• Korean Journal of Poultry Science
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• v.50 no.1
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• pp.15-22
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• 2023

This study was to investigate the relationship between chick weight in the growing period and the laying performance of Korean native chicken (KNC) breeders. We measured the body weights of 1,384 KNC breeders at 1-140 days of age at two-week intervals. The age at first egg laying, hen-day and hen-housed egg production, and the egg weights were investigated. Correlation coefficients between the body weight and egg production traits were analyzed. The results showed that the correlation coefficients between body weight and age at first egg laying were significantly positive before 4 weeks, but negative after 8 weeks of age. The correlation coefficients between body weight and egg production rate were estimated to be negative before 8 weeks and positive after 12 weeks of age. Coefficients of hen-day and hen-housed egg production were similar. There was little correlation between body weight and egg weight at 32 weeks of age, whereas a low positive correlation was with egg weight at 50 weeks. In conclusion, there was little correlation between body weight and laying performance before 8 weeks of age, whereas a significant positive correlation was with body weight after 12 weeks. The results suggest that as the chick's weight increases in the late growing stage, sexual maturity is faster, the egg production rate is higher, and the egg weight increases. Therefore, the weight management of KNC female breeders is very important in the late growing stage, and the body weight of chicks must be maintained above the standard weight.

• Korean Journal of Poultry Science
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• v.24 no.3
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• pp.127-137
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• 1997

This study was conducted to estimate the laying performance and heterosis of Korean Native Chicken(KNC), Rhode Island Red(RIR), and KNC x RIR crossbreds A total of 1,274 female pullets were produced from KNC, RIR and RIR crossbreds in National Livestock Research Institute, Korea. The experiment was conducted for 2O~64 weeks from Jan 20. to Nov.25, 1996. The age at first egg of crossbreds were 144.1~148.7 days. The first egg weight of crossbreds was 39. 4~40.3 g, and body weights at first egg of KNC dark brown strain x RlR(DR), KNC light brown strain x RlR(LR) and KNC dark black strain x RlR(BR) were 1,943 g, 1,925 g and 2,044 g, respectively. During the laying period the average viability of crossbreds was 96.6~98.3%. The hen-day egg production of crossbreds were 111.1~113.O eggs at 40 weeks of age, and 223.5~227.5 eggs at 64 weeks of age, respectively. The hen-day egg production peaks were 78.2~80.1% in KNC, and 85.8~87.5% in crossbreds. The heterosis were estimated to be 3.61%, 9.21%, 4.78%, 2.97% and -1.63% for the first egg days, body weights at first egg, layer viability, hen-day egg production, and feed conversion ratio, respectively.

• Proceedings of the Korea Society of Poultry Science Conference
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• 2002.11a
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• pp.140-142
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• 2002

This study was conducted to obtain some genetic information for developing superior Korean native chickens. Heterosis and combining ability effects were estimated with 1,080 progenies of full diallel crosses of 3 strains in Korean Native Chicken. The traits of egg productivity were Investigated, and heterosis effect, general combining ability, specific combining ability and reciprocal effect were analyzed model I of the Griffing's method 1. The general performance were 147.0 days in age at first egg laying, 71.8 eggs in egg numbers to 270 days, 50.1g in egg weight at 270 days, 75.6 in egg shape index, 356$\mu\textrm{m}$ in egg shell thickness, and 4.27kg/$\textrm{cm}^2$ in egg shell strength, respectively. According to result, heterosis effect revealed comparatively high in age at first egg laying, egg numbers, egg weight, and egg shell strength. The effects estimated highly in general combining ability for age at first egg laying, egg numbers, egg weight, egg shape Index and egg shell thickness, and in specific combining ability were egg numbers, egg weight and egg shell thickness, and in reciprocal effects for egg numbers, egg shape index, and egg shell thickness. This result could be used for developing Korean native chicken.

• Asian-Australasian Journal of Animal Sciences
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• v.27 no.8
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• pp.1075-1081
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• 2014

CRBP1 (cellular retinol binding protein 1) and CRBP3 (cellular retinol binding protein 3), are important components of the retinoid signaling pathway and take part in vitamin A absorption, transport and metabolism. Based on the role of vitamin A in chicken laying performance, we investigated the polymorphism of CRBP1 and CRBP3 genes in 349 chickens using single strand conformation polymorphism and DNA sequencing methods. Only one polymorphism was identified in the third intron of CRBP1, two polymorphisms were detected in CRBP3; they were located in the second intron and the third intron respectively. The association studies between these three SNPs and laying performance traits were performed in Erlang mountainous chicken. Notably, the SNP g.14604G>T of CRBP1 was shown to be significantly associated with body weight at first egg (BWFE), age at first egg (AFE), weight at first egg (WFE) and total number of eggs with 300 age (EN). The CRBP3 polymorphism g.934C>G was associated with AFE, and the g.1324A>G was associated with AFE and BWFE, but none of these polymorphisms were associated with egg quality traits. Haplotype combinations constructed on these two SNPs of CRBP3 gene were associated with BWFE and AFE. In particular, diplotype H2H2 had positive effect on AFE, BWFE, EN, and average egg-laying interval. We herein describe for the first time basic research on the polymorphism of chicken CRBP1 and CRBP3 genes that is predictive of genetic potential for laying performance in chicken.

• Korean Journal of Poultry Science
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• v.22 no.1
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• pp.7-13
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• 1995

To investigate the response of egg production to the artificial light to induce early egg laying. and the changes of egg weight and egg shape during the egg laying cycle, 30 Korean ring-necked pullets and their 1,284 eggs layed under artificial light control were used in this study. The first egg was ohserved at the age of 31 wk, after 4 wk of stimulating light(16 hour light: 8 hour dark). Egg production rate during seven 2-wk periods from the begining of the first egg was 43.7% and a clear peak egg production(61.7%) was shown at the 4th 2-wk period. The effects of egg production period and pullet on the egg weight, egg length, egg width and egg shape index(width/length) were significant(P<0.01). In the egg production cycle. egg weight, egg length and egg width increased steadly with time. but the value of egg shape index increased up to the 3rd 2-wk period and then decreased. Repeatabilities from intraclass correlation for the egg weight, egg length. egg width and egg shape index were 0.61. 0.53, 0.49 and 0.48, respectively.

• Korean Journal of Poultry Science
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• v.40 no.1
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• pp.17-23
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• 2013

This work was carried out to investigate the performance of early laying period of large-type Korean native ducks. One hundred sixty eight ducks were used in this work and divided into A and B strains (6 replications/strain, 14 birds/replication). The days at first egg of A and B strains were the age of 154.5 and 154.7 days, egg weights were 69.1 g and 65.5 g, and body weights were 3,187 g and 3,105 g at the period of laying the first egg, respectively. The days at sexual maturity of A and B strains were the age of 175.8 and 171.5 days, egg weights were 75.2 g and 74.9 g, and body weights were 3,245 g and 3,225 g at the period of laying the first egg, respectively. There were no significant differences on the day of first egg, the day of sexual maturity, egg weight and body weight at first egg and the sexual maturity, average body weight, and daily feed intake between A and B strains (P>0.05). The day of the sexual maturity of B strain was earlier than that of A strain (P<0.05). However, weekly body weight was the highest at the age of 28 weeks (P<0.05), and weekly feed intake increased after 26 weeks old (P<0.05). Egg production (%) of B strain was higher than that of A strain at the age of 22~24 weeks (P<0.05), but there was no significant difference on egg production (%) the other weeks. A number of egg laid of B strain was higher than A strain at 22~24 weeks old (P<0.05). Feed conversion ratio of A and B strains were 10.7 and 6.53 at 24~24 weeks old, respectively, so feed conversion ratio of A strain was higher than that of B strain (P<0.05). Weekly feed conversion ratio wes the highest at 20~22 weeks old, and significantly decreased until 24~24 weeks old, but were lowly maintained from the age of 24 weeks to the age of 30 weeks. These results provided the basic data on the record of early laying period of large-type Korean native ducks.

• Korean Journal of Agricultural Science
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• v.39 no.1
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• pp.53-60
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• 2012

This work was conducted to evaluate the laying performance of Korean Native Ducks (KND) Pure-Line (PL). A total of 400 female pullets were hatched from PL to keep in National Institute of Animal Science, Korea. Twenty weeks old PL female ducks were divided into 4 groups (5 replications/group, 20 head/replications). Four groups were compared in a $2{\times}2$ factorial arrangement with strain (White strains, WW; Celadon strains, CC) and house type (flat house, cage house). On first egg laying day, CC strain laid eggs earlier compared to WW strain (P<0.01), but there was no significant difference between flat and cage house. Egg weight (EW) and body weight (BW) at first egg laying day have no difference among strains and houses. BW of CC strain was higher than WW strain at the age of 30 week (P<0.01). Weekly feed intake (FI) have no difference between flat and cage house, but FI of WW strain was high compared to CC strain during 20~30 weeks. There was no significant difference on EW between CC and WW strains, but EW was low at flat house compared to cage house (P<0.05). Weekly egg productions of WW strain and flat house were lower than CC strain and cage house, respectively (P<0.01). Finally, These results can provide the information that needed to introducing new strains.

• Korean Journal of Poultry Science
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• v.40 no.1
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• pp.67-73
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• 2013

With an increasing concern on laying hen welfare, barn system has appeared as one of the alternatives to replace the conventional cage. This study was conducted to compare the early laying performance and egg quality at the barn system with those at the conventional cage. A total of 288 shaver-579 brown layers were used for 9 weeks ($21^{st}$ to $30^{th}$ weeks of age) feeding study. Feed consumption and egg weight were significantly (P<0.01) higher at barn than at cage. However, there were no significant differences between two housing systems on hen day egg production (HDEP), egg mass, body weight, feed efficiency and livability. In case of egg quality parameters, shell thickness, albumen height and Haugh unit were significantly (P<0.05) different between two systems. Haugh unit and albumen height were significantly higher in eggs produced at cage (88.97 and 8.16 mm) compared than those produced at barn (83.11 and 6.87 mm), whereas shell thickness was thicker in eggs produced at barn than those produced at cage. Shape index, breaking strength, blood spots and yolk index data were not influenced significantly by the types of housing system. To implement welfare bestowing production, this study showed that the barn system can replace the conventional cage without serious sacrifices on starting phase egg production. In addition, this study suggested that the barn system need to be optimized in view of daily feed consumption.

• Korean Journal of Poultry Science
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• v.24 no.2
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• pp.85-90
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• 1997

An experiment was conducted to investigate the relationship between blood hormone levels and light cycle on performance of Korean native chicken. One hundred and two Korean native chickens were grouped into three treatments of natural light cycle (Control), 13L:11D (T2), and 16L:8D (T3). The egg production, egg weight, feed intake, serum melatonin and estrogen level were periodically measured from 22 to 34 weeks, respectively. The laying rates of T2 and T3 were significantly higher than that of the Control (P

• Proceedings of the Korea Society of Poultry Science Conference
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• 2003.11a
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• pp.99-100
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• 2003

This experiment was conducted to investigate the effect of restricted feeding to pullet on growth and laying Performance, e99 qualify and endocrine profile in brown layers. 1,080 brown-layer chicks divided to three diet treatments, conventional diet and two restricted diets, for 70 weeks. Conventional diets(C) was formulated by NRC recommendation, and one of restricted diet started from seven to seventeen week of age(T1), and the other started from twelve to seventeen(T2). Overall egg Production was the highest in T1 (P＜0.05) and there were not difference in C and T2. Average egg weight also showed similar to the tendency of egg production. Feed intake was higher in T1 during maximum production(P＜0.05), but there were not difference in all treatments after the peak. Overall feed conversion ratio improved in T1 compared to C and T1(p＜0.05). Egg shell thickness and egg shell strength tended to weak in aging, but there were not significant difference by treatments. Haugh unit also tended to similar to egg shell quality. Concentration of IGF-1 was influenced by feed intake. That of T1 maintained in low concentration compared to C during restriction period. The concentration of IGF-1 was decreased dramatically after the first egg. Estradiol concentration increased slightly at twelve week, and surged greatly near the first egg. Those of profile showed similar tendency of the first egg during laying period.