Age Of First Egg Research Articles

The Effects of Rearing Systems on Incubation, Egg Production and Quality Traits in Pharaoh Quails

This study was conducted to determine the effect of rearing quails in different rearing systems on egg production, egg quality characteristics, and incubation results. The 360 quails were distributed equally to 3 different rearing groups (cage, enriched cage, and floor) in a male:female mixed at the age of 3 weeks. The eggs were individually weighed and recorded one by one daily (5487 eggs) for 3 months. To determine egg quality and incubation characteristics, 750 eggs were broken, and 3284 eggs were incubated, respectively. The results showed that female quail in the floor group have lower body weight at 6 weeks old (177.19 g), and they reached sexual maturity (age of first egg laying) later (65.36 day, P<0.01), The lowest egg production (61.14%) occurred in the floor group during the 3-month egg production period (P<0.05). The lowest average egg weight (9.07 g) was determined in the floor group (P<0.05). It was determined that the eggs of quails raised in the enriched group had a rounder shape index because they have larger widths (P<0.01). While the highest average yolk height (11.24 mm) was determined in the enriched cage group (P<0.01), the highest averages of albumen length (72.41 mm) and lowest averages of yolk index (48.43%) were determined in the cage group (P<0.01). The lowest average values (113.17) in Haugh unit were detected in the floor group (P<0.05). The highest fertility rate (98.44%) was in Floor♂:Cage♀, the highest hatchability of fertile egg rate (94.67%) was obtained from Enriched♂:Cage♀, and the highest hatchability (89.10%) was obtained from Floor♂:Cage♀ pairing (P<0.05). The lowest fertility rate (88.00%) was obtained from the Enriched♂:Floor♀, the lowest hatchability of fertile egg rate (86.01%) was obtained from the Enriched♂:Enriched♀, and the lowest hatchability (75.62%) was obtained from the Enriched♂: Enriched♀ groups. As a result, it has been revealed that the effect of various rearing systems is different on egg production, egg quality traits, and hatching results in quails. Thus, it has been shown that different programs at the rearing period to be applied to the male and female quails can achieve better incubation results and reproductive success.

Performance Evaluation of Lohman Brown Commercial Layer Chicken Breeds Under On-Station Management at Pawe, Benishangul Gumuz, Ethiopia

This study was undertaken to evaluate the performance of Lohman Brown under on-station conditions at Pawe Agricultural Research Center. To evaluate the breed production performance and to generate information for private commercial farms and multiplication centers. A total of 100 (sixty-day-old) chicks and commercial layer feed were purchased from Alema poultry farm in Bishoftu. Vaccinations were administered to the chicks while bio-security measures were employed throughout the experimental period (83 weeks). Daily feed intake, body weight, feed conversion rate, egg production, egg weight, egg mass, and mortality, were recorded. Data were analyzed using descriptive statistics free R-4.0.4 software. Average feed intake during the growing period (10-20 weeks) 59.29g/head and in the layer period (21-72weeks) 117.26g/head/day. The average feed conversion rate at12, 16 and 20weeks of age was 8.85, 8.23 and 7.35 respectively. Average body weight at age at first egg lay and peak egg production were 1368.6 and 1553.9g/head respectively. Average daily weight gain at 10-12, 12-16, and 16- 20 weeks of age was 5.43, 7.22 and 11.09g/bird respectively. Age at first and 5% egg-laying were recorded at the beginning of 21weeks (141days). Age at 50% and peak egg production were recorded at 22 weeks (151 days) and 36weeks. The average HHEP (90.71) and HDEP (92.03) were recorded at peak production, while the overall percentage of lay from 21-72(52) weeks of age were HHEP (74.77%) and HDEP (78.28%). The total amount of egg production from 21-72(52) weeks of age in terms of HHEP and HDEP was 272.2 and 284.93egg/hen/year. Average egg weight at age at first egg lay, 50% egg lay and peak egg production were 47.43, 51.5 and 57.03g. Overall mean egg weight from 21-72(52) weeks of age was 57.81g. The average daily egg mass at the age of first egg lay, 50% egg lay and peak egg production were 7.59, 25.68, and 52.48g. On the other hand, the overall mean daily egg mass from 21-72(52) weeks of age was 45.38g. The average feed conversion rate and feed conversion efficiency for egg mass from 21-72 weeks were 2.64 and 0.387. There was no mortality record up to 28 weeks but, the overall mortality rate was 10% up to 83 weeks. The higher egg production and lower mortality record showed that the breed is adapted in the study area. Lohman Brown is recommended for users with basic input packages and on-farm evaluation of chickens should be done.

Genetic parameter estimation and molecular foundation of chicken egg-laying trait

The age of first egg (AFE) in chicken can affect early and even life-time egg production performance to some extent, and therefore is an important economic trait that affects production efficiency. To better understand the genetic patterns of AFE and other production traits including body weight at first egg (BWA), first egg weight (FEW), and total egg number from AFE to 58 wk of age (total-EN), we recorded the production performance of 2 widely used layer breeds, white leghorn (WL) and Rhode Island Red (RIR) and estimated genetic parameters based on pedigree and production data. The results showed that the heritability of AFE in both breeds ranged from 0.4 to 0.6, and AFE showed strong positive genetic and phenotypic correlations to BWA as well as FEW, while showing strong negative genetic and phenotypic correlations with total-EN. Furtherly, by genome-wide association analysis study (GWAS), we identified 12 and 26 significant SNPs to be related to AFE in the 2-layer breeds, respectively. A total of 18 genes were identified that could affect AFE based on the significant SNP annotations obtained, but there were no gene overlapped in the 2 breeds indicating the genetic foundation of AFE could differ from breed to breed. Our results provided a deeper understanding of genetic patterns and molecular basement of AFE in different breeds and could help in the selection of egg production traits.

Association analysis of production traits of Japanese quail (Coturnix japonica) using restriction-site associated DNA sequencing

This study was designed to perform an association analysis and identify SNP markers associated with production traits of Japanese quail using restriction-site-associated DNA sequencing. Weekly body weight data from 805 quail were collected from hatching to 16 weeks of age. A total number of 3990 eggs obtained from 399 female quail were used to assess egg quality traits. Egg-related traits were measured at the beginning of egg production (first stage) and at 12 weeks of age (second stage). Five eggs were analyzed at each stage. Traits, such as egg weight, egg length and short axes, eggshell strength and weight, egg equator thickness, yolk weight, diameter, and colour, albumen weight, age of first egg, total number of laid eggs, and egg production rate, were assessed. A total of 383 SNPs and 1151 associations as well as 734 SNPs and 1442 associations were identified in relation to quail production traits using general linear model (GLM) and mixed linear model (MLM) approaches, respectively. The GLM-identified SNPs were located on chromosomes 1–13, 15, 17–20, 24, 26–28, and Z, underlying phenotypic traits, except for egg and albumen weight at the first stage and yolk yellowness at the second stage. The MLM-identified SNPs were positioned on defined chromosomes associated with phenotypic traits except for the egg long axis at the second stage of egg production. Finally, 35 speculated genes were identified as candidate genes for the targeted traits based on their nearest positions. Our findings provide a deeper understanding and allow a more precise genetic improvement of production traits of Galliformes, particularly in Japanese quail.

PSXII-11 Comparison of Egg-Laying Ability Among Eight Lines Including Korean Native Chicken (KNC)

Abstract Chicken egg production capacity is an important economic trait in the poultry industry. To improve the usability of Korean Native chicken (KNC), we measured the egg traits [age of first egg (AFE), first egg weight (FEW), egg number (EN), egg weight (EW)] and performed a comparative analysis. Age of first egg is the number of days an individual starts producing eggs. FEW is the weight of the first egg produced. EN and EW are the number of eggs produced between 20 and 40 weeks old and the weight of the eggs. The chicken breeds we used in our study were KNC (GBY, GWY, CNB, CNW, CNY, CNK), Ameraucana (AMR) and Leghorn (LEG). The CNK line started laying eggs at 140.75 ± 6.23 days. The AFE of CNK was faster than LEG (142.35 ± 7.20, P < 0.05). The weight of the first egg after starting egg production AMR line (44.1 ± 5.20g) produced the heaviest egg among the investigative groups (P < 0.05). The CNY line laid the lightest egg (31.9 ± 3.80g). FEW of KNC was less than that of both LEG and AMR breeds (P < 0.05). The AFE was late and FEW was the greatest in the AMR breed. The LEG which is a representative laying hen laid the most EN between 20 and 40 weeks of age (118.35 ± 10.07). LEG was greater than the CNK (106.85 ± 14.66), which laid the second most (P < 0.05). The CNB (82.45 ± 20.68) showed the least EN. The EW of the AMR (54.20 ± 4.30) was the heaviest (P < 0.05). On the contrary, Six KNC (CNK: 45.70 ± 3.00, GBY: 45.20 ± 3.10, GWY: 45.20 ± 2.20, CNB: 44.60 ± 3.20, CNY: 43.70 ± 3.90, CNW: 43.50 ± 3.40) lines produced lighter eggs than LEG (51.50 ± 3.50) and AMR (P < 0.05). In conclusion, the average egg production performance of the KNC six lines was generally less than that of the LEG and AMR breeds. However, some lines of KNC confirmed that the start date of egg production was faster than other breeds. These results will be used to investigate the genomic pattern of egg production in KNC population and provide fundamental data for gene-based selection to improve egg production.

Effect of feed particle size on growth and egg-laying parameters of Japanese quail (Coturnix japonica) in Côte d’Ivoire

In Côte d’Ivoire, the quail breeding is confronted with the lack of food specific to the species. Thus, in the south-east of this country, an experimental study was conducted at the ISMOREL farm in the sub-prefecture of Adiaké. This study, which aims to improve the productivity of day-to-day farms, focused on the grain size of the feed. From grower (GD) and layer (LD) diets, 5 experimental diets have been manufactured. There are: LD 5 with a particle size of 5 mm, LD 3 and GD 3 with a particle size of 3 mm as well as LD 2 and GD 2 with a particle size of 2 mm. The growth parameters related to 750 two-week-old unsexed subjects weighing 49.67 ± 0.17 g on average. For egg-laying, 300 female quails were used at 6-week-old. The results showed an influence of the 2 mm grain size (LD 2 and GD 2) on parameters such as feed intake (186.96 ± 4.73 g and 153.46 ± 5.33 g), average live weight (142.37 ± 1.76 g and 155.85 ± 1.85 g), the average daily gain (4.29 ± 1.22 g/d and 4.74 ± 1.25 g/d), the age of first egg laid (49.33 ± 0.58 d and 46.33 ± 1.26 d) and egg-laying rate (67.24 ± 30.97% and 74.12 ± 34.03%). At the end of this study, it appears that the 2 mm particle size induces better growth and egg-laying performance in Japanese quail.

Feed additive for quails based on fermented brewer’s spent grain

The paper discusses the effect of a newly developed complex feed additive Grainbiosorb used in complete feed on livability, age of first egg laying, egg productivity, and feed consumption for the production of 1 dozen eggs of laying quails of the Texas white broiler breed. The scientific experiment was carried out in the experimental vivarium of Krasnodar Research Centre for Animal Husbandry and Veterinary Medicine according to the standard technique recommended by the Federal Scientific Center “All-Russian Research and Technological Institute of Poultry” of Russian Academy of Sciences, (Sergiev Posad, 2013). The developed complex feed additive Grainbiosorb consists of fermented brewer’s spent grain, a mineral sorbing complex and probiotic microorganisms. Brewer’s spent grain is pre-fermented with probiotic bacterial concentrate, consisting of lactic acid, and propionic acid microorganisms. The use of fermented brewer’s spent grain in combination with a mineral complex can solve the problems of metabolism, digestion, exposure to heavy metals and thereby increase productivity and contribute to obtaining safe poultry products. The livability of the quail population in experimental and control groups was the same and amounted to 90.0%. The quails of the first group laid the first egg at the age of 44 days, while the quails of the second group at the age of 42 days. Gross egg production for the period of the experiment per the initial laying quail and the egg production for the average laying quail increased in the experimental group relative to the control by 3.8%. The intensity of egg production in the experimental group increased by 2.3 abs. % relative to that in the control group. Feed consumption for the production of 1 dozen quail eggs decreased by 5.5% in the experimental group, relative to the control.

Evaluation of different traits from day-old to age at first eggs of Fayoumi and White leghorn chickens and their reciprocal crossbreeds.

Objective:This study evaluated the different traits from day-old to age at first eggs of Fayoumi and White leghorn (WLH) F1 chickens and their reciprocal crossbreeds.Materials and Methods:In this study, 1,000 eggs were used to obtain experimental chicks. However, only 150 chicks were selected from each genotype for subsequent trial evaluation and reared on the same diet in a completely randomized design. The effects of genotype on each considered trait were analyzed by the statistical analysis system, and Duncan’s multiple range test made a significant difference.Results:Comparative evaluations made on all parameters illustrated significant differences (p < 0.05) throughout the study period. F1 acquired from WLH cocks and Fayoumi hens maximized weights almost at all ages during brooding, whereas pure line Fayoumi showed lower importance for the trait stages of growth. Offspring from the crossbreed of WLH cocks and Fayoumi hens had the highest weight gain than any other crossbreeds from 4 to 8 and 12 to 16 weeks of age. Pure line WLH and Fayoumi lay larger eggs and smaller eggs (41.67 and 34.00 g), respectively. The highest and smallest body weight at the age of first egg was 1,364.89 and 1,178.36 g in the main crossbreed and Fayoumi line. The main WLH cock and Fayoumi hens and reciprocal crossbreds advanced in age at first egg by 4 and 11 days, respectively.Conclusion:The leghorn hen and Fayoumi cock crosses could be used to develop potential egg-laying lines than their reciprocal crossbreeds.

The influence of alimentary factors on productivity hens

In the process of ontogenetic development chickens determined appropriate age periods characterized by inhibition of metabolism. These changes are most clearly observed changes during the primary feathers on second (main), and at the age preceding puberty and lead to lower projected laying hens. Therefore there is a need for correction of metabolic processes in the body of young birds by using biologically active substances.The results of studies on the efficiency in feeding of young chickens egg productive direction sulfate and polyenzyme drug «Natuzym». It is shown that in comparison with those of control group in poultry, the introduction into the diet of chickens egg productive direction cross «Hayseks brown» Sodium Sulphate with 10 days old and polyenzyme drug «Natuzym» of 20– to 40–day and 80–110 –days age led to an increase in average daily increments calves and body weight at the beginning of entry of birds. The positive effect of additives on the performance puberty of birds. The difference between age of first egg demolished bird control and experimental groups of four days. Later chickens experimental group also characterized higher ripening indicators such as age reaching 50% egg age and achieve peak performance. In particular, the difference of analog control group was 2 days. Was higher and egg chickens 18.53 pc. eggs per laying hen high. In this group of bird egg shell weight and his strength were higher compared with those in the control, respectively, 9.23% and 9.26% (P &lt;0.05). However, biological and food quality was improving of eggs obtained by increasing the content of carotenoids, vitamins A and E (P &lt;0.05) and soluble protein (P &lt;0.001)

SNP analysis reveals estrogen receptor 1 (&amp;lt;i&amp;gt;ESR1&amp;lt;/i&amp;gt;) gene variants associated with laying traits in quails

Abstract. In this study, the estrogen receptor 1 (ESR1) gene was studied as a candidate gene for laying traits of two quail populations (the yellow-feather quail and chestnut-feather quail). Five pairs of primers were designed to detect single-nucleotide polymorphisms (SNPs) of exon 1, 2, 4, 8 and intron 1 of the ESR1 gene by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) and sequencing methods. Only the products amplified from exon 8 displayed polymorphism. The results showed one novel variation: a variation in exon 8 of ESR1 gene (g.91C &gt; T, KC977991 and KC977992). It was associated with some laying traits in two quail populations including egg weight, the age of first egg and egg number at 20 weeks. And the CC genotype was associated with superior egg number at 20 weeks. Therefore, we speculated that the variation in exon 8 of ESR1 gene may have an effect on laying traits in the abovementioned quail populations.

Constraints and opportunities of village chicken production in debsan tikara keble at gonder zuria woreda, north gonder, Ethiopia

This study wasconducted to identify the constraints and opportunities of village chicken production in Debsan Tikara Keble at threevillages in Gondar Zuria Woreda by usingsemi structured questionnaire , fieldvisit and interview from 150 randomly selected respondents.The result revealed that the main constraints were feed shortage (28%),predation (30%) and flock mortality (28%). Almost 58% of chickens share thesame room with the main house. The farmers use traditional medicine to treatchickens (82%). Average age of first egg lying of chicken was 6 months, numberof eggs per clutch was 13, the clutch size was 3 and hatchability percentagewas 72%. The main opportunities for village chicken production was marketaccess 36%, credit service 28%, training and extension service 16%, feed and water access 20%. From this study,constraints and opportunities of village chicken production was merelyidentified based on this result by improving the management practice, poultrybreeds and educating the framers are viable options to improve the livelihoodof the households.

Single‐nucleotide polymorphisms in the promoter of the growth hormone‐releasing hormone receptor gene are associated with growth and reproduction traits in chickens

Growth hormone-releasing hormone receptor (GHRHR) plays a critical role in growth hormone (GH) synthesis, release and regulation in animals. The objective of this study was to investigate variations of the chicken GHRHR gene and their associations with growth and reproduction traits in 768 Beijing You chickens. Results revealed three single nucleotide polymorphisms (SNPs) in the promoter region of the gene (g.-1654A>G, g.-1411A>G and g.-142T>C). Association analysis revealed that the novel SNP g.-1654A>G had significant effects on chicken body weight at 7, 9, 11, 13, 17 weeks of age and the age of first egg as well as egg number at 32, 36 and 40 weeks. Significant association was also observed between g.-1411A>G and g.-142T>C with EN24. Moreover, the age of first egg was distinctly related with g.-142T>C (P < 0.05). Although significant statistical difference was not detected in GHRHR mRNA levels among genotypes of the SNPs (P > 0.05), strong expression variations of the gene were found between the ages 17 and 20 weeks in the population (P < 0.05). These results suggest that the three SNPs in the GHRHR promoter could be used as potential genetic markers to improve the growth and reproductive traits in chickens.

Cloning and expression profiling of the VLDLR gene associated with egg performance in duck (Anas platyrhynchos)

BackgroundThe very low density lipoprotein receptor gene (VLDLR), a member of the low density lipoprotein receptor (LDLR) gene family, plays a crucial role in the synthesis of yolk protein precursors in oviparous species. Differential splicing of this gene has been reported in human, rabbit and rat. In chicken, studies showed that the VLDLR protein on the oocyte surface mediates the uptake of yolk protein precursors into growing oocytes. However, information on the VLDLR gene in duck is still scarce.MethodsFull-length duck VLDLR cDNA was obtained by comparative cloning and rapid amplification of cDNA ends (RACE). Tissue expression patterns were analysed by semi-quantitative reverse-transcription polymerase chain reaction (RT-PCR). Association between the different genotypes and egg performance traits was investigated with the general linear model (GLM) procedure of the SAS® software package.ResultsIn duck, two VLDLR transcripts were identified, one transcript (variant-a) containing an O-linked sugar domain and the other (variant-b) not containing this sugar domain. These transcripts share ~70 to 90% identity with their counterparts in other species. A phylogenetic tree based on amino acid sequences showed that duck VLDLR proteins were closely related with those of chicken and zebra finch. The two duck VLDLR transcripts are differentially expressed i.e. VLDLR-a is mainly expressed in muscle tissue and VLDLR-b in reproductive organs. We have localized the duck VLDLR gene on chromosome Z. An association analysis using two completely linked SNP sites (T/C at position 2025 bp of the ORF and G/A in intron 13) and records from two generations demonstrated that the duck VLDLR gene was significantly associated with egg production (P < 0.01), age of first egg (P < 0.01) and body weight of first egg (P < 0.05).ConclusionsDuck and chicken VLDLR genes probably perform similar function in the development of growing oocytes and deposition of yolk lipoprotein. Therefore, VLDLR could be a candidate gene for duck egg performance and be used as a genetic marker to improve egg performance in ducks.

산란계에 대한 점등 광원 및 파장 차이에 따른 산란 특성에 관한 연구

닭의 눈은 빛의 색깔을 구별할 수 있고, 빛의 다른 파장은 닭의 번식 능력에 영향을 미칠 수 있다. 이에 본 연구는 산란계에서 발광소자(LED)를 이용한 단색광이 산란계에 미치는 영향을 확인하고자 수행되었다. 닭들은 발광소자(LED)를 이용하여 제작된 백색, 청색, 황색, 청색, 적색 전구와 대조구로써 백열전구의 점등 광원에 노출되었다. 모든 점등 광원은 빛의 세기를 20 lux로 고정하였다. 시험 결과, 산란 개시 일령과 산란 50% 도달 시기는 적색 점등 시에 다른 처리군과 비교하여 빨리 일어남이 확인되었으며, 난소 중량 또한 16주령에서 20주령까지 적색 점등 시에 다른 처리군에 비해 유의적으로 무거웠다. 또한, 59주령 기준 적색 LED 점등 광원에서 사육된 산란계의 헨하우스 산란수가 다른 처리군과 비교하여 가장 높음이 확인되었다. 황색 LED 점등 시 26주에서 45주령의 산란계에서 생산된 계란 무게는 다른 처리 점등 조건에 비해 유의적으로 높았다. 적색 LED 점등 시 20주의 산란계에서 생산된 계란의 난각 강도는 다른 처리 점등 조건에 비해 높았다. 비슷하게 적색 LED 점등 시 20주의 산란계에서 생산된 20주의 산란계에서 생산된 계란의 난각 두께는 다른 처리 점등 조건에 비해 높았다. 이와 같은 결과들은 적색 LED 점등 환경에서 사육된 산란계들은 산란 능력이 향상되고, LED를 이용한 다양한 파장의 점등은 계란 품질에 영향을 미칠 수 있다는 것으로 사료된다. The chicken eye can discriminate light color, and different light wavelengths may affect reproduction ability. This study was carried out to identify effect of monochromatic light using light emitting diode (LED) in laying hens. Chickens were exposed to white light (WL), blue light (BL), yellow light (YL), green light (GL) and red light (RL) made by using LED as well as incandescent light (IL) (control). All light sources were equalized to a light intensity of 20 lux. The results indicated that the age of first egg laying and 50 % egg laying in laying hens treated under RL is significantly younger than under other lights (P<0.05). And the ovary weight of laying hens reared under RL is significantly heavier than under other at from 16 to 20 wks (P<0.05). The largest number of eggs production was produced in a group with treated with RL by 59 wks of age compared with any other group. The egg weight of YL was greater than other treatment groups from 26 to 45 wks (P<0.05). The egg shell from hens treated with RL was the strongest and thickest at 20 wk (P<0.05). These results suggest that the egg quality of laying hens reared in different spectrum of LED can be different and RL may enhance the laying performance.

Body weight, fat content, liver weight and plasma leptin concentrations in broiler breeder females reared under ad libitum feeding, restricted feeding or combinations of both until age of first egg

Body weight, fat content, liver weight and plasma leptin concentrations in broiler breeder females reared under ad libitum feeding, restricted feeding or combinations of both until age of first egg

Effects of timing and duration of feed restriction during rearing on reproductive characteristics in broiler breeder females

The objective of this study was to determine whether there exists a critical period during rearing when restricted feeding of broiler breeder hens can be most beneficial on subsequent egg production. Broiler breeder pullets were subjected to combinations of either ad libitum or restricted feeding during three periods before sexual maturity. Body weight gain, feed intake, and egg production were recorded. Ovary and oviduct weights were noted at age of first oviposition. At 15 and 18 wk of age and at age of first oviposition, chicken luteinizing hormone releasing hormone-I (cLHRH-I) in the median eminence and the levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in the pituitary and plasma were determined. The results demonstrated that alternation between ad libitum and restricted feeding during rearing changed the growth curves of the birds. Feed restriction from 7 to 15 wk followed by either ad libitum or restricted feeding led to improved reproductive performance, suggesting that long-term feed restriction may not be necessary to attain good reproductive performance. The birds restricted from 7 to 15 wk of age had higher proportional weights of ovary (> or = 1.7%) and oviduct (> or = 1.58%) at age of sexual maturity. The cLHRH-I levels in the median eminence and gonadotrophin contents in the pituitary followed that of growth in response to feeding levels and timing of feeding and could be related to the timing of the onset of lay. At age of first egg, all groups had similar levels of cLHRH-I, LH, and FSH. However, no clear effect of level of feed intake or time period of restriction could be observed for plasma LH or FSH concentrations.

Direct and Correlated Responses to Multitrait, Divergent Selection for Immunocompetence

Leghorn lines had been selected for an immunocompetence index based on four traits: antibody production to Mycoplasma gallisepticum (MG) and Pasteurella multocida (PM) vaccines, reticuloendothelial clearance of colloidal carbon (CCA), and cell-mediated, wing web response to phytohemagglutinin (PHA). The purpose of this study was to produce replicated lines of chickens with divergent levels of multitrait immunocompetence by index selection. The objectives of analyses of Generations 5 to 7 of this study was to characterize these lines with respect to immune-response traits, correlations among these traits, and correlated responses in other important production traits.Differences (P < .05) existed between the lines selected for high or low immune response and between the two replicates in mean breeding values and in individual immune-response traits. Averages of heritability estimates, weighted by number of offspring and pooled across three generations (two cycles of selection), estimated by using sire variance components and parent-offspring correlations were, respectively, .16 and .09 for the index, .31 and .08 for MG, .21 and −.02 for PM, .06 and .05 for CCA, and .08 and .12 for PHA. Realized heritabilities (response divided by effective selection differential) pooled across the two selection cycles, were .19 and .11 for the index, .06 and −.01 for MG, .44 and .32 for PM, 1.52 and −1.21 for CCA, and .48 and .15 for PHA, for Replicates 1 and 2, respectively. Phenotypic correlations among traits were generally small, and several estimates were negative. Estimates of genetic correlation varied widely. Juvenile and adult body weights, age of first egg, 32-wk egg weight, and rate of egg production were analyzed to evaluate effects of selection on these traits of direct economic importance. Very few differences were noted.

The Egg Weight Curve in Pullets Selected for Early Sexual Maturity

An experiment was conducted in order to find a mathematical model that would describe the relationship of egg weight during the first stage of laying period with age at first egg for pullets maturing early at different ages. The curvilinear equation y = a + bX = cX2, where X = age of pullets, as well as Model AT: E = a + bA + cT + ΔT2, where E = egg weight; A = age of first egg; T = time; were fitted to the egg weight data from 576 pullets of a broiler-layer cross line used in a selection program. Overall, the curvilinear analysis gave R2 ranging from .50 to .89, whereas Model AT gave better results, with an R2 of .91 for individual hens. It was concluded that Model AT could be used to forecast from part record data the egg weight during the early laying period in relation to age at first egg.

The Transfer of Younger Chicks to the Laying Cages and their Subsequent Performances

The time of transferring the pullets to laying cages will depend on the vacant cages available for the replacement birds. In principle, birds should be placed in cages at the younger age in order to protect them from the stress to be given by the new environment.Chicks growing in the brooder were successively transferred to the laying cages at 55(A), 75(B), and 95(C) days of age. Some performances were observed during the period from the transfer to the end of the first-year egg production test.In terms of performances, no significant differences were observed among the three groups(A, B, C), that is, egg production, age at the first egg, body weight at age of first egg, weight of first egg, and mortality (cf. Tables 1-4). These results suggest that the transfer to the laying cages at 55-95 days of age has no detectable effects on the subsequent economic performances.

Decreased Feed Consumption and Increased Calcium Intake Associated with Pullet’s First Egg ,

INTRODUCTIONIT was shown many years ago (Halnan, 1925; Common, 1933) than an increase in skeletal storage of calcium by pullets begins two to three weeks before egg production commences. Common also showed that the amount of calcium stored varied with the level of dietary calcium. Tyler and Wilcox (1942) reported that calcium retention increases approximately two weeks prior to the onset of egg production. The increase in retention leads to the increased skeletal mineral which the pullet later uses as a calcium source (reservoir) for egg shell calcification (Taylor and Moore, 1958).However, it was not reported until recently (Foster, 1968; and Meyer, 1968) that a decrease in feed consumption occurred shortly before and after the first oviposition. Foster (1968) investigated the extent to which the drop in consumption was genetically controlled and what correlation existed between the decrease and such factors as age of first egg, body weight,…