Lack of interrelationship between the effects of dietary factors and food withdrawal on carcase quality of broiler chickens

1. Four factorial experiments were carried out to determine whether there is any interrelationship between dietary energy-to-protein (E:P) ratio (experiments 1, 2 and 3) or pelleting the diet (experiment 4) and the duration of food withdrawal (FW), in their effect on carcase quality of broiler male chickens. The quality was evaluated by yields of carcase and breast meat, abdominal fat pad size, and the content and composition of the fat in the meat. The effect of sex on the response to FW was also determined in experiment 3 and that of age in experiment 4. 2. The diet with an E:P ratio higher than recommended decreased the weights of carcase and breast meat significantly (P 0.05) in 2 of the 3 experiments, and consistently increased the size of the abdominal fat pad and the fat content in thigh, but not in breast meat. Abdominal fat pad and the fat in meat of birds fed on this diet contained a significantly higher amount of oleic acid and a lower amount of linoleic acid, than the fat of birds fed on the diets with the recommended and the low E:P ratios. The pellets increased significantly the weights of carcase and breast meat and the relative size of abdominal fat pad. 3. FW for 24 h decreased significantly the weight at slaughter in all 4 experiments, carcase weight in 3 experiments, and breast weight in 1 experiment. However, it did not affect the relative size of the abdominal fat pad, the fat content in thigh and breast meat, and the composition of fatty acids in these tissues and in abdominal fat. None of the variables mentioned was affected significantly by the interaction between the dietary factors evaluated, sex or age of the birds on the one hand, and FW on the other hand. 4. It is concluded that the effect of 24 h of FW on weight at slaughter, carcase and breast meat weights and on fattening, is not affected by dietary E:P ratio, pelleting the diet, or sex and age of the broilers.     

Carcase characteristics and qualitative meat traits of three Italian local chicken breeds

1. An experiment involving 60 male chickens reared in an organic production system was carried out in order to investigate carcase characteristics and qualitative meat traits of three slow-growing Italian local breeds of chicken (Ermellinata, Padovana and Pepoi). 2. Chicks were randomly selected at hatch, raised together under the same conditions, slaughtered at 190 d of age, dissected for carcase traits, and meat (breast and thigh) stored for subsequent analysis of quality parameters. 3. Ermellinata (EA) chickens were significantly different from Padovana (PA) and Pepoi (PI) chickens for live, carcase and thigh weights. Breeds were also different for breast muscle protein content (EA > PI and PA), shear force (PA < EA and PI) and cooking loss (PI > PA and EA) values. 4. The CIE system values of lightness (L*), redness (a*), and yellowness (b*) evidenced a distinctive darker meat and lighter skin colour of PA breast meat. 5. Polyunsaturated fatty acids composition of breast meat was similar among the analysed breeds. EA had significantly higher saturated but significantly lower monounsaturated fatty acid contents than the other two breeds.     

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.     

Nutrient density and slaughter age have differential effects on carcase performance,muscle and meat quality in fast and slow growing broiler genotypes

1. A 2?×?2 factorial design was used to investigate the differences in carcase, muscle and meat characteristics between fast and slow growing genotypes fed on low nutrient (LND) or high nutrient diets (HND) at their respective slaughter ages.

2. The birds were randomly assigned to treatments with 5 replicates of 145 birds for Wens Yellow-Feathered Chicken (WYFC, 5·75 birds/m²) or 115 birds for White Recessive Rock Chicken (WRRC, 7·25 birds/m²), according to the commercial recommendations for the two breeds and were fed on HND or LND. Birds were slaughtered at 63?d and 105?d of age.

3. The results showed WRRC had higher carcase yield and meat yield than that of WYFC, lower fat content, higher moisture content and lower cooking loss. The meat from WRRC was less tender and contained lower levels of polyunsaturated fatty acids (PUFA).

4. Birds fed on HND had higher breast meat yield, myofiber area and protein content in the breast muscle and lower fat content than birds fed on LND. The thigh muscle of birds fed on HND had higher levels of PUFA. Age had a positive effect on carcase parameters, but a negative effect on pH, meat tenderness and cooking loss, and the two genotypes exhibited different responses to the influence of nutrient density and age.

5. Genotype and age had the largest effect on carcase performance and meat quality. LND benefited meat quality and WRRC had larger responses in meat yield and shear force when fed on HND.     

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.     

Influence of dietary energy on bird performance,carcase parts yields and nutrient composition of breast meat of heterozygous naked neck broilers reared at natural optimum and summer temperatures

1. Heterozygous naked neck birds were raised under natural spring (average 21.2°C) and summer temperatures (average 27.1°C) to investigate the influence of dietary energy on broiler performance, carcase yield and nutrient composition of breast meat. 2. Birds were fed on a low energy diet of 12.12 MJ ME/kg, a medium energy diet of 12.96 MJ ME/kg and a high energy diet of 13.79 MJ ME/kg with 2 protein concentrations per energy treatment, 230 and 200 g/kg, from 0 to 3 and 3 to 7 weeks of age, respectively. 3. Summer rearing resulted in a decrease in body weight, body weight gain, carcase weight and carcase part yields of birds. 4. Increasing dietary energy from 12.12 to 13.79 MJ ME/kg increased body weight at 3 and 7 weeks, body weight gains from 0 to 3 and 3 to 7 weeks, carcase weights and relative abdominal fat weights of birds in a linear manner. There was no effect of dietary energy on the nutrient composition of breast meat. 5. It was concluded that there was no differences in dietary energy requirements of heterozygous naked neck birds when grown under natural optimum (21.2°C) and summer temperatures (27.1°C).     

Effects of different rearing systems on muscle and meat quality traits of slow- and medium-growing male chickens

1. This experiment was conducted to evaluate the effect of production system on the meat quality of slow- and medium-growing chickens. A total of 1075 1-d-old male chicks were equally divided into 6 experimental groups, represented by three strains (SG: TETRA-H, MG1: TETRA HB Color, MG2: Shaver Farm) and were reared in a poultry house in floor pens (12 males/m²).

2. On d 49, 150 healthy birds (50/genotype) were placed in a free-range family farm while the rest of the birds remained indoors. All birds were fed ad libitum and consumed the same diet. On d 70, 20 birds of each experimental group were slaughtered and muscle samples were taken from the left breast and thigh muscles.

3. Thigh muscle of SG males kept on free range was darker (L* = 75.12 vs. 78.33) with lower frying loss (45.9% vs. 55.9%) compared with the indoor group. Similar results were obtained from the MG1 group. Free-range MG2 males had lighter thigh meat (L* = 50.7 vs. 57.8) and lower frying loss compared to the indoor group.

4. In general, the indoor treatment had a lower impact on breast meat than the outdoor system. Regardless of the rearing system, genotypic differences were more pronounced in thigh than in breast muscle.

     

Effects of different rearing and feeding methods on meat quality and antioxidative properties in Chinese Yellow male broilers

1. This study examined responses of male broilers during a 42-d production cycle to two different rearing and feeding methods. 2. A total of 400 Chinese Yellow male broilers were allotted randomly at 21 d into two groups; the control was a typical indoor commercial rearing method and the treatment had outdoor access with scattered feeding (OS). Each group had 5 replicates with 40 birds per replicate. 3. Growth performance was similar for both groups from 21 to 63 d of age. OS birds had significantly lower abdominal fat percentage, meat shear force, drip loss, breast meat colour b* value and significantly higher pH value compared with the controls. OS birds had significantly lower muscle fibre diameter and greater muscle fibre density. Serum glutathione peroxidase and catalase activities were significantly higher and the contents of cholesterol, lactic acid, glycogen and malondialdehyde of breast muscle were significantly lower in OS birds than controls. 4. The results suggest that the OS feeding method had no negative effects on performance (weight, gain, feed conversion rate, carcase traits) compared with controls, and appeared to be beneficial for meat quality indices and oxidative stability.     

Effects of alfalfa meal on carcase quality and fat metabolism of Muscovy ducks

1. The effects of alfalfa meal on carcase quality and fat metabolism of Muscovy duck were evaluated. The objective of this research was to establish whether alfalfa meal can reduce fat content and improve carcase quality of Muscovy duck. Animal products with a high fat content present a risk factor for many diseases. Reducing fat content in poultry products is an important goal for the poultry industry.

2. A total of 240 14-d-old white Muscovy ducks were selected and randomly allocated to 1 of 4 dietary treatments containing 0, 3, 6, and 9% of alfalfa meal for 5 weeks. Growth performances were recorded and carcase characteristics and lipid parameters were analysed.

3. Results showed that 3, 6, and 9% alfalfa meal in diet had no significant effects on growth performance of Muscovy ducks from 14 to 49?d of age. Ducks given 3, 6, and 9% alfalfa meal had significantly higher dressing percentage and lower abdominal fat percentage compared with those given no alfalfa meal. Ducks given 9% alfalfa meal had higher breast meat percentage compared with those given no alfalfa meal. The concentrations of triglyceride, total cholesterol, low density lipoprotein (LDL), very low density lipoprotein (VLDL) and free fatty acid in serum of ducks fed on alfalfa meal decreased. Alfalfa meal in the diet decreased abdominal fat percentage and improved carcase traits of Muscovy duck.

4. The study showed that dietary alfalfa meal decreased abdominal fat percentage and improved carcase traits, without an adverse effect on performance.     

Effects of divergent selection for incidence of tibial dyschondroplasia (TD) on purebred and crossbred performance. 2. Processing yield

1. An experiment was conducted to determine the effect of selection for high (H) or low (L) incidence of tibial dyschondroplasia for 7 generations on processing performance of broilers. 2. Birds were obtained from diallel matings of the H and L lines (HH, HL, LH, and LL) and a randombred control (CC) line. Birds were reared to 7 weeks of age under standard management conditions. All birds were processed at 7 weeks of age. Body weight at 7 weeks, carcase weight, and carcase part weights were recorded on each bird. 3. An interaction between sire line and dam line was caused by lighter body and carcase weight at 7 weeks of age in HH birds than from the birds of the other crosses. 4. Birds by L line dams had heavier drumstick weights. The influences of sire line and dam line on weight of total breast muscle were not significant. Thigh weights and Pectoralis minor weights were lighter in HH line birds than those other matings. 5. Heterosis for body weight and for weights of carcases, drumstick and thigh was negative. Total breast muscle weight and P. major weight did not show significant heterosis. 6. It was concluded that selecting against TD does not reduce processing yield of broilers.     

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.     

Supplementation of graded levels of organic zinc in the diets of female broilers: effects on performance and carcase quality

Zinc is an essential trace element. The objective of this research was to investigate the effects of various levels of organic zinc (OZ) supplementation on growth performance and carcase quality of female broiler chickens. A total of 3200 1-d-old female broiler chicks were randomly allotted to 16 floor pens with 200 birds per pen. A maize-wheat-soyabean meal basal diet (Control) was formulated and 20 mg/kg OZ (20 OZ), 40 mg/kg OZ (40 OZ), and 80 mg/kg OZ (80 OZ) were added to the basal diet to form 4 dietary treatments with 4 replicates per treatment. The OZ source was zinc proteinate which contained 15% zinc. Results showed no significant difference between the treatments in growth performance. A significant increase in thigh skin epidermis and dermis thickness was shown in the OZ supplementation groups; however, no effect was found on the thickness of back skin epidermis and dermis. Collagen contents in breast and thigh meats were not influenced by OZ supplementation but a significant increase in collagen content was found in the back and thigh skin. This increase in collagen content was significantly greater in the back and thigh skin of OZ 80 than with OZ 20. Shear force value and zinc concentration in skins and meat were not significantly influenced by supplementation with OZ. It is concluded that dietary OZ does not improve growth performance of broilers; however, it could increase skin thickness by increasing collagen content in skin, thereby improving carcase quality.     

Increased collagen III in culled chicken meat after feeding dietary wood charcoal and vinegar contributes to palatability and tenderness

We comprehensively evaluated meat quality in chickens fed a diet consisting of wood charcoal and vinegar (WCV) using food scientific and histological approaches. In culled hens, lipid and fatty acid in Musculus semimembranosus, cooking loss and sensory tests of whole thigh meat, and meat texture of breast meat were observed. In male broilers, cross section of M. semimembranosus was used for observations on muscle area, perimysium, non‐collagen total protein and total collagen content, and anti‐collagen I and III reactions. In frozen male broilers, conventional morphology of M. semimembranosus as well as chicken anti‐collagen III reaction to selected muscles of thigh meat and breast meat were compared between the control and WCV‐fed birds. Increased lipid and fatty acids, decreased cooking loss, high score in total evaluation for sensory test of thigh meat, and decreased meat texture values were observed for culled hens fed WCV. The higher values of muscle area, total collagen and collagen III were observed for broilers fed WCV. No perimysium collapse for M. semitendinosus or increased collagen III reactions of M. tensor fasciae latae, the flexor muscle group and M. pectoralis superficialis were observed for frozen muscles in the WCV group. These total results suggest that WCV produces palatable and tender meat by increasing collagen III.     

Body weight,meat quality and blood metabolite responses to carbohydrate administration in the drinking water during pre‐slaughter feed withdrawal in broilers

This study was conducted to determine weights of body (BW), carcass (CW), gastrointestinal tract (GTW), meat quality and some blood metabolite responses to corn starch, saccharose or glucose administration in the drinking water during pre‐slaughter feed withdrawal (FW) in broilers. On day 42 of age, 200 broilers (Ross 308) were allocated randomly to five treatments with four replicates. During a 10‐h FW, control broilers (C) were provided with non‐treated water and the standard finisher diet ad libitum, whereas fasted broilers provided with non‐treated (NFW) or treated water, 3 g glucose (G), saccharose (S) or corn starch (CS)/L. Eight birds (four males and four females) per treatment were slaughtered. Birds receiving non‐treated or treated water had lower BW and higher carcass yield than the full‐fed broilers. The full‐fed broilers had higher absolute and relative GTW than the fasted birds. Broilers consumed more readily treated water compared with non‐treated water. While the a* value of breast meat from CS birds was higher than that from NFW, the b* value of that was higher than S and C birds. The c* values of breast meat from S birds were lower compared with that from the CS treatment. The thigh meat from NFW broilers had higher h* value than that from C and G broilers. The thigh meats of C and CS broilers had higher c* value than that of G birds. The full‐fed broilers had higher plasma triglyceride concentration than NFW, S and G birds. The full‐fed broilers had higher plasma uric acid and uric acid nitrogen concentrations than S birds. These results show that carbohydrate administration in the drinking water cannot be a good alternative for the FW period before slaughter due to the fact that the carbohydrates do not reduce BW losses and do not lead to increases in meat quality.     

Production and carcase traits in broiler chickens given diets supplemented with inorganic trivalent chromium and an organic acid blend

1. The study was conducted to ascertain the effects of supplemental organic acids and chromium (Cr) on production and carcase traits of broiler chickens. 2. A total of 120 1-d-old broiler chicks were divided into 4 treatment groups in a 2 x 2 factorial design (each treatment group contained 6 replicates with 5 birds per replicate). 3. The diets were supplemented with an organic acid blend containing ortho-phosphoric, formic and propionic acid and calcium propionate (1 g/kg diet) and inorganic trivalent chromium (Cr(3+)) as chromic chloride hexahydrate (0.5 mg/kg diet) either independently or together as a combination for 35 d. 4. Individual supplementation of organic acids and Cr(3+) and their combination significantly improved the food conversion ratio, hot and dressed carcase weight and weight of the wholesale cuts compared to the control group of birds. 5. Organic acids, either independently or along with Cr(3+), increased total accretion of ash in carcase. Protein accretion was improved by dietary Cr(3+) and organic acid supplementation compared to the control group and a further improvement in this regard was observed when Cr(3+) and organic acid were supplemented together. Across the treatment groups meat fat content and fat accretion were lower in birds receiving dietary Cr(3+) supplementation. 6. Circulatory Cr(3+) and meat Cr(3+) concentration increased compared to the other treatment groups when Cr(3+) was supplemented to the birds. 7. It was concluded that, instead of individual supplementation, a combination of Cr(3+) and organic acids may improve the production and carcase traits of broilers more effectively presumably because of an additive effect.     

Sensorial quality and bone strength of female and male broiler chickens are influenced by weight and growth rate

1. An experiment was conducted with 98 male and 98 female broiler chickens (Ross 308) to study the effect of growth rate, induced by different dietary means, sex and live weight (1500?g and 2000?g) at slaughter on production parameters, bone strength and sensorial characteristics of the breast meat.

2. The birds were divided into four groups and individually fed a standard commercial diet, a high energy diet or low energy diet from d?11 to slaughter at between d 28 and 39. Three groups were fed ad libitum and a further group was fed a restricted amount of the high energy feed. Half of the birds in each group were slaughtered at approximately 1500?g and the other half at 2000?g live weight.

3. The diets resulted in different growth rates. The chickens fed the high energy and the commercial diet had the highest growth rate at both live weights at slaughter. The restricted fed chickens had lower bone strength than the chickens fed the low energy diet.

4. Breast meat from male broilers was juicer, more tender and less hard than breast meat from females. Chickens slaughtered at 2000?g live weight were juicer than those slaughtered at 1500?g. Chickens given the high energy feed ad libitum and restricted had different growth rates, but the sensory parameter related to texture showed no difference.

5. It was concluded that an increased slaughter weight might improve meat quality due to improved juiciness.     

Breeder hen dietary L-carnitine affects progeny carcase traits

(1) Ross 308 broiler breeder hens were given diets containing 0 or 25 mg L-carnitine/kg from 21 weeks of age. (2) Hens were inseminated with semen from Ross broiler breeder males and subsequent growth performance and carcase traits, of progeny obtained from hatches at 30, 35 and 37 weeks of age, were evaluated. (3) Progeny were hatched in a common facility and separated by gender. Experimental treatments employed for the 30-, 35- and 37-week hatches, respectively, were: hen diet and progeny gender (16 replications with two subplots); hen diet, progeny diet (0 and 50 mg L-carnitine/kg of diet) and progeny gender (16 replications with 4 subplots); and hen diet and progeny diet (high and low density; 16 replications with two subplots). (4) Females had lower growth rate and less breast meat, but greater proportions of carcase fat and breast meat than males. Growth performance measurements of progeny were not affected by hen L-carnitine, but hen L-carnitine decreased abdominal fat in progeny. Increasing diet density in the chick diets increased growth and carcase weights. Hen and progeny dietary L-carnitine interacted to increase male mortality. However, dietary hen L-carnitine decreased carcase fat and increased breast meat in progeny fed on high nutrient density diets. (5) In conclusion, L-carnitine in the diet of hens affected carcase traits of their progeny.     

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.     

母体日粮低能量对后代肉仔鸡生长性能、胴体品质和肉质的影响

本文旨在研究母体日粮低能量对后代肉仔鸡生长性能、胴体品质及肉质的影响.试验选用低脂系肉种鸡120羽,随机分成2组,每组60个重复,每个重复1羽,即单笼饲养.在肉种鸡产蛋期产蛋率达到5%进行试验处理,试验分试验组和对照组,试验组代谢能量为对照组的80%孵化后的肉仔鸡按照母体不同能量处理各挑选健康仔鸡,在相同的试验条件下进行饲养,试验期为56 d.结果表明:1)与对照组相比,母体日粮低能量有降低1日龄肉仔鸡体重的趋势,对全期日增重和料重比影响不显著(P＞0.05);2)与对照组相比,母体日粮低能量对后代肉仔鸡胸肌和腿肌的水分、脂肪和蛋白质含量,胸肌率和腹脂率均无显著影响(P＞0.05),但显著增加腿肌率(P＜0.05);3)与对照组相比,母体日粮低能量对后代肉仔鸡胸肌和腿肌的pH、红度、黄度、滴水损失和蒸煮损失均无显著影响(P＞0.05),但pH、红度和黄度值有升高趋势,滴水损失和蒸煮损失有降低趋势,胸肌和腿肌剪切力显著降低(P＜0.05);4)与对照组相比,母体日粮低能量显著提高后代肉仔鸡胸肌和腿肌肌纤维密度(P＜0.05),显著降低后代肉仔鸡胸肌和腿肌肌纤维直径(P＜0.05).本试验的研究结果表明:母体日粮低能量对后代肉仔鸡的胴体品质及肉质能产生一定的影响.     

Effects of a meal feeding regimen and the availability of fresh alfalfa on growth performance and meat and bone quality of broiler genotypes

1. The aim of this study was to identify a feeding regimen that encourages good pasture use in slow (SG) and fast (FG) growing broiler genotypes under free-range management.

2. SG and FG birds fed on either an ad libitum (ADB) or a meal feeding (MEF) programme were given free outdoor access with or without fresh alfalfa from day 22 to 72 and from day 22 to 45, respectively. In two consecutive trials, 800 birds of each genotype were included in a factorial design using groups of 40 birds replicated 5 times.

3. Fresh alfalfa consumption did not improve growth performance and meat quality attributes, whereas the feeding regimen had significant implications. When compared with their ad libitum-fed counterparts, meal-fed birds showed a significantly lower body weight at a considerably lower feed consumption rate, leading to a more favourable feed conversion ratio (FCR) during the course of the experiment.

4. The MEF regimen with a strong feed limitation significantly increased crop and gizzard weight in both genotypes. In FG birds, water holding capacity, drip loss, cooking loss and pH 45 in the breast and thigh meat were adversely affected by MEF; however, feed restriction demonstrated benefits with significant decreases in muscle fat accumulation. In SG birds, decreases in protein and dry matter content of the breast and thigh muscle with meal feeding were conclusive.

5. In both genotypes, there was no treatment-related effect on meat yield, mineral composition of the meat or bone mechanical properties.

6. In conclusion, MEF, irrespective of alfalfa intake, may provide a viable method to decrease FCR; it may be able to contribute to the production of chickens with lean carcasses but it was not capable of improving overall meat quality.