Livestock Research for Rural Development 25 (9) 2013 Guide for preparation of papers LRRD Newsletter

Citation of this paper

Characterization of local chickens in selected districts of the Southern Highlands of Tanzania: I. Qualitative characters

F S Guni and A M Katule*

Tanzania Livestock Research Institute
Uyole, PO Box 6191 Mbeya, Tanzania
fadhili.guni@yahoo.com
* Department of Animal Science and Production, Sokoine University of Agriculture,
PO Box 3014, Morogoro, Tanzania

Abstract

A study was conducted in Chunya, Njombe and Songea districts of the Southern Highlands of Tanzania to characterize local chickens based on qualitative traits. Six hundred and ninety three chickens (538 females and 155 males) and 155 fresh eggs were sampled for the study. Traits studied were feather morphology, plumage colour, skin colour, shank colour, earlobe colour, comb type, comb size, comb colour, eye colour and presence or absence of shank feathers, earlobes, wattles, skeletal attributes and eggshell colour.

Overall, normal feather cover was the main plumage characteristic of local chicken populations in the study area. However, unique features such as crested-head, naked-necked, frizzling, vulture-hocked, rumplessness and muffed/beardedness were observed. Across districts and sexes multicoloured and black plumages appeared most frequently. Chunya and Njombe districts had chickens with predominantly yellow skin while the majority of those from Songea had white skin. Orange appeared to be the most predominantly frequent eye colour. Yellow shanks were predominantly most frequent, followed by white, green and black shanks. Only 9.23% of all the chickens had feathered shanks while the remaining 90.7% had featherless shanks. All birds studied had earlobes and 99.3% had wattles. Various comb types with different sizes and colours were observed. Most eggs had whitish colour shells. Significant associations existed among several qualitative characters studied.

On the basis of qualitative characters observed in the current study it is concluded that local chicken population of the study area constitutes various subpopulations which exist in various plumage forms and colour which may vary in frequency of occurrence from one location to another. The studied chicken populations are not unique from the rest of the Tanzania indigenous chicken populations. Further studies involving morphometric, production and molecular analyses are important for exhaustive characterization.

Key words: egg shell colour, plumage colour, unique features, variation


Introduction

Tanzania had about 35 million local chickens by the year 2010/11 which provide almost all the poultry meat in the rural areas and also contribute almost 100% and 20% eggs consumed in rural and urban areas respectively (MLFD 2011).

The Tanzania local chicken population exhibits variation in numerous observable attributes including plumage colour, skin colour, comb type and other qualitative traits. The enormous land expanse of Tanzania, as well as its numerous ecological zones may provide for the existence of several genetically distinct chicken populations with respect to both qualitative and quantitative traits. The possible existence of several genetically distinct subpopulations within a large population has called for the need to identify and define the subpopulations with a view to determining if the genes present in anyone of them are in danger of disappearing and hence if there is a need to conserve them. This is done by characterizing subpopulations constituting a large population both phenotypically and genetically. Phenotypic characterization is an initial step in the process of complete characterization of a subpopulation. 

The present study was aimed at describing the qualitative traits in different population of local chickens in Chunya, Njombe and Songea districts of the Southern Highlands of Tanzania. The information to be gained in the study would be helpful especially in planning future breeding programmes and conservation strategies of prospective local chicken ecotypes.


Material and Methods

Study area

The study was conducted in the Southern Highlands of Tanzania. The zone covers 245 000 km2 (28%) of the Tanzania mainland with six administrative regions namely Ruvuma, Njombe, Iringa, Mbeya, Rukwa and Katavi. The altitude of the study area ranges from 400 to 3000m above sea level.The average temperature is 10 C minimum and 22 C maximum. Rainfall varies from 750mm in lower altitude areas to 2600mm in the highlands and along Lake Nyasa during November to April annually. The tropical and temperate climate favour livestock and crop production which are the main activities.  

Three districts, that is Chunya, Njombe and Songea were selected for the study, one in each of the Mbeya, Njombe and Ruvuma regions respectivey. Chunya district is located between 0830׳South Latitude and 3327׳ East Longitude with an elevation of 1229m above sea level. Mean annual rainfall ranges between 600 and 1000mm mainly from December to March. Njombe district is located between 920׳ South Latitude and 3450׳ East Longitude. It has an altitude of 1696m above sea level with annual rainfall of 1000 to 1600 mm from December to April. Songea district is located between 1040' South Latitude and 3540׳ East Longitude.It has an elevation of 900m above sea level. Annual rainfall ranges from 800 to1800mm starting from November and ending during May. 

Sampling procedure

Purposive sampling was used to select wards and villages with large numbers of local chickens based on the information provided by the District Livestock Office. Households were randomly selected from a list of households that had been keeping more than ten chickens for the last five years. Sampling frame was three wards per district, three villages per ward, four households per village and six to seven chickens per household, among which one to two cocks were sampled. Furthermore, households possessing chickens with freshly laid eggs were used for external egg quality observations. 

Data collection

Data were collected on 693 mature chickens (538 females and 155 males). Among the 108 households sampled for data collection, 59 households were also used for external egg quality description with an average of two to three eggs per households, making a total of 155 eggs across the study area.  Eggs were observed for shell colour while chickens were individually observed for various phenotypic attributes including plumage characteristics and colour, skin colour, shank colour, earlobe colour, comb type, comb size, comb colour, eye colour and presence or absence of shank feathers, earlobes, wattles and skeletal attributes as described by FAO (2012).  

Data analysis

Data were analysed using frequency procedure of SAS (SAS 2003) to compute frequencies of occurrence of each qualitative trait. Chi-square tests were applied to determine associations between the characters studied and geographical areas (districts), as well as the association among pairs of different characters studied to assess if there are any specific relationships between certain traits.


Results and discussion

Plumage cover characteristics

Normal feather cover was the main plumage characteristic of local chicken populations in the study area (Table 1). However, unique features such as crested-head, naked-necked, frizzling, vulture-hocked, rumplessness and muffed/beardedness were observed.  

Of the total population studied only 8.66% were identified as crest-headed, the remaining birds had normal head shape. The distribution of crest-headed birds differed between sexes but not between districts. A higher proportion of crest-headed birds were observed in females than in males. Although the distribution was not significantly different among districts, nearly half of the crested-birds were found in Njombe district.  

The proportion of chickens with naked-necks was quite small (5.48% of the total chicken population in the study area). However, differences with respect to the distribution of naked-neck chickens were observed between districts. A relatively higher proportion of naked-neck chickens were found in Chunya than in the other two districts. The naked-neck character is described as the expression of a major gene found in local chicken populations of the tropics and is considered to have desirable effects on heat tolerance (Horst 1989). The rather rare occurrence of naked-necked chickens might be an indication of a negative selection against this character.  The proportion of naked-necked chickens observed in the current study was higher than that (˂ 2%) reported from Ethiopia (Dana et al 2010) and from Botswana (3.6% ) (Badubi et al 2006), but was close to the 6% reported from Nigeria (Gueye 1998). 

Table 1. Proportionate (%) occurrence of plumage characteristics in local chickens summarized by districts and sex

 

 

 

Districts

 

 

 

Sex

 

 

 

Character

Expression

Chunya

(n=216)

Njombe

(n=258)

Songea

(n=219)

Total

(n=693)

ϰ2-

test

Female

(n=538)

Male

(n=155)

Total

(n=693)

ϰ2
test

 

 

 

 

 

 

 

 

 

 

 

Head
shape

Crested

1.73

4.19

2.74

8.66

ns

7.65

1.01

8.66

*

Plain

29.5

33.0

28.9

91.4

 

69.9

21.4

91.4

 

 

Total

31.2

37.2

31.6

100

 

77.6

22.4

100

 

 

 

 

 

 

 

 

 

 

 

 

Neck
feather

Naked neck

3.17

0.87

1.44

5.48

***

4.33

1.15

5.48

ns

Feathered neck

28.0

36.3

30.2

94.5

 

73.3

21.2

94.5

 

 

Total

31.2

37.2

31.6

100

 

77.6

22.4

100

 

 

 

 

 

 

 

 

 

 

 

 

Body plumage

Frizzled

0.43

0.00

0.29

0.72

ns

0.29

0.43

0.72

*

Normal

30.8

37.2

31.3

99.3

 

77.3

22.0

99.3

 

 

Total

31.2

37.2

31.6

100

 

77.6

22.4

100

 

 

 

 

 

 

 

 

 

 

 

 

Hock type

Vulture hock

0.44

0.00

0.00

0.44

*

0.3

0.14

0.44

ns

 

Normal

30.8

37.2

31.6

99.6

 

77.3

22.2

99.6

 

 

Total

31.2

37.2

31.6

100

 

77.6

22.3

100

 

 

 

 

 

 

 

 

 

 

 

 

Face shape

Muffed/bearded

0.00

0.00

0.29

0.29

ns

0.14

0.14

0.29

ns

Normal

31.2

37.2

31.3

99.7

 

77.5

22.2

99.7

 

 

Total

31.2

37.2

31.6

100

 

77.6

22.3

100

 

 

 

 

 

 

 

 

 

 

 

 

Tail

Rump-less

0.29

0.00

0.00

0.29

ns

0.29

0.00

0.29

ns

Tailed

30.9

37.2

31.6

99.7

 

77.3

22.4

99.7

 

 

Total

31.2

37.2

31.6

100

 

77.6

22.4

100

 

 

 

 

 

 

 

 

 

 

 

 

Body shape

Unique

6.06

5.05

4.76

15.9

ns

13.0

2.89

15.9

ns

Normal

25.1

32.2

26.8

84.1

 

64.6

19.5

84.1

 

 

Total

31.2

37.2

31.6

100

 

77.6

22.4

100

 

*(P < 0.05); ***(P < 0.001); ns(P ˃ 0.05); n = number of chickens observed

Frizzled chickens were very rare (0.72% of the total population studied). Possible explanation for the rare occurrence of frizzled chickens in the study area is that the frizzling gene is a rare mutant with recessive effects and with no selective advantage in the population.  It could also be due to the fact that the frizzled feather pattern tends to provide poor insulation in cold climates hence the birds are disadvantaged in comparison with the normal feathered chickens. According to FAO (2010) both naked-naked and frizzled birds perform better at high ambient temperatures due to high heat dissipation ability as opposed to normal feathered chickens. 

Other characteristics such as vulture hocks, rumplessness and muffed/bearded appeared at less than 0.5% of the population each, and were localized to specific districts. Vulture-hocked and rumpless chickens were found only in Chunya district whereas muffed/bearded birds were observed in Songea district. Plates 1, 2,3,4,5 and 6 show photographs of some plumage characteristics of local chickens observed in the study area. 

Plate 1. Normal  feathered Plate 2. Frizzled Plate 3. Naked-neck



Plate 4. Crest-head Plate 5. Muffled/bearded Plate 6. Rump-less
Plumage colour

Both districts and sexes differed with respect to plumage colours (Table 2). Across districts and sexes multicoloured and black plumages occurred most frequently. Overall, multicoloured plumages appeared most frequently (50.8%) followed by black (18.6%), brown (9.81%) and white (8.37%). The remaining plumage colours occurred rarely as follows: grey (6.35%), spotted (3.03%), red (2.16%) and wheaten (0.87%). The findings of this study are in agreement with those of Msoffe et al (2001) in free ranging local chicken ecotypes in Tanzania. Related research work from Uganda (Ssewannyana et al 2008) and Ethiopia (Duguma 2006) also reported the occurrence of varied plumage colours among local chickens. The occurrence of several plumage colours observed in the local chicken population in the current study might be the result of uncontrolled breeding of chickens in the rural areas since random mating is a typical breeding practice under free range management system. Under predation conditions black and multicoloured plumage would offer a camouflage so as to avoid being spotted by predators. This could be the main reason for the higher occurrence of chickens with both black and multicoloured plumage. Preference of the people in the study area for black and multicoloured plumage might also account for the predominant occurrence of the colours since plumage colour might influence consumer preference and utilization. Assegie (2009) reported white and red plumage to be the most preferred and predominant colour in Ethiopia.  

Skin colour

The predominantly frequent skin colour in the studied population was white (51.2%) while yellow was the second most predominant skin colour (48.8%).  Differences were observed between districts with respect to skin colour. Chunya and Njombe had higher occurrences of chickens with yellow skin (17.2% and 19.5% respectively) than Songea (12.1%). No difference in skin colour was observed between the two sexes. Similar findings on occurrence of skin colours in indigenous chicken populations have been reported by Msoffe et al (2001). Research findings from studies by Iqbal and Pampori (2008) in the Philippines revealed similar skin colour trends. However, contrasting results have been reported from Ethiopia (Dana et al 2010) where yellow skin seemed to be more frequent (52%) than white (48%). The variation in skin colour observed between districts in this study might be due to differences in feedstuffs available for chickens in the respective districts. According to Smyth (1990) the yellow skin of a chicken is a result of carotenoid pigments (xanthophylls) which are consumed through feeds and deposited under the skin. The differences could also be due to different genetic determination. Even if chickens are exposed to diets containing carotenoids some birds may genetically be unable to deposit the pigment under the skin. 

Eye colour

In this study orange appeared to be most frequent (73.4%) eye colour, followed by brown (16.3%) and yellow (9.23%). Other eye colours (black, 0.72% and red, 0.29%) were least frequent.  Differences were observed between districts and between sexes with respect to eye colours. The occurrence of oranged-eyed chickens was higher in Njombe district (29.0%) than in the other two districts (i.e. Chunya and Songea) which had equal distribution of orange-eyed birds (22.2%). Overall, orange-eyed chickens were more frequent in females than in males. The orange appearance of the eyes could be due to lack of colour pigment in the eyes, and hence what is seen could be due to blood circulating the blood vessels of the eye. Eye colour to a large extent depends on the pigmentation (carotenoid pigments and blood supply) of a number of structures within the eye (Crawford 1990).The predominant occurrences of orange eye in the local chicken population have also been reported from Uganda (Ssewannyana et al 2008) and Cambodia (FAO 2009). However, contrasting results have been reported from Ethiopia (Duguma 2006) where all chickens were found to have black eyes. 

Shank feather and colour

The current study showed that 9.23% of all the chickens had feathered shanks. There were districts differences with respect to occurrence of shank feathers. A relatively higher proportion of shank-feathered birds were found in Chunya than in the other two districts (i.e. Songea and Njombe). No differences between sexes were observed with respect to the occurrence of shank feathers.

Various shank colours were observed in the current study. Overall, yellow shanks were most frequent (34.7%) followed by white (25.3%), green (14.4%) and black (11.8%) shanks. Other shank colours like grey, blue, pale and brown appeared in frequencies of less than 10%. Both districts and sexes were different with respect to shank colour. In Chunya and Njombe districts the predominant feature was yellow shanked chickens while Songea was predominantly occupied by chickens with white shanks. The observed predominant occurrence of yellow shanks in the current study was similar to that reported by other researchers (Cabarles et al 2012; Ssewannyana et al 2008; Daikwo et al 2011). In contrast, Egahi et al (2010) and El-Safty (2012) reported black as the most frequent shank colour in their studies. Msoffe et al (2001) also observed variation between ecotypes with respect to shank colour. 

Table 2. Occurrence of plumage colour, skin colour patterns and shank feathers in local chickens summarized by districts and sex

 

 

 

Districts

 

 

 

Sex

 

 

 

Character

Expression

Chunya

(n=216)

Njombe

(n=258)

Songea

(n=219)

Total

(n=693)

ϰ2-

test

Female

(n=538)

Male

(n=155)

Total

(n=693)

ϰ2-

test

 

 

 

 

 

 

 

 

 

 

 

Plumage colour

Black

6.06

8.08

4.47

18.6

***

15.7

2.89

18.6

***

Brown

4.91

4.62

0.29

9.81

 

8.95

0.87

9.81

 

 

Grey

2.45

1.30

2.60

6.35

 

6.20

0.14

6.35

 

 

Spotted

1.01

2.02

0.00

3.03

 

2.60

0.43

3.03

 

 

Multi coloured

12.1

17.9

20.8

50.8

 

37.5

13.3

50.8

 

 

Red

0.29

0.87

1.01

2.16

 

0.14

2.02

2.16

 

 

Wheaten

0.00

0.14

0.72

0.87

 

0.58

0.29

0.87

 

 

White

4.33

2.31

1.73

8.37

 

5.92

2.45

8.37

 

 

Total

31.2

37.2

31.6

100

 

77.6

22.4

100

 

 

 

 

 

 

 

 

 

 

 

 

Skin colour

White

14.0

17.7

19.5

51.2

***

38.4

12.8

51.2

ns

 

Yellow

17.2

19.5

12.1

48.8

 

39.2

9.52

48.8

 

 

Total

31.2

37.2

31.6

100

 

77.6

22.3

100

 

 

 

 

 

 

 

 

 

 

 

 

Eye colour

Black

0.72

0.00

0.00

0.72

***

0.72

0.00

0.72

*

 

Brown

3.46

6.64

6.20

16.3

 

14.4

1.88

16.3

 

 

Orange

22.2

29.0

22.2

73.4

 

54.7

18.8

73.4

 

 

Red

0.00

0.29

0.00

0.29

 

0.29

0.00

0.29

 

 

Yellow

4.76

1.30

3.17

9.23

 

7.50

1.73

9.24

 

 

Total

31.1

37.2

31.6

100

 

77.6

22.4

100

 

 

 

 

 

 

 

 

 

 

 

 

Shank feather

Absent

26.9

35.8

28.0

90.7

***

70.5

20.2

90.7

ns

 

Present

4.18

1.44

3.61

9.23

 

7.07

2.16

9.23

 

 

Total

31.1

37.2

31.6

100

 

77.6

22.4

100

 

 

 

 

 

 

 

 

 

 

 

 

Shank colour

Black

3.46

3.46

4.91

11.8

***

10.1

1.73

11.8

***

 

Blue

2.31

0.87

1.44

4.62

 

4.18

0.43

4.62

 

 

Brown

0.00

0.00

0.14

0.14

 

0.14

0.00

0.14

 

 

Green

3.46

5.19

5.77

14.4

 

12.7

1.73

14.4

 

 

Grey

0.14

7.36

1.01

8.51

 

8.23

0.29

8.51

 

 

Pale

0.00

0.00

0.43

0.43

 

0.43

0.00

0.43

 

 

White

6.20

8.80

10.3

25.3

 

16.9

8.37

25.3

 

 

Yellow

15.6

11.5

7.65

34.7

 

24.9

9.81

34.7

 

 

Total

31.2

37.2

31.6

100

 

77.6

22.4

100

 

*(P < 0.05); *** (P < 0.001); ns (P ˃ 0.05); n = number of chicken sobserved

The occurrence of various types of shank colours in this study might have been due to combinations of pigment controlling genes responsible for colour determination. Petrus (2011) reported that production of carotenoid, dermal melanin and epidermal melanin is controlled by W+ and w; Id and id+; and E and e+ genes, respectively, with the consequent occurrence of various shank colour shades.

Head appendage occurrence and characteristics
Wattles and earlobes

Almost all (99.3%) chickens had wattles, except for a small proportion (0.72%) (Table 3). There were no differences between districts and sexes with respect to wattle occurrences. All chickens had earlobes. Differences in earlobe colour were observed between both districts and sexes. Most (42.9%) of the chickens had white-patched red earlobes. The second most frequent earlobe colour was red (26.3%) while 20.1% of the chickens had yellow-patched red earlobes. The remaining earlobe colour types observed were black (5.05%), white (5.05%) and yellow (0.72%), yellow being the least occurring earlobe colour. A relatively higher proportion of white-patched red earlobe chickens were found in Songea than in the other two districts. Overall, most male chickens had red earlobes while most female chickens had white-patched red or yellow-patched red earlobes. Variations in earlobe colour among local chickens have been reported from other studies (Cabarles et al 2012; Egahi et al 2010; Ssewannyana et al 2008; Iqbal and Pampori 2008). The variation in earlobe colour of local chickens observed in the current study might be of genetic origin since earlobe colour is dependent upon several genetic factors. Warren (1928) concluded that breeds or individuals having the same earlobe colour may differ considerably in genetic constitution with respect to earlobe colour loci. 

Comb type, size and colour

Various comb types were observed in the current study.  Differences were observed between districts, as well as between sexes with respect to comb types.  Single comb was the most common (87.4%) comb type and was predominant in all districts and sexes. Other comb types (rose, cushion, pea and double combs) appeared in small proportions and occurred more frequently in Chunya than in the other two districts (i.e. Njombe and Songea). Results from the study by Msoffe et al (2001) indicated certain comb types to occur more frequently in some ecotypes than in others although the exact significance of this phenomenon could not be explained. Other research findings (Cabarles et al 2012; Egahi et al 2010; El-Safty 2012; Apuno et al 2011) reported also the predominant occurrence of single combs in local chicken populations. The occurrence of varieties of different comb types observed in this study might be due to interactions of different genes responsible for comb expression. Crowford (1990) has contended that the heredity of comb type in chickens is attributed to two autosomal pairs of genes (RR for Rose type and PP for Pea type). 

Table 3. Occurrence and characteristics of various head appendages of local chickens summarized by districts and sexes.

 

 

 

Districts

 

 

 

Sex

 

 

 

Character

Expression

Chunya

(n=216)

Njombe

(n=258)

Songea

(n=219)

Total

(n=693)

ϰ2-

test

Female

(n=538)

Male

(n=155)

Total

(n=693)

ϰ2-

test

 

 

 

 

 

 

 

 

 

 

 

Wattle

Absent

0.29

0.00

0.43

0.72

ns

0.72

0.00

0.72

ns

 

Present

30.9

37.2

31.2

99.3

 

76.9

22.4

99.3

 

 

Total

31.2

37.2

31.6

100

 

77.6

22.4

100

 

 

 

 

 

 

 

 

 

 

 

 

Earlobe

Absent

0.00

0.00

0.00

0.00

 

0.00

0.00

0.00

 

 

Present

31.2

37.2

31.6

100

 

77.6

22.4

100

 

 

Total

31.2

37.2

31.6

100

 

77.6

22.4

100

 

 

 

 

 

 

 

 

 

 

 

 

Earlobe colour

Black

2.02

0.87

2.16

5.05

***

4.76

0.29

5.05

***

Red

11.4

9.38

5.48

26.3

 

14.4

11.8

26.3

 

 

Yellow- patched red

8.08

9.38

2.6

20.1

 

17.6

2.45

20.1

 

 

White

0.72

0.87

3.46

5.05

 

4.47

0.58

5.05

 

 

White- patched red

8.23

16.7

17.9

42.9

 

35.8

7.07

42.9

 

 

Yellow

0.72

0.00

0.00

0.72

 

0.58

0.14

0.72

 

 

Total

31.2

37.2

31.6

100

 

77.6

22.3

100

 

 

 

 

 

 

 

 

 

 

 

 

Comb type

Cushion

3.75

0.14

0.00

3.90

***

3.32

0.58

3.90

***

Double

0.87

0.00

0.00

0.87

 

0.14

0.72

0.87

 

 

Pea

2.31

0.14

0.00

2.45

 

1.88

0.58

2.45

 

 

Rose

4.18

0.29

0.87

5.34

 

3.75

1.59

5.34

 

 

Single

20.1

36.6

30.7

87.4

 

68.5

18.9

87.4

 

 

Total

31.2

37.2

31.6

100

 

77.6

22.4

100

 

 

 

 

 

 

 

 

 

 

 

 

Comb size

Large

3.46

5.92

6.49

15.9

*

3.61

12.3

15.9

***

 

Medium

11.3

10.5

7.79

29.6

 

22.2

7.36

29.6

 

 

Small

16.4

20.8

17.3

54.5

 

51.8

2.74

54.5

 

 

Total

31.2

37.2

31.6

100

 

77.6

22.4

100

 

 

 

 

 

 

 

 

 

 

 

 

Comb colour

Black

2.16

1.44

2.89

6.49

***

6.20

0.29

6.49

***

Pale

2.31

8.37

7.79

18.5

 

18.1

0.43

18.5

 

 

Red

26.4

27.1

20.4

73.9

 

52.7

21.2

73.9

 

 

White

0.29

0.29

0.58

1.15

 

0.72

0.43

1.15

 

 

Total

31.2

37.2

31.6

100

 

77.7

22.3

100

 

*(P < 0.05); *** (P < 0.001); ns (P ˃ 0.05); n = number of chicken observed

The sizes of combs occurring in the population could be conveniently classified as being small, medium or large. On the basis of the classification criterion adopted it was observed that there were differences between districts and sexes with respect to comb size. In general, chickens with small combs were most frequent followed by those with medium sized combs, while birds with large combs were the least frequently observed in each district. Small and medium sized combs occurred more frequently in female chickens while male chickens tended to have large combs. Similar findings have been reported from Nigeria (Ige et al 2012). The predominant occurrence of small sized combs in the local chicken populations suggests that the size of face and head appendages could be under the influence of hormones which are connected with reproduction, particularly egg production. This is why these appendages tend to increase dramatically in size towards onset of sexual maturity. Thus one could speculate that genes for egg production rate, which is related to secretion rate of reproductive hormones such as Follicle Stimulating Hormones (FSH), could have pleitropic effects on size of face and head appendages. Since indigenous chickens have not been selected for high egg production the secretion capacity of the hormones could be low, hence correspondingly the sizes of the face and head appendages would be small. This contention conforms to that of Nesheim et al (1979) who associated the size and colour of wattles and combs with gonad development and secretion of sex hormones. Sexual dimorphism is more pronounced with respect to this trait since all male chickens in the current study appeared to have bigger combs than females. 

Four comb colours (Black, Pale, Red and White) were observed in this study with a marked difference between districts and sexes. Overall, most (73.9%) chickens had red combs, followed by pale combed birds (18.5%). A higher proportion of red combed chickens were observed in males than in females. Similar results on occurrence of red combs were reported by Faruque et al (2010) from Bangladesh. The observed differences between sexes with respect to occurrence of comb colour in the current study are in agreement in with the findings of Guhl and Ortman (1953) who reported that comb size and colour in male and female chickens are influenced by the levels of sex hormones. 

Associations among qualitative characters

The study showed the existence of associations among several qualitative characters (Table 4). The test of association among characters is important since it eases the task of describing the phenotypic characteristics of populations when groups of characters are expressed in particular combinations. In characterization work the phenotypic characteristics are used as external markers of the populations which express them. The fewer the combinations or groups of markers the easier it becomes to describe the population distinctively. 

Association of plumage colour with other characters

There was association between plumage colour and shank colour, earlobe colour, comb size, comb colour and eye colour. Black plumage tended to be associated with black, green and grey shanks. It also tended to be associated with black eyes, black earlobes, and small sized combs with black or pale in colour. On the other hand red plumage tended to be associated with white shanks, brown or orange eyes, red earlobes and large red combs. It was further observed that brown plumage tended to be associated with both grey and yellow shanks, yellow-patched red earlobes, orange eyes and small combs with red or white colour.  Association was also observed between white plumage and yellow shanks, yellow-patched red earlobes, white-patched red earlobes, orange eyes and red or white combs. 

Table 4. Chi-square summary results for tests of independency/association among various qualitative characters in local chickens

character

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

1.Plumage colour

 

-

 

ns

 

ns

 

ns

 

ns

 

ns

 

ns

 

ns

 

***

 

ns

 

***

 

ns

 

***

 

***

 ***

2.Crest  head

 

 

-

 

ns

 

 ns

 

ns

 

ns

 

ns

 

ns

 

*

 

ns

 

**

 

ns

 

ns

 

ns

 

ns

 

3.Frizzling

 

 

 

-

 

ns

 

ns

 

ns

 

ns

 

*

 

ns

 

ns

 

ns

 

ns

 

ns

 

ns

 ns

4.Muffed/

beardedness

 

 

 

 

-

 

 ns

 

ns

 

ns

 

ns

 

ns

 

ns

 

 ns

 

 ns

 

ns

 

 ns

 

ns

5.Naked-necked

 

 

 

 

 

-

 

 ns

 

ns

 

ns

 

 ns

 

ns

 

 *

 

***

 

ns

 

ns

 

ns

6.Rumpless

 

 

 

 

 

 

-

 

ns

 

ns

 

ns

 

ns

 

ns

 

*

 

ns

 

ns

 ns

7.Vulture-hocks

 

 

 

 

 

 

 

-

 

ns

 

ns

 

 ns

 

ns

 

ns

 

ns

 

 ns

 

ns

8.Shank feathers

 

 

 

 

 

 

 

 

-

 

ns

 

ns

 

*

 

ns

 

ns

 

ns

 ns

9.Shank colour

 

 

 

 

 

 

 

 

 

-

 

***

 

***

 

ns

 

**

 

***

 ***

10.Skin colour

 

 

 

 

 

 

 

 

 

 

-

 

***

 

*

 

***

 

ns

 ns

11.Earlobe colour

 

 

 

 

 

 

 

 

 

 

 

-

 

***

 

***

 

***

 ***

12.Comb  type

 

 

 

 

 

 

 

 

 

 

 

 

-

 

**

 

 ns

 *

13.Comb size

 

 

 

 

 

 

 

 

 

 

 

 

 

-

 

***

 **

14.Comb colour

 

 

 

 

 

 

 

 

 

 

 

 

 

 

-

 ***

15.Eye colour

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

-

*(P < 0.05); ** (P <0.01 *** (P < 0.001); ns (P ˃ 0.05)

 Association of shank colour with other characters

It was further observed in the current study that shank colour had an association with colours of the skin, earlobe, comb and eye as well as with comb size. White, black, grey and blue shanked birds tended to have white skin, while green and yellow shanked birds tended to have yellow skin. An association was also observed between black shanks and black earlobes, black combs, pale combs and brown eyes. Green shanked birds tended to have black or brown eyes, yellow-patched red or white-patched red earlobes as well as small sized combs with either black or pale colour. On the other hand white shanks tended to be associated with red earlobes, white earlobes, orange eyes and large sized red combs. Yellow shanks tended to be associated with red combs, red earlobes, yellow-patched red earlobes and both orange and yellow eyes. 

Association of earlobe colour with other characters

There was association between earlobe colour and comb colour, comb type, comb size and eye colour. Black ear-lobed birds tended to have black or pale combs, black or brown eyes as well as small sized pea combs. Red ear-lobed birds tended to have red combs, yellow eyes and large sized cushion, double or rose combs. Furthermore, yellow-patches red earlobes tended to be associated with small sized pea combs pale in colour whereas white-patched red earlobes tended to be associated with orange eyes as well as with medium sized single comb pale in colour. 

Association of skin colour with other characters

The study revealed the existence of associations- between skin colour and earlobe colour, comb type and comb size. White skinned birds tended to have red, white or white-patched red ear-lobes. The white skinned birds also tended to have medium and large sized single or double combs.  On the other hand yellow skinned chickens tended to have yellow-patched red earlobes and small sized cushion or pea combs. 

Association of crest-head with other characters

The crest-head character tended to be associated with shank colour and earlobe colour. It was observed that crest-headed birds tended to have green and grey shanks. Also crested birds tended to have white, white-patched red and yellow-patched red ear-lobes. 

Association of naked-neck with other characters

The naked-neck character was found to have association with comb type and ear-lobe colour. The comb types which tended to be associated with naked neck were cushion, pea and rose. Yellow-patched red earlobes also tended to be associated with the naked neck character.  

Association of comb type with other characters

There was evidence of existence of some association between comb type and comb size as well as well with eye colour. Cushion combs tended to be small in size. Rose combs tended to be medium in size and associated with orange eyed birds. It was further revealed that single combs tended to be large in size and had an association with brown or orange eyed birds.  

Association of comb size with other characters

There was association between comb size and comb colour as well as with eye colour. In most cases large and medium combs tended to be red in colour whereas small combs were found to be black or pale. The large and medium combed birds also tended to have orange eyes while small combed birds tending to have brown eyes. 

Association of comb colour with other characters

 Comb colour had an association with eye colour. Black combed birds tended to have brown eyes whereas red combed birds tending to have orange eyes.  

Association of frizzling with other characters

There tended to be a relationship between frizzling character and occurrence of feathered shanks. 

Association of rumpless-ness with other characters

There was no evidence of existence of association between rumplessness with any other character except comb type in which case it was associated with cushion combs. 

Association of feathered shanks with other characters 

There was evidence of existence of some association between feathered shank character and ear-lobe colour with feathered shanked birds tending to have red and yellow-patched red ear-lobes. 

Association between eye colour and other characters

The association between eye colours with other characters has been described in the respective traits above. 

Association of muffed/beardedness and vulture-hocks with other characters

Muffed/beardedness and vulture-hocks did not seem to be associated with any of the characters considered in the current study. This means that they were independent of all other characters. 

Possible reasons for associations
Pleitropy

This occurs when a gene or set of genes affect the expressions of two or more characters. This would occur if the expression of the different characters shares the same biochemical pathways at some point in their development. 
Gene linkage

This occurs when the genes influencing different characters are located on the same chromosome. In this case the more closely located the genes are on the chromosome the larger would be the association between the characters they control. 

Joint selection

This occurs when two or more characters are jointly selected for or against. 

Understanding the relationship among qualitative traits is very important since traits such as skin colour, plumage colour, comb type, naked neck and others are able to influence the preference of the consumers and market price as well. According to Duguma (2006) geneticists make use of inheritance of these traits by producing desirable chickens to gain market competition. 

Egg shell colour

Most eggs (50.3%) had whitish colour shells (Table 5). Brownish shelled eggs were the next most frequent (38.1%) and cream shelled eggs were the least frequent (11.6%). There were differences between districts with respect to the occurrence of egg shell colours. 

Table 5. Occurrence of various eggshell colours in the indigenous chicken population summarized by districts

 

 

Districts

 

 

 

Occurrence of shell colour, %)

Chunya

Njombe

Songea

Total

χ 2-test

Brownish

11.0

15.5

11.6

38.1

**

Cream

3.22

8.39

0.00

11.6

 

Whitish

18.7

14.8

16.8

50.3

 

Total

32.9

38.7

28.4

100

 

** (p < 0.01)

Chunya and Songea appeared to have higher percentages of chickens laying whitish eggs, while chickens from Njombe had predominantly brownish shelled eggs. The observed occurrence of egg shell colours in this study was similar to that reported by Assegie (2009) from Ethiopia. Nonga et al (2010) reported the occurrence of only two types of egg shell colours (i.e. white and brown). Location as such may not have any influence on colour of egg shell. Cavero et al (2012) reported that the pigment produced in the uterus at the time of shell formation is responsible for egg shell colour. This can be substantiated by the results of the current study as even individual chickens from the same flock varied in their eggshell colours. Shell colour is not an indication of egg quality or its nutritive value, but plays a major role in marketing as some people prefer eggs with certain colours compared to others.


Conclusion


Acknowledgements

The financial support from the Ministry of Livestock and Fisheries Development through Agricultural Sector Development Programme (ASDP) in Tanzania is highly appreciated. Heartfelt gratitude is extended to researchers and assistant researchers of Tanzania Livestock Research Institute (Taliri) – Uyole, for their tireless assistance in data collection. Special thanks to the Director of Taliri-Uyole, Dr P.A.A Mwakilembe who invested his full effort in supporting this research. Appreciation is also extended to District Livestock officers and farmers for accepting to be interviewed and for providing their chickens used in this study. 


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Received 30 July 2013; Accepted 31 July 2013; Published 4 September 2013

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