Phenotypic characterization of Tswana chickens based on quantitative traits in Kweneng and Southern Districts, Botswana

J B Machete, S J Nsoso, P M Kgwatalala, J C Moreki and A O Aganga

Department of Animal Science and Production, Botswana University of Agriculture and Natural Resources,
Private Bag 0027, Gaborone, Botswana
jmsmachete@yahoo.com

Abstract

The objective of this study was to characterize both sexes of the naked-neck, dwarf, rumpless, normal-feathered and frizzled strains of Tswana chickens in the Kweneng and Southern districts of Botswana using some quantitative traits. A total of eight (8) quantitative morphological traits such as shank length, shank circumference, spur length, comb length, wattle length, wing length and wingspan were measured using flexible measuring tape, and live body weight was measured using a Spring-Dial Hoist weighing scale.

Data were analyzed using mixed models procedures of SAS and the model included fixed effects of strain and sex and their interaction. Normal-feathered males had significantly higher shank length (9.94±0.23 versus 8.35±0.20), shank circumference (0.99±0.02 versus 0.84±0.02) wing length (20.61±0.51 versus 18.60±0.48), wingspan (41.22±1.03 versus 37.19±0.96), comb length (6.30±0.30 versus 3.48±0.26) and wattle length (3.44±0.16 versus 2.40±0.14) than their female counterparts. Normal-feathered males had the highest live weight and rumpless males had the lowest live weight.

Normal-feathered, naked- neck, frizzled and rumpless females had similar shank length and shank circumference which were all significantly higher than those of their dwarf counterparts. Only naked-neck and normal-feathered females had significantly higher wingspan and wing length than dwarf females. Finally it was noted from this study that various strains of Tswana chickens had the same quantitative traits except for shank length and shank circumference which were significantly smaller in dwarf strain compared to the other four strains. This research work will also play an important role by provision of current information on quantitative traits of Tswana chicken strains.

Key words: morphological measurements, quantitative traits, Tswana chickens

Introduction

In Botswana, indigenous chickens are referred to as Tswana chickens. They are classified into five strains: dwarf, rumpless, frizzled, naked-neck and normal with the most common strain being the normal (Badubi et al., 2006). The terms backyard, local, traditional, village, scavenging or family chickens are used synonymously to refer to indigenous chickens. Tswana chickens are usually produced under the extensive farming systems where the birds mostly scavenge for feeds, picking food items such as food scraps and insects around the households with little or no supplementation and uncontrolled breeding (Aganga et al., 2000; Moreki, 2000; Badubi et al., 2006). Indigenous chickens are subjected to challenging selection pressure due to the unsuitable management conditions under which they are reared and represent an important reservoir of genetic variation that is supposed to be conserved (Guèye, 1998). Indigenous chickens are underestimated because of their poor performance under traditional free running system (Getu et al., 2014). Most village farmers however prefer family chickens as they can survive better in local environment with available limited feed resources (Cabarles, 2013). These types of birds need minimal management to produce eggs and meat basically for household consumption and local markets (Magpantay et al., 2006).

Indigenous chickens can be recognized as gene reservoir, especially for those genes that have adaptive values in the tropical conditions (Aklilu et al., 2013). In Botswana, family chickens are the most widespread animals where almost every rural family owns chickens, which contribute greatly to the supply of eggs and meat (Badubi et al., 2006). It is believed that in the remote areas, genetic originality may still be found (Daikwo et al., 2011). The purpose of this study was therefore to evaluate various quantitative traits in male and female naked-neck, normal, frizzled, rumpless and dwarf strains of Tswana chicken in selected villages of Kweneng and Southern districts of Botswana.

Materials and Methods

Study site

The study was carried out in Kweneng and Southern districts of Botswana. The capital village of Southern district (Kanye) and is located at -24.9667 [latitude in decimal degrees], 25.3327 [longitude in decimal degrees] at an average elevation of 1406 metres above sea level. The sub-capital village of Southern district (Good Hope) lies at a latitude of -25.4852400 and longitude of 25.4475400 and has an elevation of 1259 metres above sea level. The capital village of Kweneng district (Molepolole) and is located at -24.4066 [latitude in decimal degrees], 25.4951 [longitude in decimal degrees] at an average elevation of 1146 metres above sea level.

Six remote villages were selected from each district (Figure 1) and within a district; villages were selected such that there was uniformity in the chicken production system. Large villages and villages in close proximity to towns and large villages were avoided due to their high populations of exotic chicken breeds and to minimize the influence of urban-affiliated farming systems on typical rural village-based traditional free running system (Desta et al., 2013). A total of 89 households within each district comprising of six villages each, rearing only indigenous Tswana chicken participated in the study. Households with exotic chickens or with a history of keeping exotic chicken breeds and those in close proximity to such households did not participate in the study to ascertain the genetic purity of indigenous Tswana chicken participating in the study. This however limited the number of households that participated in the study and the total number of chickens of various strains that participated in the study.

Figure 1. Map of Botswana showing Kweneng and Southern districts in blue and orange, respectively in Southern Botswana.

Data collection

A total of 618 indigenous Tswana chickens aged between six months and two years and comprising of 246 normal-feathered (54 males and 192 females), 123 naked-neck (18 males and 105 females), 129 dwarf (45 males and 84 females), 57 rumpless (27 males and 30 females) and 63 frizzled (18 males and 45 females) chickens, kept under traditional free running management system were used in the study (Figure 2-Figure 6). There were generally more females than males of various strains of Tswana chicken per household as a result of the inherent breeding system hence more females than males participated in the study. Some households selected against naked-neck, dwarf, rumpless and frizzled chickens which results in the low frequency of such strains in the general Tswana chicken population hence their lower sample size compared to the normal-feathered strain. Rumpless and frizzled strains, in particular, did not exist at all in some selected villages. The chickens used were approximately six months of age or older as per information provided by the owners. Quantitative morphologic traits such as shank length, shank circumference, spur length, comb length, wattle length, wing length, wingspan and body weight were measured in males and females of various strains of Tswana chicken in accordance with FAO (2011). A Spring-Dial Hoist weighing scale was used to measure live body weight (kg), whereas shank length, spur length, comb length, wattle length, wing length and wing span were measured using a flexible Tailor’s tape. Shank circumference was measured using a vernier caliper (Starrett tools model, Range: 30 cm, USA).

Statistical analysis

Quantitative data for the various traits measured were analyzed using PROC MIXED procedures of SAS 9.2 2008 (SAS Institute, year of publication). The model included fixed effects of sex (male or female), strain (naked-neck, normal, dwarf, rumples and frizzled), the interaction between strain and sex, and the random effect of household. Means were separated using pairwise t-tests with Scheffe’s adjustment to account for unequal sampling units per strain, and were determined to be significantly different at P<0.05.

The model being:

Y_ijk = µ + S_i + X_j + (S_i * X_j) + e_ijk

Where

Y_ijk = mean body weight,

µ = overall mean,

S_i = Effect of the i^th strain (Normal, naked-neck, frizzled, rumpless and dwarf),

X_j = Effect of the j^th sex (male and female),

(S_i * X_j) = interaction between strain and sex

e_ijk = random effect of household.

Results and discussions

There were no significant differences between males and females of naked-neck, frizzled, rumpless and dwarf strains of Tswana chickens in shank length, shank circumference, wing span, wing length and wattle length under extensive management system (Table 1). Normal males however, had significantly higher values for shank length, shank circumference, wing span, wing length, comb length and wattle length than their female counterparts. The shank length, wing span and wattle length values found for the various strains of Tswana chickens in this study are in line with the shank lengths, wing span and wattle length reported for indigenous chickens of Eastern Amahara, regions of Ethiopia reported by Getu et al., (2014). The wing span values in both males and females of various strains of Tswana chickens are lower than wing span values reported for both males and females of indigenous chickens of South-Western Ethiopia reported by Bekele et al., (2015). The Shank length of both males and females of various strains of Tswana chickens are however longer than those of indigenous male and female Nigerian chickens reported by Daikwo et al., (2011). The values for shank length in both males and females of Tswana naked-neck, normal and dwarf strains found in the current study are lower than the values reported by Kgwatalala et al., (2012) in the three strains at 20 weeks of age under intensive management system. Similar shank length between males and females of the dwarf strain and significantly higher shank length in normal males than females is consistent with Kgwatalala et al., (2012).

Similar shank length between naked-neck males and females is however contrary to Kgwatalala et al., (2012) who found significantly higher shank length in Tswana naked-neck males than females (2705.78 ± 91.42 versus 1976.55 ±100.14 mm) at 20 weeks of age.

Generally, males of the normal, naked-neck, frizzled, rumpless and dwarf strains of Tswana chickens had higher values of shank length, shank circumference, wing span, wing length and wattle length than their female counterparts. Higher values in shank length, wing span, wing length and wattle length in males than females of various strains of Tswana chickens is consistent with Aklilu et al., (2013); Bekele et al., (2015) and Getu et al., (2014) in indigenous Ethiopian chickens. Higher wing length in naked-neck males than females found in this study is consistent with Alabi et al., (2012) who reported significantly higher wing length in South-African naked-neck males than females (21.50 ±0.210 versus 17.20 ±0.18 cm). Higher wing length, shank circumference and shank length in males than females of the normal, frizzled, rumpless and dwarf strains of Tswana chickens is consistent with Alabi et al., (2012) who reported a similar pattern in three indigenous chicken breeds of South Africa.

Dwarf males had significantly higher comb length than their female counterparts. There were no significant sex differences in spur length and live weight in all the five strains of Tswana chickens, but generally males of all the five strains had higher spur length and live weight values than their female counterparts. Generally the body weights of different strains of Tswana chickens found in the current study are higher than those reported for other indigenous chickens in South Africa (Alabi et al., 2012), in Nigeria (Yakubu and Salako 2009) and in Ethiopia (Bekele et al., 2015). Higher live weight values in males than females in all the five strains of Tswana chickens is consistent with Kgwatalala et al., (2012) who found a similar pattern in the naked-neck, normal, and dwarf strains of Tswana chickens at 20 weeks of age under intensive management system. Njenga (2005) also reported higher mature live weights in naked-neck, normal and dwarf males than females in Kenyan indigenous chickens. Higher body weight and linear body measurements in males than females of all the five strains of Tswana chickens confirm the well documented sexual dimorphism in poultry species. According to Baeza et al., (2001) sexual Dimorphism in body weight and linear body measurements is attributable to differences in hormonal profiles between the sexes which ultimately lead to differential growth rates.

There were no significant differences (P > 0.05) in shank length and shank circumference among male normal, naked-neck, frizzled and rumpless strains of Tswana chickens (Table 2). However, males of the four strains had significantly higher shank length and shank circumference than dwarf males. Similar shank length between the naked-neck, frizzled and normal strains found in this study is consistent with Fayeye et al., (2006) who reported shank length of 9.7 cm, 10.2cm and 9.7 cm in the three strains, respectively, in Nigerian indigenous chicken. Similar shank length between Tswana naked-neck and normal males and significantly higher shank length in the naked-neck and normal males than dwarf males found in this study are consistent with Kgwatalala et al., (2012) under intensive management system. Among males of the five strains of Tswana chickens the naked-neck had the highest shank length and shank circumference followed by normal, frizzled, rumpless and lastly dwarfs strain. The highest shank length in naked-neck males compared to the other four strains is consistent with Getu et al., (2014) who found the highest shank length in naked-neck males compared to Gasgie and gugut types of Ethiopian indigenous chicken. Higher shank length and shank circumference in naked-neck than frizzled males found in the current study is consistent with Ige et al., (2012) in Nigerian frizzled feather and naked-neck chickens. There were no significant differences in spur length, wing span, wing length, comb length, wattle length and live weight among males of the five strains of Tswana chickens (Table 2). Similar wing length among frizzled, naked-neck and normal males found in this study is consistent with Adekoya et al., (2013) who reported wing lengths of 17.027 ±4.089, 15.791 ±2.074 and 16.036 ±2.214cm in the three strains, respectively, of Nigerian indigenous chickens. Fayeye et al., (2006) also reported similar wing length between naked-neck (17.5 cm), frizzled feather (17.8 cm) and normal (17.7 cm) strains of Nigerian indigenous chicken.

Among males of the five strains of indigenous Tswana chickens, the naked-neck had the highest wattle length and the rumpless had the lowest. The longest wattle length in naked-neck males compared to the other strains found in the current study is consistent with Faruque et al., (2010) in Bangladeshi chicken and Getu et al., (2014) in Ethiopian chicken. Among males of the five strains of Tswana chickens, normal had the highest live weight, followed by naked-neck, frizzled, dwarf and lastly rumpless. Adekoya et al., (2013) also found the highest body weight of 2.079 ±0.575 kg in the normal strain followed by naked-neck with 0.905 ±0.259 kg and lastly frizzled feather chicken with live weight of 0.904 ±0.327 kg in Nigerian indigenous chickens. Ige et al., (2012) also reported higher live weight in naked-neck (n=42) than frizzled feathered (n=56) Nigerian indigenous chicken (1.69 ±0.27 versus 1.44 ± 0.34 kg). Similar live weight between naked-neck and normal strains of Tswana chicken is however, contrary to Kgwatalala et al., (2012) who found significantly higher live weight in naked-neck males than normal males ( 2705.78 ±91.42 versus 22.70.19 ± 69.10 g) of indigenous Tswana chicken at 20 weeks of age under intensive management system. The discrepancy could be due to the differences in the production environment between intensive and extensive management systems, particularly in the feeding. Unfavorable production environment might have prevented the growth potential of naked-neck chickens under extensive management system. Higher body weight in normal males than dwarf males of Tswana chicken is however consistent with Kgwatalala et al., (2012) who reported body weight of 2270.19 ± 69.10 and 1969.47±95.48 g in the two strains, respectively, at 20 weeks of age under intensive management system.

There were no significant differences (P > 0.05) in shank length and shank circumference among females of normal, naked-neck, frizzled and rumple strains (Table 3). The four strains however had significantly higher shank length and shank circumference than the dwarf strain. Similar shank length between normal, naked-neck and frizzled strains of indigenous Tswana chickens found in this study is consistent with Liyanage et al., (2015) who found similar shank length of 127, 129 and 127mm, respectively, in the three strains of Sri Lankan indigenous chicken. Significantly higher shank length in normal than dwarf Tswana chicken is consistent with Yeasmin and Howlinder (1998) who also reported significantly higher shank length in normal than dwarf Deshi hens of Bangladesh ( 7.7 ± 0.15 versus 5.5 ± 0.17 cm). Kgwatalala et al., (2012) also reported similar shank lengths between female naked-neck and normal Tswana chickens (11.26 ± 0.33 and 10.84 ± 0.18 cm, respectively) and significantly higher shank length in the two strains than female dwarf Tswana chickens at 20 weeks of age under intensive management system. Similar shank circumference between female normal, naked-neck and frizzled Tswana chickens found in the current study is consistent with Liyanage et al., (2015) who reported shank circumference of 65, 66, and 67 mm in the three strains, respectively, in Sri Lankan village chickens.

There were no significant differences (P > 0.05) in wing span and wing length among females of normal, naked-neck, frizzled and rumpless strains, and also among frizzled, rumpless and dwarf strains of indigenous Tswana chickens. However, females of the normal and naked-neck strains had significantly higher wing span and wing length than females of dwarf strain. Similar wing length between female normal, frizzled and naked-neck Tswana chicken is consistent with Liyanage et al., (2015) who found wing length of 148, 131 and 149 cm in three strains of Sri Lankan village chickens, respectively. Among the five strains of Tswana chickens naked-neck females had the highest wing span and wing length followed by normal, rumpless, frizzled and lastly dwarfs females. There were no significant differences among females of the five strains of Tswana chickens in spur length, comb length, wattle length and live weight. Similar live weight between female normal, naked-neck and dwarf strains of Tswana chickens found in this study is consistent with Kgwatalala et al., (2012) who reported non- significant differences in body weight in the three strains at 20 weeks of age under intensive management system. Liyanage et al., (2015) also reported non-significant difference in body weight between normal, naked-neck and frizzled female Sri Lankan village chicken. Dakpogan et al., (2012) reported similar body weights between naked-neck and frizzled Benin hens (994.4 ± 42.9 and 1065.1 ± 42 g, respectively) which were significantly higher than those of normal (839.4 ± 42.7 g) and dwarf hens (651.4 ± 43 g) at sexual maturity under intensive management system. Similarly Isidahomen et al., (2012) found significantly higher slaughter weight in naked-neck (2084.00 ± 108.43 g) than frizzled (1974.10 ± 94.16 g) and normal hens (1693.00 ± 71.34 g) of Nigerian indigenous chickens under intensive management system. Females of the normal strain of indigenous Tswana chicken had the highest body weight followed by rumpless, naked-neck, frizzled and lastly the dwarf strain.

Compared to the normal, naked-neck, and frizzled strains of Tswana chickens, dwarf males and females had the lowest shank length, shank circumference, wing span, wing length and live weight and this could be due to the effect of dwarfism gene that has been reported to result in up to 30 and 40 % reduction in body weight in females and males, respectively, compared to normal strain (FAO, 2010). From the current study it is clearly demonstrated that dwarfism gene not only affects body weight but body dimensions as well. The highest body weight in the normal strain (both males and females) compared with the naked-neck and frizzled strains found in this study is contrary to the general belief that reduced feathering genes (naked-neck and frizzled genes) lead to improved body weight and dimensions due to their improved heat tolerance which consequently positively affects appetite (Islam and Nishibori, 2009). The favourable effects of naked–neck and frizzled genes on growth performance might only be realized under the favourable production environment experienced under intensive management system and not under free range management system where balanced diets and feed availability are limited.

Figure 2. A typical dominating spotted black colour (Naked-neck hen) at Malwelwe village	Figure 3. A typical brown chicken with minor white (Normal strain hen) at Sojwe village
Figure 4. A black chicken (Frizzled hen) at Salajwe village	Figure 5. A typical brown mixed colour (Rumpless hen) at Maboane village
Figure 6. A brown mixed white colour (Dwarf hen) at Sojwe village

Conclusions

• This paper contributes to the documentation of quantitative traits of Tswana chicken strains found in the Southern part of Botswana.
  
  
• The study indicated that body weights and dimensions of various morphological quantitative traits were generally higher in males than females in all the five strains of Tswana chicken.
  
  
• Different strains of Tswana chickens had similar quantitative traits with the exception of shank length and shank circumference which were significantly smaller in the dwarf strain compared to the other four strains.

Acknowledgements

The authors would like to thank farmers and district extension officers (department of Veterinary services and Crop production) at Molepolole and Kanye agricultural stations for accepting to be interviewed and for availing their chickens for use in this study. Appreciation is also extended to Botswana University of Agriculture and Natural Resources for funding the study.

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Received 5 December 2016; Accepted 15 May 2017; Published 2 July 2017

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