• Korean Journal of Poultry Science
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• v.48 no.4
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• pp.169-176
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• 2021

An experiment was conducted to investigate the effects of varying levels of hydrolyzed yeast on egg production and egg quality in aged laying randomly allotted to three dietary treatments such that egg production was similar in each treatment (6 replicates of 10 birds each). The layers were fed diets containing 0, 0.1, or 0.2% hydrolyzed yeast for eight weeks. No significant difference was observed in egg production during the first half of the experiment. Egg production and daily egg mass in groups fed diets containing hydrolyzed yeast were significantly higher (P<0.05) than those of the control groups during the second half of the experiment. Egg weight was not affected by the dietary treatment. Eggshell strength and thickness in groups fed diets containing hydrolyzed yeast were significantly higher than those of the control groups during the overall experimental period (P<0.05). Although no significant differences were observed in the Haugh units, yolk color in the group fed diets containing 0.1% hydrolyzed yeast was significantly higher than that in the control group (P<0.05). The mammillary layer thickness increased in a linear manner and significantly following treatment with dietary hydrolyzed yeast (P<0.05). Antibody titer against avian influenza virus in the group fed diets containing 0.2% hydrolyzed yeast was significantly higher (P<0.05) than that in the control group. In conclusion, dietary hydrolyzed yeast improved egg production and eggshell quality of laying hens in the late stages of production.

• Journal of Animal Science and Technology
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• v.48 no.1
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• pp.59-68
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• 2006

This experiment was conducted to investigate the effects of dietary supplementation of activated charcoal (AC) mixed with wood vinegar on performance and egg quality in laying hens. A total of one hundred ninety two, 56-wk-old Lohmann brown laying hens were divided into four groups, consisting four replicates of 12 birds each and fed one of the four experimental diets containing AC 0%, AC 0.5%, AC 1%, AC 2% for 5 wks. The blood profiles and contents of total lipid and cholesterol, fatty acid profiles in egg yolk were determined. There were no significant differences in laying performance, feed intake and vitelline membrane strength among the treatments. The eggshell breaking strength and Haugh unit were significantly increased in 2% AC group compared to the other groups (P<0.05). Egg yolk index in 2% AC group was significantly higher (P<0.05) than those of the control and 0.5% AC group and yolk color was significantly improved by the dietary AC (P<0.05). The levels of serum total cholesterol, HDL-cholesterol and enzyme activities were not influenced by feeding AC. Total lipid of egg yolk in 1 % and 2% AC groups was significantly decreased (P<0.05) compared to that of the control, although there was no significant difference in yolk cholesterol. In conclusion, the addition of activated charcoal with wood vinegar in layer diet resulted in improving egg quality by means of enhancing eggshell breaking strength, Haugh unit, yolk index and yolk color.

• Journal of Animal Science and Technology
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• v.54 no.2
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• pp.125-131
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• 2012

The study was conducted to investigate the effects of dietary supplementation of Macsumsuk and herb resources on the egg performance and quality in Korean native crossbred chickens. A total of three hundred sixty improved Korean native crossbred chickens in primary laying period were randomly allocated to four treatments (30 birds/treatment ${\times}$ 3 replications) for eight weeks. Dietary treatments included CON (basal diets), T1 (basal diets + 0.3% Macsumsuk), T2 (basal diets + 0.3% herb resources) and T3 (basal diets + 0.3% Macsumsuk + 0.3% herb resources). No significant differences were found for feed intake, egg weight and average egg production (P>0.05), however, cracked egg rate was higher in CON than in T1-T3, especially T3 was the lowest (P<0.05). The crude fat content of whole eggs, CON (11.20%) was higher (P<0.05) than the experimental treatments (9.67%-10.01%). Haugh unit, yolk color, eggshell thickness, and eggshell breaking strength tended to be higher in T1 and T2, but there were no significant differences (P>0.05). However, the experimental treatments were significantly higher than CON (P<0.05) for eggshell breaking strength, and T3 (14.91 mg/g) contained lower (P<0.05) cholesterol in egg yolk than other treatments. For fatty acid composition in egg yolk, CON group showed higher saturated fatty acid contents than the experimental treatments, but T1 (67.00%), T2 (66.78%) and T3 (66.82%) were higher than CON for unsaturated fatty acids (P<0.05). In conclusion, supplementating Macsumsuk and herb resources together in diets of Korean native crossbred chickens could decrease egg yolk cholesterol and improve egg quality.

• Korean Journal of Poultry Science
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• v.38 no.3
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• pp.205-211
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• 2011

This work was carried out to investigate the effect of the induced molting diet based on wheat bran on the postmolt performance of layers. Two hundred White Leghorn layers (65-old-wk) with over 80% egg production were used for 8 weeks in this work. Treatments were non-molt control (CO), fasting treatment for 10 days (FW), molt treatment with used molting diet for 4 wk (UM), molt treatment with molting diet based on corn-wheat bran for 4 wk (CW), and molt treatment with molting diet based on wheat bran for 4 wk (WM) as 5 treatments (4 replications/treatment and 10 birds/replication). Feed intake decreased at molting treatments at first weeks and increased after the 3rd week compared to control (P<0.05). Body weight (BW) loss were 18.6% of initial BW at first week in FW treatment, and were 11.4, 14.2 and 17.4% in UM, CW and WM treatments at 4th weeks (P<0.05). Egg production decreased at 1 week in molt treatment and stopped at 2 week in FW, whereas, other molting treatments didn't stop laying eggs. The birds started to lay egg at 4 week in FW and recovered at 5 week in other molting treatments. Egg quality (eggshell thickness, eggshell breaking strength, haugh unit) was high in molting treatments compared with control at 8th weeks (P<0.05). Finally, molting diet based on wheat bran affected BW loss and egg quality such as eggshell thickness, eggshell breaking strength and haugh unit.

• Korean Journal of Poultry Science
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• v.35 no.3
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• pp.267-274
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• 2008

There are many kinds of anti-oxidant materials in natural plant resources. The Siberian ginseng and Eucommia are well known as anti-oxidant and medicinal plants. To investigate the effect of their anti-oxidant-like activity on telomere quantity and egg quality, diets containing Siberian ginseng leaf and Eucommia leaf at 0.5% and 1% were given Hyline Brown commercial laying hens during two periods of age: 20 to 30 wks and 60 to 70 wks. The amount of telomere in lymphocyte, liver, ovary, heart and lung was analyzed by quantitative fluorescence in situ hybridization using telomeric DNA probe. Egg weight, albumin height, Haugh unit, egg yolk color, egg shell color, egg shell thickness, egg shell weight and egg shell density were measured to analyze egg quality. The chickens consuming diets Siberian ginseng and Eucommia had higher telomeric DNA in lymphocytes than control chickens in younger layers whereas no significant differences were detected in all target cells analyzed from older layers. Egg quality was increased in younger hens with dietary supplementation as determined by egg weight, albumin height and Haugh unit but there were no effects in older hens. These results imply that dietary supplementation of Siberian ginseng and Eucommia in layers improves bio-activity and egg quality at early laying stage.

• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.4
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• pp.614-620
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• 2004

This study was to determine the effect of dietary $\beta$-cyclodextrin ($\beta$CD) on egg quality and cholesterol content of egg yolk. One-hundred 28-week-old laying hens were randomly distributed into five groups of twenty hens each and maintained in individual laying cages for 10 weeks of the experiment. They were assigned to the five treatments of experimental layer diets containing 0, 3, 5, 7 or 10% pure $\beta$CD of diets. Food intake, egg production and egg weight varied slightly and insignificantly in the hens fed with 0, 3, 5 or 7% $\beta$CD-added diets. But food intake, egg production, and egg weight were uniformly lower (p＜0.05) in the hens fed with 10% $\beta$CD-added diets. Food conversion rate, when expressed per number egg, was impaired (p＜0.05) without having an obvious relation to the dietary $\beta$CD level. No difference in haugh unit, egg yolk color, and egg shell thickness was found among treatment. The cholesterol content of egg yolks was significantly decreased (p＜0.05) to 3.76, 5.12, 5.49 and 6.48 mg/g yolk in $\beta$CD 3, 5, 7 and 10% treatments respectively when compared to that of the $\beta$CD 0% group. The cholesterol content of eggs, when expressed in mg/60 g egg, was greatly (p＜0.05) decreased to 54, 71, 77 and 86 mg in $\beta$CD 3, 5, 7 and 10% treatments when compared to that of the $\beta$CD 0% group. The most striking effects (p＜0.05) were observed in $\beta$CD 5% and 7% treatments, whose cholesterol content decreased from 28.19% to 30.23%. In conclusion, $\beta$CD added-diets fed to laying hens can reduced the cholesterol content of egg yolk, and this new type of egg yolk with lower cholesterol can be considered a functional livestock food.

• Korean Journal of Poultry Science
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• v.35 no.2
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• pp.171-176
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• 2008

Animal welfare advocates, claim that the induced molting by fasting be avoided. This study was conducted to evaluate the effect of molting induced by various feeding methods on productivity and egg quality in laying hens. We used 400 flocks of 60-week-old leghorn laying hens in four treatments(five replicates of 20 hens each): fasting method (C), feeding single corn grain diet (T1), feeding single wheat bran diet (T2) and feeding single alfalfa meal diet (T3). As the result of the experiment, egg production and daily egg mass significantly decreased only in T1 compared with the control during the $1{\sim}4th$ week after the secondary egg laying (P<0.05). Although the amount of feed intake was significantly less in T1 group during the $1{\sim}4th$ week compared to the control, no significant difference was detected during the total period (P>0.05). In addition, no significant difference of feed conversion was observed between treatment groups. In terms of egg quality, the egg shell thickness was significantly improved in T1 group than the control group by feeding only corn at the 10th and 14th week after the secondary egg laying (P<0.05), but the significant decrease was observed at the corn (T1) and wheat bran (T2) fed treatment groups than the control group at the 26th week of the experiment (P<0.05). The eggshell strength and haugh unit did not show any difference by the molting methods. Egg yolk color was significantly decreased in T1 and T2 group than the control group at the 6th week (P<0.05). However, T1 and T2 group resulted to show significantly high egg yolk color at the 18th week of the experiment (P<0.05). As the result of the experiment, no large difference was observed in the productivity by the feeding molting method and by the fasting induced molting method. In addition, the single diet fed feeding induced molting method by using alfalfa revealed to show more satisfactory trend than the corn or wheat bran single diet fed feeding induced molting methods even if no statistically significant difference was found in terms of egg productivity.

• Korean Journal of Poultry Science
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• v.37 no.2
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• pp.117-123
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• 2010

This work was carried out to investigate the effect of the induced molting with low-protein and energy diet on the postmolt performance of layers. Eighty White Leghorn layers (61-old-wk) with over 80% egg production were used for 12 weeks in this work. Treatments were non-molt control (CO), fasting treatment for 10 days (FW), molt treatment with low-protein and low-energy molting diet for 3 weeks (LO), and molt treatment with standard molting diet for 3 weeks (ST) as 4 treatments (2 replications/treatment and 10 birds/replication). Body weight (BW) loss was 26.5% of initial BW at 2 week in FW treatment, and was 17.3% and 14.2% in both LO and ST treatments (P<0.05). Layers in molting treatments were fed with commercial layer diet after completion of molting since BW of layers was recovered for 7 weeks. Heart weight ratio was shown as 0.47, 0.43, 0.46 and 0.46% at CO, FW, LO and ST treatments, respectively, and liver weight ration of body weight was shown as 2.56, 1.30, 1.47 and 1.52%, respectively. Thus, those of molting treatments decreased compared to non-molt control (P<0.05). Oviduct weight ratio were shown as 3.95, 1.17, 1.54 and 1.67%, respectively, and similar with the results of liver (P<0.05). Feed intake decreased at LO and ST treatments during molting period and increased from the 5th week compared to control. Egg production decreased at 1 week in molt treatment and stopped at 2 week in FW, 3 week in LO, and 4 week in ST treatments. The birds started to lay egg at 4 week in FW and at 5 week in LO and ST treatments. Egg production was recovered until 50% at 6 week in FW and was recovered as 66.1 and 71.6% at 8 week in LO and ST treatment, respectively. Egg weights were similar among all treatments. Eggshell thicknesses were 0.41, 0.47, 0.46 and 0.46 mm at CO, FW, LO and ST treatment, respectively, but the higher in molt treatments than control (P<0.05). Eggshell breaking strength was 3.83 and 3.81 kg/$cm^2$ in FW and LO treatment, respectively, and high compared to control. However, eggshell breaking strengths were 3.54 and 3.78 kg/$cm^2$ and were not statistically different. Haugh units were 75.6, 81.1, 80.6 and 79.9 in 4 treatments and high in molt treatment. Finally, dietary low-protein and low-energy may induce molt as few effect on performance of layers.