes used (i.e., training-walking capacity).

An index to measure the activity attitude of broilers in extensive system

In organic poultry production it is important to rear animals with a dynamic attitude to take advantage of outdoor areas. Farmers are reluctant to use such strains due to their lower productivity and older slaughtering age. However, fast growing lines grown in organic system often suffer poor health and welfare conditions. The kinetic metabolism of chickens is correlated with different types of muscle fiber: type I (in red muscles or oxidative) for prolonged and moderate movement and type II (in white muscles or glycogenic) for fast movements. Red muscle metabolism produces energy mainly by β-oxidation of Highly Unsaturated n-3 Fatty Acids (HUFA). Accordingly, kinetic activity causes higher consume of HUFA in red muscles than in white muscles, so the ratio between n-3 HUFA and their precursor C18:3 n-3 (ALA) is likely to be smaller in red than in white muscles. However, these ratios are highly affected by the environment. To reduce the effect of environmental variables, we propose an "Activity index" as the difference between n-3 HUFA/ALA in white and red muscle within the same bird. This index, measured after slaughtering, should represent the activity performed by the chicken during its life. Given that birds in good health had the possibility of moving, the "Activity index" would measure the activity actually performed by the animals. Should birds of a given strain show a higher activity level, this would be an indication of the suitability of that strain to outdoor systems. This work verified the application of this "Activity index" on 90 birds from 6 genetic strains with known kinetic behavior reared in an experimental farm. The "Activity index" was also tested on chicken strains collected form commercial organic farms. The results confirmed that strains recognized for higher kinetic attitude actually walked more and their behavior was clearly detected by the "Activity index" estimated from their muscles.

Overview of Native Chicken Breeds in Italy: Small Scale Production and Marketing

Simple Summary

The loss of biodiversity is a matter of great concern worldwide. In the agricultural sector, the industrialization of livestock farming and the wide-spread use of highly selected hybrids, especially in developed countries, has led to the progressive extinction of many native breeds in these contexts. Nowadays, safeguarding poultry biodiversity is a key objective in all developed countries, Italy included. As a part of a large cross-sectional national project called ‘Conservation of biodiversity in Italian poultry breeds’, a questionnaire was designed to evaluate the diffusion of native chicken breeds and their relative product markets. The data reveal the poor diffusion of native breeds despite the existence of a niche market for their products. Indeed, increasing consumer concern about conventional production practices and the growing demand for alternative poultry products, which can fetch high retail prices, should be leveraged to encourage the diffusion of native chicken breeds in alternative poultry farming. An important knock-on effect would be the preservation of biodiversity.

Abstract

The intensive use of high-performing strains in poultry production has led to the extinction of several autochthonous chicken breeds and, consequently, loss of genetic variability. Interest in saving biodiversity is growing rapidly and has become a major objective worldwide. The aim of this study was to shed light on the production trends of native Italian poultry breeds and the related market. A questionnaire, which asked about the production cycles, the number of animals and table eggs produced per year and their retail prices was completed by 121 breeders across Italy. The surveyed breeders were divided into two categories: breeders conducting an agrozootechnical farm, referred to as ‘farmers’ (F); and breeders keeping chickens as backyard poultry, referred to as ‘fancy breeders’ (FB). Analysis of the data acquired indicated that animals were mainly slaughtered between 6 and 12 months of age, with F processing more animals per year. The same production trend was observed for table eggs. The recorded retail prices of native chicken products were higher than those for conventional products, but similar to those reported for valuable niche poultry products, such as the Poulet de Bresse in France and organic eggs. Knowledge about these highly valuable markets should be used to encourage the use of local breeds in alternative poultry farming and help protect biodiversity.

Removal of roosters alters the domestic phenotype and microbial and genetic profile of hens

Hens are raised apart from roosters in modern poultry production, a substantial change from their natural social structure. We compared productivity, injuries, behavior, physiology, microbiome and transcriptome of hens housed with (R+) or without (R-) roosters to quantify the effects of this change in social structure. Hens were raised free-range from 70 to 280 days when 30 birds per treatment were assigned to battery cages until Day 315 (R+C vs. R-C), while 30 birds per treatment remained in free-range pens (R+F vs. R-F). Response to a novel environment and object, behavioral time budgets, cecum microbiome, blood composition and transcriptomic sequencing of thigh muscle and spleen were analyzed. Hens housed without roosters showed better survival, consumed less food, produced more eggs and had better feed conversion. R+F hens clustered around the rooster and were less mobile in the novel environment and object tests. R+F hens displayed the richest microbiome, and the presence of roosters resulted in differentially expressed genes related to muscle development, cellular processes, environmental information processing and immune function. Removing roosters from housed hens intensified desirable characteristics favored by domestication probably operating by deprivation of mating behavior and reduced fear, along with altered microbial and genetic function.

The role of histidine dipeptides on postmortem acidification of broiler muscles with different energy metabolism

It is generally held that the content of several free amino acids and dipeptides is closely related to the energy-supplying metabolism of skeletal muscles. Metabolic characteristics of muscles are involved in the variability of meat quality due to their ability to influence the patterns of energy metabolism not only in living animal but also during postmortem time. Within this context, this study aimed at establishing whether the concentration of histidine dipeptides can affect muscle postmortem metabolism, examining the glycolytic pathway of 3 chicken muscles (pectoralis major, extensor iliotibialis lateralis, and gastrocnemius internus as glycolytic, intermediate, and oxidative-type, respectively) selected based on their histidine dipeptides content and ultimate pH. Thus, a total of 8 carcasses were obtained from the same flock of broiler chickens (Ross 308 strain, females, 49 d of age, 2.8 kg body weight at slaughter) and selected immediately after evisceration from the line of a commercial processing plant. Meat samples of about 1 cm³ were excised from bone-in muscles at 15, 60, 120, and 1,440 min postmortem, instantly frozen in liquid nitrogen and used for the determination of pH, glycolytic metabolites, buffering capacity as well as histidine dipeptides content through ¹H-NMR. Overall results suggest that glycolysis in leg muscles ceased already after 2 h postmortem, whereas in breast muscle continued until 24 h, when it exhibited significantly lower pH values (P < 0.05). However, considering its remarkable glycolytic potential, pectoralis major muscle should have exhibited a greater and faster acidification, suggesting that its higher (P < 0.05) histidine dipeptides' content might have prevented a potentially stronger acidification process. Accordingly, breast muscle also showed greater (P < 0.05) buffering ability in the pH range 6.0–7.0. Therefore, anserine and carnosine, being highly positively correlated with muscle's buffering capacity (P < 0.001), might play a role in regulating postmortem pH decline, thus exerting an effect on muscle metabolism during prerigor phase and the quality of the forthcoming meat. Overall results also suggest that total histidine dipeptides content along with muscular ultimate pH represent good indicators for the energy-supplying metabolism of chicken muscles.

Energy metabolism and sources of oxidative stress in wooden breast - a review

Modern broilers show dramatic growth over a short interval and contribute directly to the success of the poultry meat industry. The growth performance of commercial broilers is a result of genetic selection for "performance traits", such as body size, meat yield, and feed conversion rate. However, due to the rapid growth rate of modern commercial broilers, several growth-related conditions have arisen, increasing economic losses and consumer concerns. Among the most economically consequential is the muscle disorder called wooden breast. Together with associated myopathies such as white striping and spaghetti meat, wooden breast is causing losses of $200 million a year in the U.S. alone and occurs worldwide. No causative factors are known for wooden breast to date. Wooden breast can affect over 80% of broilers in a flock, yet no methods of amelioration are currently available. Overall, the evidence suggests that wooden breast is a genetic, age-dependent condition associated with fast growth rate. The primary features of wooden breast are muscle degeneration and fibrosis, high levels of oxidative stress, hypoxia, and altered energy metabolism. Recent work has also implicated reduced pectoral vessel density in the pathogenesis of wooden breast. This review examines the history of myopathies in commercial broilers and the relationship of myopathies to metabolism and oxidative performance. This review summarizes the foundational knowledge of wooden breast and provides a platform for further investigation of wooden breast.

Suitability of dual-purpose cockerels of 3 different genetic origins for fattening under free-range conditions

The utilization of male chickens for fattening constitutes a potential advantage of the dual-purpose concept. In addition to the use of commercial hybrids, producers could introduce alternative chicken genotypes or further develop local breeds. To gain more information about the genetic effect on growth performance, carcass characteristics, physicochemical meat traits, and sensory attributes, 60 cockerels belonging to Les Bleues (developed from the French breed Bresse Gauloise), Canarian (Spanish local breed), and Dominant Red Barred D459 (DRB D459; commercial dual-purpose hybrid) genotypes were reared under free-range conditions in a warm tropical climate and slaughtered at 15 wk of age. The major findings were as follows: (i) Les Bleues chickens exhibited the best growth rate and the body weight of 2.44 kg reached by this strain at 15 wk would be gained only after 18 to 19 wk with DRB D459 and it would take even 2 wk longer for Canarian breed, according to the growth modeling using the Morgan equation, although the body weights between the latter were statistical similar at 15 wk; (ii) Les Bleues strain had a good capability in terms of meat production performance, presenting carcasses with significantly heavier commercial cuts, and higher fleshiness than the other 2 genotypes; (iii) although significant differences among genotypes appeared in the physical characteristics of the breast meat, especially those concerning the skin and meat color and water-holding capacity, which was significantly reduced for Canarian chickens, no significant differences were detected in the chemical composition and fatty acid profile of the breast meat; (iv) trained panelists (n = 8) pointed out that leg meat of none of the genotypes is better in terms of global appreciation, but untrained consumers (n = 99) perceived that the Les Bleues leg meat was significantly more palatable than the DRB D459 leg meat.

Influence of free-range days on growth performance, carcass traits, meat quality, lymphoid organ indices, and blood biochemistry of Wannan Yellow chickens

This study investigated the effects of free-range days on growth performance, carcass traits, meat quality, lymphoid organ indices, and blood biochemical parameters of Wannan Yellow chickens. A total of 1,000 one-day-old male Wannan Yellow chickens were reared to 56 D. At 56 D of age, 960 birds with similar body weight (BW) were randomly allocated to free-range treatment at 56, 70, 84, and 98 D of age (assigned to free-range treatment for 42, 28, 14, and 0 D, respectively); 6 replicates with 40 chickens per treatment. In the free-range system, chickens were reared in indoor floor pens with an outdoor free-range paddock measuring 4 × 7 m (28 m2, 1.5 birds/m2). Results showed that BW of birds decreased significantly in the first 2 wk after birds were assigned to free-range treatment compared with those in the conventional treatment (P < 0.05). Average daily gain (ADG) and average daily feed intake (ADFI) decreased significantly (P < 0.05) for chickens assigned to free-range treatment from 56 to 70 D of age, while feed conversion ratio increased significantly (P < 0.05). Breast yield increased linearly with increasing free-range days (P < 0.05), whereas leg and foot yields decreased linearly (P < 0.05). Drip loss and L* value of thigh muscle decreased linearly with increasing free-range days (P < 0.05), while shear force improved linearly (P < 0.05). Additionally, the absolute thymus weight and thymus to BW ratio showed significant increasing and then decreasing quadratic responses to increasing free-range days (P < 0.05). Furthermore, serum glucose, total protein, cholesterol, and triglyceride content declined linearly, while high-density lipoprotein cholesterol (HDL-C) content increased linearly with increasing free-range days (P < 0.05). In conclusion, increasing free-range days had positive effects on breast yield, shear force, thymus weight, and HDL-C content, but negatively affected leg yield, foot yield, drip loss, L* value of thigh muscle, glucose, total protein, cholesterol, and triglyceride levels of Wannan Yellow chickens.

Timing Is Everything-The High Sensitivity of Avian Satellite Cells to Thermal Conditions During Embryonic and Posthatch Periods

Myofiber formation is essentially complete at hatch, but myofiber hypertrophy increases posthatch through the assimilation of satellite cell nuclei into myofibers. Satellite cell proliferation and differentiation occur during the early growth phase, which in meat-type poultry terminates at around 8 days posthatch. Thus, any factor that affects the accumulation of satellite cells during late-term embryogenesis or early posthatch will dictate long-term muscle growth. This review will focus on the intimate relationship between thermal conditions during chick embryogenesis and the early posthatch period, and satellite cell myogenesis and pectoralis growth and development. Satellite cells are highly sensitive to temperature changes, particularly when those changes occur during crucial periods of their myogenic activity. Therefore, timing, temperature, and duration of thermal treatments have a great impact on satellite cell activity and fate, affecting muscle development and growth in the long run. Short and mild thermal manipulations during embryogenesis or thermal conditioning in the early posthatch period promote myogenic cell proliferation and differentiation, and have long-term promotive effects on muscle growth. However, chronic heat stress during the first 2 weeks of life has adverse effects on these parameters and may lead to muscle myopathies.

Behavioural Variability in Chicks vs. the Pattern of Behaviour in Adult Hens

Simple Summary

Environmental requirements ensuring behavioural welfare to laying hens may vary depending on the breed. Chickens representing various breeds and reared in the same environment were found not only to differ in the level of activity, emotional arousal, and degree of curiosity, but also to prefer different enrichments of the environment, which was reflected by different levels of stress in these birds. Hence, a question was posed whether the behavioural differences observed were innate behavioural patterns typical of the breed or whether they are an effect of the modifying impact of the environment, which varies between breeds. It has been hypothesised that differences observed already in chicks of different breeds may not be associated with the modifying effect of the environment. Instead, they may be a genetically determined breed-specific behaviour. The present investigations consisted in behavioural tests and assessment of the behaviour of chicks of three laying hen breeds. The study involved 60 green-legged partridge (Zk), 60 Polbar (Pb), and 60 Leghorn (Lg) chicks. The investigations have demonstrated that the birds from the analysed breeds exhibit behavioural differences already on the first days of life. The effect of the breed was evident in the case of such traits as strategy for acquisition of food resources, fearfulness/curiosity, and interest in elements of the environment. With age, chicks may exhibit changes in their emotions, e.g., more pronounced fearfulness, and environmental preferences. However, in the latter case, there is clear tendency towards breed-specific behaviours exhibited from the first days of life. The level of activity, which largely differentiates adult birds, does not discriminate between chicks.

Abstract

The aim of the study was to assess the behaviour of chicks of three different breeds of laying hens differing in the activity, emotional reactivity, and environmental preferences. Another objective was to answer the question whether the behavioural differences between adult birds would be evident already in the chick period or whether they are an effect of the further modifying impact of the environment. 60 green-legged partridge, 60 Polbar, and 60 Leghorn chicks were used in the experiments. The chicks hatched in a flock where hens were previously assessed with behavioural tests and the corticosterone levels in their feathers was determined, indicating significant differences in the temperament and stress level between the breeds. Five tests were carried out: two on competitiveness, activity, interest and fearfulness/curiosity. The experiments revealed considerable differences between the chicks. The Zk birds coped better with situations requiring swiftness and initiative. The Pb chicks were slower than Zk and Lg and did not make quick decisions. Hence, a lower number of these birds entering and leaving the test cage and staying inside was recorded. The Zk chicks exhibited a higher level of fearfulness than the other breeds. In terms of the environment enrichment elements, sand and woodchips were more attractive to the Zk chicks, whereas the Lg and Pb birds preferred pecking the string. No differences in the time of undertaking the analysed activities were found between the breeds.

Early posthatch thermal stress causes long-term adverse effects on pectoralis muscle development in broilers

Broiler chicks in the immediate posthatch handling period are exposed to thermal stress, with potentially harmful consequences for muscle growth and structure (e.g., less protein and more fat deposition). We addressed the effects of broiler chicks' exposure to various ambient temperatures during the first 13 D posthatch on their performance, as well as on muscle development and structure, up to day 35. Body weight and pectoralis muscle growth were lower throughout the entire period in the high-heat-exposed chicks (39°C, Hot) and to a lesser extent in the mild-heat-exposed chicks (35°C, Hot Mild) than in the Control chicks that were raised under a commercial protocol. In the cold-exposed chicks (29oC, Cold), BW and pectoralis muscle absolute growth were similar to the Control group throughout the entire period. The lower body and muscle growth in the Hot and Hot Mild groups were reflected in a lower number of myonuclei expressing proliferating cell nuclear cell in pectoralis major muscle cross sections sampled on day 8, in the distribution of myofibers as the experiment progressed, and in mean myofiber diameter on day 35, whereas in the Cold group, these numbers exceeded that of the Control group. However, TUNEL assay revealed similar cell survival in all groups. Hematoxylin-eosin and Oil red O staining revealed the highest fat deposition in the pectoralis muscle derived from the Hot group, whereas lower fat deposition was observed in the Control Cold group. These results were corroborated by immunostaining for CCAAT/enhancer binding protein β in the pectoralis muscle, the levels of which were significantly higher in the Hot and Hot Mild groups on day 35 than in the Control group. Similar results were observed with Sirius red staining for collagen content in the pectoralis muscle. Together, the results imply long-term effects of chronic heat stress vs. cold stress in the early posthatch period on the broiler's body and muscle growth in general and myodegeneration of the pectoralis muscle in particular.

Wooden breast myopathy links with poorer gait in broiler chickens

Wooden breast myopathy, a condition where broiler breast muscles show a hardened consistency post-mortem, has been described recently. However, it is not known how wooden breast myopathy affects the bird activity or welfare. Altogether, over 340 birds of five commonly used commercial hybrids were housed in 25 pens, and sample birds killed at ages of 22, 32, 36, 39 and 43 days. Their breast muscle condition was assessed post-mortem by palpation. The birds were gait scored and their latency to lie was measured before killing. For further behavior observations, one affected and healthy bird in 12 pens were followed on 5 days for 20 minutes using video recordings. The connection of myopathy to gait score and activity was analyzed with mixed models. A higher gait score of wooden-breast-affected birds than that of unaffected birds (2.9 ± 0.1 v. 2.6 ± 0.1, P < 0.05) indicated a higher level of locomotor difficulties over all age groups. The wooden-breast-affected birds had fewer crawling or movement bouts while lying down compared with unaffected (P < 0.05). Wooden breast myopathy-affected birds were heavier (2774 ± 91 v. 2620 ± 91 g; P < 0.05) and had higher breast muscle yield (21 ± 1 v. 19 ± 1%; P < 0.05) than unaffected birds overall. Older birds had longer lying bouts, longer total lying time, fewer walking bouts, more difficulties to walk and to stand compared with younger birds (P < 0.05). Birds with poorer gait had longer total lying time and fewer walking bouts (P < 0.05). Birds with greatest breast muscle yield had the largest number of lying bouts (P < 0.05). It was concluded that wooden breast myopathy was associated with an impairment of gait scores, and may thus be partly linked to the common walking abnormalities in broilers.

Physicochemical determinants of pH in pectoralis major of three strains of laying hens housed in conventional and furnished cages

1. Post-mortem decline in muscle pH has traditionally been attributed to glycogenolysis-induced lactate accumulation. However, muscle pH ([H⁺]) is controlled by complex physicochemical relationships encapsulated in the Stewart model of acid-base chemistry and is determined by three system-independent variables - strong ion difference ([SID]), total concentration of weak acids ([A_tot]) and partial pressure of CO₂ (PCO₂). 2. This study investigated these system-independent variables in post-mortem pectoralis major muscles of Shaver White, Lohmann Lite and Lohmann Brown laying hens housed in conventional cages (CC) or furnished cages (FC) and evaluated the model by comparing calculated [H⁺] with previously measured [H⁺] values. 3. The model accounted for 99.7% of the variation in muscle [H⁺]. Differences in [SID] accounted for most or all of the variations in [H⁺] between strains. Greater PCO₂ in FC was counteracted by greater sequestration of strong base cations. The results demonstrate the accuracy and utility of the Stewart model for investigating determinants of meat [H⁺]. 4. The housing differences identified in this study suggested that hens housed in FC have improved muscle function and overall health due to the increased opportunity for movement. These findings support past studies showing improved animal welfare for hens housed in FC compared to CC. Therefore, the Stewart model has been identified as an accurate method to assess changes in the muscle at a cellular level that affect meat quality that also detect differences in the welfare status of the research subjects.

Muscle structure and gene expression in pectoralis major muscle in response to deep pectoral myopathy induction in fast- and slow-growing commercial broilers

1. The objective of this study was to determine muscle structure and gene expression in pectoralis major (p. major) muscle of broilers in response to deep pectoral myopathy (DPM) induction. 2. A total of 160 chickens from slow- and fast-growing broilers were raised under same conditions. Half of the broilers from each strain were encouraged to wing flap when they reached 2800 g body weight. Pectoralis minor (p. minor) muscle of the broilers was inspected for the occurrence of DPM and p. major samples were collected from broilers with or without DPM. The muscle fibre area and number, capillary number and the signalling pathways of vascular development (vascular endothelial growth factor A, VEGFA) and muscle contraction regulation (actin alpha 1, ACTA1; myosin light chain kinase 2, MYLK2 and ATPase Ca⁺² transporting gene 1, ATP2A1) were studied in p. major muscle. 3. DPM induction increased fibre area of p. major muscle with a greater rate in the slow-growing strain compared with fast-growing line. Although the capillary number was higher in slow-growing compared with fast-growing broilers, in the case of DPM induction, the number of capillaries was similar between strains. 4. Expression of VEGFA, MYLK2 and ATP2A1 was greater in slow- than in fast-growing broilers. DPM induction increased expression of ACTA1, VEGFA and ATP2A1 in p. major muscle of broilers from both strains; however, MYLK2 expression was downregulated. 5. Changes in capillary density and expression of VEGFA found in the p. major muscle of broilers with DPM suggest increased blood flow to increase oxygen availability. The upregulation of ATP2A1 by DPM induction could be attributable to alterations in calcium ion transportation from the cytoplasm into the sarcoplasmic reticulum. 6. The results are evidence of changes in muscle structure and gene expression pathways in p. major muscle of broilers with DPM.

Breast meat quality of chickens with divergent growth rates and its relation to growth curve parameters

Abstract. The effects of the increase of body weight of contemporary broilers during growth on functional meat quality and color characteristics of the chicken breast muscle are controversially debated. Therefore, male chickens (n = 264) of a fast-growing commercial broiler (Ross 308) and two slow-growing experimental meat-type chicken lines were compared at equal age and at similar body weight in order to investigate the effect of growth rate on selected functional breast meat traits and meat color. Additionally, the breast meat characteristics of birds with different growth profiles were compared within lines. When the body weight of commercial broilers reached about 40 to 60 % of their growth potential, they exhibited particularly high ultimate pH values compared with slow-growing lines. The ability of the meat of fast-growing broilers to retain water during cooking was impaired (5 to 16 percentage points increased cooking loss compared to slow-growing lines), which, in contrast to pH, was only marginally affected by body weight and/or age at slaughter. No unfavorable correlations of breast meat quality traits with the growth profile, represented by growth curve parameters derived from the Gompertz–Laird equation, were detected within any of the investigated chicken lines. It is noteworthy that the associations of ultimate pH and cooking loss with maximum growth speed indicate a non-linear relationship. Thus, some of the functional characteristics of breast meat of the fast-growing broiler resembled the white-striping defect described for poultry meat, but the hypothesis that selection on increased growth rates is detrimental for meat quality per se could not be confirmed. In fact, an elevated growth potential in particular, i.e., body weight at maturity, could have some beneficial effects for the water-holding capacity of breast meat, regardless of the genotypic growth rate.

Temperature alterations during embryogenesis have a sex-dependent influence on growth properties and muscle metabolism of day-old chicks and 35-day-old broilers

Broiler eggs were either incubated at 37.8°C during the whole incubation period (control), or at higher (38.8°C, group H) and lower temperatures (36.8°C, group L) from embryonic day (ED) 7 up to ED 10 (ED 7 to 10) or from ED 10 up to ED 13 (ED 10 to 13). Before and after this temperature treatment the eggs were incubated at 37.8°C. The day-old chicks were weighted, sexed and fed up to day 35. On days 1 and 35 samples were taken from the breast and leg muscles for analyzing of the mitochondrial respiratory activity (MRA) and from the breast muscles for analysis of the cross-sectional areas (CSA) and the glycogen phosphorylase (GP), phosphofructokinase (PFK), lactate dehydrogenase (LDH), citrate synthase (CS) and cytochrome oxidase (COX) activities. Statistical analysis showed that treatment (control, group H, group L), sex and their interaction, but not the treatment period (ED 7 to 10; ED 10 to 13), significantly influenced the results. Group H chicks had lower (P⩽0.05) body and heart weights but higher (P⩽0.05) liver weights, CSA values, leg MRA as well as PFK, LDH, CS, GP and COX activities compared with the group L chicks. The results of the control chicks differ (P⩽0.05) from those of the group H (body, heart weight, COX), the group L chicks (liver weight, PFK, LDH, CS, GP) or the birds of both other groups (CSA). The group H broiler had higher (P⩽0.05) body and leg weights as well as LDH, CS, COX and GP activities than the group L broilers. The BWs and the LDH and GP results of the control broiler differ (P⩽0.05) from those of both other groups or from the results of the group H (CS) and group L broiler (COX). Female broilers had lower (P⩽0.05) body, breast and leg weights, but higher (P⩽0.05) CSA, LDH, CS and GP activities than the male animals. Analysis of treatment×sex interaction showed that group H hens had higher (P⩽0.05) body and breast weights, LDH and GP activities compared with the group L hens, whereas in the male broiler no effect of the interaction could be found, except for the lower (P⩽0.05) CSA values in the group H than group L cocks. The treatment effects are probably due to altered embryonic activity and related molecular mechanisms. The sex-related differences in the broiler indicate that these alterations already occur in the embryos and chicks, but become significant with the sexual dimorphism after hatch.

Expression profiles and associations of muscle regulatory factor (MRF) genes with growth traits in Tibetan chickens

1. Muscle regulatory factors (MRFs), including Myf5, Myf6 (MRF4/herculin), MyoD and MyoG (myogenin), play pivotal roles in muscle growth and development. Therefore, they are considered as candidate genes for meat production traits in livestock and poultry. 2. The objective of this study was to investigate the expression profiles of these genes in skeletal muscles (breast muscle and thigh muscle) at 5 developmental stages (0, 81, 119, 154 and 210 d old) of Tibetan chickens. Relationships between expressions of these genes and growth and carcass traits in these chickens were also estimated. 3. The expression profiles showed that in the breast muscle of both genders the mRNA levels of MRF genes were highest on the day of hatching, then declined significantly from d 0 to d 81, and fluctuated in a certain range from d 81 to d 210. However, the expression of Myf5, Myf6 and MyoG reached peaks in the thigh muscle in 118-d-old females and for MyoD in 154-d-old females, whereas the mRNA amounts of MRF genes in the male thigh muscle were in a narrow range from d 0 to d 210. 4. Correlation analysis suggested that gender had an influence on the relationships of MRF gene expression with growth traits. The RNA levels of MyoD, Myf5 genes in male breast muscle were positively related with several growth traits of Tibetan chickens (P < 0.05). No correlation was found between expressions of MRF genes and carcass traits of the chickens. 5. These results will provide a base for functional studies of MRF genes on growth and development of Tibetan chickens, as well as selective breeding and resource exploration.

Implications of white striping and spaghetti meat abnormalities on meat quality and histological features in broilers

During the past few years, there has been an increasing prevalence of broiler breast muscle abnormalities, such as white striping (WS) and wooden breast conditions. More recently, a new muscular abnormality termed as spaghetti meat (SM) because of the altered structural integrity of the Pectoralis major muscle often associated with WS has emerged. Thus, this study aimed at evaluating the effects of WS and SM conditions, occurring alone or combined within the same P. major muscle, on meat quality traits and muscle histology. In two replications, 96 P. major muscles were classified into four classes: normal (N), WS, SM and WS/SM. The whole fillet was used for weight assessment and morphometric measurements, then each sample was cut in order to separate the superficial layer from the deep one and used to evaluate proximate composition, histological features, nuclear magnetic resonance relaxation times, functional properties and both myofibrillar and sarcoplasmic proteins profile. Fillets affected by WS and SM abnormalities exhibited higher weights and increased thickness and length. SM condition was associated with a relevant decrease in protein content coupled with a significant increase in moisture level, whereas fat content was affected only by the simultaneous presence of WS. Histological evaluations revealed that abnormal samples were characterized by several degenerative aspects that almost completely concerned the superficial layer of the fillets. White striped fillets exhibited necrosis and lysis of fibers, fibrosis, lipidosis, loss of cross striation and vacuolar degeneration. Moreover, SM samples were characterized by poor fiber uniformity and a progressive rarefaction of the endo- and peri-mysial connective tissue, whereas WS/SM fillets showed intermediate histological features. Nuclear magnetic resonance relaxation analysis revealed a higher proportion of extra-myofibrillar water in the superficial section of all the abnormal fillets, especially in SM samples, which consequently led to a reduction of the water holding capacity of meat. As for functional properties, abnormal fillets exhibited a lower protein solubility and higher ultimate pH values on both the superficial and deep sections. Although abnormal fillets exhibited higher yellowness values, no relevant effect on meat color was observed. The occurrence of WS and SM abnormalities led to increased carbonylation levels and more intense proteolytic processes. Overall, muscle abnormalities mainly affect the superficial layer of P. major muscle and particularly the occurrence of SM myopathy seems to implicate a more pronounced modification of meat quality traits than the mere presence of WS.

Effect of housing environment on laying hen meat quality: Assessing Pectoralis major pH, colour and tenderness in three strains of 80-81 week-old layers housed in conventional and furnished cages

1. Meat quality is affected by factors such as stress, genetic strain and activity and is determined in part by measures of pH, colour and tenderness. In conventional laying hen cages (CC), lack of physical space and inability to perform highly motivated behaviours leads to stress and inactivity. Furnished cages (FCs) permit expression of highly motivated behaviours, but typically house larger group sizes than CC, thereby contributing to social stress. The objective of this study was to evaluate the effects of CC and FC laying hen housing environments and strain differences on meat quality of 80-81-week-old birds. 2. Pectoralis major meat quality was assessed for two flocks of Shaver White (SH), Lohmann Lite (LL) and Lohmann Brown (LB) hens housed in either 5-hen CC or 40-hen FC. Between 80 and 81 weeks, muscle samples were collected from randomly selected hens and analysed for muscle pH, colour and shear force (SF) using established methods. 3. In both flocks, the combined treatment body weights (BWs) were higher for CC than FC hens and the combined strain BWs were higher for LB than LL and SH hens. Flock 1 LB had lower initial and ultimate pH than SH and LL, and greater pH decline than SH. Muscle redness (a*) was higher for CC SH than FC SH in both flocks. Muscle a* was higher for LL than SH and LB in Flock 1, and higher than SH in Flock 2. Housing differences in muscle SF were absent. In CC, SF was higher for SH than LL and LB in Flock 1, and higher than LB in Flock 2. 4. Lack of housing differences suggests that environmental stressors present in both housing systems similarly affected meat quality. Strain differences for muscle pH, a* and SF indicate increased stress experienced by SH and LL hens. The absence of Flock 2 strain differences is consistent with the cannibalism outbreak that occurred in this flock and most severely impacted LB hens.

Impact of divergent selection for ultimate pH of pectoralis major muscle on biochemical, histological, and sensorial attributes of broiler meat

The impact of divergent selection based on the ultimate pH (pHu) of pectoralis major (P. major) muscle on the chemical, biochemical, and histological profiles of the muscle and sensorial quality of meat was investigated in broiler chickens. The protein, lipid, DM, glycogen and lactate content, glycolytic potential, proteolysis, lipid and protein oxidation index, muscle fiber cross-sectional area, capillary density, and collagen surface were determined on the breast P. major muscle of 6-wk-old broilers issued from the high-pHu (pHu+) and low-pHu (pHu-) lines. Sensory attributes were also evaluated on the breast (roasted or grilled) and thigh (roasted) meat of the 2 lines. Protein, lipid, and DM content of P. major muscle were not affected by selection ( > 0.05). However, the P. major muscle of the pHu+ line was characterized by lower residual glycogen (-16%; ≤ 0.001) and lactate (-14%; ≤ 0.001) content and lower glycolytic potential (-14%; ≤ 0.001) compared with the pHu- line. Although the average cross-sectional area of muscle fibers and surface occupied by collagen were similar ( > 0.05) in both lines, fewer capillaries per fiber (-15%; ≤ 0.05) were observed in the pHu+ line. The pHu+ line was also characterized by lower lipid oxidation (thiobarbituric acid reactive substance index: -23%; ≤ 0.05) but protein oxidation and proteolysis index were not different ( > 0.05) between the 2 lines. At the sensory level, selection on breast muscle pHu mainly affected the texture of grilled and roast breast meat, which was judged significantly more tender ( ≤ 0.001) in the pHu+ line, and the acid taste, which was less pronounced in the roasted breast meat of the pHu+ line ( ≤ 0.002). This study highlighted that selection based on pHu does not affect the chemical composition and structure of breast meat. However, by modifying muscle blood supply and glycogen turnover, it affects meat acidity and oxidant status, both of which are likely to contribute to the large differences in texture observed between the 2 lines.

Meat quality and the histological structure of breast and leg muscles in Ayam Cemani chickens, Ayam Cemani × Sussex hybrids and slow-growing Hubbard JA 957 chickens

BACKGROUND

The purpose of this study was to determine the quality of meat and the histological structure of muscles of Ayam Cemani chickens, Ayam Cemani × Sussex hybrids and slow-growing Hubbard JA 957 chickens and to examine whether crossing generally available Sussex chickens with little available Ayam Cemani gives a good quality product of interest to the poultry industry and in food technology.

RESULTS

The size of breast and leg muscle fibers varied among genotypes. The breast and leg muscles of slow-growing Hubbard JA 957 chickens had the largest fiber diameter. The histological and biochemical properties of muscles, including the type, number, proportions, diameter and metabolic profile of fibers, had a significant effect on the pH and water-binding capacity of meat, thus affecting its quality. The muscle fibers of Ayam Cemani chickens were approximately half the size of the muscle fibers of Hubbard JA 957 chickens. Ayam Cemani and Ayam Cemani × Sussex gave a product of as good quality as Hubbard JA 957 chickens.

CONCLUSION

Meat from Ayam Cemani chickens is a rich source of protein and could be highly valued by gourmet consumers, connoisseurs and dieticians for its rarity and originality. The results of this study show that genotype (Ayam Cemani, Ayam Cemani × Sussex, Hubbard JA 957) affected the quality and color of meat and the histological profile of chicken breast and leg muscles.

Genetic effects of polymorphisms in myogenic regulatory factors on chicken muscle fiber traits

The myogenic regulatory factors is a family of transcription factors that play a key role in the development of skeletal muscle fibers, which are the main factors to affect the meat taste and texture. In the present study, we performed candidate gene analysis to identify single-nucleotide polymorphisms in the MyoD, Myf5, MyoG, and Mrf4 genes using polymerase chain reaction-single strand conformation polymorphism in 360 Erlang Mountain Chickens from three different housing systems (cage, pen, and free-range). The general linear model procedure was used to estimate the statistical significance of association between combined genotypes and muscle fiber traits of chickens. Two polymorphisms (g.39928301T>G and g.11579368C>T) were detected in the Mrf4 and MyoD gene, respectively. The diameters of thigh and pectoralis muscle fibers were higher in birds with the combined genotypes of GG-TT and TT-CT (p<0.05). Moreover, the interaction between housing system and combined genotypes has no significant effect on the traits of muscle fiber (p>0.05). Our findings suggest that the combined genotypes of TT-CT and GG-TT might be advantageous for muscle fiber traits, and could be the potential genetic markers for breeding program in Erlang Mountain Chickens.

Myogenic regulatory factor (MRF) expression is affected by exercise in postnatal chicken skeletal muscles

The MyoD1, MyoG, Myf5, and Mrf4 proteins belong to the family of muscle regulatory factors (MRFs) and play important roles in skeletal muscle hyperplasia and hypertrophy. We hypothesized that exercise would affect MRF mRNA and protein abundance in postnatal chicken skeletal muscle driving molecular changes that could ultimately lead to increased muscle fiber diameter. At day (d) 43, twelve hundred chickens with similar body weight were randomly assigned to cage, pen, and free-range groups. The MRF mRNA abundance was measured in the pectoralis major and thigh muscle at d56, d70, and d84, and the protein levels of MRFs were determined from the thigh muscle at d84. The results showed no significant difference in mRNA of the MRFs among the three groups at d56 (P>0.05). At d84, chicken in the pen and free-range group showed higher MyoD1, MyoG, Myf5, and Mrf4 mRNA abundance compared to the caged chickens (P<0.05). Free-range chickens had higher Mrf4 and MyoG expression than those in penned ones (P<0.05). Protein abundances of all four factors were lowest in the caged group, and Mrf4 and MyoG protein quantities were greatest in free-range chickens (P<0.05), but Myf5 and MyoD1 protein abundance did not differ between penned and caged groups. The results suggested that exercise up-regulated MRF expression in the postnatal skeletal muscles, which led to an increase in muscle fiber diameter, and eventually affected the meat quality of the skeletal muscles in adult chickens.

The occurrence of giant fibres in different muscles of two chicken genotypes

1. The occurrence of Giant Fibres (GF) in three muscles (Pectoralis major (PM), Iliotibialis lateralis and Semimembranosus) with different types of energy metabolism was studied in slow- and fast-growing chicken strains. 2. A total of 20 one-day-old Leghorn chicks (slow-growing) and 20 broiler (Ross 508) chicks (fast-growing) were reared to 100 and 45 d, respectively. 3. A small percentage of GF was seen in pre rigor muscle samples even at 3 min post mortem in both genotypes and in all muscle types studied. 4. From 3 min to 24 h post mortem GF increased both in Leghorn and broiler chickens but to a different extent according to muscle type and genotype. 5. The highest GF 24 h post mortem value was found in the PM muscles belonging to the fast-growing broiler line. 6. It was concluded that every type of muscle can develop GF, but this phenomenon is more evident in the PM especially in animals selected for increased growth rate.

Characterization of muscle fiber type in the pectoralis major muscle of slow-growing local and commercial chicken strains

The study aimed to characterize muscle fiber type of the pectoralis major muscle of slow-growing chickens belonging to the Padovana local breed, the commercial strain Berlanda gaina, and their cross. Forty-five chickens (both males and females) from the different genotypes were grown up to 180 d. Histochemical and morphometrical analyses were performed to characterize muscle fiber types, myofiber density, and myofiber size of the different genotypes. The effects of genotype, sex, and their interaction were estimated. Muscle samples appeared almost entirely made up of IIB fiber type, whereas a low percentage of area (5 to 6%) was composed of hypercontracted fiber. Myofiber density was significantly higher (P < 0.05) in Padovana strains and cross-sectional area was significantly lower (P < 0.01) than in Berlanda strain. Muscle fiber characteristics appeared not to be affected by the interaction of genotype × sex.

Genetics of behavioural adaptation of livestock to farming conditions

Behavioural adaptation of farm animals to environmental changes contributes to high levels of production under a wide range of farming conditions, from highly controlled indoor systems to harsh outdoor systems. The genetic variation in livestock behaviour is considerable. Animals and genotypes with a larger behavioural capacity for adaptation may cope more readily with varying farming conditions than those with a lower capacity for adaptation. This capacity should be exploited when the aim is to use a limited number of species extensively across the world. The genetics of behavioural traits is understood to some extent, but it is seldom accounted for in breeding programmes. This review summarizes the estimates of genetic parameters for behavioural traits in cattle, pigs, poultry and fish. On the basis of the major studies performed in the last two decades, we focus the review on traits of common interest in the four species. These concern the behavioural responses to both acute and chronic stressors in the physical environment (feed, temperature, etc.) and those in the social environment (other group members, progeny, humans). The genetic strategies used to improve the behavioural capacity for adaptation of animals differ between species. There is a greater emphasis on responses to acute environmental stress in fish and birds, and on responses to chronic social stress in mammals.

Fatty acid composition of meat and estimated indices of lipid metabolism in different poultry genotypes reared under organic system

According to EC regulation 889/08, different European countries should draw up a list of slow-growing strains adapted to an organic system, and in the meantime, provide this information to operators and the European Union commission. Thus, the aim of the present work was to evaluate the effect of poultry genotype on fatty acid composition and lipid indices of poultry meat. Six poultry genotypes (100 birds each), each with a different growth rate (slow-growing: Leghorn, Ancona, Cornish×Leghorn; medium-growing: Kabir, Naked neck; fast-growing: Ross), were reared under an organic system. Breast meat fatness, fatty acid composition, and indices were largely related to genotype, as slow-growing strains had higher elongase, thioesterase, and Δ5/Δ6 desaturase indices accompanied by a lower Δ9. Differences in the fatty acid profiles were observed by varying contents of total saturated fatty acids, with a higher value seen in Leghorn chickens and a lower value seen in commercial lines. On the contrary, Leghorn and Ancona chickens exhibited higher amounts of stearic acid and total polyunsaturated fatty acids compared with commercial genotypes, both in the total content and in the different fractions (total n-3 and total n-6). Despite the increased consumption of fresh forage, the lower linolenic acid in meat of the slow-growing strain could be explained by the higher conversion of this fatty acid to its long-chain derivatives.