• Korean Journal of Poultry Science
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• v.13 no.2
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• pp.173-178
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• 1986

Data on egg production, egg weight and egg mass were obtained from a sample of the Synthetic White Leghorn population which was raised at Poultry Breeding Farm, Seoul National University. Egg mass was not measured directly, but was calculated from the egg numbers and the average egg weight for same period. Phenotypic means, components of variance and covariance, heritabilities and genetic correlations were computed. Egg mass was estimated to be a lowly heritable trait (0.204-0.270). High heritability estimates were found for age at sexual maturity and egg weight. Genetic correlation estimates were high and positive between egg mass and egg number(combined estimates 0.711). Egg mass and egg weight were moderately correlated genetically (0.431). Genetic correlation estimates was -0.280 between egg number and age at sexual maturity, but was 0.524 between egg weight and age at sexual maturity. Results show that selection for total egg mass based on record from a single period will not be satisfactory unless the single period chosen is one in the latter part of the laying year.

• Korean Journal of Poultry Science
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• v.37 no.4
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• pp.383-388
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• 2010

The chicken eye can discriminate light color, and different light wavelengths may affect reproduction ability. This study was carried out to identify effect of monochromatic light using light emitting diode (LED) in laying hens. Chickens were exposed to white light (WL), blue light (BL), yellow light (YL), green light (GL) and red light (RL) made by using LED as well as incandescent light (IL) (control). All light sources were equalized to a light intensity of 20 lux. The results indicated that the age of first egg laying and 50 % egg laying in laying hens treated under RL is significantly younger than under other lights (P<0.05). And the ovary weight of laying hens reared under RL is significantly heavier than under other at from 16 to 20 wks (P<0.05). The largest number of eggs production was produced in a group with treated with RL by 59 wks of age compared with any other group. The egg weight of YL was greater than other treatment groups from 26 to 45 wks (P<0.05). The egg shell from hens treated with RL was the strongest and thickest at 20 wk (P<0.05). These results suggest that the egg quality of laying hens reared in different spectrum of LED can be different and RL may enhance the laying performance.

• Korean Journal of Poultry Science
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• v.48 no.4
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• pp.161-168
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• 2021

The present study investigated production traits, including body weight, egg production, egg weight, and egg quality in Korean indigenous parent stocks. Parent stocks produced from a nine-combination association from five pure line strains (C, D, F, K, and Y) were used. The body weight analyses results showed that the CY combination had the highest body weight (1,604.9 g) and the DK combination had the lowest (1,424.4 g). The average age at first egg of the nine combinations was 118.6 days; however, that of the YD combination was 111.6 days, making it the fastest growing combination, whereas the DK combination was the slowest, at 126 days. Hen-day egg production was 74% or more for the CF, CK, and DK combinations. The DK combination hens showed excellent persistence in egg laying. Hen-housed egg production exhibited results similar to those of hen-day egg production. Egg weight was significantly higher in the DK combination than in the other combinations and was observed to increase from 20 (43.9 g) to 40 (58.1 g) weeks. The egg quality analyses results showed that the combinations based on the F and K strains had a bright eggshell color, with relatively high egg weights. Eggshell strength and thickness were the highest in the DK combination (3.8 kg/cm², 0.38 mm). In summary, the CF and DK combinations showed excellent egg production ability and egg quality, while the YC, YD, and YK combinations with the Y strain as the paternal strain exhibited poor performance.

• Proceedings of the Korea Society of Poultry Science Conference
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• 2004.11a
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• pp.111-112
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• 2004

참옻나무 추출액이 산란계의 생산성과 계란품질, 장내미생물 변화 및 영양소 소화율에 미치는 영향을 구명하고자 산란졔 Isa brown 57주령 480수를 공시하여 8주간 케이지에서 사양시험을 실시하였다. 산란율, 산란량 및 사료요구율은 참옻나무 추출액 5000 ppm 급여구가 산란율이 무첨가 대비 유의적으로 향상되었으며, 전반적으로 추출물 급여구의 산란율이 증가하였다. 평균난중과 사료섭취량은 처리간 차이가 없었다. 난각강도, 난각후도는 추출액 급여구가 무첨가 대비 유의적으로 개선되었으며, 난황색 및 Haugh unit은 전 기간에서 추출액 첨가구가 개선되는 경향을 보였다. 맹장내 유산균과 E. coli는 처리간 차이를 보이지 않았으며, Salmonella는 무첨가 대비 추출액 급여구가 약간 낮은 경향을 보였으나 통계적 유의성은 인정되지 않았다. 영양소 소화율은 옻나무 추출액 급여구가 무첨가 대비 전반적으로 향상되는 결과를 보였다.

• Journal of Animal Science and Technology
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• v.50 no.3
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• pp.343-354
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• 2008

The objective of this study was to investigate the effect of restricted feeding to pullet on growth and endocrine profile in layers(Isa brown). One thousand eighty brown-layer chicks were divided into three treatments; conventional feeding(ad libitum) and two restricted feedings(80% of conventional diet) for 70 weeks. One of restricted feeding started from seven to seventeen weeks of age, and the other started from twelve to seventeen weeks of age. Diets were formulated by NRC(1994) recommendation. Body weight and feed intake were measured every two weeks, and body composition and organ weight analyzed every week in rearing period and every eight weeks in laying period. Blood was collected at weighing body weight and was analyzed for the concentration of insulin-like growth factor-Ⅰand estradiol. Body weight and feed intake decreased as restriction of feeding begins comparing to ad libitum group(P<0.05), but reached to similar body weight and feed intake at 20 wk of age regardless of restriction. There were no significant differences in development of digestive tract and attached organs among the treatment groups. During rearing period, however, they were slightly higher in restricted group which was low in body weight. In terms of body composition, fat contents of restricted group were significantly lower(P<0.05) than that of ad libitum group around 1,000 grams of body weight. High concentration of IGF-Ⅰwas observed.

• Korean Journal of Poultry Science
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• v.50 no.4
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• pp.203-212
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• 2023

This study conducted a diallel-crossbreeding test using four Korean native chicken parent stock lines (YC, YD, CK, and CF) to develop a native commercial layer with high egg-laying performance. A total of 312 chickens in six combinations were examined for various traits, including livability, body weight, age at first egg-laying, hen-day, and hen-housed egg production, egg weight, and egg quality, from hatching to 60 weeks of age. The results showed that the average survival rate was 77.1±18.8% with the YDYC combination having the highest survival rate along with excellent specific combining ability. The YDYC combination exhibited significantly higher body weight compared to the other combinations (P<0.01). The average age at first egg-laying was 121.3±2.5 days, with no significant difference between the combinations. The average hen-day egg production was 74.0±6.4%, and the hen-housed egg production was 181.4±33.8 eggs with the YDCF and YCCK combinations demonstrating the highest laying performance, while the YDYC and CKCF combinations had the lowest (P<0.05). Laying performance was more influenced by specific combining ability than general combining ability. The eggs from the YDYC combination were significantly lighter and had the darkest shell color (P<0.01), whereas the YDCF combination exhibited the thickest eggshells. There was no difference in internal egg quality among combinations, except the YDCF combination had the darkest yolk color. Overall, we concluded that the YCCK combination, characterized by high laying performance and livability, and the YDCF combination with high laying performance and good egg quality are the most desirable combinations for Korean native commercial layers.

• Korean Journal of Poultry Science
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• v.30 no.4
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• pp.229-233
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• 2003

A study was conducted to investigate the effects of different BW control methods during rearing on laying performance of broiler breeder pullets. D-old 540 female breeder chicks (Arbor Acres) were assigned to three treatments consisted of standard BW (Control), 110% of standard BW at 12 wk of age (T1), and 90% of standard BW at 12 wk of age (T2), with three replicates of 60 birds per replicate (pen) for each treatment. At 20 wk of age, all birds from three treatments reached the BW reqired in the Arbor Acres Manual. There were no significant differences in egg production, egg weight and viability during laying period(p>0.05). However, total egg production rates were improved in T2 and T3. Average egg weight was the highest in T1 among all treatments. Fertility and hatchability were similar among treatments, but T2 tended to be higher than other treatments at 37 and 53 wk of age. No significant difference was found in hatchability among three treatments. The number of hatching egg of T2 reached 168 per year, showing higher number of eggs than did the other treatments. The number of hatched chicks in T2 was 131, which was also higher than the other treatments, but the difference was not significant. It appears that the laying performance of broiler breeder hens could be improved when their BW at 12 wk of age are kept at 90% of standard BW, and reach the standard BW at 20 week of age.

• Korean Journal of Poultry Science
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• v.39 no.3
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• pp.177-182
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• 2012

This work was carried out to investigate the performance of growing period of two-way crossed of Korean native chickens parental stocks. A total of four hundred eighty female 2-crossbred chicks were used in this study and they were from National Institute of Animal Science. Groups were four crossbreds (4 replications/crossbred, 30 birds/replication) as A) C strain ${\times}$ Y strain, B) C strain ${\times}$ L strain, C) C strain ${\times}$ G strain and D) C strain ${\times}$ W strain. Body weight of A crossbred was the highest at the age of 8 week (P<0.05) and that of D strain was the lowest for growing period (P<0.05). Body weights of A and B crossbreds were higher than those of C and D crossbreds at the 12 and 16 weeks (P<0.05). Weekly body weights of A and B crossbreds were higher than C and D crossbreds (P<0.05), and weekly body weight of B crossbred was higher compared to other crossbreds at 0~20 weeks old. Weekly feed intake of D crossbred was the lowest among all crossbreds at 0~12, 0~16 and 0~20 weeks old (P<0.05). Weekly feed conversion ratio of C crossbred was the highest among crossbreds (P<0.05). These results can give the basic information for growth related data in 2-way crossbreed Korean Native Chickens, which can be used for the parental stocks for the laying-type of Korean native commercial chickens.

• Korean Journal of Poultry Science
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• v.10 no.2
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• pp.75-81
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• 1983

The records on 787 white Leghorn hens from two different strains, A and K were wed in this study to find out the pattern of increase in egg weight with age and the optimum age of early selection for maximizing the genetic gain. The pattern of increase in egg weight with age in two lines which was expressed on graph showed that the amount of increase was larger in the early part of the laying year and it decreased gradually. Regression equations suggested that egg weight increased linearly with age at the rate of 0.46 gram per week for line A and 0.83 gram for line K. And in the regression analyses of each period mean egg weight on annual mean egg weight, the coefficients of EW 30 that is mean egg weight from 29 weeks of age to 32 weeks of age were 0.86 for line A, 0.88 for line K, and those were the highest figures among the all regression coefficients of each mean egg weight on annual mean egg weight. In estimating the relative selection efficiency of each period mean egg weight on annual mean egg weight in EW 46, selection on EW 34 for line A and on EW 30 for line K was the most efficient for improving egg weight. These results suggested that one periods from 29 weeks of age to 36 weeks of age could be used for the best predictable time for improving annual mean egg weight.

• Korean Journal of Poultry Science
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• v.44 no.1
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• pp.41-49
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• 2017

This study was conducted to identify the quality and functional properties of meat and meat batter among commercial broilers and two different ages of spent layers. Breast and whole leg meat samples were prepared from the broilers and spent layers to compare meat quality traits: Commercial broiler (Arbor Acre; 6-week-old) and two different ages of spent layers (Hy-Line; 70 and 95-week-old). Three types of meat batters containing breast meat as 50% of total ingredients were also prepared to analyze processing qualities. The broiler showed the highest water holding capacity (p<0.05) and the lowest cooking loss value (p<0.05) in both meat and meat batter samples. The breast and leg meat of the 95-week-old layers showed the highest shear force value (p<0.05), and also showed the highest shear force and hardness values in the meat batter. Although the oldest layer meat showed tougher textural traits than the 70-week-old layers, no significant differences were found for cooking loss and water loss values in both the meat and meat batter samples. Besides, panelists gave equivalent scores within different ages and parts of the cooked layer meats in the sensory evaluation. Similar ratios of polyunsaturated fatty acids to saturated fatty acids, and omega-6 to omega-3 fatty acids were obtained from both the 70-week-old layer and 95-week-old layer meats. In conclusion, the 95-week-old spent layers, especially for breast meat, had equivalent potential as raw materials for processed meat products compared to the 70-week-old layers.