Phenotypic characterization of some indigenous chicken ecotypes of Ethiopia

R Duguma

Ethiopian Institute of Agricultural Research, P.O.Box 32, Debre Zeit, Ethiopia
retadhuga@yahoo.com

Abstract

A study was conducted to characterize three indigenous chicken ecotypes of Ethiopia based on some phenotypic traits. The study was based on the collected eggs for hatching from three geographical origins of the respective chicken ecotypes and the chickens were reared under confinement at Debre Ziet Agricultural Research Center, central Ethiopia. Data collection was made on a total of 581 chicken ecotypes (257 Horro, 105 Tepi, 219 Jarso) concerning their body parameters such as plumage color, eye color, earlobe color, comb type, comb color, skin color, body size, and body height to back level, and body weight.

The Horro ecotype was built from chickens that had 25.7% red brown plumage color followed by white (21.8%) and red (19.5%) coloration then black (13.2%). The Tepi ecotype had red (29.9%) and gray (29.5%) plumage coloration followed by black (16.2%) then white (11.4%) color. The Jarso ecotype was dominated by red (21.5%) and gray (21.0%) followed by white (18.7%) then red brown color (15.5%). The plumage color of the chickens differed significantly (p<0.000) among the three ecotypes. The three ecotypes had black (100%) type of eye coloration. In terms of earlobe, the white color predominantly distributed in the three ecotypes of Ethiopia in that the Horro (54.5%), Tepi (57.1%) and Jarso (86.3%) followed by silver color in the Horro and Tepi ecotype but red colored earlobe in the Jarso. The Horro ecotype significantly dominated with double comb pattern (75.5%) while the majority of the other two ecotypes had single comb (p<0.000). The widely distributed color of the comb in the Horro ecotype was red (52.1%) whereas in the Tepi (56.2%) and Jarso (66.7%) were pale comb color. The body height and weight, thus the body size, of the ecotypes differed significantly (p<0.000).

The study showed presence of a considerable diversity of phenotypic characters within and between the Ethiopian chicken ecotypes. More phenotypic and genetic information that involves all traits and all ecotypes of the country together with the role of the traits and the underlying genes on socio-economic factors should be assessed to fully characterize them in order to use in promotion of their utilization, conservation of genetic variability and preservation of further adulteration.

Keywords: Ethiopia, indigenous chickens, phenotypic characteristics

Introduction

Developing countries have indigenous chickens with diverse uses and benefits. The origin of each breed or strain /ecotype is the product of mutation and genetic drift, as well as separate adaptation and evolution, with differing selection pressures imposed by climate, endemic parasites and diseases, available nutrition and selection criteria imposed by man (Barker 1994). Similarly, Hartl (1988) indicated that natural and directed selection; migration and mutation may lead to non-random or directional changes in the allele frequencies of the population. Thus, each breed or ecotype comprises a unique set of genes (a number of diversified adaptive and productive traits and genes) with special utility in the tropics.

In Ethiopia, therefore, where diverse agro-climates, religions and cultures exist coupled with enormous migration following natural and/or man-made challenges and the strategic location in Horn of Africa mid-way to the ancient trade route between Asia and Western countries; there is adequate reason to assume substantial genetic diversity for various traits in the indigenous chicken genetic resources.

Ethiopia is blessed with huge number of indigenous chickens distributed in different agro-ecologies. Their widespread distribution in the villages demonstrates the importance of these small and easily managed farm animals. According to Alamargot (1987), they comprise of about 99% of Ethiopian 58 million poultry population. They are predominantly raised where traditional family-based free-range scavenging management system is practiced (Alemu and Tadelle 1997). Thus, the birds are left to depend primarily on what nature offers. Meanwhile, the poor farmers derive food and good income from the sale of village poultry especially the indigenous chickens.

The improvement of domestic animals including chickens to meet human needs is dependent on variation, both variations within and between breeds. Such variation among individuals or groups of chickens gives room and opportunity for breeding and selection. However, the volume of work pertaining to the phenotypic and genetic constitution of the indigenous chicken of Ethiopia is very small. So far information on characterization and description of indigenous chickens of Ethiopia is scanty.

Therefore, the objective of this study was to collect preliminary data and characterize three indigenous chicken ecotypes of Ethiopia based on some phenotypic traits.

Materials and methods

Study sites

The study was conducted at the Debre Zeit Agricultural Research Center (DZARC) 45km south east of Addis Ababa. The site is located at an altitude of 1900m above see level. The area receives an average annual rainfall of 851mm and a minimum and maximum temperature of 8.9^oc and 26.2^oc, respectively. The average humidity level of the site is 58.6 %.

Origin of the study animals and management of the source population

The indigenous chickens that included in this study were located at different geographical areas of the country: Horro, Tepi, and Jarso located in the west, southwest and east of the country, respectively. The chickens were named after their area of origin. Indigenous chickens were predominantly managed traditionally and practiced at family-based free-range scavenging management system. Thus, the birds were left to depend primarily on what nature offers. The feed resource base for native chickens was scavenging. It consisted of household wastes, anything edible found in the immediate environment and small amounts of grain supplements provided by the farmers. Therefore, the scavenging feed resource was not constant. Feed supplies from home and the environment varied with farming activities such as land preparation, sowing, harvesting, and grain availability in the household, season of the year and the life cycle of insects and other invertebrates.

Management of study animals

Eggs of each ecotype were collected from the geographical origin of the respective chicken ecotypes and made to hatch at Debre Ziet Agricultural Research Center, central Ethiopia. The hatchery room was cleaned and disinfected with 1% formalin spray 3 hours before the arrival of the eggs. The eggs were selected for physical quality and fumigated for hygiene with 17 g potassium permanganate + 100 mL of 20% formalin and incubated for hatching. Three hours before transfer of eggs from the setter to the hatcher and before each candling, 1% formalin was sprayed in the hatchery room to disinfect and avoid infection of the ovo with pathogens while in the hatchery. Egg candling was undertaken at 7 and 18 days of setting.

All chickens were vaccinated against Newcastle disease with HB1 at Day 1 and LaSota at Days 21 and 56 and every 6 months of life in accordance with the producer's recommendation. Marek's disease vaccine (1 mL) was also given on the neck subcutaneously.

The poultry house (both brooder and grower houses) with all poultry equipments and beddings were disinfected by 2% formalin 1 day before the introduction of the chickens. The house was bedded with Teff straw and had infrared bulbs for heating. The baby chicks were supplied with starter ration and clean potable water. The chicks were fed a commercial starter ration during the brooding period (starter phase), which lasted for 2 months. After the end of the starter phase, the chickens were transferred to a grower house where they were fed a grower ration for about 3 months. Antibiotics and vitamins were supplied for all chick flocks under study when disease was suspected in a pen.

Study design and data collection

The study involved 3 indigenous ecotypes. Data collection was made on a total of 581 chicken ecotypes (257 Horro, 105 Tepi, and 219 Jarso). Data collection was focused on the body parameters such as plumage color, skin color, eye color, earlobe color, comb type, comb color, body size, and body height to back level, and body weight. Body height was measured by centimeter (cm) from the leg on the ground up to the level of back of the body of the chickens and its data also employed to measure the body size. Their body weight was measured at 20 weeks of age using a sensitive balance (gram).

Data analysis

Prevalence of the distribution of the traits among the chicken ecotypes was calculated by dividing the number of animals having the trait by the total number of animals examined. Percentages (%) were used to measure the rate of a trait in each ecotype. Measurement of association between prevalence of the trait and chicken ecotypes was tested using chi-square (χ²). Thus, the data were analyzed using simple descriptive statistics and a chi-square test at 95 % confidence interval (α=5%). The Version 12 SPSS software (SPSS Inc., Chicago, Ill, USA) was employed for data analysis.

Result

The three studied Ethiopian chicken ecotypes showed significantly (p<0.000) different plumage coloration within and between the ecotypes (Table 1).

Of the Horro ecotype, one quarter (25.7%) had red brown plumage color followed by white (21.8%) and red (19.5%) coloration then black (13.2%). The Tepi ecotype built from chickens that had relatively equal red (29.9%) and gray (29.5%) plumage coloration that followed by black (16.2%) then white (11.4%) color. The Jarso ecotype was dominated by red (21.5%) and gray (21.0%) followed by white (18.7%) then red brown color (15.5%). Between the three ecotypes the red, black and reddish gray plumage coloration was distributed relatively fairly whereas the distribution of the rest plumage color varied between the three ecotypes. Unlike in others, the Horro ecotype was blessed with a special type of trait, naked neck (0.04%).

The three ecotypes had black (100%) type of eye coloration (Table 2).

In terms of earlobe the ecotypes significantly (p<0.000) different. The white color predominantly distributed in the three ecotypes of Ethiopia in that the Horro (54.5%), Tepi (57.1%) and Jarso (86.3%) followed by silver color in the Horro and Tepi ecotype but red colored earlobe in the Jarso. The comb type of the ecotypes varied significantly (p<0.000). The Horro ecotype significantly dominated with double comb pattern (75.5%) while the majority of the other two ecotypes had single comb. The comb color of the chicken ecotypes varied significantly (p<0.000). The widely distributed color of the comb in the Horro ecotype was red (52.1%) where as in the Tepi (56.2%) and Jarso (66.7%) was pale comb color. The color of the skin did not differ significantly (p>0.127) among ecotypes.

The body height of Horro (22.6cm) and Tepi (22.7cm) chicken ecotypes was higher than that of Jarso (21.8cm) and the body height of the male chickens were higher than that of females within ecotypes (Table 3).

The body size of Horro, Tepi and Jarso ecotypes as measured by their body height indicated the presence of very smaller (dwarf) chickens that were less by about one third (30%) than the average normal body size indicated on Table 3. In this case 31.1% of Jarso ecotypes had dwarf body size in that their body height was less than average body height of the ecotype (i.e.21.8cm) by 30% as indicated on Table 4.

The average individual body weight of Ethiopian ecotypes at the age of puberty (20 weeks) varied in that Horro (876g), Tepi (822g) and Jarso (663g), respectively (Table 5).

This indicated the three chicken ecotypes were very distinct from each other phenotypically.

Discussion

Many traits are economically important and are transferred to descendants via inheritance. According to Nesheim et al (1979) and Ensminger (1992), plumage color and pattern, skin color, shank and feet feathering, naked neck and comb type are inherited by single pairs of genes. Such traits are able to influence the preference of the consumers. Geneticists of developed nations are well aware of the inheritance of these traits and make use of it in the production of the desired chicken type to win the market competition.

Scientific reports or investigations on indigenous chickens of Ethiopia are lacking to contrast head to head with this finding. The preliminary information observed here indicates that indigenous chickens of Ethiopia have fairly diverse phenotypic characteristics. Some attempts have been made to characterize the African chickens elsewhere. Agbede et al (1995) in Cameroon, Ndegwa et al (1999) in Kenya and Benabdeljelil and Arfaoui (2001) in Morocco tried to describe and characterize the chickens but none of them done a comprehensive and extensive study.

In current study very diverse plumage coloration has been observed within and between three chicken ecotypes of Ethiopia. Indigenous chickens anatomically have diverse plumage color that aid for camouflage against predators. Currently, the function of plumage color goes beyond camouflaging. According to Ensminger (1992), plumage colors such as white or light colored feathers have become an important factor in breeding particularly in broilers because they are easier to pick clean and preferred for appearance of carcass and cut-up parts, thus, have market implications.

Naked neck trait has been observed within the Horro ecotype with low proportion (0.04%) in current study. The use of this gene for feather restriction (Na) has been found to be particularly relevant for the tropics. Research into the effects of this gene on economic factors has been undertaken in Malaysia. The result indicated that feather restriction (Na) or Naked Neck gene results in 40% less feather coverage overall, with the lower neck appearing almost "naked". This considerably reduces the need for dietary nutrition to supply protein input for feather production, and protein is a limiting factor in many scavenger feed resource bases (Horst 1989). Thus, protein is shifted to meat and egg production than to feather synthesis.

The white and red coloration of the skin dominates in the chicken ecotypes of current study. Skin color depends on combination of pigments in the upper and lower layers of the skin that particularly associated with presence or absence of melanic pigments in dermis and epidermis of the skin. Yellow skin coloration is currently more preferred by consumers of developed nations and such color is associated with carotinoid pigments in the epidermis which obtained through the dietary origin (Nesheim et al 1979).

Horst (1989), have indicated that indigenous chicks have the most important traits (ranging from seven to nine important major genes) that are genetically conserved for their special utility in tropical environment. These include Na (naked neck), f (frizzle), dw (dwarf), h (silky), k (slow feathering), id (non-inhibitor), Fm (fibro-melanosis), p(peacomb) and O (blue shell). The incorporation of such genes could be significant in the development of appropriate breeds and strains for smallholder poultry production in the tropics

In the current study very diverse color and type of comb and earlobe is observed within and between the ecotypes studied. According to Nesheim et al (1979), the size and color of the comb and wattles are associated with gonad development and secretion of sex hormones. Large combs, large wattles and long legs are important morphological traits that allow better heat dissipation in the tropical hot environment. The comb and wattles have a large role in sensible heat losses. This specialized structure makes up about 40% of the major heat losses, by radiation, convection and conduction of heat produced from body surfaces at environmental temperature below 80⁰F (Nesheim et al 1979). According to Horst (1989), the gene coding for these traits, which are not major genes but the result of multiple genes and their interactions, could be considered for incorporation into the development of high performer local birds for the tropical hot environments.

In the Jarso ecotypes about one third (31.1%) of the chickens has subnormal (dwarf) body size in that they are very small in body size as measured by body height. They also have very small body weight as to their body size at the age of beginning of laying phase. Ensminger (1992) have indicated that subnormal body size (dwarfism) is a sex-linked recessive gene for reduced body size (dw) and a trait of chickens in which body size is about one third (30%) of smaller than the normal body size. This trait is interesting in that feed requirement for maintenance is lowered and thereby increases the efficiency of feed utilization. Thus, this trait solves the persistent problem of feed scarcity in rural village setting of poultry production in Ethiopia and has also been found to be particularly relevant for the tropics. It also serves the commercial poultry industry to reduce high feed cost if the gene is incorporated to commercial chicken lines.

A considerable diversity of phenotypic characters within the Ethiopian chicken ecotypes is observed in this study. It is therefore more appropriate and meaningful to describe the indigenous domestic chicken ecotypes based not only on their geographical origin, but also using and stratifying ecotypes by observable physical parameters such as size of the adult bird, shape of the comb or the plumage characteristics within specific ecotype. Finally it would be possible to standardize these phenotypic characters within the country and come up with some criteria for characterization and description of the indigenous domestic chickens into breeds.

Conclusions

• This preliminary study shows a considerable diversity of phenotypic characters within and between the Ethiopian chicken ecotypes.

• More phenotypic information that involves all traits and all ecotypes of the country should be collected to fully characterize them.

• Studies on genetic characterization of our indigenous chicken populations should be emphasized.

• Research into the effects of the traits and the underlying genes on economic factors should be undertaken for future rural (tropical) oriented breeding plans.

• The assessed phenotypic and genetic information should be employed to preserve genetic variability and further adulteration. Such information should also be used in conservation and promotion of their utilization.

Acknowledgement

The author appreciates the Ethiopian Institute of Agricultural Research for funding.

References

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Received 15 June 2006; Accepted 27 June 2006; Published 13 September 2006

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