Effect of genotype, sex and rearing temperature on carcase and meat quality of guinea fowl

1. The aim of our study was to analyse the effect of genotype (label and standard), sex and rearing temperature (simulating daily outdoor in the summer or winter) on the carcase and meat quality of guinea fowl. Using 20 animals per treatment, slaughtered at 96 d of age we measured the breast angle and the thickness of the skin on the wing membrane. Carcases were weighed and cut into parts according to a standardised procedure to determine the percentages of abdominal fat, breasts, wings and thighs with shanks. 2. At slaughter, standard guinea fowl were heavier than label guinea fowl and for both genotypes, the females were heavier than the males (+5.6%). The mean value of breast angle was 85 degrees. This value was significantly higher for the standard guinea fowls and for the females of both genotypes compared with males. Thus, female carcases, particularly standard females, were more compact. The skin was thicker for the standard guinea fowls (0.84 mm vs 0.77 mm) which could be due to more subcutaneous fat. 3. Carcase yield was higher for the males (68.7% vs 68.2%). The percentage of abdominal fat was higher for the standard guinea fowls (2.8% vs 2.4%) and for the females of both genotypes compared with males. The label guinea fowls had higher yields of breasts and thighs with shanks. For both lines, the breast and thigh meat of females was judged more tender and less stringy. 4. Low rearing temperature decreased growth performance but had no significant effect on carcase quality.     

Effect of the naked neck gene on carcase composition and immunocompetence in chicken

1. An experiment was conducted to study the effect of naked neck gene (Na) on carcase measurements and some immunological responses of chickens. 2. The presence of naked neck gene in a single or double state increased body weight. 3. The naked neck genotypes (NaNa or Nana) exhibited higher relative weight of dressed carcase, drumstick and breast muscles compared to normally feathered individuals (nana). The proportion of abdominal fat was decreased in both naked neck genotypes compared with normally feathered ones. 4. A higher (non-specific) cell-mediated immune response was evoked in Na gene bearing birds. 5. Higher concentrations of antibodies occurred after injection of sheep red blood cells into naked neck birds, particularly at 14 d post-secondary injection. 6. The NaNa birds had a higher heterophil/lymphocyte ratio than Nana and nana siblings.     

Influence of food intake and sex on the growth and carcase composition of Pekin ducks

1. The effects of food intake on growth and carcase composition of male and female meat‐type Pekin ducks were investigated between 14 and 56 d of age and between 0.416 kg (14 d) and 2.5 kg live body weight.

2. Males grew faster between 14 and 56 d of age and contained less fat and more protein and water in the eviscerated carcase at 56 d than females.

3. For both sexes, food : gain ratio deteriorated as food intake increased from 0.49 ad libitum intake to ad libitum intake. Growth rate, carcase weight and carcase fat content increased linearly with increase in food intake. Carcase fat content at 56 d was more sensitive to change in the amount of food consumed than either growth rate or carcase weight.

4. Between 0.42 kg (14 d) and 2.50 kg live body weight, growth rate and food :gain ratio improved as food intake was increased from 0.61 ad libitum to ad libitum. Males grew faster and produced leaner carcases than females.

5. Carcase fat content at 2.50 kg live body weight (1.60 kg carcase) increased in a curvilinear fashion with increase in food intake, and the magnitude of the response was lower for females than for males. A similar interaction existed between the effects of sex and the amount of food consumed for the proportions of protein and water in the eviscerated carcase at 2.50 kg live body weight.     

Effect of less intensive rearing conditions on litter characteristics, growth performance, carcase injuries and meat quality of broilers

1. The objective was to compare the effect of two litter types (wheat straw and wood shavings) and two different rearing conditions (Treated and Control) on welfare indicators, broiler performance, carcase injuries, particularly hock and foot pad dermatitis (FPD), litter characteristics and meat quality. 2. Treated conditions were characterised by a low stocking density (11 birds/m(2)), short photoperiod (16 h light: 8 h dark) and a large amount of litter (3 to 4.5 kg/m(2), respectively, for wheat straw or wood shavings). Control conditions were a high stocking density (14 birds/m(2)), long photoperiod (23 h light:1 h dark) and small amount of litter (2.3 to 3 kg/m(2), respectively, for wheat straw or wood shavings). In addition, the effects of two widely used litter materials, wheat straw and wood shavings, were investigated. 3. The combined effects of lower stocking density, greater amount of litter material and a photoperiod similar to the natural one, reduced the occurrence of FPD in Treated groups keeping the FPD score under the European threshold. 4. Improved rearing conditions led to faster growth rate associated with inferior feed efficiency, whereas litter type exerted negligible effects on broiler performance. 5. Litter moisture content, nitrogen and ammonia released by the litter were lower in Treated groups than Control groups. The use of wood shavings resulted in lower moisture and nitrogen concentrations in the litter.     

Effect of electrical and gaseous stunning on the carcase and meat quality of broilers

1. The aim of the experiment was to investigate the effect of gaseous stunning methods on the carcase and meat quality of broilers (dead weight 1.0 to 2.3 kg) in comparison with electrical stunning.

2. Two replicates of broilers (age 54 and 59 d respectively) were stunned in carbon dioxide, in argon or by electric current, and the carcases were plucked either by a mechanical plucker or by hand.

3. Carcase and meat quality were evaluated to determine the effect of these stunning treatments and plucking methods. The quality factors measured included pH at 20 min post‐mortem, ultimate pH, texture and colour of the pectoralis major muscle, and the incidence of carcase appearance defects, cooking loss, broken bones and bruises in the breast and leg muscles.

4. Stunning method had a significant effect on pH at 20 min, ultimate pH, texture and colour of breast meat. Plucking method had a significant effect on the cooking loss and texture.

5. Argon stunning resulted in fewer muscle haemorrhages, a more rapid early post‐mortem fall in pH and more tender breast meat than in the electrically stunned broilers; carbon dioxide stunned broilers had intermediate values for pH decline and meat tenderness but were not significantly different from argon stunning regarding muscle haemorrhages.

6. Appearance defects occurred to a similar extent in all the stunning methods and mechanical plucking resulted in 4 times as many defects compared with hand plucking; the incidence of broken bones was higher in mechanically plucked broilers than in hand plucked carcases.

7. Gaseous stunning of broilers produced relatively better quality carcases and meat than electrical stunning, and therefore may have commercial advantages.     

Effect of conjugated linoleic acid on growth performances, carcase composition, plasma lipoprotein lipase activity and meat traits of chickens

1. The effects of dietary conjugated linoleic acid isomers (CLAs) on productive traits, carcase yield and meat quality were investigated in Beijingyou (Chinese) chickens. A total of 360 male chicks were allocated to 5 dietary treatments (0.00, 0.25, 0.50, 1.00 and 2.00% CLA) and fed for 126 d. 2. The results showed that CLA supplementation did not significantly influence body weight, but increased feed conversion and decreased intramuscular fat in breast and thigh muscles. Mortality was significantly higher in the control group. 3. The addition of 1.0 and 2.0% CLA decreased abdominal fat percentages. At CLA dietary levels greater than 0.5%, lipoprotein lipase activity in plasma was significantly decreased. 4. Hunter L* and a* values were not significantly affected by CLA supplementation. However, Hunter b* values were lower in chickens supplemented at levels greater than 0.5% CLA. Supplementing diets with CLA modified the fatty acid composition of breast muscle. The proportions of CLA, saturated and polyunsaturated fatty acids were increased whereas the proportion of monounsaturated fatty acids was decreased.     

Effects of dietary threonine and crude protein on growth performance, carcase and meat composition of broiler chickens

1. The aim of the study was to investigate the effects of dietary threonine (Thr) and crude protein (CP) in maize-soybean meal based diets on the growth performance, carcase traits and meat composition of broiler chickens and to determine the dietary Thr requirement for optimum performance (weight gain and feed conversion efficiency (FCE)) at 0 to 3 weeks and 3 to 6 weeks of age. 2. Two basal diets that differed in CP (191.3 or 179.7 and 176.7 or 165.4 g/kg at 0 to 3 and 3 to 6 weeks, respectively) were formulated to have identical contents of Thr (6.0 and 5.4 g/kg), energy (12.97 and 13.39 MJ ME/kg) and other essential amino acids except for Gly + Ser. Basal diets were supplemented with L-Thr from 0.6 to 1.8 g/kg in 0.6 g/kg increments. Broiler chicks (540) were randomly allocated to 9 dietary treatments with 6 replicates of 10 (5 female, 5 male) chicks. 3. A significant interaction between dietary CP and Thr was found for feed intake, body weight (BW) gain and FCE. Increasing Thr supplementation improved feed intake, BW gain and FCE, especially in high CP diets in both feeding periods. 4. Incremental increases in dietary Thr increased breast yield at both CP levels and drumstick yield only on high CP diets. The proportion of thigh decreased with Thr concentration. Liver weight was significantly reduced by Thr supplementation; abdominal fat was not affected. 5. Estimated Thr requirements for FCE increased as dietary CP increased according to an exponential model. This model indicated higher Thr requirements than those of broken-line models for growth performance.     

Effect of dietary methionine on performance, carcase characteristics and breast meat composition of heterozygous naked neck (Na/na+) birds under spring and summer conditions

1. Heterozygous naked neck (Na/na+) birds and their normally feathered counterparts (na+/na+) were fed from 0 to 7 weeks on 3 diets differing in methionine concentrations. From 0 to 3 and 3 to 7 weeks, respectively, the concentrations were: low containing 4.3 and 3.3 g/kg; optimum containing 5.0 and 3.8 g/kg and; high with 5.7 and 4.4 g/kg under spring (optimum ambient temperature) and summer conditions (high ambient temperature). Performance, carcase characteristics and breast meat chemical composition were determined. 2. Summer rearing resulted in a decrease in body weight, body weight gain, food consumption, and yields of carcase and breast. The summer temperature effect was more pronounced in males. Under summer temperatures, the protein content of the breast decreased while the fat content increased compared to birds reared in spring. 3. By 7 weeks of age, both genotypes reached similar body weights in the spring experiment while, in summer Na/na+ birds were 3.3% heavier and gained more in the period from 3 to 7 weeks than na+/na+ birds. Carcase and breast yields of Na/na+ birds were greater than in na+/na+ birds. 3. Second order polynomial coefficients of the dietary methionine effect were found to be significant for body weight at 3 and 7 weeks. Daily body weight gain between 3 and 7 weeks was linearly affected by the dietary methionine concentration. There was no interaction between genotype and methionine. 4. Methionine had no significant effect on carcase yield. Second order polynomial coefficients of the dietary methionine effect were found to be significant for breast yield while the methionine effect on abdominal fat was linear. Na/na+ females fed on the low methionine diet had lower protein content than the Na/na+ males. 5. It is concluded that the methionine requirement of Na/na+ birds did not differ from that of their normally feathered counterparts under either spring or summer ambient temperature conditions.     

Effect of chicken meat replacement by spent laying hen meat on physicochemical properties and sensorial characteristics of fresh sausage

1. Sausages were used to assess the effects of chicken meat replacement by spent laying hen meat on the quality parameters and sensorial properties.

2. Five formulations were developed: control (CON) containing 100% chicken meat and 4 levels of chicken meat replacement with spent laying hen meat: 25% (T25), 50% (T50), 75% (T75) and 100% (T100).

3. Appearance, texture, succulence, flavour and overall consumer acceptance were analysed. Parameters such as moisture, ash, fat and protein content, pH, cooking loss and colour parameters (lightness (L*), redness (a*), yellowness (b*)) were analysed, as well as the texture properties (hardness, elasticity, cohesiveness and chewiness).

4. Statistical analysis did not reveal significant (P > 0.05) differences in chemical composition and colour parameters among formulations. On the other hand, CON treatment showed the lowest (P < 0.05) cooking loss (20.45%) that increased as spent laying hen meat increased in the formulation (24.92% vs. 27.65% vs. 28.12% vs. 33.05%, for T25, T50, T75 and T100 batches, respectively).

5. Regarding textural parameters, T75 and T100 formulations presented higher (P < 0.05) hardness and chewiness compared to the other ones.

6. Concerning to sensorial characteristics, the T100 formulation presented the lowest average scores (P < 0.05) for all attributes studied. However, the other batches (T25, T50 and T75) did not show significant differences for appearance, texture, succulence, flavour and overall acceptability attributes compared with the CON formulation.

7. The results indicated that the substitution of up to 75% of chicken meat by spent laying hen meat did not decrease the sensory acceptance of the sausages by consumers, demonstrating that this level of substitution in sausages allows better use of spent laying hen meat.     

Effect of tibal dyschondroplasia on carcase part weights and bone characteristics

1. The effect in broilers of tibial dyschondroplasia (TD) on carcase part weights and bone characteristics was investigated by studying the progeny of 10 sires and 40 dams. The correlations between TD and bone variables were also estimated.

2. The incidence of TD was 59% at 42 d of age. There were no significant differences in slaughter weight of birds with and without TD. However, in females, breast weight was heavier in affected birds. Neck plus back weight of birds with TD was significantly heavier than in birds without TD.

3. Breast blister frequency of birds was independent of the presence of TD.

4. Birds with TD had longer bones than birds without TD. However, TD had no effect on tibiotarsus weight, width, ratio of tibiotarsal to body weight and ash. A negative correlation was observed between TD score and bone ash percentage.     

Genetic evaluation of meat quality traits and their correlation with growth and carcase composition in Japanese quail

1. Estimates of heritability, genetic and phenotypic correlations of performance and meat quality traits were obtained in a population of Japanese quail using restricted maximum likelihood (REML) procedures.

2. The heritability estimates for body weight (BW) traits ranged from 0·15 at hatch to 0·42 at six weeks. For carcase composition traits, heritability estimates ranged from 0·12 for carcase yield to 0·26 for abdominal fat yield and for meat quality traits they ranged from 0·18 for drip loss to 0·54 for yellowness of the meat.

3. Negative genetic correlations were found between BW and carcase traits with ultimate pH and drip loss ranging from ?0·01 (BW at hatch) to ?0·40 (skin yield). Redness and yellowness showed negative genetic correlations with BW and carcase traits, whereas the genetic correlations with lightness were positive (from 0·04 to 0·43).

4. Shear force and cooking loss showed positive genetic correlations with carcase, breast, abdominal and skin yield.

5. In conclusion, meat quality traits have the potential to be improved through genetic selection but selection for higher BW and carcase composition may reduce the meat quality of Japanese quail through reducing redness, ultimate pH and intramuscular fat and increasing lightness, shear force and cooking loss of the meat.     

Ratification of broiler carcase condemnations in poultry meat inspection

1. In the years 1985 to 1989 decisions (approvals and condemnations) made by poultry meat inspectors were examined by the individual reinspection of 26,815 broiler carcases.

2. The extent of agreement between inspection and revision ranged between 83.2 and 86.2%.

3. Agreement between inspectors and revisors was higher for the category of approved birds than for the condemned category.

4. Differences in the criteria used to assess the birds were observed.

5. The conclusion was drawn that findings in meat inspection require further discussion to reach an agreed standard.     

Effect of saturated fat on growth,body fat composition and carcase quality in chicks

1. The effects of feeding two fats with different degrees of saturation on skin tearing, carcase quality and body fat composition were examined in male and female chickens.

2. No differences in growth or efficiency of food utilisation were apparent on feeding the more saturated fat. Skin tearing was slightly reduced and carcase quality slightly improved on feeding the more saturated fat for 28 d.

3. Decreases in linoleic acid content in intra‐abdominal fat were apparent after 14 d feeding the diet containing saturated fat. These decreases were greater after feeding the saturated fat for 28 d.     

Effect of environmental temperature,dietary energy,age and sex on broiler carcase portions and palatability

1. Two environmentally‐controlled houses, one at a constant 21°C (low temperature), the other diurnally cycling at 21 to 30°C (high temperature) and two diets of 13.0 MJ ME/kg (low energy, LE) and 13.8 MJ ME/kg (high energy, HE) were used to study the effects of age and sex on broiler carcase portions, dissected tissue proportions, and meat quality.

2. Slaughtering at 54 d instead of 34 d produced broilers with breast and leg weights of 277 and 308 instead of 284 and 319 g/kg carcase respectively, and a higher cutting loss (31 versus 6 g/kg carcass).

3. Males had lower proportions of breast, breast meat and fat, but higher proportions of leg, leg bone, and total meat to fat ratio than females.

4. Cycling high temperature resulted in higher breast, and lower leg proportions than constant low temperature.

5. High dietary energy content increased cutting loss, proportion of breast fat and lowered meat to fat ratio when compared to low energy, but did not affect the flavour of the meat, which was improved by age and high environmental temperature.     

Effect of clenbuterol on growth,carcase and skeletal muscle characteristics in broiler chickens

1. Male and female broiler chickens (144 in total) were given diets supplemented with clenbuterol (CB) at 0 (control) and at 1 mg/kg between 28 and 49 d of age to study the effect of CB on growth, carcase and skeletal muscle.

2. CB improved growth in males by increasing daily weight gain and final live weight and by lowering food conversion ratio. In females it changed the carcase composition by reducing abdominal fat pad and by increasing the proportion of protein. Consequently, carcase protein gain was increased in both sexes (11% and 16%, respectively).

3. Skeletal muscle weights were enhanced by between 6% and 22%. Muscle fibre diameters were increased in extensor hallucis longus (EHL) but not in gastrocnemius (GAS) muscle. This increase was more pronounced in females. EHL total muscle fibre number remained unchanged. The proportion of fast‐twitch glycolytic fibres was increased at the expense of fast‐twitch oxidative fibres in males only. Nuclear/cytoplasm and DNA/protein ratios tended to be decreased by CB.

4. From the elevated EHL muscle RNA/DNA, unchanged protein/RNA and translation activity it is suggested that CB stimulated protein synthesis at the pretranslational level. Reduced protein degradation is deduced from decreased neutral calcium‐dependent proteolytic activity.

5. It is concluded that broiler chickens respond to long‐term CB treatment as has been shown in various mammals. However, the sex‐specific response in growth, carcase composition and skeletal muscle cellularity is more clearly apparent in broiler chickens.     

Effect of avoparcin interaction with anticoccidial compounds on the growth and carcase composition of broilers

The anticoccidial drugs narasin, lasalocid, monensin and salinomycin, with and without avoparcin, were fed to 1280 broiler chickens from 1 to 49 d old. At day 49 significant interactions were detected between avoparcin and the anticoccidial compounds for body weight and food consumption. This indicated that the increases in body weight and food consumption obtained with avoparcin were greater with some anticoccidial compounds (lasalocid and salinomycin for body weights and lasalocid for food consumption) than with others (monensin and narasin for body weights and monensin, narasin and salinomycin for food consumption). Overall there was evidence that avoparcin increased body weight (5.8%), food consumption (2.5%) and efficiency of food utilisation (2.9%). In addition avoparcin produced significant increases in plucked weight and the proportion of visceral fat together with and decreases in the proportions of edible giblets and waste offal.     

Effect of stunning method,carcase chilling temperature and filleting time on the texture of turkey breast meat

1. Three hundred and sixty turkeys comprising 16 week‐old stags (medium stags), 22 week‐old stags (large stags) or 52 week‐old hens (hens) were stunned with either argon‐induced anoxia, 30% carbon dioxide in argon with 2% residual oxygen (gas mixture) or electric current and the carcases were processed under commercial conditions. The carcases were chilled at either 16°C or 3°C using a commercial immersion chiller and the carcases were held in a cold room (3°C).

2. Breast muscles (pectoralis major) were filleted at either 2, 3, 5 or 18 h post‐mortem, and pH and muscle temperature were measured at the time of filleting for the medium and large stags. The breast fillets removed soon after killing were stored at 3°C until transported to the laboratory.

3. All the breast fillets were cooked to an internal muscle temperature of 85°C and their texture was measured instrumentally. The fillets were weighed before and after cooking to determine the proportional cooking loss.

4. The results showed that, for electrical stunning, the rate of pH fall soon after killing differed between the bird types, and it resulted in a variable texture in the breast meat when filleting was performed soon after killing. The medium stags had a relatively slower rate of pH fall and filleting them soon after killing resulted in tougher breast meat.

5. By contrast, in all the three bird types, gas stunning resulted in a rapid pH fall soon after killing and produced tender breast meat at all the filleting times tested.

6. The cooking loss was higher in the large stags than in the medium stags or hens.

7. Stunning turkeys by anoxia or 30% carbon dioxide in argon would enable filleting to be performed soon after killing, and produce less variable‐and more tender breast meat.     

Effect of selection for improved body weight and composition on muscle and meat characteristics in Muscovy duck

1. For 25 years, the Muscovy duck has been selected for greater body weight at slaughter age, higher meat yield and lower fat content. The aim of this study was to analyse the effects of such selection on the biochemical and technological characteristics of duck meat. 2. A line which has been maintained without any selection since 1975 (control line) and a heavy line now commercialised (selected line) were reared under the same conditions. We compared growth performances, dressing and dissection yields and biochemical and technological characteristics of duck meat at 8, 10 and 12 weeks of age. 3. Our results showed that an indirect effect of selection was to increase the duck growth rate. At a given age, muscle weights and yields as well as carcase fat content were higher for selected ducks. In the selected line, muscle fibres were larger and the collagen content in muscles lower. 4. The Sartorius muscle in ducks from the selected line exhibited a higher percentage in numbers of white type IIb fibres to the detriment of red type IIa fibres. Its glycolytic enzyme activity was higher and its oxidative enzyme activity lower. 5. In breast muscle, selection decreased the rate of post-mortem decline in pH value, increased protein and mineral contents and decreased moisture. It did not affect fibre type, colour, haem pigment and lipid contents, collagen solubility or drip loss. 6. In conclusion, the effects of Muscovy duck selection on meat quality were relatively moderate.     

The effect of a diet containing grasshoppers and access to free-range on carcase and meat physicochemical and sensory characteristics in broilers

1. Research was conducted to evaluate the impact of a diet containing grasshoppers on the carcase, physicochemical and sensory characteristics in a free-range, grassland-based broiler production system.

2. A total of 80, 28-d-old male broilers were reared on grassland containing a large population of grasshoppers (treatment PB). Control birds were reared intensively on a maize-soybean diet (treatment CB). At 91?d of age, 24 birds from each treatment were slaughtered to evaluate carcase, meat and sensory characteristics.

3. Treatment PB produced birds with significantly lower live weights, breast, wing, thigh and drum weights, and higher dressing percentage and breast percentage of carcase, compared with CB. Treatment PB produced breast meat with significantly higher redness values, shear force and protein content, and lower pH values, cooking loss, moisture and fat content compared with CB. Sensory panel results for breast and thigh meats showed no treatment effect on colour and juiciness, but significantly higher scores for chewiness, flavour, aroma and overall appreciation, and lower scores for tenderness from treatment PB compared with CB.

4. Rearing chickens on rangeland may provide an alternative way to produce poultry meat which is considered superior by modern consumers.