• Korean Journal of Agricultural Science
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• v.46 no.4
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• pp.991-997
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• 2019

This study was conducted to investigate the laying period performance of two crossbred Korean native chicken (KNC) grand parent stock (GPS) layer during 20 to 40 weeks. A total of 351 20-week-old KNC GPS were allocated in a completely randomized design to give 4 birds per each cage. The chickens were fed commercial diets [i.e., week 20 - 32, crude protein (CP) 18.0% and metabolizable energy (ME) 2,850 kcal/kg; week 32 - 40, CP 17.0% and ME 2,800 kcal/kg)] and fresh water during the whole experiment period ad libitum basis. Body weight, age of sexual maturity, egg weight, hen-day egg production (HDP) and feed conversion ratio (FCR) were measured during the experiment period (week 20 - 40). The results show no significant difference in the Body weight, age of sexual maturity, egg weight, and hen-day egg production (HDP) except for egg weight. 1B had a higher egg weight on week 36 only. We expect that the reason why most factors showed no significant difference is the lack of nutrients caused by limited feeding which follows the standard feeding system for the grand-parent stock. These results provide basic information for laying data in 2-way crossbred Korean native chickens.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.7
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• pp.930-938
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• 2019

Objective: Estimate genetic parameters, the rate of inbreeding, and the effect of inbreeding on growth and egg production traits of a Thai native chicken breed Lueng Hang Kao Kabinburi housed under intensive management under a tropical climate. Methods: Genetic parameters were estimated for weight measured at four weekly intervals from body weight at day 1 (BW1D) to body weight at 24 weeks (BW24) of age, as well as weight at first egg, age at first egg (AFE), egg weight at first egg, and total number of eggs (EN) produced during the first 17 weeks of lay using restricted maximum likelihood. Inbreeding depression was estimated using a linear regression of individual phenotype on inbreeding coefficient. Results: Direct additive genetic effect was significant for all traits. Maternal genetic effect and permanent environmental hen effects were significant for all early growth traits, expect for BW24. For BW24, maternal genetic effect was also significant. Permanent environmental hen effect was significant for AFE. Direct heritabilities ranged from 0.10 to 0.47 for growth traits and ranged from 0.15 to 0.16 for egg production traits. Early growth traits had high genetic correlations between them. The EN was lowly negatively correlated with other traits. The average rate of inbreeding for the population was 0.09% per year. Overall, the inbreeding had no effect on body weight traits, except for BW1D. An increase in inbreeding coefficient by 1% reduced BWID by 0.09 g (0.29% of the mean). Conclusion: Improvement in body weight gain can be achieved by selecting for early growth traits. Selection for higher body weight traits is expected to increase the weight of first egg. Due to low but unfavorable correlations with body weight traits, selection on EN needs to be combined with other traits via multi-trait index selection to improve body weight and EN simultaneously.

• Korean Journal of Poultry Science
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• v.44 no.2
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• pp.123-134
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• 2017

This study was conducted to establish new synthetic lines of Korean Native Chicken. We performed $5{\times}5$ diallel crossings with GPS lines of Korean Native Chicken for the selection of parent stock. The production traits including viability, body weight, age at first egg laying, egg weight, hen-day egg production, and hen-housed egg production were measured and analyzed for 25 crosses with 1,157 hens. The heterosis effects of these traits were also estimated. The results showed that the average survival rate during laying periods was 67.7% in the pure lines and 77.1% in the crosses. The 25 cross combinations were shown to be distinctly divided into three groups according to body weight; nine crosses in the high-weight group, 12 crosses in the medium-weight group and four crosses in the light-weight group. The average body weight at 12 weeks of age was $1,873.8{\pm}43.0g$ in the high group, $1,595.4{\pm}56.6g$ in the medium group and $1,152.7{\pm}24.7g$ in the light group, and $1,560.2{\pm}339.3g$ in the pure lines and $1,640.9{\pm}213.7g$ in the crosses. In terms of egg production performance, the age at first egg laying was $139.7{\pm}4.9$ days in the pure lines and $135.8{\pm}5.1$ days in the crosses. The average egg weight was $52.3{\pm}1.6g$ in the pure line and $53.0{\pm}1.6g$ in the crosses. The average hen-housed egg production from 20 to 40 weeks was $58.3{\pm}12.9$ eggs in the pure line and $69.2{\pm}10.4$ eggs in the crosses. The average heterosis effect was 16.9% for survival rate, 5.4% for body weight at 12 weeks, -2.7% for age at first egg laying, 1.3% for egg weight, and 14.3% for hen-day egg production. Generally, the heterosis effect for viability and egg production traits was higher than that for growth trait. On the basis of these results, it is expected that the selection of the HF combination, which had excellent growth performance, is the most desirable as the paternal strain, and the selection of GW and FW combinations, which had excellent laying performance, are preferable as the maternal strain.

• Korean Journal of Poultry Science
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• v.27 no.2
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• pp.115-132
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• 2000

Eggshell strength and eggshell pigmentation are described in this paper since these are needed for quality egg production. A strong eggshell is determined by the components of the shell (cuticle, true shell and membranes) as well as the proper function of the gastrointestinal tract, the shell gland, the Kidneys and the endocrine system. When the puller reaches sexual maturity, the medullary bone must be ready for the laying hen at the peak egg shell formation. The amount of calcium in the layer diet, sources of calcium feed, the ratio of calcium and phosphorus in the layer diet, adequate levels of vitamin D and the dietary mineral (electrolyte) balance in the body fluid are important factors along with the levels of other nutrients. Biological, environmental and managerial factors such as the age of laying flock, temperature and humidity of the hen house, bird strain, disease, egg collection through transportation and others and influence the shell breakage at various stages of movement of the eggs from the producer to the consumer. The pigments present in eggshells are protoporphyrin-Ⅸ, biliverdin-Ⅸ and its zinc chelate and occasional traces of coproporphyrin-Ⅲ. However, there are several causes of changes in eggshell pigmentation such as the age of hen, disease, drugs and surface defects due to abnormal post-cuticular deposits.

• Preventive Nutrition and Food Science
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• v.1 no.1
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• pp.99-105
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• 1996

Effects of conjugated linoleic acid(CLA), known as an effective anticarcinogen in several aminal models, on the egg production and egg weight of laying hens, and the weight gains of broilers were investigated. CLA was synthesized from corn oil by the alkaline isomerization method and purified by the low-temperature precipitation method. Diets for laying hens and for broilers were synthesized to meet the specification of their NRC standard rationals. Two separated experiments(Experiment I and II) were conducted for laying hens. in experiment I, 45 hens(300 days of age) were divided into 15 hens per treatment group; each hen was housed in wired cage located in a temperature and humidity-controlled house and adopted to the control diet. One week later, each group was subjected to one the four treatment groups for 5 weeks : control, 1.0% CLA, 2.5% CLA and 5.0% CLA diets. Diet and water were ad libitum. The condition of experiment II was the same as that of experiment I except for the addition of 5% corn oil diet and the extension of feeding period to 7 weeks. Egg production, egg weight and feed intake were recorded every week. Forty-five broilers(10day of age) were adopted to the control diet for a week and then switched to the treatment diets for 5 weeks : control, 1.0% CLA, 2.5% CLA, 5% CLA and 5% corn oil, Body weight and feed intake of broilers were measured every week. Diets supplemented with various amounts of CLA enhanced the egg production and increased the egg weight regardless laying hen's age(150 days or 300 days) as compared to control diet. The most effective diet for the egg production and egg weight of young hens(150 days of age) was found to be 1.0% CLA diet, but relatively higher CLA diet(2.5% CLA) was required for old hens (300 day of age) to obtain similar results as seen in younger hens. All hens treated with CLA ate greater amount of feed than control hens. Broilers treated with various amount of CLA ate less feed as compared to control ones, but the body weight gain was greater than the control broilers. These results indicate that CLA enhanced the egg production and agg weight of laying hens, and increased the body weight gain of broilers with less diet consumption.

• Asian-Australasian Journal of Animal Sciences
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• v.25 no.4
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• pp.559-568
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• 2012

White (Lohmann LSL) and Brown (ATAK-S) laying hens, were reared under organic and conventional cage rearing systems, and the effects of the rearing system on performance parameters, egg production, egg characteristics, and immune response were investigated. For this purpose, a total of 832 laying hens of two commercial hybrids, i.e., 416 white (Lohmann LSL) and 416 Brown (ATAK-S) layers, were used. The experiment lasted between 23 and 70 wk of age. In this study, the white layers yielded more eggs as compared to the brown layers in both organic and conventional production systems. Egg weight exhibited a similar pattern to that of laying performance. However, the total hen-housed egg number for the white birds in the organic system was fewer than that of white birds in the conventional cage facility; conversely, a contradictory tendency was observed for the brown birds. Livability of the white layers in the organic system was remarkably lower (14%) than that of the brown line, whereas the white line survived better (3.42%) than their brown counterparts in conventional cages. The feed conversion ratio of the white hens was markedly inferior in the organic system as compared to that of the white hens in the conventional system, whereas relatively lower deterioration was reported in brown layers when reared in an organic system. The organic production system increased egg albumen height and the Haugh unit in eggs of the brown layers. The yolk color score of organic eggs was lower than that of conventional eggs for both brown and white hens. The egg yolk ratio of eggs from white layers was found to be higher in organic eggs as compared to those obtained in the conventional system. All organic eggs had heavier shells than those produced in the conventional system. Eggs from brown layers had more protein content than eggs from white layers. Neither housing systems nor genotype influenced egg yolk cholesterol concentration. When compared to conventional eggs, n-3 fatty acid content was lower in organic eggs, and the n-6:n-3 ratio was higher in organic eggs. In conclusion, two hen genotypes showed different responses in terms of performance and egg quality to two different rearing systems. A commercial white strain produced more eggs with higher egg quality as compared to a native brown strain. The brown strain was found to have adapted well to organic production conditions when survival and total egg number was taken into consideration.

• 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.23 no.1
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• pp.27-37
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• 1996

This experiment was carried out to study the effects of feeding split diets for a.m. and p.m. on laying hen performance and feed cost with 480 ISA Brown layers for three periods during 32∼36, 52∼56 and 72∼76 wk of age, respectively. The control group(C) was fed a conventional single diet throughout the day and split diet groups (T$_1$, T$_2$, T$_3$, T$_4$ and T$\_$5/) were offered high energy-high protein-low Ca diets, and low energy-low protein-high Ca diets in a.m. and p.m., respectively. In split diet groups, feed intake, ME and CP consumption, and feed cost were significantly reduced(P<0.05) compared to the C, while the hen-day egg production was significantly improved. However, the average egg weight was not influenced by the feeding system. Due to the reduced daily feed, ME, and CP intakes, and the improved egg production, the conversions of feed, ME, CP, and feed cost required per kg egg mass were also significantly improved (P<0.05) in splits diet groups. Among split diet groups, the T$_2$ group fed the diet devoid of Ca supplement from the conventional laying hen diet in a.m., and the diet containing the Ca supplement 2 times the conventional diet in p.m., was superior in conversion of nutrients and feed cost per kg egg mass to the other split diet groups. It was concluded that daily feed and nutrients cousumption and daily feed cost could be reduced 5∼6％ while hen-day egg production could be improved about 4％, so that about 10％ of the feed and nutrients and feed cost per kg egg mass could be spared by introducing the split diet feeding for a.m. and p.m. based on T$_2$ treatment in laying hens.

• 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.

• Asian-Australasian Journal of Animal Sciences
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• v.16 no.11
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• pp.1565-1571
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• 2003

Physiological mechanisms, involved in unusual ovulatory sequences in domestic hen are remaining undefined. One hundred individually caged white leghorn birds were divided into two equal groups viz. control and treatment, and 2-bromo-$\alpha$-ergocryptine, was administered to birds in the treatment group to modulate prolactin (PRL) secretion from anterior pituitary gland. The effect of modulation of PRL concentrations on egg production, sequence length and intersequence pause length were studied by analysis of oviposition records of the birds from 24 to 72 weeks of age. The surviving 48 birds in the control and treatment groups averaged $34.58{\pm}1.7$ and $25.67{\pm}1.15$ sequences of oviposition, with a mean sequence length of $9.92{\pm}0.63$ and ${\pm}1.12$ days respectively. Most of the birds had a single characteristically long sequence during the entire reproductive cycle, which averaged $46.04{\pm}3.09$ days in the control birds and $59.33{\pm}4.44$ days in the treated birds. 2-bromo-$\alpha$-ergocriptine treatments had significantly decreased (p$\leq$0.01) the circulating concentrations of PRL compared to the birds of the control group. This resulted in a significant increase (p$\leq$0.01) in the number of laying days in birds of the treatment group with a concomitant decrease in the intersequence pause length. The decreased PRL levels during prime sequences in birds of the both groups, reveals the negative role of the circulating PRL levels on egg production with concomitant shorter intersequence pause length. Hence, modulation of PRL with dopamine agonist may enhance the reproductive efficiency of hens later in life.