Genetics and breeding of a black-bone and blue eggshell chicken line. 3. Visual eggshell color and colorimeter parameters in 3 consecutive generations.

The BG line, originated by crossing 2 Chinese indigenous breeds, Dongxiang blue eggshell and Jiangshan black-bone, has been bred for black carcass and blue-greenish eggs. Aiming to study the genetic parameters and selection aspects of these eggshell colors, the 4 colorimeter parameters (L*, a*, b*, SCI = L*-a*-b*) were measured on ∼5 eggs/hen/age (200 d and 300 d) from each hen in 3 generations (G4 = 452, G5 = 508, G6 = 498). Visual eggshell color was classified as either "Light," "Blue," "Green," or "Olive," and data from G4 and G5 indicated that visual eggshell color was more accurately determined by combining the classifications of single representative egg/hen by 4 independent observers.

Genetics and breeding of a black-bone and blue eggshell chicken line. 2. Laying patterns and egg production in two consecutive generations.

The BG line was originated from the cross between 2 Chinese indigenous breeds, Dongxiang blue eggshell, and Jiangshan black-bone, and has been bred to combine dark heavy black-bone body and high production of blue-shell eggs, into single dual-purpose line. Full-pedigree hens from 2 generations, G4 (n = 441) and G5 (n = 464), were reared in the same single-cage laying facility in 2019-2020 and 2020-2021, respectively. Starting from the first egg of each hen, its daily egg production was recorded until 300 days-of-age.

Genetics and breeding of a black-bone and blue eggshell chicken line. 1. Body weight, skin color, and their combined selection.

An experimental population of chickens was developed from the cross between 2 indigenous Chinese breeds, Dongxiang blue eggshell and Jiangshan black-bone. This breeding was aimed at eventually combining dark heavy black-bone body and blue eggshell, into a single dual-purpose breed. BW was recorded and skin L∗, a∗, and b∗ color parameters were measured by a Chroma Meter at several ages (56, 105, 150, 200, 250, and 300 d).

From broiler breeder hen feed to the egg and embryo: The molecular effects of guanidinoacetate supplementation on creatine transport and synthesis.

Supplementation of broiler breeder hens with beneficial additives bears great potential for affecting nutrient deposition into the fertile egg. Guanidinoacetate (GAA) is the endogenous precursor of creatine that is used as a feed additive for improving cellular energy metabolism in animal nutrition. In the present study, we have investigated whether GAA supplementation in broiler breeder feed affects creatine deposition into the hatching egg and molecular mechanisms of creatine transport and synthesis within hens and their progeny.

Dual-purpose production of genetically different chicken crossbreeds in Ethiopia. 2. Egg and meat production of the final-crossbreed females and males.

Females and males of 7 commercial (ComCb) and 3 experimental (ExpCb) crossbreeds were produced by 6 imported parent stocks (PS) and 1 local PS. The ComCb were Dominant Red Barred (DR), Dominant Sussex (DS), Lohmann Brown (LB), Lohmann-Dual, NOVOgen Brown (NB), NOVOgen Color (NC), and local Koekoek (KK). The ExpCb were (dams × sires) DR × KK (R × K), DS × DR (S × R), and KK × DS (K × S).

Dual-purpose production of genetically different chicken crossbreeds in Ethiopia. 1. Parent stocks' feed intake, body weight, and reproductive performance.

A total of 6 chicken parent stocks (PS) bred by European companies, and 1 local PS, were evaluated under Ethiopian condition for their reproductive performance, to be followed by testing dual-purpose performance of their crossbreed progeny. The imported PS were Lohmann Brown (LB), Lohmann Dual (LD), NOVOgen Brown (NB), NOVOgen Color (NC), Dominant Sussex (DS), and Dominant Red Barred (DR); Koekoek (KK) was obtained locally. They were reared in replicated floor-pens from 16 to 60 wk of age, and evaluated for feed intake, body weight (BW), egg production, fertility, and hatchability.

Maternal and genetic effects on broiler bone properties during incubation period.

In order to examine the differences in bone properties between fast-growing and slow-growing broiler embryos and to understand the effects of genotype and egg size on these differences, fast- and slow-growing hens and males were reciprocally crossed to create 4 egg groups: FST (laid by fast-growing hens, inseminated by fast-growing males), H-FST (fast-growing hens and slow-growing males), H-SLW (slow-growing hens and fast-growing males), and SLW (slow-growing hens and slow-growing males). Embryos (n = 8) from these 4 groups were sacrificed and weighed, and both tibiae were harvested on embryonic d (E) 17, 19, and 21. Left tibiae were tested for their whole-bone mechanical properties using a micromechanical device.

Featherless and feathered broilers under control versus hot conditions. 2. Breast muscle development and growth in pre- and posthatch periods.

Breast meat yield (% of BW) of featherless broilers (sc/sc) is higher than that of their feathered sibs (+/sc) and contemporary broilers (+/+) under hot temperature (32°C) conditions. This study tested the hypothesis that the advantage to the featherless broiler condition with respect to breast meat yield and quality is due to differences in muscle development during pre- and posthatch periods. Broilers from the 3 genetic groups were reared under normal (26°C) and hot (32°C) conditions and slaughtered on d 29 and 47.

Featherless and feathered broilers under control versus hot conditions. 1. Breast meat yield and quality.

The improved genetic potential of contemporary commercial broilers cannot be fully expressed under hot conditions that depress growth rate, decrease breast meat yield, and reduce meat quality. The negative heat effects are attributed to the insulating feather coverage, which, under high ambient temperatures (AT), hinders dissipation of the excessive internally produced heat. Accordingly, featherless broilers (sc/sc), their feathered sibs (+/sc), and contemporary broilers (+/+) were subjected to control AT (26°C) and hot AT (32°C) to test the hypothesis that lack of feathers contributes to higher breast muscle yield and better meat quality, especially under hot conditions, and that differences related to lack of feathers are related to cardiovascular capacity.

Genome-wide SNP scan of pooled DNA reveals nonsense mutation in FGF20 in the scaleless line of featherless chickens.

Background: Scaleless (sc/sc) chickens carry a single recessive mutation that causes a lack of almost all body feathers, as well as foot scales and spurs, due to a failure of skin patterning during embryogenesis. This spontaneous mutant line, first described in the 1950s, has been used extensively to explore the tissue interactions involved in ectodermal appendage formation in embryonic skin. Moreover, the trait is potentially useful in tropical agriculture due to the ability of featherless chickens to tolerate heat, which is at present a major constraint to efficient poultry meat production in hot climates.

The viability and performance under hot conditions of featherless broilers versus fully feathered broilers.

Hot conditions decrease the difference between ambient temperature (AT) and the average temperature of the body surface. A smaller difference reduces the rate of sensible heat loss of excessive internal heat, elevates the body temperature (BT), and may lead to mortality during heat waves. Under conditions of chronic heat, broilers avoid lethal BT elevation by reducing their feed intake; consequently, growth rate and meat yield are lower.

Yolk sac nutrient composition and fat uptake in late-term embryos in eggs from young and old broiler breeder hens.

In the present study, we examined the composition, amount, and uptake of yolk nutrients [fat, protein, water, and carbohydrates (COH)] during incubation of eggs from 30- and 50-wk-old broiler breeder hens. Eggs were sampled at embryonic d 0 (fresh eggs), 13, 15, 17, 19, and 21 (hatch). Egg, embryo, yolk content, and yolk sac membrane were weighed, and the yolk sac (YS; i.

The effects of feed restriction and ambient temperature on growth and ascites mortality of broilers reared at high altitude.

The development of ascites was investigated in broilers at low versus high altitudes, cold versus normal ambient temperatures (AT), and 3 feeding regimens. One-day-old chicks obtained at sea level were reared at high altitude (highA; 1,720 m; n = 576) with 2 AT treatments, low AT from 3 wk onward at highA (highA/cold) and normal AT from 3 wk onward at highA (highA/norm), or at sea level (normal AT from 3 wk onward at low altitude, lowA/norm; n = 540). Under highA/cold, AT ranged between 16 to 17 degrees C in the fourth week, 17 to 19 degrees C in the fifth week, and 19 to 21 degrees C thereafter.

Physiological parameters in broiler lines divergently selected for the incidence of ascites.

Ascites syndrome (AS) is manifested in flocks of contemporary broilers that are allowed to fully manifest their genetic potential for rapid growth. After successful selection, a pair of divergent lines was established, AS-susceptible (AS-S) and AS-resistant (AS-R). These lines facilitate comparisons between genetically resistant and susceptible healthy young broilers when reared under standard brooding conditions (SBC).

Effects of the genetically reduced feather coverage in naked neck and featherless broilers on their performance under hot conditions.

Under hot conditions, contemporary commercial broilers do not reach their full genetic potential for growth rate, body weight (BW), or breast meat yield because dissipation of their excessively produced internal (metabolic) heat is hindered by the feathers. Therefore, it was hypothesized that heat stress can be alleviated by using the naked-neck gene (Na) or the featherless gene (sc). The study consisted of 4 experimental genetic groups (fully feathered, heterozygous naked neck, homozygous naked neck, featherless), progeny of the same double-heterozygous parents (Na/na +/sc), and commercial broilers.

Unique co-expression of immune cell-related genes in IBDV resistant chickens indicates the activation of specific cellular host-response mechanisms.

Infectious bursal disease virus (IBDV) causes highly contagious, immunosuppressive disease that leads to high mortality in young chickens. The purpose of this study was to look for the genetic regulation of the immune acute immune response to IBDV in our selected lines. Chicks of a F2 generation of two lines divergently selected for early high (HH) or low (LL) antibody (Ab) response to Escherichia coLi vaccination were challenged with virulent IBDV.

QTLs detected in a multigenerational resource chicken population.

The genetic structure of resource populations affects the power of tests to detect associations between DNA markers and complex traits. Following a chicken interline cross (White Plymouth Rock background), we produced a multigenerational resource population based on 4 pedigreed generations. In this large sibship, 265 parents have been genotyped, and their 3317 progenies have been phenotyped for BW21, BW42, breast meat weight, fat pad weight, and egg production.

Sex and genotype dependence on the effects of long-term high environmental temperatures on cellular enzyme activities from chicken organs.

The effects of long term hyperthermia on enzyme levels in the chicken heart and breast muscles, brain, kidney, liver and lung, in relation to sex and degree of feathering, were studied. The enzymes studied were alanine and aspartate amino-transferases, alkaline phosphatase, creatine kinase, lactic dehydrogenase and gamma-glutamyltransferase. Double heterozygote frizzled naked neck and normally feathered male and female broilers were exposed to 24 degrees C (control group) and 32 degrees C (experimental group), for 5 weeks, starting at the age of 3 weeks.

Growth rate of ascites-resistant versus ascites-susceptible broilers in commercial and experimental lines.

The high growth rate (GR) of contemporary broilers is driven by high rate of feed intake and metabolism. Because of the consequent high oxygen demand, especially when coupled with exposure to high altitude or low temperatures, some broilers fail to regulate oxygen supply and develop the ascites syndrome (AS), which leads to mortality and economic losses. Because of the association between high GR, oxygen demand, and AS, it has been suggested that AS is induced by high GR.

The expression patterns of hypoxia-inducing factor subunit alpha-1, heme oxygenase, hypoxia upregulated protein 1, and cardiac troponin T during development of the chicken heart.

Oxygen is one of the critical determinants of appropriate embryonic and fetal development, including cardiogenesis. When the demand of tissues for oxygen exceeds oxygen supply, hypoxic conditions develop. In the developing embryo, hypoxia is associated with increased fetal mortality, cerebrovascular anomalies, cardiovascular dysfunction, and altered angiogenesis.

Segregation among test-cross progeny suggests that two complementary dominant genes explain the difference between ascites-resistant and ascites-susceptible broiler lines.

Ascites syndrome (AS) is a major cause of economic losses to the broiler industry. The tendency of broilers to develop AS was found to be heritable, suggesting that selective breeding could provide a solution to this problem. To further elucidate the genetic control of AS, AS-susceptible (AS-S) and AS-resistant (AS-R) lines were established by 3 cycles of divergent selection on pedigree data of AS mortality under AS-inducing conditions.

Development of ascites-resistant and ascites-susceptible broiler lines.

The rapid growth of modern broilers is associated with enhanced appetite and high metabolic rate and, consequently, high O(2) demand. Ascites syndrome (AS) develops in individuals that fail to fully supply the increasing demand for O(2) in their bodies under ascites-inducing conditions (AIC) such as high altitude or low temperatures. The tendency of broilers to develop AS is heritable, but efficacious selection against AS susceptibility (without affecting the normal expression of other important traits) requires identification of indirect selection criteria.

Evaluation of growth rate, body weight, heart rate, and blood parameters as potential indicators for selection against susceptibility to the ascites syndrome in young broilers.

The continuous selection for rapid growth has been accompanied by an increasing occurrence of ascites syndrome (AS), which develops in broilers failing to supply the increasing demand for O(2) in their bodies. Moderate heritability has been reported for AS in broiler populations, suggesting that selection against AS is feasible. However, direct selection based on AS mortality requires exposure of candidate birds to AS-inducing conditions (AIC), which hinder selection for performance traits.

Marker-assisted selection based on a multi-trait economic index in chicken: Experimental results and simulation.

A method proposed herein allows simultaneous selection for several production traits, taking into consideration their marginal economic values (i.e. the economic value of a trait's additional unit).

Genetic variation in major histocompatibility complex class I alpha2 gene among broilers divergently selected for high or low early antibody response to Escherichia coli.

The MHC genes have a profound effect on animal abilities to respond to specific antigens because they play a role in presenting foreign antigens to T cells during the course of the humoral or cellular immune response. In the current study, polymorphism in the MHC class I alpha2 domain was compared in 2 lines divergently selected for high (HH) or low (LL) antibody response to Escherichia coli vaccine. These lines also differ markedly in their antibody response to natural E.