Post mortem muscle metabolism and meat quality in three genetic types of turkey

Effect of crossbreeding on growth performance, meat quality, and the economics of production of the pure and reciprocal crosses between the Sasso and Wassachie chickens

The interplay between genetics and economics is important in understanding how crossbreeding can be harnessed to optimize sustainable poultry production, meat quality, and economic viability. This study was conducted to investigate the effect of crossbreeding on growth performance, meat quality, and production economics. A total of 451 unsexed day-old chicks were raised for 12 wk in a pure (Sasso X Sasso [SS]; Wassachie X Wassachie [WW]) and reciprocal cross (Sasso X Wassachie [SW]; Wassachie X Sasso [WS]) design. Data was collected on growth performance, meat quality, sensory evaluation, proximate analysis, and production economics. Genotype did not affect (P > 0.05) moisture, dry matter, ash, sensory evaluation, pH, and meat temperature. The carcass weights, final body weight, and cumulative weight gain of the hybrids were intermediate while the SS recorded the highest (P < 0.05) values. Drip loss between the WW and the reciprocal crosses was similar (P > 0.05) but lower (P < 0.05) than the SS genotype. Protein contents between the purebreds were similar likewise the crossbreds (P > 0.05). The SW cross recorded a higher (P < 0.05) lipid content compared to the WW cross while the WS recorded a higher (P < 0.05) protein content compared to the SS. The SS incurred higher feeding costs, and gross and net returns followed by the SW and then the WS with the WW having the lowest values. Crossbreeding improved growth performance, carcass traits, meat quality, chemical composition, and the gains in the crossbreds with the SW genotype having better results. The SW cross is recommended for better performance.

Data-Mining Methodology to Improve the Scientific Production Quality in Turkey Meat and Carcass Characterization Studies

The present research aims to describe how turkey meat and carcass quality traits define the interest of the scientific community through the quality standards of journals in which studies are published. To this end, an analysis of 92 research documents addressing the study of turkey carcass and meat quality over the last 57 years was performed. Meat and carcass quality attributes were dependent variables and included traits related to carcass dressing, muscle fiber, pH, colorimetry, water-holding capacity, texture, and chemical composition. The independent variables comprised publication quality traits, including journal indexation, database, journal impact factor (JIF), quartile, publication area, and JIF percentage. For each dependent variable, a data-mining chi-squared automatic interaction detection (CHAID) decision tree was developed. Carcass or piece yield was the only variable that did not show an impact on the publication quality. Moreover, color and pH measurements taken at 72 h postmortem showed a negative impact on publication interest. On the other hand, variables including water-retaining attributes, colorimetry, pH, chemical composition, and shear force traits stood out among the quality-enhancing variables due to their low inclusion in papers, while high standards improved power.

Discriminant canonical analysis as a tool for genotype traceability testing based on turkey meat and carcass traits

The present study aims to develop a statistical tool for turkey breed traceability testing based on meat and carcass quality characteristics. To this end, a comprehensive meta-analysis was performed, collecting data from a total of 75 studies approaching meat and carcass attributes of 37 turkey strains and landraces since the late 1960s. A total of 22 meat and carcass traits were considered variables, grouped in the following clusters: carcass dressing traits, muscle fiber properties, pH, colorimetry, water-capacity traits, texture-related attributes, and nutritional composition of the meat. Once the multicollinearity analysis allowed the deletion of redundant variables, cold carcass weight, slaughter weight, muscle fiber diameter, sex-female, carcass/piece weight, meat redness, ashes, pH24, meat lightness, moisture, fat, and water-holding capacity showed explanatory properties in the discriminating analysis (p < 0.05). In addition, strong positive and negative correlations were found among those variables studied. Carcass traits were positively associated, particularly slaughter weight and cold carcass weight (+0.561). Among meat physical traits, pH showed positive correlations with drip loss (+0.490) and pH24 (+0.327), and water-holding capacity was positively associated with cholesterol (+0.434) and negatively associated with collagen (-0.398). According to nutritional traits, fat and ash showed a strong correlation (+0.595), and both were negatively associated with moisture (-0.375 and -0.498, respectively). Strong negative correlations were found as well between meat protein and fat (-0.460) and between collagen and cholesterol (-0.654). Finally, the Mahalanobis distance suggested a clustering pattern based on meat and carcass characteristics that report information about interbreeding and variety proximity. This study establishes a departure point in the development of a tool for breed traceability guaranteeing aimed at enhancing distinguished, local breed-based turkey meat.

Study of Meat and Carcass Quality-Related Traits in Turkey Populations through Discriminant Canonical Analysis

The present research aimed to determine the main differences in meat and carcass quality traits among turkey genotypes worldwide and describe the clustering patterns through the use of a discriminant canonical analysis (DCA). To achieve this goal, a comprehensive meta-analysis of 75 documents discussing carcass and meat characteristics in the turkey species was performed. Meat and carcass attributes of nine different turkey populations were collected and grouped in terms of the following clusters: carcass dressing traits, muscle fiber properties, pH, color-related traits, water-retaining characteristics, texture-related traits, and meat chemical composition. The Bayesian ANOVA analysis reported that the majority of variables statistically differed (p < 0.05), and the multicollinearity analysis revealed the absence of redundancy problems among variables (VIF < 5). The DCA reported that cold carcass weight, slaughter weight, sex-male, carcass/piece weight, and the protein and fat composition of meat were the traits explaining variability among different turkey genotypes (Wilks' lambda: 0.488, 0.590, 0.905, 0.906, 0.937, and 0.944, respectively). The combination of traits in the first three dimensions explained 94.93% variability among groups. Mahalanobis distances cladogram-grouped populations following a cluster pattern and suggest its applicability as indicative of a turkey genotype's traceability.

Quality Characterization of Different Parts of Broiler and Ligor Hybrid Chickens

The quality characterization of different parts of male and female Ligor hybrid chickens was investigated and compared with those of commercial broiler. Genotypes, muscle types, and sex had effects on the composition, physicochemical, and textural properties of chicken samples. Ligor hybrid chicken contained higher percentages of protein, moisture, ash, and collagen content but lower fat content than those of commercial broiler (p < 0.05), except in the case of breast, where no significant difference in moisture and ash was observed (p ≥ 0.05). The pH in breast meat of both chickens was lower than that of thigh meat. The color (L*, a*, and b*) values of male and female chickens were not significantly different, except for the L* value of broiler chicken, which was higher in female chickens than in male chickens. Higher cooking loss and shear force were found in male Ligor hybrid chicken. A similar protein pattern was observed for the protein from the same muscle type, irrespective of sex and genotype tested. It was observed that Ligor hybrid chicken contained higher glutamic acid and aspartic acid than commercial broilers. Therefore, Ligor hybrid chicken is a promising new source of nutrition, which can be beneficial for consumers.

Influence of Post Mortem Muscle Activity on Turkey Meat Quality

Wing flapping and body movement can occur during the slaughter of poultry. Wing movement and flapping are driven primarily by the breast muscles (Pectoralis major and minor), and this muscle activity may have implications for meat quality. The objective of this study was to evaluate turkey post mortem activity during slaughter at a commercial poultry processing plant. Post mortem activity (during bleeding) was scored on 5,441 male turkeys, from six different genetic lines, using a 1–4 scale from none to severe wing flapping. Meat quality was measured on these birds in terms of pH (initial, ultimate, delta or change), color (L^*, a^*, b^*), and physiochemical traits (drip loss, cooking loss, shear force). Linear mixed models were used to analyze the effect of activity (score 1–4), genetic line (A–F), and season (summer vs. autumn) on the nine meat quality traits. Post mortem activity influenced a^*, drip loss, and shear force although the magnitude of the effects was small. There was an effect (P < 0.05) of genetic line on all the meat quality traits except for L^*, cooking loss, and shear force. In general, larger, faster-growing lines had higher pH, but the relationship between the lines for the other traits is not as clear. Season affected all the meat quality traits, except for pH_delta, with meat having a higher pH, L^*, b^*, drip loss, cooking loss, and shear force in the summer. This study provides an exploratory assessment of post mortem activity in turkeys and identifies meat quality traits which are most affected while also accounting for the effects of genetic line and season. Although identified effect sizes are small, the cumulative effect on turkey meat quality may be more substantial.

Evaluation of Meat from Native Chickens: Analysis of Biochemical Components, Fatty Acids, Antioxidant Dipeptides, and Microstructure at Two Slaughter Ages

This study examined biochemical components, fatty acids, antioxidant dipeptides, and muscle fiber density of breast and thigh muscles from Korean new native chicken strains (A and B) at two slaughter ages, compared with white semi-broiler (W) or broilers. The pH values were different by chicken breed. The new native strains had the lowest fat content in the breast at 12 wk (p<0.05). Regardless of the muscles, A and B at 12 wk had higher levels of arachidonic acid (ARA; C20:4), docosahexaenoic acid (DHA; C22:6), and nervonic acid (C24:1) than broilers (p<0.05). A similar result was observed for the polyunsaturated fatty acids (PUFAs) and polyunsaturated and saturated fatty acids ratio (P/S) content in the breast. Irrespective of the muscles, A and B enriched with omega-3 fatty acids had a lower ω-6/ω-3 PUFA ratio than broilers (p<0.05) at 12 wk. Of the antioxidant di-peptides, the anserine contents were highest in A and B than in the W or broilers (p<0.05), regardless of the muscles and slaughter ages. Furthermore, the breast meat from A and B contained a higher muscle fiber density for both slaughter ages than the W and broilers (p<0.05). Based on these findings, even if the commercial birds (broilers or W) are raised under the similar environmental conditions as A and B, the new native chicken strains have distinct meat quality attributes, particularly higher ARA and DHA levels, lower ω-6/ω-3 PUFA ratio, and higher anserine contents.

Forced locomotor activity improves walking ability of male turkeys and modifies carcass characteristics

1. This trial investigated the effect of forced locomotor activity (training) on walking ability, leg posture, and growth performance, as well as carcass composition and meat quality in male fattening turkeys.2. A flock of 744 commercial turkeys was divided into three experimental groups, either without any training period (control), training from weeks 2 to 8 (short-term), or training from weeks 2 to 21 (long-term). All birds were slaughtered at an age of 21 weeks. To study the effect of short vs. long time lapse between shackling and stunning (suspension time), each training group was split into two halves that were hooked on the shackle for either 15 s or 3 min prior to stunning.3. Long-term physical training, compared to short-term or no training, resulted in better walking ability and in a lower percentage of leg malposition, as assessed at the end of fattening. No effect on final body weight was detected.4. In a subsample, the composition of 80 carcasses was determined by dissection. Long-term training favoured the percentage of the drumstick over that of the breast cut in comparison to the group without any training.5. Meat quality parameters were determined for breast muscle. The pH values 20 min post-mortem were reduced by long-term training, and the highest value was observed for a combination of no training with short suspension. After 24 h, pH values did not differ between experimental groups. The breast muscles were characterised as fast-glycolysing. Prolonged suspension time resulted in higher electrical conductivity after 24 h, and in higher a* values (redness).6. In conclusion, the study revealed that a long-term training period improved walking ability and leg posture of heavy male turkeys. Thus, training can contribute to the improvement of animal welfare in turkey husbandry. Meat quality variables of breast muscles were partially influenced by locomotor activity and suspension time.

Is Meat of Breeder Turkeys so Different from That of Standard Turkeys?

The technological, nutritional, and sensorial quality of breasts and thighs with drumsticks of turkey male and female breeders was characterized by comparison with breasts and thighs with drumsticks of growing male and female turkeys from the Grademaker line (hybrid turkeys, n = 20 birds per sex and per physiological stage). The breeder turkeys were slaughtered at 397 and 410 days of age and 10.42 and 32.67 kg of body weight for the females and males, respectively. The standard turkeys were slaughtered at 75 and 103 days of age and 5.89 and 13.48 kg of body weight for the females and males, respectively. The differences observed between males and females on one hand and between standard and breeder turkeys on the other hand were mainly induced by differences in slaughter ages and sexual dimorphism on body weight. The meat of female breeders had characteristics close to those of female and male standard turkeys, whereas the meat of male breeders was clearly distinguishable, particularly by displaying lower tenderness and water holding capacity.

Carcass and meat quality characterization of indigenous and improved variety of chicken genotypes

A study was conducted to examine four genotypes of chicken for their carcass and meat quality characteristics. From each genotype, 20 birds were slaughtered at their respective age of maturity. Breast and thigh muscles were evaluated for meat quality characteristics. Transport loss and carcass weight were highest in the white commercial broiler (WBR) and lowest in Aseel (ASL) and Indbro Aseel (ASR). Dressing percentage ranged between 66.41 and 72.56 and was not significantly different among genotypes. The yield of various cut-up parts for different genotypic birds was significantly different (P < 0.05). Highest percent yield for breast (29.15), thigh (15.57), drumstick (13.82) and wings (18.44) were observed in WBR, rainbow rooster (RR), ASR and rainbow rooster Plus (RRP), respectively. Giblet % was highest in RR and meat:bone ratio of thigh portion was highest in WBR. Higher ultimate pH was recorded for RR, RRP, and WBR, and higher water-holding capacity was detected in ASL and ASR. Further, bound water was higher in RR, RRP, and WBR, and free water was maximum in ASL and ASR. A significant (P < 0.05) higher shear force was observed in ASL and higher muscle fiber diameter in WBR. Cooking yield did not differ significantly among genotypes. The breast meat from ASL showed significantly (P < 0.05) higher redness value and WBR showed the lower redness. Further, ASL and ASR meats were darker and red in color than broiler meat. Meat from two indigenous birds (ASL and ASR) had significantly (P < 0.05) lower fat content compared to broilers and other crosses. ASL gave a slightly firmer meat as liked by consumers. The sensory evaluation showed breast meat from RR birds and ASL birds had better flavor scores than other birds. These results indicated that meat of indigenous chickens (ASL and ASR) has some unique features over commercial fast-growing birds that would increase their demand by consumers who prefer chewy, low-fat chicken meat.

Carcass Quality, Meat Quality and Sensory Properties of the Dual-Purpose Chicken Lohmann Dual

Over 40 million day-old layer line cockerels are culled in Germany each year, due to economic reasons, leading to a recently instigated research focus on the potential of dual-purpose breeds as an alternative to conventional poultry husbandry, especially the practice of culling. This paper aims to explore and assess the dual-purpose chicken breed “Lohmann Dual” (LD) performance (n = 30) and sensory characteristics (n = 48). Carcass and meat quality traits are evaluated, and descriptive sensory analysis of breast muscles is conducted. To define the scope of characteristics, a market sample of “Ross” Line (n = 35) is adducted. LD carcasses are characterized by higher leg than breast yield; carcass, breast and leg weights are higher in Ross. LD meat has a lower pH, differs in color, has higher drip and thawing losses, but lower cooking loss. LD breast muscles are firmer as indicated by shear force measurements, which is confirmed through the sensory analysis. Appearance, odor and flavor differ between the lines. Overall, distinguishable differences are found between both breeds. Further research should focus on the marketing aspect of the dual-purpose line, as some characteristics could draw consumers to this product. Animal welfare and ethical concerns should further be considered when considering dual-purpose breeds as a feasible alternative to culling.

A comparison of the effects of post-mortem aging on breast meat from Cobb 500 and Hubbard ISA broilers

We compared the physical and chemical characteristics of the pectoralis major muscle from Cobb 500 and Hubbard ISA broilers and evaluated the effect of aging process for up to 7 days on meat quality. We used breast samples from male Cobb 500 (42 days of age; n = 60) and Hubbard ISA (85 days of age; n = 60) broilers. Twenty samples of each genotype were analysed 4 h post-slaughter (Control group). Another 20 samples of each genotype were aged in an incubator (2 ± 0.5°C) for 3 and for 7 days. Breast fillets were 23% heavier in the Cobb 500 group (306 g vs 248 g; P = 0.0009). Before aging, meat from Hubbard ISA broilers had higher (P < 0.001) water-holding capacity, which promotes the production of less exudate and possibly reduces nutritional losses during storage, which may be beneficial to the poultry industry. Despite being initially less tender, breast meat from Hubbard ISA broilers showed, during the aging process, a reduction (P < 0.05) of shear force (48.46–15.04 N), total collagen amount (6.0–4.8 g/kg) and myofibrillar fragmentation index (150.17–97.42) and had the same (P = 0.134) fat concentration (0.87 g/100 g) as that of breast meat from Cobb 500 broilers (0.93 g/100 g, respectively). Breast meat from Hubbard ISA broilers had a higher (P < 0.001) polyunsaturated fatty acid concentration, especially docosahexaenoic acid, which is beneficial to human health. Aging breast fillets for 3 days at 2°C is sufficient to tenderise the meat without reducing its juiciness, which suggests that the aging process can add value to free-range meat.

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.

Influence of carbon dioxide stunning procedure on quality of turkey meat

1. The objective of this study was to evaluate the effect of sex and gas stunning on quality attributes of turkey breast meat. 2. One hundred B.U.T. Premium turkeys (50 males and 50 females) were divided into four groups of 25 animals and subjected to one of two CO₂ stunning procedures: G1 stepwise (step 1: 30% CO₂, 15 s; step 2: 55% CO₂, 40 s; step 3: 70% CO₂, 45 s) or G2 fixed concentration (80% CO₂, 100 s). The pH and meat colour at 20 min post-mortem, and pH, colour (L*, a*, b*), water holding capacity (WHC), drip loss (DL), cooking loss (CL) and Warner-Bratzler shear force (WBSF) in breast samples at 24 h and 7 d post-mortem were assessed. 3. There were significant differences between stunning groups for pH, meat colour and CL, whereas no significant differences were found for DL and WBSF. Sex had a significant effect on pH and b* and ageing of meat affected pH, colour coordinates, DL and WBSF. 4. It was concluded that the G2 treatment affected negatively the pH value and colour coordinates. However, G2 stunning affected positively the WHC parameters. Female turkeys had better results than males for pH, and the colour of female turkey breast meat was less yellow than male breast meat.

Hyperspectral deep ultraviolet autofluorescence of muscle fibers is affected by postmortem changes

After slaughter, muscle cells undergo biochemical and physicochemical changes that may affect their autofluorescence characteristics. The autofluorescent response of different rat extensor digitorum longus (EDL) and soleus muscle fiber types was investigated by deep ultraviolet (UV) synchrotron microspectroscopy immediately after animal sacrifice and after 24 h of storage in a moist chamber at 20 °C. The glycogen content decreased from 23 to 18 μmol/g of fresh muscle in 24 h postmortem. Following a 275 nm excitation wavelength, the spectral muscle fiber autofluorescence response showed discrimination depending upon postmortem time (t0 versus t24 h) on both muscles at 346 and 302 nm and, to a lesser extent, at 408 and 325 nm. Taken individually, all fiber types were discriminated but with variable accuracy, with type IIA showing better separation of t0/t24 h than other fiber types. These results suggest the usefulness of the autofluorescent response of muscle cells for rapid meat-aging characterization.

Comparison of growth performance, carcass characteristics and meat quality of korean local chickens and silky fowl

This study was conducted to compare growth performance, carcass characteristics and meat quality of 4 breeds of local chicken. A total of 480 1-d-old chicks were distributed to 16 pens, with 4 treatments of breed, 4 replicates and 30 chicks per pen. Three Korean local breeds of white-mini broiler, Hanhyup-3-ho, and Woorimatdag, and a breed of silky fowl were raised under identical rearing and feeding conditions for 31-d, 37-d, 36-d, and 59-d, respectively. The BW and feed consumption on a pen basis were weekly measured for all pens, and ADFI, ADG and gain:feed were calculated for each pen. The ADFI and ADG of 3 breeds of Korean local chicken were greater than those of silky fowl (p<0.05). Within the Korean local breeds, ADFI of white-mini broiler was the highest (p<0.05), and ADG of Hanhyup-3-ho and white-mini broiler was the highest (p<0.05). Gain:feed of silky fowl was less than that of the 3 breeds of Korean local chicken. The carcass and breast yield of white-mini broiler were the greater than those of other breeds (p<0.05). The breast meat color (CIE L*, a*, and b*) of 3 breeds of Korean local chicken were higher than that of silky fowl (p<0.05). The breast meat of Hanhyup-3-ho had greater cooking loss (p<0.05), whereas water holding capacity and pH were less than those of other breeds (p<0.05). The color score of 3 breeds of Korean local chicken was higher than that of silky fowl (p<0.05). Woorimatdag had a higher score on tenderness (p<0.05), whereas flavor score was less than that of other breeds (p<0.05). In conclusion, 4 local breeds of chicken have some unique features and seem to have more advantages, and this information can help consumers who prefer healthy and premium chicken meat.

Comparison of carcass yields and meat quality between Baicheng-You chickens and Arbor Acres broilers

This study examined carcass yields and meat quality traits between Baicheng-You (BCY) chickens and Arbor Acres (AA) broilers. Thirty birds for each strain were selected and slaughtered at market ages of 49 d for AA broilers and 120 d for BCY. The results showed that BCY chickens had lower dressing (2.99%), semi-evisceration (5.10%), breast muscle (5.80%), and abdominal fat (1.55%) than those for AA broilers (P < 0.05). However, the leg muscle (%) of BCY chickens was greater (3.14%) than that of AA broilers (P < 0.05). The meat pH45min and pH24h value variations of these 2 breeds were within the normal range (5.53-6.70). The meat color density (optical density, OD) of thigh muscle was darker than breast muscles in both strains (P < 0.05). The cooking loss (%) of breast and thigh muscles of BCY chickens (18.81 and 20.20%, respectively) was also significantly lower (P < 0.05) than that of same muscles of AA broilers (26.41 and 27.33%, respectively). The shear force of breast meat in both breeds was lower (P < 0.05) than that of their thigh meat. The moisture of breast muscle of BCY chickens (72.93%) was lower (P < 0.05) than breast muscles of AA broilers (74.43%). The CP content of breast muscles was greater (P < 0.05) than its thigh muscles of same strain, but it had no significant (P > 0.05) difference of CP content in the same muscles of the 2 strains. The intramuscular fat (IMF) content was greater (P < 0.05) in thigh muscles of BCY chickens (6.80%) than those of AA broilers (4.28%), and inosine-5'-monophosphate (IMP) content was greater (P < 0.05) in breast and thigh muscles of BCY chickens (IMP: 3.79 and 1.47 mg/g) than same muscles in AA broilers (1.42 and 0.47 mg/g). In this study, muscle from 120-d-old BCY chickens was judged to have better quality traits with regard to cooking loss, drip loss, contents of IMF, and IMP compared with meat from 42-d-old AA broilers. At the same time, greater carcass yields, greater thigh pH24, and lower IMF content were observed in AA broilers compared with the BCY chickens.

The European perspective on pale, soft, exudative conditions in poultry

Over the past 15 yr, the European poultry processing industry has gradually increased the availability of poultry meat in a large variety of processed ready meals following what occurred a few years before in North America. This shift toward further processed products has emphasized the necessity for higher standards in poultry meat to improve sensory characteristics and functional properties. In parallel to this market change, the consciousness of the pale, soft, and exudative (PSE)-like meat issue has extensively grown. In poultry, PSE-like meat can be generally considered meat having low ultimate pH, pale color, and poor functional properties (i.e., low water-holding capacity). In the last 10 yr, some studies have been undertaken in Europe to both characterize and evaluate the overall incidence of PSE-like chicken and turkey breast meat. According to these studies, the occurrence of PSE-like meat can be up to 40% within a flock during hot climate. Several key factors have been identified and their effects have been analyzed, including genetics, season, antemortem factors, and slaughtering conditions.

Meat Quality of Slow- and Fast-Growing Chicken Genotypes Fed Low-Nutrient or Standard Diets and Raised Indoors or with Outdoor Access

Consumer interest in free-range and organic poultry is growing. Two concurrent experiments were conducted to assess 1) the impact of alternative genotype and production system and 2) the impact of genotype and diet on meat quality of chickens for specialty markets. Specifically, a slow-growing genotype (slow) and a fast-growing genotype (fast) were raised for 91 and 63 d (females), respectively, or 84 and 56 d in the case of the second trial (males). In each trial, the slow birds were placed before the fast birds to achieve a similar final BW at processing. Each genotype was assigned to 4 pens of 20 birds each and raised in indoor floor pens in a conventional poultry research facility; each genotype was also assigned to 4 floor pens in a small facility with outdoor access. A low-nutrient diet was used, formulated for a slower rate of production. Birds were commercially processed and deboned at 4 h postmortem. In the second trial, the diets compared were a conventional diet that met NRC requirements or the low-nutrient diet, and all birds were raised indoors. There was an interaction between genotype and production system for the color (b*; P < 0.05). The meat and skin of the slow birds became more yellow when the birds had outdoor access; however, this did not occur when the fast birds had outdoor access. The breast meat of the slow birds had more protein and alpha-tocopherol (P < 0.05) than the fast birds and half the amount of fat (P < 0.05). In addition, the meat of the outdoor birds had more protein than the indoor birds (P < 0.05). The slow birds had poorer water-holding capacity but were more tender than the fast birds (P < 0.05). The type of diet had little impact on meat quality. These data indicate that meat quality differences exist between genotypes with different growth rates and raised in alternative production systems.

Behavioural and physiological responses of three chicken breeds to pre-slaughter shackling and acute heat stress

1. The aim of this study was to compare the behavioural and physiological responses to hanging and acute heat stress in three different chicken breeds. Chicks were obtained from a slow-growing French 'Label Rouge' line (SGL), a fast-growing standard line (FGL) and a heavy line (HL). The SGL, FGL and HL birds were slaughtered at their respective market ages of 12, 6 and 6 weeks, in an attempt to achieve similar body weights. Before stunning, birds were either shackled by their legs on the moving line for 2 min (shackling stress: SH) or placed in a room at 35 degrees C and 60% of humidity for 3.5 h and then shackled for 2 min (acute heat stress plus shackling: H + SH) or subjected to minimal stress by shackling for 10 s before stunning (control group: C). 2. Bird physiological responses to the three pre-slaughter treatments were estimated by measuring blood corticosterone, glycaemia, creatine kinase activity, acid-base status and electrolyte concentration as well as lactate content and glycolytic potential in the breast (Pectoralis major) and thigh (Ilio tibialis) muscles. Behavioural responses to shackling stress were evaluated by measuring wing flapping duration, straightening up attempts and vocalisations. 3. Blood corticosterone was higher in SH and H+SH groups than in the C group, regardless of genotype. The struggling activity on the shackle line differed among chicken breeds. It was more intense and occurred more rapidly after hanging in the SGL birds than in both other breeds. Furthermore, SGL struggling activity was not affected by hanging duration while it increased with hanging duration in FGL and HL birds. 4. Wing flapping duration was negatively correlated with blood pH, bicarbonate concentration and positively correlated with breast muscle lactate content, indicating that struggling stimulated antemortem glycolysis activity in breast muscle. Acute heat stress affected blood Ca2+ and Na+ concentration and increased glycaemia and glycolytic potential of thigh muscle. 5. Both acute heat stress and shackling before slaughter were experienced as stressful events by all types of birds.

In ovo temperature manipulation influences post-hatch muscle growth in the turkey

1. The effect of manipulating egg incubation temperature for short periods on turkey muscle development was determined using the M. semitendinosus, a thigh muscle, as the model. 2. Experiment 1. Eggs were incubated at a control temperature of 37.5 degrees C. For a 4-d period of 0 to 4, 5 to 8, 9 to 12, 13 to 16, 17 to 20 or 21 to 24 embryonic days (ED) eggs were transferred to either 38.5 or 35.5 degrees C. A regime of 38.5 degrees C at 5 to 8 and 9 to 12 ED caused an increased myonuclei number and muscle fibre number, respectively. 3. Experiment 2. Eggs were incubated at a control temperature of 37.5 degrees C. At 5 to 8 ED eggs were transferred to 38.5 or 35.5 degrees C. Temperature-manipulated embryos showed a delay in differentiation (myogenin expression) of the semitendinosus muscle compared to controls. 4. Manipulating the incubation temperature for 4 d in early incubation alters muscle development in the turkey with no observation of deformities or reduction in hatchability. We speculate that this increase in temperature may result in an improved muscle growth in the post-hatch bird.

Effect of Ultimate pH on the Physicochemical and Biochemical Characteristics of Turkey Breast Muscle Showing Normal Rate of Postmortem pH Fall

This experiment aimed to study the effect of ultimate pH (pH(u)) on the biochemical and physicochemical characteristics of turkey breast muscle with normal rate of postmortem pH fall. Five hundred turkey toms (12 wk old, 10 kg live weight) were randomly chosen from a commercial flock. At 24 h postmortem, 64 birds were randomly selected within the subgroup showing pH higher than 6.0 at 20 min postmortem and pH(u) lower than 6.1. These pH levels were used to exclude pale, soft, and exudative (PSE) meat and dark, firm, and dry (DFD) meat, respectively. The pH(u) was significantly correlated with luminance (L*; r = -0.37) and yellowness (b*; r = -0.36) at 24 h postmortem, drip losses (r = -0.56 to -0.62), thawing loss (r = -0.47), 80% compression (r = -0.29), yield of curing and cooking (r = 0.37), glycolytic potential at slaughter (r = -0.44) and lactate at 24 h postmortem (r = -0.47). Significant correlations were found between drip losses and compression test on cooked meat (r = 0.27 to 0.34). Cooking loss was correlated with WB shear force (r = 0.32). These results show that when PSE defects are excluded, the intensities of the correlations between pH(u) and meat quality traits are lower than those usually reported. The present data also indicate that the level of glycogen at time of slaughter poorly explains the variability in pH(u). Thus, further research is needed to identify the mechanisms explaining pH(u) variation in poultry muscle.

Variation of chicken technological meat quality in relation to genotype and preslaughter stress conditions

The present study was aimed at estimating the genetic variability between lines of breast and thigh meat quality (pH decline, color, drip loss, and curing-cooking yield) by comparing a slow-growing French label-type line (SGL) and a fast-growing standard line (FGL) of chickens exposed to different preslaughter stress conditions. The birds were slaughtered under optimal conditions or after exposure to 2 h of transport or acute-heat stress (2 h at 35 degrees C). Relationships between meat quality and stress sensitivity were investigated by measuring struggle during shackling and tonic immobility (TI) duration, 1 wk before slaughter, as an indicator of the basal level of fear of the birds. Although most of the meat quality indicators varied between the 2 lines, differences were muscle dependent. In concordance with a lower ultimate pH, curing-cooking yield of thigh meat was decreased for the FGL birds. In contrast, these birds had a higher curing-cooking yield and a lower drip loss of breast meat resulting from a less rapid pH decline in this muscle compared with SGL birds. Thigh meat characteristics were influenced by both preslaughter stresses, but no significant effects were detected for breast meat. The main effect of heat stress in thigh meat was a decrease of the ultimate pH and led to paler color and lower curing-cooking yield; opposite effects were obtained for transport. Breast meat was much more sensitive to physical activity of birds on the shackle line. Longer durations of wing flapping on the shackle line gave more rapid initial pH decline. Whatever the line, no relationship between TI duration and meat quality characteristics or activity was observed. The present study suggested that SGL birds could be at disadvantage due to more struggle during shackling and accelerated postmortem glycolysis, which is detrimental to the quality of breast meat.