Hen-housed Egg Production Research Articles

닭의 스트레스 연관 표지인자들의 발현도와 생산능력 간의 상관 분석

본 연구는 닭의 개체 별 스트레스 연관 표지의 발현도와 이들의 생산능력 간의 연관성을 살펴보기 위한 것으로 토종종계 25계통을 대상으로 텔로미어 함량, 열 스트레스 단백질(HSPs) 유전자 발현율 및 DNA 손상율을 분석하고, 동일 개체들의 생존율, 성장능력 및 산란능력을 조사하여 이들 간의 상관관계를 분석 고찰하였다. 분석 결과, 생산능력 및 스트레스 표지 값들 간에 계통별로 유의한 차이가 나타났는데, 대체적으로 고체중 순계들의 스트레스 지표가 상대적으로 높았으며, 저체중 교잡계들의 스트레스 지표가 낮게 나타났다. 텔로미어 함량과 생산능력 간의 상관성은 20주령 이후부터 유의한 상관관계를 보였는데, 성장능력과는 약한 부(-)의 상관 양상을, 산란능력 및 생존율과는 약한 정(+)의 상관관계를 나타내었다. HSPs 유전자 발현율과 생산능력과의 상관에서 생존율 및 산란지수와는 저도 및 중도의 부의 상관을 보였고, 체중과는 약한 정의 상관관계를 나타내었다. DNA 손상율 분석 또한 체중과는 약한 정의 상관을, 산란지수 및 생존율과는 중도 및 저도의 부의 상관관계를 나타내었다. 이는 체중이 증가할수록 HSPs 유전자 발현율, DNA 손상율 및 텔로미어 감축량이 증가함을 의미하고, 반면 산란능력 및 생존율이 높을수록 HSPs 유전자 발현율과 DNA 손상율은 낮아지고, 텔로미어 함량은 상대적으로 높다는 것을 시사한다. 스트레스 표지 인자들 간의 상호 관계에서 모든 표지 값 간에 유의한 상관관계가 나타났는데, HSPs 발현값과 텔로미어 함량과는 부의 상관을, DNA 손상율과는 정의 상관을 보이고, 텔로미어 함량과 DNA 손상율과는 높은 부의 상관을 나타내었다. 이상의 스트레스 표지 값과 생산능력 간의 상관분석 결과에 따라 닭에 있어 HSPs 및 DNA 손상율의 증가는 텔로미어 감축을 촉진하고, 이에 따라 개체의 항병성 및 강건성을 저하시켜 산란능력과 생존율에 나쁜 영향을 미치는 것으로 판단된다. This study was conducted to verify the relationships between the expression values of stress-related markers and their production performances in 25 strains of Korean domestic chicken breeds. For stress response markers, the amount of telomeric DNA; expression levels of heat shock protein (HSP)-70, <TEX>$HSP-90{\alpha}$</TEX>, and <TEX>$HSP-90{\beta}$</TEX>; and comet scores were analyzed. Production performances were measured by the survival rate, body weights, days at first egg laying, egg weight and hen housed egg production. The results showed that the production traits and values of stress-related markers showed significant differences between strains. In general, the stress response of pure bred chickens with heavy weights was relatively high, while that of hybrid chickens with light weights was relatively low. The correlation coefficients between telomere contents and body weights showed that there were weak negative relationships. However, the correlations of telomere content with the survival rate and egg production were weakly positive after 20 weeks old. The expression levels of HSP genes and DNA damage rate (comet scores) were positively correlated to body weight, but were negatively correlated to the survival rate and egg production. The results implied that increasing body weight was associated with increasing HSPs expression and the DNA damage rate was associated with decreasing telomere content. In addition, increasing HSPs expression and the DNA damage rate decreased the survival rate and egg production, but the relationships with the telomere content was the reverse. Correlations among the stress-related markers showed that there were significant correlation coefficients between all of the marker values. HSPs expression was negatively correlated to the telomere content, while it was positively correlated to the DNA damage rate. There was a highly negative correlation between the telomere content and DNA damage rate. In conclusion, increasing the HSP values and DNA damage rate can promote telomere reduction, which led to a decrease in disease resistance and robustness of the chicken. Thus, increasing the stress response was verified to adversely affect the laying performance and viability of chickens.

Effect of using insect larvae meal as a complete protein source on quality and productivity characteristics of laying hens

This study was conducted to evaluate the effect of black soldier fly larvae (BSFL) as a source of protein in layer diets on product performance, egg quality, hatchability, fertility, and sensory characteristics of eggs. The BSFL contained a high percentage of protein (559.9 g kg−1), metabolizable energy (696.3 kcal kg−1), crude fat (18.6 g kg−1), and dry matter (178 g kg−1) and a good balance of amino acids. A total of 54 Arabic strain hens at nine months of age were mixed with nine cocks at 12 months old; all were divided into three treatments. The diets were formulated based on three levels of energy-to-protein ratio: 155, 140, and 170. The BSFL meal was added at 0, 50, and 10 g kg−1 respectively. The results showed that feed intake, weight gain, Haugh unit, and hatchability were not affected by dietary treatments with BSFL. However, there was significant improvement in hen day egg production and hen house egg production due to dietary treatments of BSFL. Also, feed conversion ratio, egg weight, shell thickness, shell weight, egg yolk color, fertility, and egg mass were affected by dietary treatments. In addition, a significant improvement was observed in appearance, texture, taste, and acceptance of eggs of hens fed BSFL at 50 g kg−1. The odor was not affected by dietary treatments. Black soldier fly larvae can be a good source of protein in layer diets.

Body weight, egg production, and egg quality traits of gray, brown, and white varieties of Japanese quail (Coturnix coturnix japonica) in coastal climatic condition of Odisha.

Aim:The present study was conducted to evaluate the performance of gray, brown, and white varieties of Japanese quail (Coturnix coturnix japonica) with respect to body weight, egg production, and egg quality traits in the coastal climatic condition of Odisha.Materials and Methods:A total of 500-day-old straight run Japanese quail chicks of three varieties, viz., gray, brown, and white were randomly selected and reared in deep litter system at Central Poultry Development Organization, Eastern Region, Bhubaneswar. The weekly body weight of the birds was recorded till their egg production stage (up to 6 weeks of age). The average egg production was recorded every biweekly from 6th to 20th week. Exterior and interior quality of eggs from each variety was determined at 6 weeks of age.Results:The initial average weekly body weight of three varieties did not differ (p>0.05) among the varieties. However, from 1st to 6th week significantly higher body weight was observed in gray than white and brown. Brown varieties had reached 50% egg production 1 week earlier than gray and white. Brown had higher peak hen day (HD) production or hen-housed egg production followed by white and gray. External quality such as: Egg weight, egg length, egg width, volume, shape index, shell weight, shell thickness depicted no significant difference among the varieties except circumference length and circumference width, which were significantly higher (p≤0.05) in gray varieties than brown varieties. Internal egg characteristics such as: Albumen length, albumen width, albumen height, albumen index, yolk length, yolk width, yolk height, yolk index, albumen weight, yolk weight, Haugh unit revealed no significance difference among the varieties.Conclusion:It may be summarized from the findings that gray excelled in body weight followed by white and brown. Egg production potential in terms of hen house egg production or HD egg production was higher for brown followed by white and gray in the coastal climatic condition of Odisha.

Associations of the Novel Polymorphisms of Periostin and Platelet-Derived Growth Factor Receptor-Like Genes with Egg Production Traits in Local Chinese Dagu Hens

ABSTRACTThe periostin (POSTN) and platelet-derived growth factor receptor-like (PDGFRL) genes are implicated in regulation of hen ovarian development. In the present study, these genes were explored as possible molecular markers associated with egg production, egg weight and body weight in Chinese Dagu hens. Samples were analyzed using the PCR-single strand conformation polymorphism (PCR-SSCP) method, followed by sequencing analysis, and three novel single nucleotide polymorphisms (SNPs) were identified within the candidate genes. Among them, an A/T transversion at base position 2727 in intron 2 of POSTN gene was found to be polymorphic and named SNP A2727T; and two transitions, G/A at position 6761 and A/G at base 6839 in exon 2 of PDGFRL gene were detected and named SNPs G6761A and A6839G, respectively. For the SNP A2727T, a total of 360 Dagu hens were classified as AA and AB genotypes, allele A was found present at a higher frequency. Moreover, the AA genotype was significantly correlated with higher hen-housed egg production (HHEP) at 43, 57, and 66 weeks (wks) of age and with a higher egg weight (EW) at 30 wks (P < 0.05). For the two linked SNPs (G6761A and A6839G) in the PDGFRL fragment, the hens were typed into TT, TC and CC genotypes, with the T allele shown to be dominant. The TT genotype was correlated with higher HHEP at 57 and 66 wks of age; genotype CC associated with the highest body weight and EW at 30 and 43 wks (P < 0.05), while it was correlated with the lowest HHEP at 57 and 66 wks of age (P < 0.05). Furthermore, five haplotypes were reconstructed based on these SNPs, with the AATT haplotype associated with the highest HHEP at 43 to 66 wks of age and higher EW at 30 wks (P < 0.05). Collectively, these SNPs identified in this study might be used as a potential molecular marker favorable to genetic improvement of egg productivity in chicken breeding.

Differential contribution of genomic regions to marked genetic variation and prediction of quantitative traits in broiler chickens.

BackgroundGenome-wide association studies in humans have found enrichment of trait-associated single nucleotide polymorphisms (SNPs) in coding regions of the genome and depletion of these in intergenic regions. However, a recent release of the ENCyclopedia of DNA elements showed that ~80 % of the human genome has a biochemical function. Similar studies on the chicken genome are lacking, thus assessing the relative contribution of its genic and non-genic regions to variation is relevant for biological studies and genetic improvement of chicken populations.MethodsA dataset including 1351 birds that were genotyped with the 600K Affymetrix platform was used. We partitioned SNPs according to genome annotation data into six classes to characterize the relative contribution of genic and non-genic regions to genetic variation as well as their predictive power using all available quality-filtered SNPs. Target traits were body weight, ultrasound measurement of breast muscle and hen house egg production in broiler chickens. Six genomic regions were considered: intergenic regions, introns, missense, synonymous, 5′ and 3′ untranslated regions, and regions that are located 5 kb upstream and downstream of coding genes. Genomic relationship matrices were constructed for each genomic region and fitted in the models, separately or simultaneously. Kernel-based ridge regression was used to estimate variance components and assess predictive ability. Contribution of each class of genomic regions to dominance variance was also considered.ResultsVariance component estimates indicated that all genomic regions contributed to marked additive genetic variation and that the class of synonymous regions tended to have the greatest contribution. The marked dominance genetic variation explained by each class of genomic regions was similar and negligible (~0.05). In terms of prediction mean-square error, the whole-genome approach showed the best predictive ability.ConclusionsAll genic and non-genic regions contributed to phenotypic variation for the three traits studied. Overall, the contribution of additive genetic variance to the total genetic variance was much greater than that of dominance variance. Our results show that all genomic regions are important for the prediction of the targeted traits, and the whole-genome approach was reaffirmed as the best tool for genome-enabled prediction of quantitative traits.

Studies on production of vitamin E and selenium enriched Japanese quail egg

This study was conducted to assess the alpha-tocopherol and selenium level of Japanese quail egg. This trial was conducted in two hundred and ten female Japanese quail birds from seven to twenty six weeks of age. Experimental birds were randomly divided into seven groups viz., T1-Control: Basal diet (standard Japanese quail ration), T2-Basal diet with Vitamin E 150 mg/kg, T3-Basal diet with Vitamin E 300 mg/kg, T4-Basal diet with selenium 0.3 mg/kg, T5-Basal diet with selenium 0.6 mg/kg, T6-Basal diet with combination of Vitamin E 150 mg/kg and selenium 0.3 mg/kg, T7-Basal diet with combination of Vitamin E and selenium 0.6 mg/kg. During the laying period the data on hen housed egg production and hen day egg production showed significant increase in egg production from 7 to 26 weeks of age by supplementation of Vitamin E and Selenium in the Japanese quail. Dietary supplementation with the combination of Vitamin E 300 mg/kg and selenium 0.6 mg/kg indicated significantly enrichment of alpha-tocopherol and selenium level in Japanese quail egg.

Comparison of different poultry breeds under station and on-farm conditions in Ethiopia

A selective breeding program was implemented to improve the performance of indigenous chickens. Improved chicken from the 7th generation was compared with commercial layer, crossbred and unselected indigenous chickens both on-station and on-farm. A total of 870 chickens were used. More than 600 chickens (n=150 and n=120 from each breed during growing and laying period respectively) arranged in completely randomized design were followed on-station, and 270 (90 from commercial, crossbred and improved during laying period) were evaluated on-farm in Ada (n=6 farms) and Horro (n=9 farms) districts in a split-plot design. Body weight, cumulative feed intake, and survival were recorded while feed conversion ratio was calculated at week 8, 12, 16 and 20 during the growing period on-station. Age at first egg and total egg number during lifetime were recorded once. Survival and hen housed egg production were recorded at month 3, 6, 9 and 12 of age both on-station and on-farm. Egg weight, and feed per egg were recorded and used to calculate feed conversion ratio during the laying period on-station. Significant effect of breed (P<0.001) and interaction with time (P<0.001) was observed for traits measured on-station during the growing and laying period. Similarly significant effect of breed, village and breed–village interactions were observed on-farm (P<0.001). Improved indigenous chickens had higher performance than indigenous chickens for all traits measured on station (P<0.05). 10 farmers out of 16 in the Ada district and 7 out of 16 in the Horro district dropped out after month 3 at different times either due to high chicken mortality or reduced motivation of the farmer. Improved chickens have been genetically improved as compared to unimproved, but their performance is still low compared to commercial chickens.

Novel Polymorphisms of Adrenergic, Alpha-1B-, Receptor and Peroxisome Proliferator-activated Receptor Gamma, Coactivator 1 Beta Genes and Their Association with Egg Production Traits in Local Chinese Dagu Hens.

Adrenergic, alpha-1B-, receptor (ADRA1B) and peroxisome proliferator-activated receptor gamma, coactivator 1 beta (PPARGC1B) genes are involved in regulation of hen ovarian development. In this study, these two genes were investigated as possible molecular markers associated with hen-housed egg production, egg weight (EW) and body weight in Chinese Dagu hens. Samples were analyzed using the polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) technique, followed by sequencing analysis. Two novel single nucleotide polymorphisms (SNPs) were identified within the candidate genes. Among them, an A/G transition at base position 1915 in exon 2 of ADRA1B gene and a T/C mutation at base position 6146 in the 3′-untranslated region (UTR) of PPARGC1B gene were found to be polymorphic and named SNP A1915G and T6146C, respectively. The SNP A1915G (ADRA1B) leads to a non-synonymous substitution (aspartic acid 489-to-glycine). The 360 birds from the Dagu population were divided into genotypes AA and AG, allele A was found to be present at a higher frequency. Furthermore, the AG genotype correlated with significantly higher hen-housed egg production (HHEP) at 30, 43, 57, and 66 wks of age and with a higher EW at 30 and 43 wks (p<0.05). For the SNP T6146C (PPARGC1B), the hens were typed into TT and TC genotypes, with the T allele shown to be dominant. The TC genotype was also markedly correlated with higher HHEP at 57 and 66 wks of age and EW at 30 and 43 wks (p<0.05). Moreover, four haplotypes were reconstructed based on these two SNPs, with the AGTC haplotype found to be associated with the highest HHEP at 30 to 66 wks of age and with higher EW at 30 and 43 wks (p<0.05). Collectively, the two SNPs identified in this study might be used as potential genetic molecular markers favorable in the improvement of egg productivity in chicken breeding.

Seasonal sensitivity of genotypes in the humid tropics and its application to chicken breeding

Abstract. The study was aimed at elucidating the effect of seasons, namely the early wet (EW), late wet (LW), early dry (ED) and late dry (LD) seasons, on genotype sensitivity, its magnitude and application for selection and management of chickens of Bovan Nera (BN) and ISA Brown (IB) origins. Breeding and hatching records from 1999 to 2008 were collected from CHI (Ajanla) Farms and hatchery records, Ibadan, Nigeria. Cock weight (CW), hen weight (HW), hen-house egg production (HHP), egg weight (EW), fertility of egg set (FES) and pullet day-old chicks (PDC) hatched were examined. ANOVA revealed that there was significant (P &lt; 0.05) genotype × season interaction effect. This interaction was observed between genotypic values when compared between seasons within parameters. Within-season sensitivity parameters indicated that BN was more sensitive than IB in HW and FES for all seasons. In ED and LD seasons, sensitivity values were inconsistent in pattern with output levels of FES, HES and PDC hatched because of interaction between genotypes and seasons. Within the LW season, all sensitivity indices for genotypes were consistent in magnitude with productive and reproductive values. Therefore, a genotype's seasonal sensitivity indices could be utilized for direct antagonistic selection in LW season between genotypes in humid tropics.

Assessment of bagging GBLUP for whole-genome prediction of broiler chicken traits.

Bootstrap aggregation (bagging) is a resampling method known to produce more accurate predictions when predictors are unstable or when the number of markers is much larger than sample size, because of variance reduction capabilities. The purpose of this study was to compare genomic best linear unbiased prediction (GBLUP) with bootstrap aggregated sampling GBLUP (Bagged GBLUP, or BGBLUP) in terms of prediction accuracy. We used a 600K Affymetrix platform with 1351 birds genotyped and phenotyped for three traits in broiler chickens; body weight, ultrasound measurement of breast muscle and hen house egg production. The predictive performance of GBLUP versus BGBLUP was evaluated in different scenarios consisting of including or excluding the TOP 20 markers from a standard genome-wide association study (GWAS) as fixed effects in the GBLUP model, and varying training sample sizes and allelic frequency bins. Predictive performance was assessed via five replications of a threefold cross-validation using the correlation between observed and predicted values, and prediction mean-squared error. GBLUP overfitted the training set data, and BGBLUP delivered a better predictive ability in testing sets. Treating the TOP 20 markers from the GWAS into the model as fixed effects improved prediction accuracy and added advantages to BGBLUP over GBLUP. The performance of GBLUP and BGBLUP at different allele frequency bins and training sample sizes was similar. In general, results of this study confirm that BGBLUP can be valuable for enhancing genome-enabled prediction of complex traits.

Production performance of indigenous Nicobari fowls, Vanaraja and their various F1 crosses under hot humid climate of Andaman and Nicobar Islands, India

The present study evaluates the production performance of indigenous Nicobari fowls, Vanaraja and their various F1 crosses under hot humid climate of Andaman and Nicobar Islands, India. Birds (600) with 60 in each group were used for the study. The birds were evaluated for weekly body weight (g) from 0 day to 8 weeks of age, monthly body weight (g) from first month to fourth month of age, shank length (mm), feed intake and feed conversion ratio (FCR) up to 8 weeks of age, age at sexual maturity (ASM in days), annual egg production as hen house egg production (AEP as HHEP), and different egg quality traits at 40 weeks of age. At the end of fourth month of age, the body weight of Vanaraja was highest (3,394.24±23.31 g) among all the genetic groups studied. White Nicobari × Vanaraja recorded significantly higher body weight (1923.10±18.81 g) in comparison to all the F1 crosses except Vanaraja × White Nicobari. Age at laying was found lowest (136 days) in White Nicobari among pure varieties and White Nicobari × Vanaraja (146 days) among F1 crosses. Annual egg production of Black Nicobari was found highest (192.14) among pure varieties and White Nicobari × Vanaraja (184.95) excelled in annual egg production among the F1 crosses. The highest egg weight was observed in Vanaraja and White Nicobari × Vanaraja among the pure and crosses respectively. In conclusion, White Nicobari × Vanaraja was a very suitable and promising dual purpose bird under the local climatic condition of Andaman and Nicobar Islands.

Association of novel polymorphisms of forkhead box L2 and growth differentiation factor-9 genes with egg production traits in local Chinese Dagu hens

Transcription factor forkhead box L2 (FOXL2) and growth differentiation factor-9 (GDF9) genes have critical roles in the regulation of hen ovarian development. In the present study, these genes were explored as possible molecular markers associated with BW, hen-housed egg production, and egg weight in Chinese Dagu hens. Samples were analyzed using the PCR–single strand conformation polymorphism (PCR-SSCP) technique followed by sequencing analysis, and two novel single nucleotide polymorphisms (SNPs) were identified within these candidate genes. Among them, an A/G transition at base position 238 in the coding region of the FOXL2 gene and a G/T transversion at base position 1609 in exon 2 of the GDF9 gene were found to be polymorphic and named SNPs A238G and G1609T, respectively. The SNP A238G (FOXL2) leads to a nonsynonymous substitution (isoleucine77-to-valine), and when the 360 Dagu hen samples were divided into genotypes AA and AB, allele A was found to be present at a higher frequency. Furthermore, the AA genotype correlated with significantly higher hen-housed egg production at 30, 43, 57, and 66 wk of age and with a higher egg weight at 43 wk (P < 0.05). For the SNP G1609T (GDF9), the hens were typed into TT and TC genotypes, with the T allele shown to be dominant. The TC genotype was also markedly correlated with higher hen-housed egg production and a higher egg weight (P < 0.05). Moreover, four haplotypes were reconstructed based on these two SNPs, with the AATC haplotype found to be correlated with the highest hen-housed egg production at 30 to 66 wk of age and with higher egg weights at 43 wk (P < 0.05). Collectively, the two SNPs identified in this study might be used as possible genetic molecular markers to aid in the improvement of egg production traits in chicken breeding.

Assessing the Performance Characteristics of Chicken Layers Fed with Pito Mash Inclusion Diets Treated with Cocoa Pod-Husk Ash Extract

2 Abstract: A nutritional balance trial was conducted, with 176 strain of Lohmann breed of brown layers at 8 weeks old, weighing between 340-341 g. The chickens were grouped into 4 dietary treatments of 4 4 chickens per group. A complete randomized design (CRD) was applied in which the dietary treatments included 0, 5, 10 and 15% level of the alkali-treated pito mash. Feed and water were provided ad libitum over the 11-month experimental period. The parameters measured were body weight changes, feed intake, water intake, hen-day egg production, hen-housed egg production, feed conversion ratio (kg/dozen egg), age at the onset of e gg production, body weight at the onset of egg laying, weight of the first egg laid, shell thickness, number of broken egg, yolk colour, yolk diameter, albumen height, Haugh unit and mortality rate. Results showed that apart from body weight at the start of feed trial, feed/dozen eggs and body weight at the onset of egg laying, shell thickness and mortality of chickens, all the alkali-treated pito mash based diets exhibited significantly (p<0.05) higher performances than the control group in all the other parameters considered, although at varying magnitudes. The costs/100 kg grower and layer diets were progressively reduced as the level of treated pito mash increased in the diets. Alkali-treated pito mash inclusion in grower and layer chicken diets up to 15% is therefore recommended.

Effects the combinations of light color and intensity of light to age at first laying and production egg of Alabio Laying ducks

The purpose of the study to see the effect of the combination of light color and intensity of light on the age at first laying, hen day egg production and hen house production Alabio ducks from South Kalimantan. This study used a completely randomized design factorial 4 x 3 with 3 replications. There are 4 levels of light color consists of yellow color (W1), red (W2), blue (W3) and green (W4), while there are 3 levels of light intensity consists of 5 lux (T1), 10 lux (T2) and 15 lux (T3), so there are 12 combinations of treatments. Data were analyzed for variance (ANOVA) and if there is a treatment effect followed by Duncan's test (DMRT). The results showed the combinations of light color and intensity of light was significant effect on accelerating the age at first laying ducks (p<0.05), in which the color combination of light blue with a light intensity of 10 lux (W3T2) is the best combination that can produce Alabio ducks for the first spawn faster at the age of 159 ± 1.9 days. The combination of light colors and light intensity significantly affected hen day egg production (p<0.05), in which the color combination of light blue color with a light intensity of 10 lux (W3T2) generates highest Alabio duck egg production by 85 ± 0.7%, while the hen house egg production,the combination of light colors and light intensity significantly affected hen house egg production (p<0.05), in which the color combination of light blue with a light intensity of 10 lux (W3T2) generates highest egg production by 83 ± 1.0%.

Is dietary iron requirement of broiler breeder hens at the late stage of production cycle influenced by phytase supplementation?

The purpose of this study was to investigate the effects of phytase on iron requirement of broiler breeder hens at the late stage of production cycle. Ninety-six Cobb (500) broiler breeder hens were weighed and individually placed in galvanized wire cages at 59 weeks of age. In order to depletion of hens iron reserved, after placement, hens were offered a semi-purified iron-deficient (37 mg iron/kg) diet for three weeks. At 62 weeks of age, hens were randomly allocated to eight dietary treatments in a factorial arrangement with four replicates of three hens in each. Factors included two levels of phytase (0 and 600 U/kg) and four levels of iron (37, 52, 67 and 82 mg/kg). Hens were fed the experimental diets from 62 to 68 weeks of age. Iron in the diet had significant effects on egg weight (P < 0.05). Increasing dietary iron content significantly increased the concentration of iron in the bone marrow, liver, spleen (P < 0.05), egg yolk and blood serum (P < 0.01). Added phytase enhanced the iron concentration of the egg yolk and serum (P < 0.01). It seems that phytase can release iron from inositol in old broiler breeder hens and increased chicken iron reserve. Two slope, broken-line analysis of hen house egg production regressed on the dietary added iron indicated that 65 mg/kg supplemental iron without phytase and 58 mg/kg supplemental iron with phytase were required for the optimal egg production of broiler hens.

Dissection of additive genetic variability for quantitative traits in chickens using SNP markers

The aim of this study was to separate marked additive genetic variability for three quantitative traits in chickens into components associated with classes of minor allele frequency (MAF), individual chromosomes and marker density using the genomewide complex trait analysis (GCTA) approach. Data were from 1351 chickens measured for body weight (BW), ultrasound of breast muscle (BM) and hen house egg production (HHP), each bird with 354 364 SNP genotypes. Estimates of variance components show that SNPs on commercially available genotyping chips marked a large amount of genetic variability for all three traits. The estimated proportion of total variation tagged by all autosomal SNPs was 0.30 (SE 0.04) for BW, 0.33 (SE 0.04) for BM, and 0.19 (SE 0.05) for HHP. We found that a substantial proportion of this variation was explained by low frequency variants (MAF <0.20) for BW and BM, and variants with MAF 0.10-0.30 for HHP. The marked genetic variance explained by each chromosome was linearly related to its length (R(2) = 0.60) for BW and BM. However, for HHP, there was no linear relationship between estimates of variance and length of the chromosome (R(2) = 0.01). Our results suggest that the contribution of SNPs to marked additive genetic variability is dependent on the allele frequency spectrum. For the sample of birds analysed, it was found that increasing marker density beyond 100K SNPs did not capture additional additive genetic variance.

Effect of allele frequencies, effect sizes and number of markers on prediction of quantitative traits in chickens

The objective was to assess goodness of fit and predictive ability of subsets of single nucleotide polymorphism (SNP) markers constructed based on minor allele frequency (MAF), effect sizes and varying marker density. Target traits were body weight (BW), ultrasound measurement of breast muscle (BM) and hen house egg production (HHP) in broiler chickens. We used a 600K Affymetrix platform with 1352 birds genotyped. The prediction method was genomic best linear unbiased prediction (GBLUP) with 354564 single nucleotide polymorphisms (SNPs) used to derive a genomic relationship matrix (G). Predictive ability was assessed as the correlation between predicted genomic values and corrected phenotypes from a threefold cross-validation. Predictive ability was 0.27±0.002 for BW, 0.33±0.001 for BM and 0.20±0.002 for HHP. For the three traits studied, predictive ability decreased when SNPs with a higher MAF were used to construct G. Selection of the 20% SNPs with the largest absolute effect sizes induced a predictive ability equal to that from fitting all markers together. When density of markers increased from 5K to 20K, predictive ability enhanced slightly. These results provide evidence that designing a low-density chip using low-frequency markers with large effect sizes may be useful for commercial usage.

Genome-enabled prediction of quantitative traits in chickens using genomic annotation

BackgroundGenome-wide association studies have been deemed successful for identifying statistically associated genetic variants of large effects on complex traits. Past studies have found enrichment of trait-associated SNPs in functionally annotated regions, while depletion was reported for intergenic regions (IGR). However, no systematic examination of connections between genomic regions and predictive ability of complex phenotypes has been carried out.ResultsIn this study, we partitioned SNPs based on their annotation to characterize genomic regions that deliver low and high predictive power for three broiler traits in chickens using a whole-genome approach. Additive genomic relationship kernels were constructed for each of the genic regions considered, and a kernel-based Bayesian ridge regression was employed as prediction machine. We found that the predictive performance for ultrasound area of breast meat from using genic regions marked by SNPs was consistently better than that from SNPs in IGR, while IGR tagged by SNPs were better than the genic regions for body weight and hen house egg production. We also noted that predictive ability delivered by the whole battery of markers was close to the best prediction achieved by one of the genomic regions.ConclusionsWhole-genome regression methods use all available quality filtered SNPs into a model, contrary to accommodating only validated SNPs from exonic or coding regions. Our results suggest that, while differences among genomic regions in terms of predictive ability were observed, the whole-genome approach remains as a promising tool if interest is on prediction of complex traits.

Assessing the thermo-tolerance potentials of five commercial layer chicken genotypes under long-term heat stress environment as measured by their performance traits

This study was conducted to test the thermo-tolerance ability of five commercial chicken genotypes (Lohmann Brown, LB; Lohmann White, LW; New Hampshire, NH; White Leghorn selected for low feed expenditure, WL-FE and White Leghorn with sex-linked dwarf gene, WL-dw) under long-term heat exposure. Two-hundred forty female chickens were assigned to a completely randomized design in a 5 × 2 factorial arrangements (five genetic groups and two ambient temperatures [thermo-neutral, 18–20 °C; heat stress, 30–32 °C]). Individual eggs were collected on daily basis while egg weight and feed intake were determined on individual and group basis at 28-days intervals, respectively. Shell quality traits were determined at 25, 40 and 56 weeks age. No Genotype × ambient temperature interactions were found except for body weight and egg deformation. Chickens at thermo-neutral temperature produced significantly heavier eggs than those of heat-exposed (60 g vs. 54 g). Hen-housed egg production of chickens in thermo-neutral temperature was significantly higher than those of heat-stressed (76.8 % vs. 66.2 %). Daily egg mass production at thermo-neutral and heat stressed chickens was 46 g and 35.8 g, respectively. Feed consumption in heat-stressed and thermo-neutral chickens was 109 and 80.8 g, respectively. Shell thickness, breaking strength and Haugh unit values were significantly reduced in heat-stressed chickens. Among heat-exposed chickens, the NH had the highest body weight while the LW produced 10 % more eggs than the group average. The heat-induced effect on shell quality traits was lowest in LW chickens. The results indicated that the magnitude of heat stress was breed dependent in which the LB showed poor adaptability to heat stress while both NH and LW genotypes demonstrated better thermo-tolerance ability.

Efficacy of pre-lay diet

A biological study was carried out to review the Bureau of Indian Standards (BIS) recommendations for layer pullet feed. Commercial layer chicks were fed till 14 weeks of age as per BIS. At 15 weeks, pullets were randomly assigned to each of the five pre-lay feeding strategies, namely T1 (BIS control), T2 (16/2700), T3 (18/2700) (%CP/kcal ME/kg), T4 (same as T2 + lysine and methionine by 10% higher than BIS) and T5 (same as T4 with 2% oil). At 5% egg production, all groups were fed as per BIS. Pullets fed on high energy and protein pre-lay diets of 2700 kcal and 18% protein-advanced sexual maturity with good body composition. Pre-layers fed 2700/18 feed had the best hen day (85.44±1.52), hen-housed egg production (84.21±1.52), layed heavier eggs, had a higher egg mass output (47.14±0.95g), gave the best feed efficiency, had the lowest pullet production cost and high egg feed price ratio. It was concluded that pre-lay pullets have to be provided with 2700/18 kcal of metabolisable energy and protein level as against the BIS recommendation of 2500/16 dietary energy and protein level.