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Öğe Bone characteristics and body weight of broilers in different husbandry systems(Carfax Publ Co, 1997) Tolon, B; Yalcin, S1. An experiment was conducted to determine the effect of husbandry systems on bone characteristics and body weight. Broilers were reared in 5 different husbandry systems: wire mesh (WM) floored cages from 0 to 7 weeks; WM floored cages from 0 to 3 weeks and then transferred to floor pens plastic mesh (PM) floored cages from 0 to 7 weeks; Ph. floored cages from 0 to 3 weeks and then transferred to floor pens floor pens from 0 to 7 weeks. 2. Body weight at 3 weeks of age was affected by the husbandry systems, being greatest for the birds reared in floor pens. At 7 weeks of age, male broilers reared in PM floored cages had the lowest body weight and body weight gain from 4 to 7 weeks. 3. Humerus weight and ash content were affected by cage rearing whereas tibia weight and ash were not. Birds reared in Phl cages had shorter tibia and humeri than birds reared in floor pens.Öğe Carcass Characteristics of Quail (Coturnix-Coturnix-Japonica) Slaughtered At Different Ages(Carfax Publ Co, 1995) Yalcin, S; Oguz, I; Otles, S1. The present study was conducted to evaluate the relationship between slaughter ages and carcase characteristics of Japanese quail. 2. Chicks were slaughtered at 5, 6, 7, 8 and 9 weeks of age. Carcase yield, carcase parts weight, weight of liver, heart, gizzard and alimentary tract were obtained. Protein, fat, dry matter and ash contents of meat were analysed for each sex. 3. Body weight and eviscerated weight were affected by age. Age had no significant effect on the weight of liver, alimentary tract, gizzard and heart. Age had first and second order polynomial effects on breast weight and relative leg weight. Meat compositions of leg and breast were significantly affected by age.Öğe Collagen content and electrophoretic analysis of type I collagen in breast skin of heterozygous naked neck and normally feathered commercial broilers(Scientific Technical Research Council Turkey, 1999) Bilgen, G; Oktay, G; Tokgoz, Z; Guner, G; Yalcin, SThis study was conducted to evaluate the breast skin collagen content and electrophoretic analyses of type 1 collagen in heterozygous naked neck and normally feathered commercial chicks. A total of 72 birds from each genotype were randomly selected at 7 weeks and slaughtered. Breast skin was separated from each carcass and was analysed for collagen content and gel electrophopresis of type 1 collagen was performed. Males had significantly higher level of skin collagen content than females in both genotypes. In the naked neck chickens alpha(1), and alpha(2) bands were highly intensive than the commercial ones indicating that the collagen has become cross-linked by non-reducible covalent bands. On the other hand, normally feathered chickens had higher intensity of beta and gamma bands than the naked neck chickens.Öğe Comparative evaluation of three commercial broiler stocks in hot versus temperate climates(Poultry Science Assoc Inc, 1997) Yalcin, S; Settar, P; Ozkan, S; Cahaner, AHot climate is a major Limiting factor of broiler production in tropical and subtropical regions. The use of standard stocks in hot climates may result in large economic losses because genotypes selected in temperate climates may respond differently to the high ambient temperatures in hot regions or seasons. The summer and fall in Izmir, Turkey, provided the natural hot and temperate climates, respectively, for this study. Broiler chicks were obtained from three commercial stocks, all bred in temperate climates. Male and female chicks, 60 per pen, were housed in four pens per stock per season. Individual BW was determined at hatch, and at 4 and 7 wk of age. Feed consumption and efficiency were determined per pen. Feathering was scored at 4, 5, and 6 wk of age. Body temperature was measured twice on three birds per sex per pen, 16 h and immediately before slaughter, and feather weight was determined for each of these birds. The two seasons clearly differed in ambient temperature at the broiler house, and consequently, BW at 7 wk was significantly lower in the summer than in the fall in all stocks, with an average reduction of 23%. The season effect was largest (33.5%) on BW gain from 4 to 7 wk, along with 23 and 15% reductions in feed consumption and efficiency, respectively, during these 3 wk. A significant season by stock interaction was detected for BW gain from 0 to 4 wk and 4 to 7 wk. The three stocks exhibited similar 4- to 7-wk BW gains under the temperate fall climatic conditions, but differed significantly in the summer. These differences were not related to normal differences in feather coverage or body temperature, suggesting that standard broiler stocks must be tested in hot climates in order to find the one most suited to these conditions.Öğe Criteria for evaluating husbandry practices to alleviate heat stress in broilers(Poultry Science Assoc Inc, 2003) Yalcin, S; Ozkan, S; Cabuk, M; Siegel, PBThis study was undertaken to investigate the effects of management techniques used under heat stress on growth as well as developmental instability, duration of tonic immobility (TI), and heterophil-to-lymphocyte ratios (H:L) of broilers. Three-hundred sixty cockerels obtained from a commercial hatchery were randomly assigned to 12 floor pens. When the cockerels reached 21 d of age, three pens were kept as controls. Broilers in the other nine pens were moved to a room heated from 32 to 35degreesC between 1000 and 1700 h each day from 21 to 42 d of age. Broilers in the heated room were randomized into three treatment groups consisting of 1) conditioned (chicks exposed to 36degreesC for 24 h at 5 d of age), 2) feed-restricted (during the heat stress, feed was withdrawn 2 h before the hot period, and chicks were fed between 1700 and 0800 h), 3) and heat-stressed only. Conditioned and feed-restricted broilers gained 3.2 and 2.8%, respectively, more BW than heat-stressed broilers. Relative asymmetry (RA) averaged across several bilateral traits for the prolonged heat stressor was more informative than the RA for a single bilateral trait. Corrrelations suggest that RA were not closely associated with duration of TI and H:L under the conditions of this experiment.Öğe Criteria for evaluating husbandry practices to alleviate heat stress in broilers(Poultry Science Assoc Inc, 2003) Yalcin, S; Ozkan, S; Cabuk, M; Siegel, PBThis study was undertaken to investigate the effects of management techniques used under heat stress on growth as well as developmental instability, duration of tonic immobility (TI), and heterophil-to-lymphocyte ratios (H:L) of broilers. Three-hundred sixty cockerels obtained from a commercial hatchery were randomly assigned to 12 floor pens. When the cockerels reached 21 d of age, three pens were kept as controls. Broilers in the other nine pens were moved to a room heated from 32 to 35degreesC between 1000 and 1700 h each day from 21 to 42 d of age. Broilers in the heated room were randomized into three treatment groups consisting of 1) conditioned (chicks exposed to 36degreesC for 24 h at 5 d of age), 2) feed-restricted (during the heat stress, feed was withdrawn 2 h before the hot period, and chicks were fed between 1700 and 0800 h), 3) and heat-stressed only. Conditioned and feed-restricted broilers gained 3.2 and 2.8%, respectively, more BW than heat-stressed broilers. Relative asymmetry (RA) averaged across several bilateral traits for the prolonged heat stressor was more informative than the RA for a single bilateral trait. Corrrelations suggest that RA were not closely associated with duration of TI and H:L under the conditions of this experiment.Öğe Effect of dietary methionine on performance, carcase characteristics and breast meat composition of heterozygous naked neck (Na/na plus ) birds under spring and summer conditions(Carfax Publishing, 1999) Yalcin, S; Ozkan, S; Acikgoz, Z; Ozkan, K1. Heteroxygous 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 die methionine requirement of Na/na+ birds did not differ from that of their normally feathered counterparts under either spring or summer ambient temperature conditions.Öğe Effect of dietary protein content on live and carcase performance of heterozygous naked neck and normally feathered broilers(Taylor & Francis Ltd, 1996) Yalcin, S; Ozkan, S; Acikgoz, Z; Ozkan, K1. An experiment was conducted to determine the effect of different dietary protein contents on the performance of naked neck (Na/na) and normally feathered (na/na) broilers. 2. Chicks from the two genotypes were reared in wire-floored cages and divided at random into 3 groups. Birds were fed on high protein (HP, 12.99 MJ ME, 238 g crude protein/kg and 12.94 MJ ME, 216 g crude protein/kg from 0 to 3 and 3 to 7 weeks, respectively), medium protein (MP, 12.99 MJ ME, 219 g crude protein/kg and 12.87 MJ ME, 201 g crude protein/kg from 0 to 3 and 3 to 7 weeks), and low protein (LP, 12.94 MJ ME, 205 g crude protein/kg and 12.75 MJ ME, 184 g protein/kg from 0 to 3 and 3 to 7 weeks) diets. 3. The LP diets resulted in a significantly lower daily body weight gain of males from 0 to 3 weeks. Dietary protein content had no effect on body weight gain from 3 to 7 weeks, body weight at 7 weeks, and the food intake of birds. Carcase composition of birds from both genotypes was unaffected by dietary protein. 4. Naked neck birds had significantly higher body weights at 7 weeks. Yields of carcase and breast of Na/na males were significantly higher than those of na/na males. There were no significant differences between females from the two genotypes as regards carcase yield. 5. It was concluded that the dietary protein requirements of naked neck birds were similar to those for normally feathered birds.Öğe Effect of Prolonging the Non-Productive Period on the Performance of Molted Broiler Breeders(Carfax Publ Co, 1989) Hazan, A; Yalcin, SÖğe Effect of season and dietary energy concentration on composition and strength of skin in naked neck fowl(Carfax Publishing, 1998) Yalcin, S; Bilgen, G; Oktay, G; Acikgoz, Z; Bilgili, SF1. Two experiments, in spring and summer, were conducted to evaluate the effect of dietary energy concentration on the composition and strength of the skin of naked neck fowl. The heterozygous naked neck birds were also compared with their normally feathered sibs under summer temperatures. 2. The average temperatures were 21.2 degrees C and 27.1 degrees C in spring and summer experiments, respectively. Three concentrations of dietary energy were fed to the birds. The diets used were: 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. Two protein concentration per energy treatment, 230 and 200 g/kg, respectively were used from 0 to 3 and 3 to 7 weeks of age. 3. A significant season sex interaction showed that the skin of males had higher protein and collagen and lower dry matter and fat content than that of females, when grown under summer conditions. No sex differences were present under spring conditions. 4. The differences between sexes was not significant in spring but males had stronger skin than females in summer. Neither ambient temperature nor dietary energy concentration significantly affected skin displacement of naked neck birds. 5. In comparing the naked neck and their normally feathered sibs in the summer experiment, it was found that naked neck birds had lower skin fat content and higher skin protein content than normally feathered birds.Öğe Effect of tibal dyschondroplasia on carcase part weights and bone characteristics(Carfax Publ Co, 1996) Yalcin, S; Akbas, Y; Settar, P; Gonul, T1. 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.Öğe Effects of divergent selection for incidence of tibial dyschondroplasia (TD) on purebred and crossbred performance. 1. TD incidence and calcium and phosphorus plasma concentrations(Carfax Publishing, 2000) Yalcin, S; Zhang, X; Christa, LM; McDaniel, GR; Kuhlers, DL1. The effect of divergent selection for high (H) or low (L) incidence of tibial dyschondroplasia (TD) for 7 generations on blood calcium (Ca) and phosphorus (P) concentrations was studied. 2. The chicks used in this experiment were obtained from diallel crosses between H and L lines to obtain HH, HL, LH, and LL lines. A random-bred control (CC) line was also used. 3. The chicks were reared under standard management conditions. Body weight and plasma Ca and P concentrations were measured at 2, 4, and 7 weeks of age. Incidence of TD was recorded at 4 and 7 weeks. 4. Although HH birds had lower body weights than the other lines, there was no significant effect attributable to line selection for body weight at 2, 4, and 7 weeks of age. 5. The LL line birds had no incidence of TD at 4 weeks of age; however, the incidence of TD in LL line birds was 5.3% at 7 weeks of age. The incidence of TD was higher in HH line birds than the other line at 4 and 7 weeks of age. 6. Plasma Ca and P concentrations and Ca:P ratios increased with age. These results showed that HH line birds had higher plasma Ca, lower plasma P and higher Ca:P ratios than birds of the LL line.Öğe Effects of divergent selection for incidence of tibial dyschondroplasia (TD) on purebred and crossbred performance. 2. Processing yield(Carfax Publishing, 2000) Yalcin, S; Zhang, X; McDaniel, GR; Kuhlers, DL1. 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.Öğe Effects of selection for four week body weight on reproductive performance in Japanese quail(Scientific Technical Research Council Turkey, 1999) Turkmut, L; Altan, O; Oguz, I; Yalcin, SThis research was carried out to determine the genetic effects of divergent selection under two different selection pressures for four week body weight over three generations on reproductive characteristics and some egg characteristics in Japanese quail. Birds were weighed individually. Individual selection for body weight was carried out at four weeks, separately for each sex. The proportion kept was 10% for males and 30% for females in 10Y and 10D lines, and 20% for males and 60% females in 20Y and 20D lines. 10Y and 20Y lines were selected for high body weight, 10D and 20D lines were selected for low body weight. Age at sexual maturity was not affected by lines and generations. Average age at sexual maturity was 46 days. Early death rates were decreased by selection. But mid term and late deaths were not affected by selection. Average early, mediavel and late embryonic mortalities were %7.99. %13.47 and %15.93 in Y lines and %7.25, %10.36 and %20.49 in D lines. There were not differences in fertility and hatchability among lines. Fertility was increased by selection. Hatchability did not change. Fertility hatchability of fertile eggs and hatchability of all eggs over generations were %79.82, %54.46 and %43.39 respectively All egg characteristics except shell weight per unit surface area were changed by selection. Egg weight, shape index, albumen index was affected by lines. Egg weight, albumen index and yolk index during the selection increased from 10.2A g to 11.45 g, from 11.56 to 14.03 and from 45.37 to 48.86 respectively. Yolk percentage and form index decreased from 33.83 to 32.22 and from 82.23 to 79.74 respectively. Average Haugh unit and shell weight per unit surface area over the generations were 95.21 and 40.39 mg/cm(2) respectively.Öğe Effects of selection for four week body weight on slaughter, carcass, and abdominal fat and some organ weights and blood serum parameters in Japanese quail(Scientific Technical Research Council Turkey, 1999) Turkmut, L; Altan, Z; Oguz, J; Yalcin, SThis research was carried out to determine the genetic effects of divergent selection under two different selection pressures for four week body weight over three generations on slaughter weight, carcass weight, abdominal fat and some organ weights and blood serum parameters in Japanese quail. Birds were weighed individually. individual selection for body weight was carried out at four weeks, separately for each sex. The proportion kept was 10% for males and 30% for females in 10Y and 10D lines. and 20% for males and 60% females in 20Y and 20D lines. 10Y and 20Y lines were selected for high body weight, 10D and 20D lines were selected for low body weight. Slaughter weight, carcass weight, carcass yield. abdominal fat weight, organ weights and organ yield of female quails were affected by selection. Carcass characteristics of male quails except abdominal fat and yield changed by selection. Slaughter weight, carcass weight and yield, abdominal fat weight and yield, liver weight of female quails and slaughter weight, carcass weight and yield, liver weight and yield of male quails were affected by lines. However, sex organ weights and yields in both sexes were similar between lines. Average slaughter weight, carcass weight, abdominal fat weight, liver weight, ovarium weight, oviduct weight over the generations in the female quails were 194.53 g, 122.05 g, 1.16 g, 5.77 g, 5.27 g, 6.03 g respectively. Slaughter weight, carcass weight. abdominal fat weight, liver weight, testes weight over the generations in male quails were 173.92 g, 124.93 g, 1.76 g, 2.98 g, 4.80 g. respectively. The average slaughter weight, carcass weight, abdominal fat weight, liver weight, ovarium weight, oviduct weight for females in Y and D lines were 204.18 g and 188.51 g, 127.79 g and 117.27 g, 1.41 g and 1.00 g, 6.07 g and 5.61 g, 5.57 g and 4.84 g, 6.12 g and 5.99 g. The average slaughter weight, carcass weight, abdominal fat weight, liver weight, testes weight for males in Y and D lines were 184.51 g and 162.59 g, 134.52 g and 117.18 g, 2.14 g and 1.44 g, 2.96 g and 3.06 g, 4.92 g and 4.69 g. Whole blood serum parameters except level of trigiserid changed by generations. But the level of serum calcium was affected by lines. Blood serum parameters over the generations were 213.17 mg/dl, 237.79 mg/dl, 98.09 mg/dl, 17.02 mg/dl and 7.10 mg/dl for cholesterol, lipid, trigliserid, calcium and phosphor, respectively.Öğe Effects of strain, maternal age and sex on morphological characteristics and composition of tibial bone in broilers(Carfax Publishing, 2001) Yalcin, S; Ozkan, S; Coskuner, E; Bilgen, G; Delen, Y; Kurtulmus, Y; Tanyalcin, T1. This study was to determine the effects of strain, age of the maternal flock and sex on morphologic:ll characteristics and composition of tibial bone of broilers horn hatch to 48 d of age. 2. A total of 600 chicks was obtained from 2 strains of broiler breeder flocks (150/chicks/strain/maternal age). Maternal flock age was classified as young (32 to 35 weeks of age) or old (56 to 58 weeks of age). Birds were reared under standard feeding and lighting regimes. 3. On day 1, 16, 32 and 48, twelve birds were selected at random from each maternal group, strain and sex and killed. The wet bone weight and volume were measured. Morphological characteristics of tibia were determined using radiography. Bone breaking strength was tested. Tibia dry matter, ash content, mineral density and collagen level were determined. 4. A quadratic increase occurred with increase in age of broilers fur all variables, except proximal width, medial cortex thickness and distal condyle width which increased in a linear manner. 5. Maternal age had a significant effect only on the variably measured at the time of hatch. On day of hatch bone weight, ash content and hone volume were affected by maternal age, but the extent of this also depended on the strain. 6. The differences observed between strains for bone anatomy and bone mineralisation during the rapid growth period of 16 d were not significant at later ages, with the exception of bone volume. Differences between sexes were evident from 16 to 49 d of age with females having lower values.Öğe Exposure to cold or heat during incubation on developmental stability of broiler embryos(Oxford Univ Press, 2003) Yalcin, S; Siegel, PBAn experiment was conducted to measure the effects of exposure to heat or cold during incubation on the size of skeletal bilateral traits (face, wings, shank, tibia, and femur) and weights of heart and lungs of broiler embryos. Measurements were obtained at 10 and 18 d of incubation and at hatch on d 21. Treatments consisted of eggs incubated at 37.8degreesC throughout (control; C), cooled to 36.9degreesC for 6 h daily from d 0 to 8 (C0-8), heated to 39.6degreesC for 6 h daily from d 0 to 8 (H0-8), cooled to 21.0degreesC for 24 h on d 14 (C14), cooled to 36.9degreesC for 6 h daily from d 10 to 18 (C10-18), and heated to 39.6degreesC for 6 h daily from d 10 to 18 (H10-18). Although cooling and heating of eggs during incubation influenced growth of the skeletal traits on d 10 and 18, compensation generally occurred by the time of hatch. The developmental stability of bilateral traits varied with the specific trait, with those observed earlier in incubation tending to decrease by hatch.Öğe Exposure to cold or heat during incubation on developmental stability of broiler embryos(Oxford Univ Press, 2003) Yalcin, S; Siegel, PBAn experiment was conducted to measure the effects of exposure to heat or cold during incubation on the size of skeletal bilateral traits (face, wings, shank, tibia, and femur) and weights of heart and lungs of broiler embryos. Measurements were obtained at 10 and 18 d of incubation and at hatch on d 21. Treatments consisted of eggs incubated at 37.8degreesC throughout (control; C), cooled to 36.9degreesC for 6 h daily from d 0 to 8 (C0-8), heated to 39.6degreesC for 6 h daily from d 0 to 8 (H0-8), cooled to 21.0degreesC for 24 h on d 14 (C14), cooled to 36.9degreesC for 6 h daily from d 10 to 18 (C10-18), and heated to 39.6degreesC for 6 h daily from d 10 to 18 (H10-18). Although cooling and heating of eggs during incubation influenced growth of the skeletal traits on d 10 and 18, compensation generally occurred by the time of hatch. The developmental stability of bilateral traits varied with the specific trait, with those observed earlier in incubation tending to decrease by hatch.Öğe Genetic relationships between tibial dyschondroplasia (TD) incidence and carcass and tibia characteristics in a pure line of a commercial broiler stock(Eugen Ulmer Gmbh Co, 2001) Yalcin, S; Akbas, YGenetic correlations of TD incidence with carcass and bone characteristics were estimated by studying the progeny of one paternal and two maternal pure lines of a commercial broiler stock. Heritability estimates of TD incidence were 0.43 and 0.21 from sire and animal model. Negative genetic correlations were estimated between incidence of TD and carcass characteristics. The genetic correlation between TD severity index and carcass conformation tended to be negative and moderate. This observation indicated that carcass conformation would be decreased when birds had a higher severity index of TD.Öğe 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(Carfax Publishing, 1998) Yalcin, S; Ozkan, S; Acikgoz, Z; Ozkan, K1. Heterozygous naked neck birds were raised under natural spring (average 21.2 degrees C) and summer temperatures (average 27.1 degrees 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 degrees C) and summer temperatures (27.1 degrees C).
