From 2020, Korean Animal and Plant Quarantine Agency has reset the withdrawal time (WT) for veterinary drugs typically used in livestock in preparation for the introduction of positive list system (PLS) program in 2024. This study was conducted to reset the MRL for tiamulin (TML) in broiler chickens as a part of PLS program introduction. Forty-eight healthy Ross broiler chickens were orally administered with TML at the concentration of 25 g/L (TML-1, n=24) and 50 g/L (TML-2, n=24) for 5 days through drinking water, respectively. After the drug treatment, tissue samples were collected from six broiler chickens at 1, 2, 3 and 5 days, respectively. According to the previously established analysis method, residual TML concentrations in poultry tissues were determined using LC-MS/MS. In TML-1, TML in all tissues was detected less than LOQ at 2 days after drug treatment. In TML-2, TML in liver and kidney was detected more than LOQ at 2 days after treatment. According to the European Medicines Agency’s guideline on determination of withdrawal periods, withdrawal periods of TML-1 and TML-2 in poultry tissues were established to 0 and 2 days, respectively. In conclusion, the estimated WT of TML in poultry tissues is shorter than the current WT recommendation of 5 days for TML in broiler chickens.

This study was conducted to reset the maximum residue limit (MRL) for didecyldimethylammonium chloride (DDAC) in broiler chickens. The disinfectant containing DDAC (10%, w/w) was diluted 160 times and evenly sprayed on the bodies of twenty-four broiler chickens at a rate of 15 mL per day per bird for 7 days. After the disinfectant treatment, tissue samples were collected from six broiler chickens at 0.25, 1, 3 and 5 days, respectively. Residual DDAC concentrations in poultry tissues were determined using LC-MS/MS. Correlation coefficient (0.99 >), the limits quantification (LOQ, 2.0~10.0 μg/kg), recoveries (86.9~118.6%), and coefficient of variations (<19.98%) were satisfied the validation criteria of Korean Ministry of Food and Drug Safety. In all tissues except for liver, DDAC was detected more than LOQ at 5 days after the disinfectant treatment. In liver tissues, DDAC was detected more than LOQ at 3 days after treatment. According to the European Medicines Agency’s guideline on determination of withdrawal periods, withdrawal period of DDAC in poultry tissues was established to 26 days. In conclusion, the developed analytical method is sensitive and reliable for detecting DDAC in poultry tissues. When DDAC disinfectant is sprayed on a poultry house in the presence of broiler chickens, it is necessary to keep the disinfectant from contacting the body of the livestock.

This study investigated ethopabate (EPB) residues in edible tissues of broiler chickens given in drinking water and established the withdrawal time (WT) of EPB in poultry tissues. Twenty-four healthy Ross broiler chickens were orally administered with EPB at the concentration of 3.8 mg/L for 14 days (EPB-1, n=24) and 15.2 mg/L for 7 days (EPB-2, n=24) through drinking water, respectively. After the drug treatment, tissue samples were collected from six broiler chickens at 0, 1, 3, and 5 days, respectively. EPB residue concentrations in poultry tissues were determined using LC-MS/MS. Correlation coefficient values ranged from 0.9980 to 0.9998, and the limits of detection and quantification (LOQ) were 0.03~0.09 and 0.1~0.3 μg/kg, respectively. Mean recoveries in muscle, liver, kidney and skin/fat tissues were 95.9~109.8, 108.7~115.3, 89.9~96.6 and 86.7~96.8%, respectively, and coefficient of variations were less than 17.11%. At the end of the drug-administration period (0 day), EPB was detected at levels under the LOQ in all tissues from both the EPB-1 and EPB-2 groups. According to the results of EPB residue in Ross broiler tissues, withdrawal periods of both EPB-1 and EPB-2 in poultry tissues were established to 0 day. In conclusion, the developed analytical method is suitable for the detection of EPB in poultry tissues, and the estimated WT of EPB in poultry tissues will contribute to ensuring the safety of Ross broiler chickens.

From 2020, Korean Animal and Plant Quarantine Agency has reset the withdrawal time (WT) for veterinary drugs typically used in livestock in preparation for the introduction of positive list system (PLS) program in 2024. This study was conducted to reset the MRL for amprolium (APL) in broiler chickens as a part of PLS program introduction. Forty-eight healthy Ross broiler chickens were orally administered with APL at the concentration of 60 mg/L (APL-1, n=24) for 14 days and 240 mg/L (APL-2, n=24) for 7 days through drinking water, respectively. After the drug treatment, tissue samples were collected from six broiler chickens at 0, 1, 3 and 5 days, respectively. Residual APL concentrations in poultry tissues were determined using LC-MS/MS. Correlation coefficient (0.99 >), the limits quantification (LOQ, 0.3~5.0 μg/kg), recoveries (81.5~112.4%), and coefficient of variations (<15.5%) were satisfied the validation criteria of Korean Ministry of Food and Drug Safety. In APL-1, APL in all tissues except for kidney was detected less than LOQ at 3 days after drug treatment. In APL-2, APL in liver and kidney was detected more than LOQ at 5 days after treatment. According to the European Medicines Agency’s guideline on determination of withdrawal periods, withdrawal periods of APL-1 and APL-2 in poultry tissues were established to 3 and 2 days, respectively. In conclusion, the developed analytical method is sensitive and reliable for detecting APL in poultry tissues. The estimated WT of APL in poultry tissues is longer than the current WT recommendation of 2 days for APL in broiler chickens.

This study was conducted to evaluate the effects of ImmunoSEB as an immune-booster additive on the performance of broiler chicks. A total of 1150 broiler chickens were randomly allotted to three treatments on the basis of body weight (10 pens per treatment with 40 broilers in each pen): the control (CON), CON + ImmunoSEB 0.025% in feed (SEB25), and CON + ImmunoSEB 0.050% in feed (SEB50). The experiment was conducted for d 42 in three phases (phase 1, d 0–14; phase 2, d 15–28; and phase 3, d 29–42). There were significant differences in the average daily gain (ADG) and feed intake. The ADG at d 14 in the SEB50 treatment was greater than that in the CON treatment. The overall ADG in the SEB50 treatment was greater than that in the CON treatment. During d 0–14, the feed intake of chickens in the SEB50 treatment increased compared to that in the CON treatment. The crude protein and lysine digestibility improved in the SEB25 and SEB50 treatments compared to those in the CON treatment at d 28. Superoxide dismutase concentration significantly increased in the SEB50 treatment compared to that in the CON treatment. The interleukin-1β and tumor necrosis factor-α concentrations were higher in the cecum of chickens in the CON treatment than in the SEB25 and SEB50 treatments. A lower population of E. coli was detected in the ileum and cecum of broilers fed the SEB50 diet compared to those of broilers fed the CON diet. The overall result showed the beneficial effects of using ImmunoSEB at a dose of 0.050% in broiler chickens.

케냐에서 토종 닭의 낮은 생산성은 부분적으로 열악한 관리 관행, 특히 적절한 건강 관리, 열악한 사육장 및 영양 부족 때문으로 알려져 있다. 이 연구의 목표는 케냐에서 산란계를 위한 신배합사료 배합 가능성 확인과 신배합사료 식 A와 B의 급이를 통한 계란 생산성을 분석하고자 하였다. 1. 2018년 7월 1일부터 2021년 3월 31일까지 Embu 및 Tharaka Nithi 카운티에서 닭 생산에 관심이 있는 농부 그룹을 선정하였다. 농부 그룹 선정에 사용 된 기준은 닭의 수, 닭 사육 및 장비에 대한 투자 수준, 사료 혼합에 대한 관심, 농가 집단의 응집력, 교육 수준 및 집단 구성원의 연령 등 이었다. 2. 총 3,968명의 농업인이 산란계를 위한 신배합사료 식 A와 B에 따른 사료조제 및 이용에 참여하였으며, 총 136,683 kg의 배합 사료를 조제하였다. Embu 지역에서는 2,774명의 농업인이 53,770 kg을, Tharaka Nithi 지역에서는 1,194명의 농업인이 41,313 kg의 신배합사료를 각각 조제하였다. 3. 신배합사료 식 A와 식 B가 케냐 표준 국 [KEBS] (2014)의 품질 표준을 충족하는지 평가하기 위해 사료 영양 성분을 분석한 결과, 신배합사료 식 A와 식 B, 상업용 사료 모 두 건물중(dry matter) 이 88%이상으로 표준을 충족 하였고, 최대 25% 이하의 회분(ash), 15% 이상의 조단백질(crude protein) 과 7.5% 이하의 조섬유(crude fiber) 기준과 대부분 부합하였다. 4. 신배합사료 식 A와 시판용 사료를 급여한 산란계 10마리의 일일 평균 계란 생산량을 비교한 결과 Embu 지역에서는 7.2개와 5.1개, 그리고 Tharaka Nithi 지역에서는 8.2개와 5.7 개로 유의적으로 높은 생산성 차이가 확인되었다. 5. 신배합사료 식 B와 시판용 사료를 급여한 산란계 10마리의 일일 평균 계란 생산량을 비교한 결과 Embu 지역에서는 7.3개와 4.9개, 그리고 Tharaka Nithi 지역에서는 7.1개와 5.2 개로 유의적으로 높은 생산성 차이가 확인되었다.

This study identified single nucleotide polymorphisms (SNPs) that affect the body weight of chickens. Analysis of body weight showed that the Cornish breed had the highest body weight, and the Korean native chicken (Gray Brown) had the lowest body weight. TSH is composed of an α-subunit and a β-subunit, and the TSH-β gene encoding the β-subunit has been reported to be associated with obesity. In chickens, it is located on chromosome 26 and is reported to be associated with growth. The calcium-sensing receptor gene (CaSR) plays a role in the regulation of extracellular calcium homeostasis and is responsible for calcium absorption in the urinary tract, which affects the eggshell quality in poultry. It was shown that TSH-β was strongly correlated with weight in Cornish and Korean native (Gray Brown) chickens, particularly in those with the CC trait. However, CaSR showed no association with body weight in poultry; it was associated with calcium and the eggshell. Thus, selection for TSH-β can be used to produce individuals with more favorable traits in terms of body weight.

Quantitative real-time polymerase chain reaction (RTqPCR) is a rapid and precise method of analysis to quantify the level of gene expression and is widely used in the diagnosis of diseases and quantitative analysis of genes. In RT-qPCR analysis, a reference gene (or housekeeping gene) is used for normalization of experimental results. Since this method of analysis detects a small quantity of the product, it is highly sensitive and it is important for the accuracy and reproducibility of the experiment to select a reference gene suitable for gene expression studies. As the expression levels of the reference gene are affected under different conditions, in order to determine the suitability of the housekeeping gene used as the reference gene, it is necessary to verify the expression stability. In the current study, the stability of the expression of 11 housekeeping genes (B2M, SDHA, GAPDH, RPL13, VIM, EEF1A1, HPRT1, GUSB, RPL19, ACTB, and ABL1) was investigated in the tissues of long-tailed chickens (heart, thigh, and breast). Expression stability evaluation was analyzed with four software: BestKeeper, NormFinder, geNorm, and RefFinder. In our study, GAPDH in heart tissue, HPRT1 in thigh tissue, and RPL13 in breast tissue were selected as the most stable reference genes. Evaluation of the expression stability of housekeeping genes can provide important data in gene expression studies by selecting an appropriate reference gene according to various conditions.

Colibacillosis, which is caused by Escherichia coli (E. coli), is one of the most common infectious diseases affecting poultry and causes the great economic losses to poultry production worldwide. The present study investigated the presence of E. coli in broiler chickens affected by colibacillosis and reared at various locations in Tiaret Province as well as evaluated the susceptibility of isolated E. coli strains to various antimicrobial agents. A total of 110 samples collected from 55 broiler chickens representing liver (n=55) and spleen (n=55) showing lesions suspected to be colibacillosis were analyzed by conventional methods, and 33 E. coli isolates were tested on a panel of seven antimicrobial agents using the disk diffusion method. The overall isolation rates of E. coli were 60% (33/55) and 50.9% (56/110) in whole chickens and organs, respectively. There was no variation in the isolation rate between organs: 50% (28/56) for liver and 50% (28/56) for spleen. All E. coli isolates tested showed 100% resistance to Nalidixic acid and Ofloxacine, followed by 93.93%, 90.90%, and 51.51% resistance to Tetracycline, Trimethoprim-sulfamethoxazole (Co-trimoxazole), and Chloramphenicol, respectively. However, low resistance to Gentamycin was observed (12.12%), whereas all E. coli isolates were susceptible to Colistin sulfate. Multidrug resistance was observed in 96.96% (32/33) of the isolates tested. We conclude that E. coli was largely present in broiler chickens affected by colibacillosis in Tiaret Province, and multidrug-resistant E. coli isolates showed high resistance to multiple antibiotics.

서울시내에 위치한 프랜차이즈 매장과 대형마트 내 판매되고 있는 4종(후라이드, 양념, 간장, 치즈가루 치킨)의 치킨제품 123건에 대하여 당과 나트륨 검사를 실시하였다. 전체 치킨제품의 평균 당 함량은 100 g 당 4.5 g이었으며, 양념치킨(8.7 g), 치즈가루 치킨(4.3 g), 간장치킨(3.6 g), 후라이드 치킨(0.6 g) 순으로 나타났다. 평균 나트륨 함량은 전체 치킨제품의 경우 100 g 당 552.4 mg이었으며, 치즈가루 치킨(627.0 mg), 간장치킨(536.3 mg), 양념치킨(511.2 mg), 후라이드 치킨(448.0 mg) 순으로 나타났다. 프랜차이즈와 대형마트 내 판매 치킨제품을 비교하였을 때, 평균 당 함량의 경우 100 g당 대형마트 내 판매 후라이드 치킨(0.8 g) 과 양념치킨(8.9 g)에서 모두 프랜차이즈의 후라이드 치킨 (0.5 g)과 양념치킨(8.6 g)보다 높았으며, 프랜차이즈와 대형 마트 내 판매 제품에 따른 유의적으로 차이를 보였다(P<0.05). 평균 나트륨 함량의 경우 100 g당 프랜차이즈 양념치킨 (516.0 mg)과 대형마트의 후라이드 치킨(471.5 mg)이 높은 값을 보였으며, 유의적인 차이는 보이지 않았다. 포장량 전체를 섭취했을 경우, 평균 당 함량의 섭취비율은 후라이드 치킨은 모두 WHO에서 권고하는 1일 당류 섭취권고량인 50 g 이하였고, 간장치킨(47.6%)과 치즈가루 치킨(55.4%)은 절반 수준이었으나, 양념치킨은 프랜차이즈(140.4%)와 대형마트(148.8%) 제품 모두 권고량을 넘어섰다. 나트륨은 WHO의 1일 나트륨 섭취권고량인 2,000 mg 대비 섭취비율이 후라이드 치킨은 프랜차이즈(140.1%)와 대형마트(170.3%) 제품과 간장치킨(167.9%)에서 높게 나타났다. 특히, 양념치 킨은 프랜차이즈(203.7%)와 대형마트(208.4%) 제품 모두와 치즈가루 치킨(202.4%)에서 섭취권고량의 2배를 넘어선 것으로 나타났다.

본 연구는 열 스트레스 (heat stress, HS)에 노출된 브로일러에서 혼합 생균제의 급여가 혈 액 생체지표, 면역반응, 맹장 미생물 및 생산성에 미치는 영향을 조사하였다. 총 400마리의 브로일러 수 컷 (Ross 308)을 각각 100마리씩 4그룹, C (대조군, 실온 25℃), HS (열 스트레스 33℃), HSP (HS플 러스 혼합 생균제 500, 750 mg/kg) 그룹으로 배치하였다. 브로일러의 증체량, 사료섭취, 사료요구율 및 면역기관 무게는 HSP 그룹에서 HS 그룹과 비교했을 때 증가하였다. 혈액 IgG, lymphocytes 농도는 HS 그룹에서 HSP그룹과 비교했을 때 증가하였고, heterophil과 lymphocyte(H:L)비율, 코르티코스테론 농도 및 폐사율은 낮았다. 맹장의 Lactobacillus는 HS 그룹과 비교했을 때 HSP 그룹에서 증가하였으나 Escherichia coli (E. coli), coliform bacteria, aerobic bacteria는 낮아졌다. 본 연구결과는 열 스트레스 에 노출된 브로일러에게 B. subtilis, S. galilaeus 및 Sphingobacteriaceae등 3가지 균주가 포함된 혼합 생균제를 급여해주면 면역반응 증진, 미생물 균형을 유지해줌으로써 폐사율을 낮추고 생산성을 개선할 수 있음을 시사해준다.

The purpose of this study was to investigate the effects of ionized calcium treatment on total bacterial cross-contamination of chicken carcass surface in the slaughtering process. The growth of Escherichia coli was strongly inhibited in a medium prepared by using a 0.5% ionized calcium solution. The total bacterial cross-contamination of chicken carcass surface and the scalding water was significantly increased as the number of scalding was increased (p<0.05). The total bacterial cross-contamination of chicken carcass surface reached a plateau without a further increase as scalding was performed consecutively for 10 or more times. The total bacterial cross-contamination of the scalding water was significantly increased as the number of scalding was increased (p<0.05). The total bacterial cross-contamination of chicken carcass surface of the chickens raised on a floor type farm was significantly higher than that of the chickens raised in a battery cages (p<0.05). The total bacterial cross-contamination of chicken carcass surface of the chickens raised on a floor type farm was significantly lower in the 0.5% ionized calcium solution treatment group than in the control group (p<0.05).

Human interferon alpha 2b (hIFNα-2b) is an important immune regulator widely used in clinic, for the treatment of chronic hepatitis, hairy cell leukemia, chronic myelogenous leukemia and multiple myeloma, etc. The clinically used hIFNα-2b is generally produced by E. Coli, which lacks the post-translational O-glycosylation of naturally synthesized protein, and has a short serum half-life. In this study, we report the successful generation of transgenic chickens that produce hIFNα-2b in the egg white using a feline immunodeficiency virus (FIV)-based lentiviral vector. In preliminary in vitro study, the hIFNα-2b gene under the control of CMV promoter expressed as much as 2,650 ng/㎖ in CEF-LNC-hIFNα-2bW cell. A FIV vector packaged with vesicular stomatitis virus G glycoprotein (VSV-G) was injected underneath the blastoderm of freshly laid chicken eggs (stage X) to produce a hIFNα -2b transgenic chicken. Out of 187 injected eggs, 55 chicks were hatched after 21 days of incubation, and 27 of the G0 hatched chicks expressed the vector-encoded hIFNα-2b gene. The expression of recombinant hIFNα-2b in transgenic chickens constitutes an important step towards low-cost and full biological activity production of this protein drug in bioreactor. This work was supported by the Bio-industry Technology Development Program, Ministry of Agriculture, Food and Rural Affairs, Republic of Korea, and by a grant from the Next-Generation BioGreen 21 Program (No. PJ011178), Rural Development Administration, Republic of Korea.

In the present study, using a MoMLV-based retrovirus vector, we successfully generated a new transgenic chicken line expressing high levels of hEPO. A replication-defective Moloney murine leukemia virus (MoMLV)-based vectors packaged with vesicular stomatitis virus G glycoprotein (VSV-G) was injected beneath the blastoderm of non-incubated chicken embryos (stage X). One rooster was mated to wild-type hens to produce 748 G1 progeny. PCR analysis of blood samples from these progeny revealed that there were seven G1 transgenic offspring, corresponding to a 0.9% germline transmission rate. Subsequently, Southern blot analysis of the genomic DNA from three G1 transgenic chickens was carried out to verify the stable genomic integration and copy number of the transgene in the genome. Quantitative analyses of the blood samples taken from G1 transgenic chickens resulted in 4,150 ～ 10,823 IU/㎖ (34.6 ～ 90.2 ㎍/㎖) of hEPO in the blood. The biological activity of the recombinant hEPO in transgenic chicken serum was comparable to its commercially available counterpart. Red blood cell numbers were more than three-fold higher in the transgenic chickens compared to the non-transgenic chickens. Successful germline transmission of the transgene was also confirmed in G2 transgenic chicks produced from crossing G1 transgenic roosters with non-transgenic hens. We confirmed that 13 transgenic chicks of 45 G2 progeny, corresponding to a 28.9% germline transmission rate. These results will help establish a useful transgenic chicken model system for studies of embryonic development and for efficient production of transgenic chickens as bioreactors. This work was supported by the Bio-industry Technology Development Program, Ministry of Agriculture, Food and Rural Affairs, Republic of Korea, and by a grant from the Next-Generation BioGreen 21 Program (No. PJ011178), Rural Development Administration, Republic of Korea.

Recently, the consumption of chickens meat has been gradually increased in Korea. However, most of the chickens breeds in Korea were imported from overseas. This study was conducted to evaluate the genetic distances and single nucleotide polymorphism by the mtDNA D-loop control analysis method for the Korean native chickens(red plumage, red-line plumage, Ogol) and white leghorn. For the initial investigation of the relationships between Korean native chickens(red plumage(KCR), red-line plumage(KCRD), Ogol(KCO)) with white leghorn breeds, the sequences from D-loop control region in mitochondrial DNA (mtDNA) was used. The results from phylogenetic analysis indicated that both KNC and white leghorn breeds were classified well with wild duck breeds. However, KCR was not discriminated well with KCRD. The haplotype analysis indicated that KCR and KCO have ten different haplotypes with nineteen SNPs. Three haplotypes (haplotype 1, 2, 3, 5, 17) were shared both in KNC(KCR, KCRD) and KCO. On the other hand, haplotype 4, 6, 7 was appeared only KCR and haplotype 13, 16, 18 were identified only in KCRD population. In addition, haplotype 8, 9, 11, 12, 14, 15, 19 was appeared only KCO. With further verifications, the results presented here can be used for the on servation and commercialization of the Korean native chickens. This work was supported by a grant from the “Livestock Preservation of Genetic Resources", Rural Development Administration, Republic of Korea.

This study was conducted to evaluate the genetic distances and specific DNA makers by the randomly amplified polymorphic DNA (RAPD)-PCR method for the Korean native chickens(red plumage, red-line plumage, Ogol) and white leghorn. Genomic DNA was extracted from plumage from chickens after they were slaughtered. The extracted DNA was observed by nano-spectrometer. RAPD analysis was performed using 13 different primers. Statistical analysis was made for the estimation of the genetic distance among the chicken’s and the cluster tree was drawn by using MEGA 5.05 software. Genetic relations among them were determined by RAPD analysis. The polymorphic bands were observed 72% and the rest of 28% was monomorpic. The largest genetic distance (2.266) was found between the native chickens(red, red-line) and the ogol chickens by UPGMAP method and the closest distance was observed between the ogol in korean chickens as expected. The highest genetic distance between them was estimated 2.266 and in the dendrogram analysis, among I and II within cluster II, most of the ogol chickens were in IIB, indicating the expression of the ogol color could be due to original and the ancestral genetic crossing. Thus, this genetic distance can be useful as the differential genomic information in the normal(red plumage, red-line plumage) and ogol of korean native chickens. This work was supported by a grant from the “Livestock Preservation of Genetic Resources", Rural Development Administration, Republic of Korea.

The HNF4α (hepatocyte nuclear factor 4, alpha) is a hepatic transcription factor related to the lipid metabolism and regulation of insulin secretion in humans. The current study about commercial broiler reported that the A543G single nucleotide polymorphism (SNP) within HNF4α gene has an effect on fat deposition and wing yield in the chicken. This study was performed to investigate the association between the SNP within HNF4α gene and growth trait and to verify the applicability as a molecular marker for the improving the performance in Korean native chickens (KNCs). A total of 764 KNCs was collected from the livestock farm of Gyeongnam National University of Science and Technology in Korea and genotyped by PCR-RFLP. The body weight measured at birth, 2, 4, 6, 8, 10, 12, 14, 15, 16, 18, 20, 24, 28, 32, 36, and 40 weeks of age for the association analysis between chicken growth and the SNP genotype. Statistical analysis of the SNP with phenotypic traits was performed using SAS program. The KNC strain was classified by the genotypes of the A543G SNP. The frequencies of three genotypes were 0.47 (AA), 0.43 (AG) and 0.10 (GG), respectively. The SNP of HNF4α has highly significant association (p<0.001) with all-round growth in KNCs. These results suggest that the A543G SNP within HNF4α gene could be a genetic marker for the breeding in Korean native chickens.

The insulin-like growth factor binding proteins (IGFBPs) is involved in the regulating effects and the biological activities of the insulin-like growth factors (IGFs). Recently, It has been reported that the IGFBP2 gene polymorphism was associated growth and skeletal development in chicken. This study was designed to investigate the association of the C1032T SNP of IGFBP2 gene with growth and egg production traits in Korean native chicken (KNC) population as well as other chicken breeds. A total of 225 chickens from the three breeds (Rhode Island Red, Cornish, Leghorn) and 245 chickens from the six strains of Korean native chickens including Black, Gray, Ogol, Red, White, and Yellow, were genotyped by PCR-RFLP (polymerase chain reaction-restricted fragment length polymorphism) and analyzed the association between their genotypes and economic traits by SAS program. The results showed that the SNP (single nucleotide polymorphism) was significantly associated with multiple traits, including body weight of 150 days (p<0.001 and p<0.05) in the Rhode Island Red and the KNC (White) and egg production number (p<0.05) in the KNC (Black) breed. These results suggest that IGFBP2 C1032T SNP could be used as a DNA marker for the improvement of economic traits in Korean native chicken breeding.

Antibiotics have been used to prevent disease, promote growth rate, and improve feed efficiency. However, the use of antibiotics in livestock has been restricted worldwide due to problems such as bacterial resistance. Therefore, probiotics among alternatives to antibiotics have gained attention in the livestock feed industry these days. This study was conducted to investigate the effects of dietary supplementation with probiotic 379D on safety, growth rate, and feed efficiency. In this study, bacterial strain 379D was isolated from soil and identified as a Bacillus sp. according to 16S rRNA sequence analysis. In an in vitro test, in-gel activity assay and antimicrobial susceptibility test were conducted to evaluate 379D. In an in vivo study, 379D was administered at concentrations of 0.1% and 1% to broiler chickens for 28 days. The results of in-gel activity assay and antimicrobial susceptibility test showed that strain 379D had broad spectrum antimicrobial activity. Furthermore, no adverse 379D-related effects were observed in 0.1% and 1% groups. Feed efficiency was higher in the 379D-treated groups than in the control group. In conclusion, 379D is expected to be used as a safe alternative to antibiotics in a feed supplement and will improve feed efficiency in broiler chickens.