Immunocompetence and Some Hematological Parameters of Naked Neck and Normally Feathered Chicken

The genetic basis and robustness of naked neck mutation in chicken

Chicken is a homeothermic animal; consequently, regardless of fluctuation in weather conditions, it maintains constant body temperature. However, in hot regions and seasons, chickens suffer from heat stress. To dissipate excess heat, besides modifying the environment, which is costly, however, chickens with efficient heat dissipation capacity might be utilized. Naked neck chickens have a higher capacity for heat loss attributable to reduced feather mass. The naked neck mutation (Na) was originated from a large insertion (~ 180 bp) integrated ~ 260-kb downstream of a protein-coding gene-GDF7 (Growth Differentiation Factor 7). Na possesses a cis-regulatory function and upregulates the expression of GDF7-a gene that exhibits a tissue-specific effect by the sensitizing action of retinoic acid. Na suppresses the development of feathers in the neck and vent. Na shows autosomal incomplete dominance and regulates several developmental processes. Na usually segregates at low frequency, which might be attributed to limited socio-cultural preferences. Specifically, in hot and humid regions, although to a varying extent, Na enhances performance, immunocompetence, and resilience to disease both in the homozygous and heterozygous state. Occasionally, naked neck chickens (especially the homozygous ones) lose comparative advantage in cool environments. Homozygous Na also results in high embryo death and reduced hatchability and diminishes floating and flying capacity. Nevertheless, selective breeding of naked neck chickens for fertility traits enhances the performance and welfare of chickens in hot and humid regions. The comparative advantage of Na needs to be studied not only from a temperature perspective and under controlled experiment but also from humidity, body weight, feed intake (absolute and relative to body weight), age, agroecology insights, and under field condition. Due to the incomplete dominant expression pattern of Na, studies need to separately report their findings for homozygous and heterozygous naked neck chicken.

In vivo cell-mediated immune, hemagglutination inhibition response, hematological and biochemical values in native vs. exotic chicken breeds

Birds (364) of both sexes, 11-wk-old, belonging to 2 native (Brown Nicobari and Ghagus) breeds and 1 exotic breed (Dahlem Red) were evaluated for cell-mediated immune response (CMI) by phytohemagglutinin-P (PHA-P), hemagglutination inhibition (HI) assay against Newcastle disease virus (NDV) antigen (LaSota stock virus), flow cytometric analysis of CD8+ cytotoxic T lymphocytes (CTLs), and hematology and biochemical assays. The cutaneous basophil hypersensitivity response PHA-P% increase in wattle thickness (mm) was highest in Ghagus (431.14 ± 22.56) which differed significantly with that of Brown Nicobari (269.1 ± 22.66) and Dahlem Red (218.42 ± 22.30). Sex-wise observation showed that females are having significantly higher response than males. Hemagglutination inhibition test was performed to determine the serum antibodies against Newcastle disease (ND) virus. Brown Nicobari showed highest HI antibody titer than Ghagus and Dahlem Red to similar vaccination program after booster NDV dose. Flow cytometry assay revealed significantly higher CTLs proliferation in Brown Nicobari than Ghagus and Dahlem Red. Moreover, CTLs were found to be higher in control group than the treatment group. Other hematological parameters (103/μL) significant difference was found in white blood cell count between Dahlem Red (38.41 ± 1.03) with that of Brown Nicobari (35.28 ± 1.04) and Ghagus (34.57 ± 1.04) in treatment groups. Same trend was observed in the Lymphocyte treatment group. However, in Granulocyte treatment group, Brown Nicobari (11.04 ± 0.35) was found to be significantly different from Dahlem Red (8.68 ± 0.34) and Ghagus (9.27 ± 0.35). Correlations between body weight at 11 wk of age and CMI, HI, cytotoxic T cell were -0.093, 0.047, and -0.036, respectively. Egg weight was found to be positively correlated with that of chick weight. Serum biochemical values showed that Dahlem Red was having significantly higher creatinine levels compared to Ghagus. Triglycerides level was also significantly higher in Ghagus compared to Dahlem Red. No significant breed effect was observed for alkaline phosphate, aspartate transaminase, and alanine transaminase. Cholesterol and total serum protein levels were significantly higher in Dahlem Red compared to Brown Nicobari.

Effect of incorporation of thermo-regulatory genes into exotic layers on egg production and quality under tropical environment

A breed development strategy aimed at making exotic layers (Lohmann Brown) more productive under tropical environment using thermo-regulatory genes is underway at Akate Farms in Kumasi, Ghana. The present experiment was carried out to find out the effect of the genes on egg production in hot and humid environments. Three genetic groups comprising naked-neck, frizzle and their normally feathered sibs were obtained after successive generations of crossing between naked-neck and frizzle cocks and Lohmann brown hens. A total of 270 18-week-old pullets, 90 each of the 3 groups, were selected randomly and assigned to a completely randomized design experiment with 3 replicates, with 30 birds in each replicate group and kept up to a period of 72 weeks. The birds were kept in a partitioned open-sided deep-litter house constructed with sandcrete blocks with 30 pullets in each compartment. They were fed ad libitum with layer diets containing 18 % crude protein and 2,800 kcal ME/kg. Results obtained showed that the crossbred naked-neck and frizzle phenotypes produced eggs at a significantly (P < 0.05) higher rates than their normally feathered sibs and also out-performed their normally feathered sibs in other egg production parameters measured, even though they all segregated from similar parents. This is an indication of the favourable effect of the genes on egg production under hot and humid environments.