Effect of sex and genotype on carcase composition and nutritional characteristics of chicken meat

1. The aim of this study was to examine the effect of sex and genotype on carcase composition and nutritional and sensory characteristics of chicken meat. The “Géline de Touraine” (GT) characterised by high carcase fatness was compared with an experimental crossbreed (EC) and “Label rouge” (LR) genotype.

2. Females compared with males, and GT chickens compared with LR and EC chickens were characterised by increased carcase fatness and an increased lipid level in thigh meat.

3. In both breast and thigh meat, the percentage of monounsaturated fatty acids was increased and the percentage of polyunsaturated fatty acids was decreased. However, these effects did not affect sensory characteristics of meat particularly those of roasted breast fillets containing very low lipid level by comparison with thigh meat.

4. Finally, in our study, high carcase fatness was related to high intermuscular fatness affecting the nutritional characteristics of meat but not its sensory attributes.     

Crossbreeding effects for body weight and carcase traits in Pekin duck

1. Three sire lines of Pekin duck, three dam lines and 9 crosses between these two groups were tested in replicated tests from 1987 to 1991. Body weight at the age of 7 weeks (n = 5189), carcase percentage, percentage of abdominal fat and thickness of breast muscles were recorded (n = 1432 for carcase traits).

2. The data were analysed by linear models. All models contained the factors test and sex. When analysing only crosses, general and specific combining abilities (GCA and SCA respectively) were included as well as their interactions with the test. Using the complete data set (lines and crosses), direct genetic and heterotic effects were considered.

3. The factors test and sex were significant in both data sets for all traits.

4. For body weight, all genetic factors were significant. The average heterosis was 65 g ± 9 g (2.2%); the highest observed heterosis was 7.7%.

5. For carcase percentage, the heterosis was always negative (up to — 2.1%), whereas in abdominal fat, a desirable negative heterosis was observed only in one cross. No significant heterotic or combining ability effects were observed in the thickness of breast muscles.

6. Significant interactions between at least one genetic factor and test were found in all traits.

7. The relative importance of GCA and SCA, possible sources of confounding estimates of genetic effects, the importance of heterotic effects and genotype × environment interactions are discussed.     

Effect of egg composition on hatchability and on growth and slaughter characteristics of meat-type chicks

1.?Using the so-called TOBEC (Total Body Electrical Conductivity) method, which allows the determination of egg composition in vivo, correlations between egg composition, hatchability and hatched chicks’ development were studied.

2.?A total of 1500 hen eggs (Ross-308) were measured by TOBEC, and eggs with extremely high (10%, n = 150), extremely low (10%, n = 150) and average (10%, n = 150) electrical conductivity values were chosen for further investigation.

3.?During the incubation period, it was observed that eggs with high electrical conductivity had a significantly higher mortality than eggs with low electrical conductivity.

4.?It was observed that both the increase in electrical conductivity at the same egg weight, and the increase in egg weight at the same electrical conductivity resulted in an increase in the hatching weight.

5.?It was found that the dry matter, protein and fat content of the chicks hatched from eggs with low electrical conductivity was higher at hatching than that of the chicks hatched from eggs with high electrical conductivity.

6.?At 42 d of age the liveweight of cocks and pullets hatched from eggs with low electrical conductivity was 3·2 and 8·2% higher than the liveweight of cocks and pullets hatched from eggs with high electrical conductivity.

7.?Because of the higher liveweight at slaughter, there was a significant superiority of the chicks hatched from eggs with low electrical conductivity in the case of the examined carcase traits at slaughter.

8.?Similar tendencies were found also in the ratios of carcase variables to liveweight, but the between group differences were not statistically significant in this case.

9.?Based on the results it was concluded that TOBEC seems to be a useful method for separating eggs with different composition.

10.?This could be a good starting point for further in vivo investigations in order to clarify the effect of egg composition on hatchability and further development.     

Kaempferol improves carcase characteristics in broiler chickens by regulating ANGPTL3 gene expression

1. The objective of this study was to examine the beneficial effects of kaempferol, a naturally occurring polyphenol, on carcase characteristics in broiler chickens and the mechanisms involved in this regulation.

2. Broiler chickens were randomly divided into 7 groups: control, carrier control, kaempferol (0·3%), kaempferol (0·6%), hypercholesterolemic (HLD), HLD and kaempferol (0·3%), HLD and kaempferol (0·6%).

3. Seven weeks after treatment, carcase characteristics, lipid levels in the blood and liver, expression of hepatic Angiopoietin-like protein 3 (ANGPTL3) mRNA, and expression of adipose lipoprotein lipase (LPL) protein were determined.

4. Treatment with kaempferol (0·3 or 0·6%) significantly increased plasma high-density lipoprotein cholesterol levels, decreased percentage of abdominal fat, thickness of subcutaneous fat, plasma and hepatic total cholesterol and triglyceride concentrations, muscle malondialdehyde level and down-regulated expression of ANGPTL3 mRNA concomitantly with up-regulated expression of LPL protein in normal and hypercholesterolemic broiler chickens.

5. Kaempferol (0·3 or 0·6%) treatment had no significant effect on the values of percentage of breast muscle, percentage of leg muscle, carcase weight and eviscerated percentage.

6. The results suggest that kaempferol improves carcase characteristics by decreasing expression of ANGPTL3 in broiler chickens.     

Effect of age and carcase composition on the onset of sexual maturity in quail under normal feeding regimens

1. The effect of age and carcase composition on the onset of sexual maturity was investigated in Japanese quail (Cotumix coturnix japonica) reared under a normal feeding regimen.

2. At 42 d of age, when the quail had started to lay and hen day production was about 60%, layers were heavier and contained more carcase fat than those that were not laying.

3. The liver and the ovary weight were greater following the onset of sexual maturity than 1 or 2 weeks before (35 and 28 d respectively).

4. Carcase fat as well as age are critical requirements for the onset of sexual maturity in quail.     

Correlations between body measurements and tissue composition of oat-fattened White Kołuda geese at 17 weeks of age

1.?The aim of the present study was to evaluate the yield and tissue composition of carcases from White Ko?uda® ganders (males) and geese (females), and to determine the relationships between body measurements and carcase tissue composition.

2.?The experiment was carried out on 200 geese (100 males and 100 females) reared to 14 weeks of age and then fed with oats for the next 3 weeks. Live body weight and body dimensions, slaughter yield, weight and percentage of muscles and skin with fat in carcase were measured and correlation coefficients were calculated between body measurements and slaughter values and carcase tissue composition.

3.?White Ko?uda® geese reared to 17 weeks of age were characterised by high body weight (6705 g) and good muscle yield (29·9%). Males had greater body weight, musculature and fatness than females. Sternum length and breast circumference, width and depth were good indicators of carcase muscle weight in 17-week-old geese.

4.?Negative coefficients of correlation between sternum length and weight of skin with subcutaneous fat indicate that increased selection pressure in pedigree flocks of geese on sternum length should be paralleled by reduced carcase fatness in these birds.     

Yield and composition of raw and cooked meat of small white turkeys as influenced by dietary nutrient density and energy to protein ratio

1. Raw and cooked meat yields and the dry matter and fat contents of meat samples were determined on 144 carcases of Small White turkeys fed on diets that varied in nutrient density (ND) and energy to protein ratio (E:P).

2. High ND diets increased body weights, eviscerated carcase weights, relative carcase yields and carcase skin yield, but not breast or total meat yields.

3. Feeding a low ND diet to 6 weeks followed by diets with progressively increasing ND yielded performance and carcases with qualities comparable to feeding diets of constant medium or high ND; consequently cost savings could be made.

4. Increasing E:Ps reduced body weights, eviscerated carcase weights and carcase yields. Breast and total meat yields from male but not female carcases, and skin yield of female but not male carcases decreased with higher E:Ps.

5. The fat contents of breast and thigh meat samples increased with ND. The fat content of breast but not thigh meat decreased with higher E:P. Dry matter contents of meat samples did not vary consistently with changes in fat content.     

Fat deposition and heat production as responses to surplus dietary energy in fowls given a wide range of metabolisable energy: Protein ratios

1. Female broiler fowl between 21 and 42 d of age were given diets with apparent metabolisable energy (AME) contents ranging from 8 to 15 MJ/kg at each of two crude protein (nitrogen x 6.25; CP) contents (130 and 210 g/kg).

2. Food intake was measured daily for 21 d. Body composition was determined at 42 d and gains in body mass, protein, fat and gross energy calculated by comparison with a group analysed at 21 d. Heat production was calculated by difference between AME intake and energy gain.

3. Decrease of food mass intake with increased dietary AME concentration limited the increase in AME intake to about 25%, despite the near 2‐fold range of AME concentrations.

4. There was no effect of CP concentration on food mass intake. CP intake was directly related to CP: AME ratio.

5. When body weight differences were taken into account, heat production was independent of dietary AME concentration, but increased by about 8% on the higher‐protein diets.

6. There were strong linear correlations between dietary CP:AME ratio and carcase protein: energy ratio, carcase fat content and carcase protein content.

7. It was concluded that the growing fowl responded to dietary nutrient: energy ratio, and the associated differences in nutrient and energy intakes, by varying the rate of energy deposition as fat, without regulatory variation of energy dissipation as heat.     

Effect of lighting treatment on the productivity,health, behaviour and sexual maturity of heavy male Turkeys

1. Turkey poults (1620) were used to compare the effects of three lighting programmes on heavy strain males reared to 188 d: constant light (24L:0D, CON); increasing light (6L:18D at 7 d gradually increasing to 20L:4D by 63 d, INC); a pattern identical to INC followed by a decrease in daylength from 84 d to 10L:14D at 112 d (DID).

2. Lighting affected growth pattern but had no effect on body weight at 118 d or overall food to gain ratio.

3. Both INC and DID lighting reduced overall mortality in comparison to CON light primarily because of a reduction in the incidence of skeletal disease and spontaneous cardiomyopathy. INC and DID lighting increased the incidence of cannibalism.

4. Turkeys given INC or DID lighting had a superior ability to walk in comparison to those birds given CON light.

5. INC and DID males stood, ate and drank more frequently, and sat less often than CON turkeys during behavioural observation.

6. There were no lighting effects on carcase composition except that INC and DID birds had heavier keel bones. The ultimate force per cm² (stress) required to break femora was greater for turkeys given INC and DID lighting (P = 0.065).

7. Plasma testosterone concentrations at 117 d were 272.5, 115.2 and 29.5 pg/ml for turkeys given CON, INC and DID lighting, respectively (P= 0.072). Testosterone concentration was not related to growth rate.     

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.     

Effects of a beta‐adrenergic agonist clenbuterol) on performance,carcase composition,hepatic microsomal mixed function oxidase and antibody production in female broilers treated with or without corticosterone

1. Beta‐adrenergic agonist (Clenbuterol, 0.33 mg/kg) and corticosterone (10 mg/kg) were incorporated into a diet based on maize and soyabean meal. Their effects on performance, carcase composition, hepatic microsomal mixed function oxidase and antibody production were investigated in female broilers.

2. Dietary corticosterone reduced the titre to sheep red blood cells, while it was unchanged by clenbuterol.

3. Clenbuterol exerted a promoting effect on gain‐to‐food ratio, carcase protein and hepatic microsomal cytochrome P‐450 content.

4. Addition of clenbuterol to the corticosterone‐containing diet prevented the increase in abdominal fat weight and uric acid excretion induced by corticosterone, but did not affect total fat mass.

5. The results showed that clenbuterol reduced abdominal rather than carcase fat and prevented protein degradation in the body when chicks were treated with corticosterone. Clenbuterol also influenced the content of cytochrome P‐450, but not the humoral immunity.     

Relationship between body fatness,ovarian structure and reproduction in mature females from lines of genetically lean or fat broilers given different food allowances

1. Reproductive and other characteristics were measured at 34 and 60 weeks of age in broiler breeder hens on 6 different feeding regimes. The hens came from genetically lean and fat lines selected on the basis of low or high 7‐week plasma very low density lipoprotein (VLDL) concentration.

2. Plasma VLDL concentrations were consistently higher at all ages in fat line hens but were not affected by dietary treatment.

3. Mature body weight did not differ between the lines in birds fed ad libitum but with food restriction throughout life, fat line birds were lighter at 34 weeks.

4. There was little difference between the lines in abdominal fatness of birds fed ad libitum up to 60 weeks. Fat line birds were always fatter than lean line counterparts under food restriction.

5. Egg production was higher in lean line birds fed ad libitum but food restriction improved egg production in both lines. Peak egg productions were similar in both lines but there was evidence that the optimal food allowances for egg production was higher in the lean compared with the fat line.

6. Ovarian yellow follicle numbers were highest at 34 weeks in ad libitum fed lean line birds and declined linearly with decreasing body weight caused by food restriction but there was no such relationship in fat line birds.

7. White follicle numbers were higher and follicular atresia was lower in the lean line.

8. It is concluded that poor reproduction in fat line birds was associated with inhibition of follicular development and atresia rather than by high plasma VLDL concentrations promoting excessive yolk formation.     

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.     

Influence of various dietary protein levels on carcase composition in the male Japanese quail (Coturnix coturnix japonica)

1. The present study was conducted to determine the effect of various dietary protein concentrations on the carcase composition of male Japanese quail.

2. Six diets varying in protein from 160 to 300 g/kg and containing approximately 11–72 MJ/kg ME were fed for 5 weeks and analysed for dry matter, protein, fat and ash.

3. Treatments affected carcase weight, dry matter, protein, ether extract and ash

4. The water content of the carcases decreased with increasing dietary protein concentrations, while the carcase protein content increased with higher dietary protein. The carcases with the highest fat content were obtained from quail receiving the low protein diet.     

Effects of short intermittent lighting on food consumption and performance of dwarf broiler breeders and progeny

1. Two hundred and sixty four dwarf broiler breeder hens were subjected to ad libitum or restricted feeding and to four lighting patterns: 15L (bright light):9D (dark), 15L:9d (dim light), 2L:10d: 1L:11d, (0.5L:3.5d) × 6.

2. Breeder hens fed ad libitum and subjected to either conventional or intermittent lighting ingested respectively, 25 g and 14 to 17 g more than hens restricted to 115 g/d.

3. Body weight was greater in hens fed ad libitum irrespective of the lighting pattern and of the amount of food intake.

4. Persistency of egg production was impaired by intermittent lighting.

5. Ad libitum feeding reduced egg fertility. The decrease was larger in breeder hens on intermittent lighting.

6. Hatchability was increased in hens submitted to the symmetrical lighting pattern (0.5L:3.5d).

7. Egg and chick weights were higher in hens fed ad libitum.

8. Shell index and shell breaking strength increased in restricted hens on the intermittent lighting pattern (0.5L:3.5d) × 6.

9. The best performance was obtained in restricted hens on the conventional lighting pattern.     

Effect of choice feeding on the performance of broilers

1. Male broilers from 21 to 56 d of age were fed their diet either mixed as pellets or mash, or as separate ingredients presented on a free‐choice basis, to determine whether feeding method affected growth, carcase composition or profitability to 56 d of age.

2. The 12 treatments were: 2 completely balanced diets fed as mash or pellets, 8 choice fed diets containing maize or sorghum as the energy source (whole or mash) and protein concentrate (pellets or mash) and 2 unbalanced mixed mash diets containing 50% grain (maize or sorghum) plus 50% protein concentrate.

3. For the choice treatments, one food, grain (maize or sorghum) or protein concentrate (mash or pellets), was placed in each feeder. Broilers fed the complete pelleted or mash diet received the diet in both feeders. Food consumption was recorded weekly. Broilers were weighed at 42 and 56 d of age.

4. There were no significant differences between treatments and the pelleted control diet with regard to body weight, food consumed, food efficiency, carcase ash, dressing percentage and mortality.

5. Choice fed broilers receiving the energy source as whole grains had larger gizzards while the higher protein diets (50/50) resulted in a higher carcase moisture and protein but lower carcase fat than the broilers fed the pelleted control diet.

6. The main advantage of choice feeding appears to be the economical savings of feeding whole grains as the energy source.     

Influence of heated vegetable oils and α‐tocopheryl acetate supplementation on α‐tocopherol,fatty acids and lipid peroxidation in chicken muscle

1. Chicks were fed on diets containing fresh, heated or α‐tocopheryl acetate‐supplemented heated vegetable oils. The effects on α‐tocopherol status, and on the fatty acid composition and oxidative stability of thigh and breast muscle were determined.

2. Plasma α‐tocopherol was significantly correlated with α‐tocopherol concentrations in thigh and breast muscle.

3. The fatty acid profiles of muscle lipids reflected dietary fatty acid composition.

4. The consumption of heated sunflower and linseed oils reduced α‐tocopherol status, altered fatty acid composition of muscle lipids and increased susceptibility of muscle to lipid oxidation.

5. Supplementation of diets containing heated oils with α‐tocopheryl acetate resulted in some alleviation of these effects.

6. The results indicate that caution should be exercised in the use of thermally oxidised oils in poultry diets if undesirable changes in composition and oxidative stability of carcase lipids are to be avoided.     

Weight of internal organs and carcase yield of early food restricted broilers

1. Effects of food restriction on growth rate and relative growth rates of supply organs (liver, heart, lungs and kidneys, digestive tract) and demand organs (breast, back, thighs, abdominal fat) of broiler chickens were studied.

2. Birds were restricted in intake to 50% (group FI 50) or 75% (group FI 75) of ad libitum from 5 to 11 d of age; all birds were fed ad libitum from 12 to 39 d of age.

3. Relative growth rates from 12 to 39 d of age of group FI 50 were higher (P<0.05) than group FI 75 and control group.

4. No significant differences in food conversion ratio, carcase fat and abdominal fat between groups were observed.

5. At 12 d of age, relative weight of the empty digestive tract of group FI 50 was higher (P< 0.05) than that of the control group and group FI 75.

6. The increased weight of the empty digestive tract may have contributed to the ability of the chickens to achieve compensatory growth after the restriction period.     

Comparison of nutritive values of groundnut oil cake and Niger oil cake for laying pullets

1. The nutritive value of Niger oil cake (Guizotia abyssinica, Cass.) as a protein supplement for layers’ diets has been assessed.

2. Replacing groundnut oil cake (GNC) by Niger oil cake (NC) on an isonitrogenous basis, did not affect egg production, egg weight or the amount of food required per dozen eggs.

3. The percentage retention of nitrogen from diets containing 30% GNC or 30% NC was similar.

4. The ME value of NC used was 3025 kcal/kg.

5. It is concluded that NC can replace GNC in layers’ diets.     

Microbial status of chicken portions and portioning equipment

1. The sources and numbers of microbes contaminating poultry portions, which form an increasing proportion of poultry meat production were investigated. Total aerobic count at 30°C, pseudomonads, coliforms, enterococci and Staphylococcus aureus were enumerated.

2. Samples which had undergone different degrees of portioning, from whole birds to individual retail portions of poultry meat, were collected at points along the portioning line. Equipment surfaces, utensils and hands/gloves of factory personnel were examined.

3. In general, microbial numbers on carcase sampling sites were related to ‘exposure factor’, that is, the length of time the site was exposed to potential contamination during processing and portioning.

4. When results for individual sampling sites were analysed separately, no significant differences were found between sites on whole birds and the corresponding half bird sample sites. Comparison of numbers on half birds and on portions revealed a more variable situation.

5. Sites touched by rubber gloves when carcases were hung on the automatic portioning lines had greater contamination than other sites.

6. Provided factory and operative hygiene standards are high, portioning does not significantly increase numbers of microorganisms.