Naked Neck Gene Research Articles

A comparative study of population structure and genetic diversity of commercial and indigenous chickens from different agro-ecological zones in Ghana using SilicoDArT and SNP markers

Chicken production, both in the local and commercial sectors, contributes significantly to human livelihood and food security. Precise use of diverse genetic resources is primary in breeding programs. The study analyzed the genetic diversity and population structure of commercial chickens and indigenous chicken ecotypes from three different agro-ecological zones (Semi-Deciduous Rainforest Zone, Guinea Savannah, and Coastal Savannah) using SilicoDArT and SNP markers, utilizing whole-genome sequencing and phenotypic data. Phenotypic data were collected from 72 indigenous chicken ecotypes across the three AEZs, and 32 commercial birds kept at the Kwame Nkrumah University of Science and Technology (KNUST). DNA samples used for sequencing were obtained from 88 chickens (62 indigenous chicken ecotypes and 26 commercial chickens). A total of 54,995 SilicoDArT and 85,396 SNPs markers were generated from DArTseq genotyping. After filtering, 44,784 SilicoDArT and 58,353 SNP were used for genetic diversity and population structure analysis. Both markers showed high reproducibility and call rate. Polymorphic information content (PIC) values ranged from 0.00 to 0.50, while ≥ 50 % showed PIC values more than the median. Furthermore, we obtained FST values, Nei’s genetic distance, dendrogram analysis, and principal component analysis (PCA) of commercial and indigenous chickens. The FST and Nei’s genetic distance showed that there is high genetic diversity between the commercial chickens and the indigenous chicken ecotypes. However, there was low genetic diversity among the indigenous chicken ecotypes. The PCA analysis indicated a clear separation between the commercial and indigenous chicken ecotypes, while no clear separation was observed between the indigenous chicken ecotypes. The phenotypic data and the dendrogram indicated that naked and frizzle genes do not markedly alter the genetics of indigenous and commercial birds, and their influence on economic traits may be solely determined by the prevailing environmental conditions. The results indicate that there is high genetic differentiation between commercial and indigenous chickens based on SilicoDArT and SNP markers. The indigenous chickens from the agro-ecological zones have low genetic diversity and might have a common origin. Naked neck and frizzle genes do not markedly alter the genetic performance of birds in terms of economic traits. Therefore, the superiority of birds carrying these genes in economic traits may be solely due to environmental variation.

Impact of a 15% spirulina (Limnospira platensis) dietary inclusion on productive performance and meat traits in naked neck and fully feathered slow-growing broiler strains

Global population is rising, leading to higher demand for meat and concerns on environmental and economic impacts of conventional feedstuffs that corn and soybean meal have. Recently there has been a shift towards more sustainable feedstuffs such as Spirulina (Limnospira platensis) due to its nutritional value and ability to be produced locally. Consumer awareness prompts shifts towards free range poultry production but presents environmental challenges due to climate change. The naked neck (Na) gene, which reduces feather coverage, and enhances growth under adverse conditions offers a possible solution for improved welfare and efficiency. This study aims to investigate the impact of a diet with 15% Spirulina inclusion on growth performance, carcass traits, and meat quality of two slow-growth broiler strains: naked neck (NN) and fully feathered (FF). Forty, 1-day-old male broilers, 20 per strain, were randomly assigned to either a control or a diet containing 15% Spirulina, housed individually in cages and fed ad libitum for 84 d. Growth, carcass, and meat traits were evaluated. Results indicated that animals fed a control diet generally outperformed those fed a Spirulina diet in final body weight (BW), average daily gain (ADG), feed intake (FI), and feed conversion rate (FCR) (P < 0.001). Additionally, Spirulina incorporation led to an increase in the length of the gastrointestinal tract and digesta viscosity in the duodenum plus jejunum (P < 0.05). Although there were no significant differences in breast muscle yield between dietary groups, SP-fed broilers had higher yellowness (*b) values in meat (P < 0.05). Except for the decrease in water holding capacity (WHC) observed in the NN group animals (P < 0.05), there were no significant differences between the strains for the remaining meat quality traits (P > 0.05). The 15% Spirulina inclusion increased the concentrations of n-3 polyunsaturated fatty acids (PUFA) (P < 0.0001) in breast meat and decreased (P < 0.0001) nutritional ratios. Overall, under thermoneutral conditions, animals from the NN strain showed negative effects on growth parameters. Spirulina inclusion improved certain aspects of breast meat quality, particularly fatty acid profiles.

Effect of the “Naked neck” gene (Na) on the growth of indigenous chicken fed with suboptimal feed rations in Cameroon

The effect of the naked neck gene (Na) was assessed on growth parameters of the native chicken fed with two suboptimal rations (R1 and R2), and one optimal ration (R3) from 6 to 16 weeks of age. A total of 270 hens of 3 genetic types (homozygous (NaNa) naked neck, heterozygous (Nana) and normal type (nana) chicken) for three different feed rations including two sub-optimal rations (R1, R2) and one optimal ration (R3). Hence, 30 pullets per experimental unit for each genetic type receiving the same ration were used. The animals were subjected to the same experimental conditions except for the tested factor. The starter ration was served during the first six weeks then relayed by the experimental rations. A two-way ANOVA was used to test the main effects and interactions whereas the animal model was used for the estimates of the genotype and feed ration on the growth and related traits. Irrespective of the genotype, the highest growth parameter (p&lt;0.05) was obtained with R3 with the lowest feed efficiency from 12 to 16 weeks. The mortality rate (MR) ranged from 3 to 9% cumulated at 6 and 8 weeks of age. The overdominance effect was confirmed for both the bodyweight (BW) and MR. The Na gene improved the weight gain from +1 to + 14 g from 10 to 16 weeks with optimal feed conditions against -6.67 to +4.33g with suboptimal feed. The more beneficial effect on FCR has been observed in homozygote NaNa with +1.07 to +1.27g and -0.43 to -1.63g for R3 and R1 respectively. This study confirms the importance of the Na gene as a good candidate to improve the growth rate and feed efficiency of native chickens. It also provides an effective protocol for the evaluation of major gene candidates for selection in low input production systems.

Naked neck gene and intermittent thermal manipulations during embryogenesis improve posthatch performance and thermotolerance in slow-growing chickens under tropical climates

Many studies have shown that thermal manipulations during the incubation (TMI) and naked neck gene (Na) positively affect heat-stressed broilers' thermotolerance, hatching process, and posthatch performance. Their combination could increase the beneficial effect on broilers reared under natural tropical climatic conditions. The aim of this study was to investigate the effects of the Na gene and TMI on hatching and posthatch performance of slow-growing broilers under tropical climates. The study included 1,200 hatching eggs from 2 different crosses: 1) females and males, both with a normal or fully feathered neck (na na group), and 2) females (with a normal neck) and males (bare neck) (Na na group), incubated in similar conditions until d 7. Thereafter, they were assigned to 3 subgroups for each cross: the control group (C) was incubated at standard incubation conditions (37.8°C, 60% RH). The TMI-1 group was subjected to TMI-1 (T=38.5°C, RH=65%, E10-18, 6 h/d) and TMI-2 group to TMI-2 (T=39.5°C, RH=65%, E7-16, 12 h/d). Between 450 and 504 h of incubation, eggs were checked for hatching events. During the posthatch phase, chicks from each incubation subgroups (Na na-C, Na na-TMI-1, Na na-TMI-2, na na-C, na na-TMI-1, na na-TMI-2) were raised for 12 wk at a tropical natural ambient temperature. Hatchability, hatching time, chick's temperature, final body weight (FBW), and feed conversion ratio (FCR) were determined. The results revealed that the Na gene reduced (P ˂ 0.05) hatchability. The control group had the highest mortality rate compared to TMI-1 and TMI-2 groups. There was an interaction between genotype and TMI on incubation duration, hatching weight, chick quality, FBW, and FCR (P ˂ 0.05). In conclusion, the Na gene influenced the effects of thermal manipulation. TMI-1 combined with Na gene improved the productive performances of broilers in a tropical climate.

The Naked Neck Gene in the Domestic Chicken: A Genetic Strategy to Mitigate the Impact of Heat Stress in Poultry Production—A Review

The poultry sector is one of the most important food industries in the world. Poultry production generates high-value protein products (meat and eggs) that are produced efficiently without the need for large areas. In poultry production, especially in the tropics, environmental factors, such as temperature and humidity, play a major role. Heat stress (HS) causes behavioral, physical, and physiological changes in poultry, with severe financial impacts. Therefore, it is important to find strategies to minimize it. The naked neck (Na) is an autosomal, incompletely dominant gene. Compared with normal feathered birds, these animals are known for their ability to adapt, perform, and reproduce under hot and humid climate conditions. Due to the absence of feathers on the neck, these animals increase heat dissipation, alleviating adverse heat effects, especially on productive performance. Genetic improvement of heat tolerance may provide a low-cost solution, of particular interest for developing countries in the tropics. The focus of this review is to evaluate the impact of HS in poultry with a special emphasis on the advantages of using the Na gene.

English

An eleven-month experiment was conducted to establish the influence of phenotype and feeding systems on growth performance and carcass characteristics of F1 crossbred broilers. One hundred normal feathered broiler breeder females were mated with 10 naked neck males to obtain the F1.&nbsp; Two hundred and seventy-two chicks obtained from the F1 generation and from four hatches were randomly assigned into four treatments (naked neck full feeding, naked neck feed withdrawal, normal feathered full feeding and normal feathered feed withdrawal) in an RCBD 2 &times; 2 factorial arrangement and studied for 12 weeks. The naked neck broilers had superior (P &lt; 0.05) weight and better feed conversion compared to their normal feathered counterparts. Chickens on full feeding had higher (P &lt; 0.05) feed intake in comparison to their counterparts on feed withdrawal. Normal feathered birds had higher (P &lt; 0.05) average rectal temperature compared to the naked neck ones. Mortality was lower (P &lt; 0.05) in naked neck birds compared to their normal feathered siblings. Birds on feed withdrawal had higher (P &lt; 0.05) average rectal temperature in contrast to their counterparts on full feeding. The naked neck gene improves growth performance, carcass yield and survivability hence should be incorporated into broiler breeding programmes for tropical countries. Key words: Broiler, carcass, feed withdrawal, naked neck, phenotype, traits.

Influence of thermoregulatory (Na & F) genes on performance and blood parameters of F2 and F3 generations of crosses of local and commercial chickens.

High ambient temperatures pose serious productive challenges to poultry farmers in the tropics with adverse consequences such as reduced egg production. A study was undertaken to assess the effect of naked neck (Na) and frizzle (F) genes on the performance of F2 and F3 generations of crosses of commercial and indigenous chickens in Ghana. One thousand, five hundred and sixty-five (1,565) eggs distributed in a randomized complete block design comprising 4 genotypes and 15 hatches were used for the first study. The eggs were produced from 33 each F2 crossbred normal-feathered (nanaff), naked neck (Na), frizzle (F) and both (Na and F) alleles carrying chickens to determine the effects of these genes on fertility and hatchability. Data were analysed using the mixed model procedure of GenStat statistical software. Eggs from birds with the heat-tolerant genes, either in the single or double doses, were significantly more fertile than those from birds without the genes. Eggs of birds carrying the F allele had significantly (P < 0.05) higher hatchability than eggs from birds carrying the Na allele.Subsequently, 199 F3 crossbred chickens obtained from six hatches generated by the F2 generation were used for the evaluation of growth, egg production, haematological and blood biochemical parameters. The genotypic groups were normal feathered (nanaff), homozygous naked neck (NaNaff), heterozygous naked neck (Nanaff), homozygous frizzle (nanaFF), heterozygous frizzle (nanaFf), double homozygous naked neck-frizzle (NaNaFF) and double heterozygous naked neck- frizzle (NanaFf). The Nanaff recorded a significantly (P < 0.05) heavier day-old body weight compared to all other genotypes except the NaNaff birds.The nanaff genotype reached sexual maturity significantly earlier than all other genotypes. Hen day egg production and egg weight were also significantly higher in nanaff birds compared to birds carrying either Na or F allele, or both alleles. All birds carrying the naked neck and frizzle genes had significantly higher packed cell volume (PCV) concentration than the nanaff genotype. The Nanaff genotype recorded a significantly higher blood haemoglobin concentration compared to the nanaff, nanaFf and NaNaFF ones. However, birds carrying the thermoregulatory genes recorded significantly (P < 0.05) higher haemoglobin values except for the heterozygous frizzle. The thermoregulatory genes are of importance in chicken populations in Ghana as they positively influence percentage fertility of chicken eggs and PCV concentrations of chicken blood.

EGG QUALITY OF THE NIGERIAN LOCAL CHICKEN AS INFLUENCED BY SOME MAJOR GENES

An investigations was carried out to determine the effect of the major genes of frizzling and naked neck on the external and internal egg quality traits of the Nigerian local chicken. Egg weight significantly (P &lt; 0.01) favoured the frizzled local chicken and the naked-necked local chicken over the fully feathered (normal ) local chicken. The frizzling gene, F, caused an increase of 8.13% in weight while the naked neck gene Na, increased egg weight by 5.85%. The Na gene caused the production of better egg shape index (0.73) when compared to F and nana, ff genotypes. Eggs of frizzed and naked-neck locals also had significantly (P &lt; 0.05) better Haugh unit, percent shell, percent albumen and percent yolk than the normal feathered counterpart. It is therefore reasonable to incorporate the major genes frizzling and naked-neck in producing a locally-adapter commercial egg strain

Growth rates of main and reciprocal crosses of Isa Brown and local chickens

The absolute and relative instantaneous growth rates of F1 hybrid chickens were determined at 2- 10 and 12-20 week periods of growth. The hybrids were hatched from eggs laid by 69 Isa Brown and local chicken parents. A total of 123, 49 and 116 chicks of Isa Brown x frizzle feathered (IBxF), Isa Brown x naked neck (IBxNa) and Isa Brown x normal feathered IBxN) main crosses and 137, 42 and 64 chicks of frizzle feathered x Isa Brown (FxIB), naked neck x Isa Brown (Na x IB) and normal feathered x Isa Brown (NxIB) reciprocal crosses, respectively were produced at day-old. The greatest absolute growth rates of 49.44g/week at 2-10 weeks and 71.11 g/week at 12-20 weeks were obtained from IBxN and FxIB genotypes, respectively. Instantaneously, IBxNa had the greatest rate of 0.28 g/time at 2-10 weeks, while IB x F and Na x IB each at 12-20 weeks were found to grow at the greatest rate of 0.091 g/time, respectively. It was concluded that normal and naked neck genes could be utilised in main crosses to develop fast growing broiler chicks while frizzle and naked neck genes could be used in reciprocal crosses to improve good laying pullets without precocious maturity.

Impact of Heat Stress on Poultry Health and Performances, and Potential Mitigation Strategies.

Simple SummaryHigh environmental temperature alters the poultry health and performances by causing heat stress. Heat stress elicits physiological, behavioral, and production changes in poultry. This review article summarizes these changes along with the strategies that have been used in the poultry industry to ameliorate the adverse effects of heat stress in poultry.Heat stress is one of the major environmental stressors in the poultry industry resulting in substantial economic loss. Heat stress causes several physiological changes, such as oxidative stress, acid-base imbalance, and suppressed immunocompetence, which leads to increased mortality and reduced feed efficiency, body weight, feed intake, and egg production, and also affects meat and egg quality. Several strategies, with a variable degree of effectiveness, have been implemented to attenuate heat stress in poultry. Nutritional strategies, such as restricting the feed, wet or dual feeding, adding fat in diets, supplementing vitamins, minerals, osmolytes, and phytochemicals, have been widely studied and found to reduce the deleterious effects of heat stress. Furthermore, the use of naked neck (Na) and frizzle (F) genes in certain breed lines have also gained massive attention in recent times. However, only a few of these strategies have been widely used in the poultry industry. Therefore, developing heat-tolerant breed lines along with proper management and nutritional approach needs to be considered for solving this problem. Thus, this review highlights the scientific evidence regarding the effects of heat stress on poultry health and performances, and potential mitigation strategies against heat stress in broiler chickens and laying hens.

Laying performance, immune response and antioxidant properties of hens segregating for naked neck and frizzle genes under low ambient temperature

Major genes could be introgressed into laying hens to attenuate heat stress. However, under cold and/or moderate ambient temperature, these genes might possess different behaviour. The main objective of this study was to evaluate laying performance, immune response, and antioxidant status of native laying hens segregating for naked neck (Na) and frizzle (F) genes under low ambient temperature. Five genotypes were studied: homozygous naked neck (NaNaff), heterozygous naked neck (Nanaff), homozygous frizzle (nanaFF), heterozygous frizzle (nanaFf), and normally feathered (nanaff). The hens were raised under temperature range 22.2–16.7°C. No adverse effect due to ambient temperature was detected in laying performance for naked neck genotypes. Significant decrease in egg weight was recorded in nanaFF genotype compared to the other genotypes leading to significant decrease in egg mass. Significant improvement in shell thickness was associated with Na and F genes. NaNaff genotype had a significantly higher eggshell strength compared to nanaff. Furthermore, Na and F genes improved cellular mediated immune responsiveness, whereas this improvement did not extend to humoral immunity. Birds carrying F gene in homozygous state had a higher total antioxidant activity compared to the remaining genotypes. It could be concluded that the presence of Na and F genes in laying hens raised under low ambient temperature significantly increased shell thickness and, in turn, improved shell strength. Moreover, they greatly enhanced cellular immunity, particularly in heterozygous naked neck status.

Expression levels of HSP70 and CPT-1 in three local breeds of chickens reared under normal or heat stress conditions after the introduction of the naked neck gene

The naked neck gene was introduced by crossbreeding into Egyptian breeds to improve body weight. Expression levels of HSP70 and CPT-1 were used to assess the heat tolerance of three Egyptian local breeds (Fayoumi, Dandarawi and Sinai) with and without the naked neck gene and under normal and heat stress conditions.There were two genotypes from each breed that had the same genetic origin (the naked neck and normal plumage genotypes). For each genotype, chicks were divided into two groups, a control group and a treated group. Chicks in the treated group were subjected to heat stress (40 °C) for four hours when they were between 3 and 5 days old.This treatment was associated with a highly significant increase in HSP70 and CPT-1 gene expression for the Dandarawi breed compared to the levels in the Fayoumi and Sinai breeds.Moreover, the introduction of the naked neck gene into these local breeds caused marked increases in CPT-1 gene expression, but these increases did not significantly differ among different naked neck genotypes.Therefore, it could be concluded that the Dandarawi breed exhibited the best heat tolerance, followed by the Sinai breed, whereas the Fayoumi breed was inferior in this respect. Furthermore, the naked neck gene improved heat tolerance by increasing HSP70 gene expression rather than only by reducing feather cover.The results obtained recommended using the Sinia naked neck chicken as a male line in commercial parent stock to produce broiler chicks adapted to the hot and warm climates.

Genetic diversity of Saudi native chicken breeds segregating for naked neck and frizzle genes using microsatellite markers.

ObjectiveRecently, there has been an increasing interest in conservation of native genetic resources of chicken on a worldwide basis. Most of the native chicken breeds are threatened by extinction or crossing with ecotypes.MethodsSix Saudi native chicken breeds including black naked neck, brown frizzled, black, black barred, brown and gray were used in the current study. The aim of the current study was to evaluate genetic diversity, relationship and population structure of Saudi native chicken breeds based on 20 microsatellite markers.ResultsA total of 172 alleles were detected in Saudi native chicken breeds across all 20 microsatellite loci. The mean number of alleles per breed ranged from 4.35 in gray breed to 5.45 in normally feathered black with an average of 8.6 alleles. All breeds were characterized by a high degree of genetic diversity, with the lowest heterozygosity found in the brown breed (72%) and the greatest in the frizzled and black barred populations (78%). Higher estimate of expected heterozygosity (0.68) was found in both black breeds (normal and naked neck) compared to the other chicken populations. All studied breeds showed no inbreeding within breed (negative inbreeding coefficient [FIS]). The phylogenetic relationships of chickens were examined using neighbor-joining trees constructed at the level of breeds and individual samples. The neighbor-joining tree constructed at breed level revealed three main clusters, with naked neck and gray breeds in one cluster, and brown and frizzled in the second cluster leaving black barred in a separate one.ConclusionIt could be concluded that the genetic information derived from the current study can be used as a guide for genetic improvement and conservation in further breeding programs. Our findings indicate that the Saudi native chicken populations have a rich genetic diversity and show a high polymorphism.

Influence of different tropical stress conditions on biochemical parameters invarious broiler strains

The present experiment was conducted to study the effect of different tropical stress conditions on biochemical traits in various broiler strains during 3 to 4 weeks of age. Introgressing some important major genes likes Naked neck (Na) and Frizzle (F) into broiler germplasm may substantially improve the heat tolerance. Hence, the experiment was designed to evaluate three indigenously developed broilers &lt;italic&gt;viz&lt;/italic&gt;. CARIBRO-Tropicana (Naked neck and Frizzle gene bearing), CARIBRO-Mritunjai (Naked neck gene bearing) and CARIBRO-Vishal (Normal plumaged) under different THI (i.e. 72, 85 and 91) for 4 hours daily for 7 days. Total 324 broiler chicks (i.e. 36 chicks in each group) of 3 weeks of age were used in this study. The changes in blood biochemical parameters (i.e. Na, K, Glucose and ACTH) were examined in these experiments at 0&lt;sup&gt;th&lt;/sup&gt;, 3&lt;sup&gt;rd&lt;/sup&gt; and &lt;sub&gt;7&lt;/sub&gt;th into exposure trials. The glucose, ACTH were observed lowest in frizzle and highest in normal plumaged birds under different THI. In experiment Na and K were observed higher in Frizzle and lowest in normal plumaged birds under different THI. The CARIBRO-Vishal showed highest stress as compared to other group. Higher the THI more severe was the effect on the traits. During the 7 day of exposure trial, birds of all the genetic group exhibited the phenomenon of acclimatization as reveled by the averages of various traits at different days into the exposure.

Evaluating the Age-Dependent Potential for Protein Deposition in Naked Neck Meat Type Chicken

Simple SummaryGrowth rates of fast-growing chickens are reduced by a higher ambient temperature (AT) because of difficulties in dissipating heat through the feather coverage. Naked neck meat type genotypes could be helpful in increasing the tolerance for high AT. However, basic model parameters of this genotype necessary to further assess amino acid requirements are as yet unavailable. The experiments were conducted to estimate both the daily nitrogen maintenance requirement (NMR) and the potential for daily nitrogen retention NRmaxT). These observed model parameters provide the basic information to characterize the growth potential of the genotype for further application in modeling of individual amino acid requirements of naked neck meat type chicken.The introduction of the naked neck gene (Na) into modern meat type chicken is known to be helpful in increasing the tolerance for a high ambient temperature (AT) by reducing the feather coverage which allows for a higher level of heat dissipation compared to normally feathered (na/na) birds. In addition, reduced feather coverage could affect requirements for sulfur containing amino acids. As a prerequisite for further modeling of individual amino acid requirements, the daily N maintenance requirement (NMR) and the threshold value of daily N retention (NRmaxT) were determined. This was carried out using graded dietary protein supply and exponential modeling between N intake (NI) and N excretion (NEX) or N deposition (ND), respectively. Studies with homozygous (Na/Na) and heterozygous (Na/na) naked neck meat type chicken utilized 144 birds of average weight (50% of each genotype and sex) within two N balance experiments during both the starter (days 10–20) and the grower period (days 25–35). Birds were randomly allotted to five diets with graded dietary protein supply but constant protein quality. The observed estimates depending on genotype, sex and age varied for NMR and NRmaxT from 224 to 395 and 2881 to 4049 mg N/BWkg0.67/day, respectively.

THE EFFECT OF EGGSHELL ULTRASTRUCTURE ON HATCHABILITY PERCENTAGE OF EGGS LAID FROM NAKED NECK, FRIZZLED AND NORMALLY FEATHERED HENS

This experiment was designed to evaluate the effect of naked neck (Na) and frizzle (F) genes on eggshell ultrastructure at different intervals of incubation period. 81 eggshell samples (9 samples/ genotypes/ incubation studied intervals) were taken before incubation period, at 12 days of incubation period and after hatching. Before incubation period, the present results showed that the presence of Na or F genes in a single manner significantly increased the palisade layer compared to normally feathered genotype. The Na had effected used calcium from mammillary layer during embryonic development . It is well known that local strains enjoined with higher percentage of fertility. Introducing naked neck (Na) or frizzle (F) genes did not depress this higher fertility. Moreover, under high ambient temperature, naked neck and frizzled genotypes recorded higher fertility percentage than that recorded for normally feathered one. On the other hand, it is noticed that, naked neck gene decreased hatchability percentage; this may be attributed to the positive effect of naked neck gene on increasing the length of palisade layer of eggshell ultrastructure. The decreasing of hatchability associ ated with naked neck gene was a major cause that impeded the spread of using this gene in commercial strains. In order to solve this problem and avoiding the disadvantage of naked- neck gene, it could be beneficial to insert this gene in a commercial strain and select for a decreased palisade length.

Effect of Dwarf and Naked Neck Gene on the Egg Production Performance in Tropics

Cocks and pullets from each of 4 genotypes; Redbro (RbRb), Naked neck (NaNa), Redbro dwarf (Rbdw) and Naked neck dwarf (Nadw) were crossed reciprocally for egg production trial. Egg quality (egg weight, egg diameter, egg length, shell thickness, membrane thickness, membrane weight, shell weight, % of shell, yolk color score, albumen diameter, albumen height, yolk diameter and yolk weight) were compared among 4 genotypes. Daily feed intakes, almost related to respected body size were reduced in Rbdw and Nadw hens by 7.41 and 19.89% than in normal sized RbRb hens. The feed conversion and hen day egg production were highest in Rbdw, intermediate in RbRb and Nadw and lowest in NaNa. Naked neck (Na) and dwarf genotypes had favorable effect on egg fertility and hatchability. Parents in both Na and dw inheritance had favorable shell thickness, shell membrane weight (%), albumen height and diameter, yolk height and diameter, albumen weight and albumen weight (%) and yolk weight, while NaNa had highest yolk weight (%). Both egg weight and chick weight percent were highest in RbRb x Rbdw genotypes, followed by RbRb, RbRb x Nadw, RbRb x NaNa, Rbdw x RbRb, Rbdw, Rbdw x Nadw, Rbdw x NaNa, Nadw x RbRb, Nadw x Rbdw, Nadw, Nadw x NaNa, NaNa x RbRb, NaNa x Rbdw, NaNa x Nadw and NaNa respectively. Chick weight as percent of egg weight irrespective of genotype was simply the functions of egg weight.DOI: http://dx.doi.org/10.3329/pa.v18i2.18167 Progress. Agric. 18(2): 115 - 121, 2007

Naked neck and frizzle genes for improving chickens raised under high ambient temperature: I. Growth performance and egg production

High ambient temperatures in tropical and subtropical regions adversely affect the growth and egg productive performance of both broiler and laying chickens. Relative humidity and ventilation rate influences bird's performance, particularly when they are reared in open sided poultry houses. Genetic approaches that aid in reducing or altering the extent of plumage cover has, as a result, been adopted in many hot regions. Fortunately, there are some major and marker genes can reduce the deleterious effects of heat stress, naked neck (Na) and frizzle (F) genes being the most notable ones. The bulk of relevant literature has shown that their favourable effects on growth and laying performance are well established. Therefore, the naked neck and frizzle genes can be a viable alternative for broiler and layer production particularly, in the tropical countries where summer temperatures are very high.

The effect of plumage modifier genes on egg quality indices of the Nigerian local chicken

The effect of plumage modifier genes on some internal and external egg quality indices in the Nigerian local chicken in the guinea savanna was evaluated. The frizzle (ff) and naked neck (Na) local birds had a significantly (p<0.05) higher egg weight than the normal feathered birds (na). Mean egg weights were 33.29 0.27, 36.16 0.20 and 43.15 0.21 in the na, ff and Na genetic groups respectively. The frizzle and naked neck genes positively increased egg weights by 8.62 and 29.62 per cent over the normal feather gene. However, egg shape index significantly (p<0.05) favoured the normal feathered birds over the other two genetic groups of the Nigerian local chicken studied. Similarly, shell thickness was significantly (p<0.05) higher in the ff and Na birds than in the na. Consequently, the modifier genes of frizzling and naked neck are relevant in the development of a layer breed for the local environment.

The effect of naked neck gene and ambient temperature and their interaction on reproductive traits of heavy broiler dams

High ambient temperature is a major factor for diminishing reproductive performance of broiler parent stocks. Homozygous naked neck (NaNa) broilers, which possess a higher adaptation to heat due to a reduction of feather coverage, exhibited higher growth rates and meat yield. This study was conducted to investigate the influence of genotype x temperature interactions on the reproduction traits of heavy broiler dams caused by different feathering genotypes induced by naked neck gene (Na). In an additional experiment, the effect of Na gene on embryonic activity using oxygen uptake was examined. Normal-feathered (nana) and NaNa hens were maintained in separate cages under high (30 degrees C) and moderate (19 degrees C) temperatures, with RH of 55% from the 18th to 72nd week of age. Egg production, fertility, hatchability, and the time of embryonic mortality were recorded. In comparison with the NaNa genotype, the nana hens showed clear performance depressions under thermal stress with respect to egg production (63%), fertility (20%), hatchability, and number of chicks (72%). Under temperate ambient temperature, there were no differences in laying performance and fertility between both genotypes, with the exception of hatchability due to an increase in embryonic mortality as a result of the Na gene and consequently in the complex trait number of chicks. The early embryonic mortality of eggs laid by nana hens exposed to heat stress is clearly higher than of eggs by nana hens kept under temperate ambient temperature. In contrast, there were no significant differences in early embryonic mortality of eggs of NaNa birds kept under high and temperate environmental temperatures, demonstrating that heat stress leads to reduced early embryonic livability. Embryonic mortality in the late developing stage is significantly increased, and the homozygous genotype is much more affected than the heterozygous embryo. The possible reason for the Na gene-induced embryonic mortality is still not clear. In this investigation, it is shown that the phenomenon cannot be explained by the oxygen consumption.