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.     

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.     

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.     

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.     

Food intake and growth in chickens given food in the wet form with and without access to drinking water

1. Individually caged growing chickens were offered a commercial grower food mixed with 1–5 to 2^‐25 times the weight of water and the effects, compared to giving the same food in air‐dry form, on food intake, body weight gain and carcase composition were investigated.

2. Male broilers (24) were given either a grower food in the air‐dry form with access to drinking water or the same food mixed with 2–0 parts of water (700 g water/kg of mixed food) with no drinking water from 28 to 49 d of age. From 49 to 63 d all birds were given dry food and drinking water and were then killed for carcase analysis. Food intake and weight gain were significantly increased during the wet‐feeding period, as was carcase protein but not abdominal or carcase fat at the end of the experiment.

3. Five male broilers were given each of 5 dietary treatments containing 0 (control), 1.5, 1.75, 2.0 and 2.25 times added water (640, 673, 700 and 723 g water/kg) from 28 to 49 d. Food intakes, body weight gains and carcase weights were significantly increased for all water additions compared with dry food, but there were no significant differences between different water additions.

4. Female broiler chicks responded to wet feeding (700 g water/kg) in a similar manner to males and the dry matter approximate digestibility was increased from 0.65 for the dry food to 0.73 for the wet.

5. Cockerels of an egg‐laying strain did not increase their intake of dietary dry matter when it was fed in the wet form (700 g water/kg), but there was a significant increase in body weight gain.

6. Male broilers were offered wet food (700 g water/kg) with or without access to drinking water. There was equal stimulation of food intake, growth and carcase weight with both wet‐feeding treatments.

7. Providing food mixed with sufficient water to give a porridge‐like consistency significantly increased weight gains in each of the five experiments and significantly improved food conversion efficiency in three of the five. It is not necessary to withold drinking water in order to obtain this effect.     

Fat accumulation,fatty acids and melting point changes in broiler chick abdominal fat as affected by time of dietary fat feeding and slaughter age

1. This work aims to quantify changes in fatty acid profile, melting point, abdominal fat accumulation and 2-thiobarbituric acid-reactive substances production depending on dietary fat source and age at slaughter, and to estimate the optimal date for the change from an unsaturated fat to a saturated fat diet or vice versa.

2. Treatments established were (1) birds fed 8% tallow from 21 to 49 d (TTT); (2) birds fed 8% tallow from 21 to 37 d and 8% sunflower oil from d 38 to 49 (TSS); (3) birds fed 8% sunflower oil from 21 to 37 d and 8% tallow from d 38 to 49 (STT); (4) birds fed 8% sunflower oil from 21 to 41 d and 8% tallow from d 42 to 49 (SST); (5) birds fed 8% sunflower oil from 21 to 49 d (SSS). Birds from each group were slaughtered on d 21, 29, 38, 40, 42, 44, 46 and 49.

3. The polyunsaturated fatty acids (PUFAs) proportion in the SSS group reached maximum values at d 40 and fitted a quadratic response. This group also showed a decrease in saturated fatty acids (SATs) and monounsaturated fatty acids (MUFAs) of lower intensity than the PUFA increase. The highest synthesis of SAT + MUFA was found in the SSS and TSS groups, whereas these had the lowest body-to-dietary PUFA ratio.

4. A high and quadratic increase in the MUFA proportion was observed during the first 10 d of feeding with the tallow-enriched diet at the expenses of the proportion of PUFA that quadratically decreased (minimum values at d 38).

5. Lipogenic and desaturation capacity decreased with age.

6. The TSS group increased tissue PUFA content faster that the SST group decreased PUFA content after the change in diet which indicates that the earlier feeding has to be taken into consideration for obtaining higher or lower changes in quality parameters.

7. The melting point of the SSS group showed a lower response to the dietary treatment in the initial period when compared to the TTT treatment.

8. The TTT, STT, SST and TSS groups showed similar fat accumulation, and changes in lipid oxidation were related to the day of dietary sunflower oil supplementation.

9. Based on the results, it would be possible to determine the most appropriate dietary programme and optimum slaughter age to obtain chicken meat with the desired quality characteristics.     

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.     

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.     

Fatty acid composition of broiler abdominal fat as influenced by temperature,diet, age and sex

1. Two environmentally controlled houses at 21°‐30°‐21°C (HT) and 21°C (LT) were used to study the effect of temperature on fatty acid composition of the abdominal fat of male and female broilers fed 13.8 and 13 MJ ME/kg diets and slaughtered at 34 and 54 d.

2. Extracts from the abdominal fat of 160 carcases and of the experimental foods were analysed for fatty acids by gas liquid chromatography.

3. Birds reared in HT had a significantly lower proportion of polyun‐saturated fatty acids (PUFA) in their abdominal fat between 34 and 54 d than birds in LT. The depot fat contents of oleic, linoleic and linolenic acids were all reduced by HT at 54 d.

4. For broilers slaughtered at 54 d, saturated fatty acid (SFA) content was much higher in females at high temperatures than in males while at low temperatures PUFA, especially linoleic, was much lower in males than in females.

5. Early finishing of broilers is advantageous from the viewpoint of fatty acid composition because the PUFA/SFA ratio declines significantly with age regardless of temperature.     

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.     

Selecting broilers for low or high abdominal fat: Initial observations

1. Two lines of broiler breeders were selected for three generations using a high (fatty line) or a low (lean line) ratio of abdominal fat to live weight as criterion in males at 9 weeks of age.

2. The heritability of this character remained high in both lines.

3. By the third generation, the progress achieved was much more marked in males than in females. The difference between the females of both lines was nevertheless significant.

4. The differences between the two lines were already discernible at 4 weeks of age.

5. Selecting for low or high abdominal fat content was accompanied by a better food conversion ratio in males of the lean line.

6. Selecting for the amount of abdominal fat produced similar effects on the other fatty deposits.     

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.     

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.     

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.     

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.     

Selecting broilers for low or high abdominal fat: Distribution of carcass fat and quality of meat

1. Carcass fat distribution and meat quality were studied in 52‐d‐old cockerels of the 4th generation of selection for low ('lean') or high ('fat') abdominal fat content.

2. Compared with lean birds, there was four times more abdominal fat, 2.8 times more subcutaneous fat and 1.5 times more fat deposited between the leg muscles in fat birds. Chemical estimation of the fat content of thigh muscle, however, revealed no difference between these two lines.

3. No clear differences were observed for cooking losses, flavour and juiciness, while tenderness appeared to be a little higher in fat birds.

4. These results suggest that breeding for a low abdominal fat depot is advantageous in terms of carcass quality.     

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.     

Effects of selection,over three and four generations,on meat yield and fatness in Muscovy ducks

1. Two experiments were undertaken to analyse the effects of selection for lowering carcase fatness and improving meat yield of Muscovy ducks. The control generation N and the selected generations N+ 3 and N+ 4 of the same heavy line (Grimaud) were reared under similar conditions.

2. We compared growth, carcase characteristics, chemical composition of breasts and plasma concentrations of very low density lipoproteins (VLDL), triglycerides and phospholipids.

3. Selection induced an increase of body weight ( + 8% to 10% at slaughter age), a decrease of abdominal fat percentage (? 10%) and an improvement of breast and thigh plus shank yields (+ 3% to 7% and + 4% respectively).

4. The lipid content of breast meat decreased in the selected ducks (? 14% to ?20%), particularly phospholipids and triglycerides. Breasts appeared paler and less red which suggested modifications of muscular fibre composition.

5. We found no significant correlations between plasma VLDL, triglyceride and phospholipid concentrations and carcase fatness. It therefore seems difficult to use these variables as selection criteria for lowering carcase fatness of Muscovy ducklings.     

Growth,carcase composition and profitability of meat chickens given pellets,mash or free‐choice diet

1. Equal numbers of 21‐d‐old male and female meat chickens were given their dietary ingredients either mixed and presented as pellets or mash, or as separate ingredients presented on a free‐choice basis, to determine whether presentation method caused any differences in growth, carcase composition or profitability to 42 d of age.

2. The proportions of ingredients eaten by the chickens given a free choice varied widely during the first 56 h of the trial. Thereafter, the proportions did not vary widely and birds given the free choice ate approximately ½ of their intake as whole wheat, ? of their intake as concentrate (high protein meals plus vitamin and mineral premixes), and 1/7 of their intake as whole sorghum each week for the three‐week trial period.

3. The nutrient composition of the free‐choice diet selected by the birds over the trial period averaged 12.09 MJ ME/kg feed, 210 g/kg crude protein, 14 g/kg calcium and 7 g/kg phosphorus.

4. At the end of the trial the average live body weights of the birds differed significantly according to method of feeding, in the descending order of pellets > mash > free choice.

5. The empty gizzard weight of birds differed significantly according to the method of feeding, in the descending order of free choice > mash > pellets.

6. The plucked empty bodies of birds given the free choice had a significantly lower concentration of crude protein than the plucked empty bodies of birds fed on mash or pellets. There were no significant differences between the treatments in the plucked empty body concentrations of fat, calcium or phosphorus.

7. Financial analysis indicated that free‐choice feeding was more profitable than feeding mash or pelleted diets to broiler chickens by 3.6% and 33.4% respectively.     

A simple caliper technique for the estimation of abdominal fat in live broilers

1. A caliper technique for estimating the amount of abdominal fat in live broilers is described.

2. Sixty‐three male and 47 female broilers sampled at 63 d of age from an unselected control line were used to examine the accuracy of the caliper measure in predicting abdominal fat.

3. Phenotypic correlations between caliper measure and the proportion of abdominal fat were + 0.80, +0.79 and +0.81 in males, females and the heaviest 20% of males respectively.

4. The application of the technique as an indirect means of selecting for decreased abdominal fat in commercial broiler breeding programmes is discussed.