Livestock Research for Rural Development 14 (3) 2002

http://www.cipav.org.co/lrrd/lrrd14/3/msof143.htm

Productivity and Natural Disease Resistance Potential of Free-ranging Local Chicken Ecotypes in Tanzania

 

P L M Msoffe, M M A Mtambo, U M Minga,* P S Gwakisa,* R H Mdegela and J E Olsen^**

 Department of Veterinary Medicine and Public Health, Sokoine University of Agriculture,
P O Box 3021, Chuo Kikuu, Morogoro, Tanzania.
msoffepl@suanet.ac.tz
* Department of Veterinary Microbiology and Parasitology, Sokoine University of Agriculture,
 P. O. Box 3019, Chuo Kikuu, Morogoro, Tanzania.
**Department of Veterinary Microbiology, The Royal Veterinary and Agricultural University,
Stigbøjlen 4, 1870 Frederiksberg C, Denmark.

 

Abstract

This study was carried out to investigate the productivity and the natural disease resistance potential of free-ranging local chickens in Tanzania. A total of 84 adult free-ranging local chicken ecotypes were studied, namely: Mbeya, Morogoro-medium, Ching’wekwe, Kuchi and Singamagazi. Adult body weight, body length, shank length and egg weight were assessed and compared.

 

Average body weight for hens and cocks was 1441g (800 to 2,300g) and 2261g (1000 to 3500g), respectively. Egg weight averaged 41.6g (27 to 72g). Mean body length for hens and cocks was 21.6cm (17 to 26cm) and 24.6cm (21 to 29cm), respectively, and mean shank length 9.7cm (7 to 12cm) and 12.7cm (8.5 to 15cm), respectively. Between ecotypes significant differences were seen in the above parameters. The disease resistance potential was tested on 10 offspring of each ecotype, excluding the Mbeya. Twenty chickens (five from each of the four ecotypes) aged 12 weeks were inoculated with Newcastle disease virus while another 20 aged 20 weeks were inoculated with Salmonella gallinarum. Five chickens per group that were not challenged were used as controls. Following oral, ocular and nasal drop inoculation with Newcastle disease virus, the chickens developed clinical signs of Newcastle disease as from day three after infection. Mortality started on day five after infection, and all but one chicken were dead by day seven after infection. The 20 chickens, infected orally with S. gallinarum, showed clinical signs of fowl typhoid on day three after infection. Mortalities started on day seven after infection and by day 12 after infection 13 chickens had died. Seven birds survived without visible signs of the disease, including all five from the Kuchi ecotype and one each of the Morogoro-medium and Ching’wekwe ecotypes. At necropsy enlarged and congested liver and spleen, and catarrhal enteritis of the small intestines were seen. The surviving birds were sacrificed on day 14 after infection. Neither the sacrificed surviving birds nor the controls showed the above necropsy picture.

 

It was concluded that free-ranging local chicken ecotypes in Tanzania differ in both productivity and disease resistance potential.

 

Key words: Indigenous chicken, scavenging, ecotypes, disease resistance, performance traits

 

Introduction

Free-ranging local chickens account for most of the 27.8 million poultry kept in Tanzania (MOA 1995). From time immemorial free-ranging local chickens have been living in Tanzania and are present wherever there are human settlements (Kabatange and Katule 1989; Melewas 1989). Chickens, with their short generation interval and the ability to survive on leftovers, grasses and insects, are widely distributed (Kabatange and Katule 1989).

 

Free-ranging local chickens are known for their ability to survive under various types of shelter, including makeshift chicken houses, kitchens and even roosting in trees (Andrews 1990; Horst 1990; Musharaf 1990; Yongolo 1996).

Breeding under the free-ranging system of management is random, and cocks and hens mate in an uncontrolled manner (Horst 1990; Williams 1990). It is usually the most aggressive, strong and dominant cock, which sires most offspring in the neighbourhood (Williams 1990).

 

Considerable variations in adult body weight, anatomical features, body size, egg weight and production capacity and plumage characteristics have been reported among the free-ranging local chickens in Tanzania (Kabatange and Katule 1989; Minga et al  1989).

The major production constraint in free-ranging local chickens in developing countries is disease (Mitchell 1984; Minga et al 1989; Sonaiya 1990; Awan et al 1994). Newcastle disease (ND) has been ranked as the number one killer disease of free-ranging local chickens (Minga et al 1989; Musharaf 1990). Other diseases reported in local chickens include; Gumboro disease (Sonaiya 1990; Yongolo et al 1996), Fowl pox and coccidiosis (Sonaiya 1990) and Helminthoses (Msanga and Tungaraza 1985; Permin et al 1997). In Tanzania, in a study by Minga et al (1989) it was shown that, based on serology, Fowl typhoid and Newcastle disease (ND) were the most prevalent chicken diseases

 

Local chickens are believed to be resistant to many common diseases, partly because little attention is paid to disease control measures (Melewas 1989; Kulube 1990; Chrysostome et al  1995). However, other studies have shown that local chickens appear to be more susceptible to diseases than exotic commercial types (Lin and Lee 1996; Okoye and Aba-Adulugba 1998).

 

Natural resistance to different Salmonellae infections has been reported in some lines of White Leghorn chickens (Bumstead et al  1989; Bumstead and Barrow 1993) but natural resistance to ND has not been reported. However, so far no work has been done to compare the susceptibility or resistance of the heterogeneous free-ranging local chickens to different diseases.

 

The current study was undertaken to investigate the potential of the free-ranging local chickens in terms of productivity and natural disease resistance and the possibility of utilising the available potential in the improvement of chickens in this sector.

 

Materials and methods

Source of chickens

A total of 84 adult free-ranging local chickens originating from the five local ecotypes, namely: Ching’wekwe (n =15), Mbeya (19), Morogoro-medium (19), Kuchi (16) and Singamagazi (15) were used (Msoffe et al 2001). The chickens were used for the assessment of the quantitative parameters, and were the parents of chicks used in the experimental infection study. The chickens were bought from villages without history of crossbreeding programmes involving exotic chickens. The selected chickens were wing tagged, vaccinated against Newcastle disease, treated with broad-spectrum antibiotics and against ectoparasites, and then transported to the research station at Sokoine University of Agriculture, Morogoro, Tanzania. The chickens were assigned to separate pens (according to ecotype) where feed and water were given ad libitum. A group of 50 naturally bred offspring was used in an experiment to test the natural resistance of the different free-ranging local chicken ecotypes to Newcastle disease virus (NDV) and S. gallinarum infection. A total of 20 chickens aged 12 weeks were used for the NDV experiment, while another 20 birds aged 20 weeks were used for the S. gallinarum experiment. Five chickens of each ecotype were taken in each experiment as controls. Chickens were from the Ching’wekwe, Kuchi, Singamagazi and Morogoro-medium ecotypes (five per ecotype). 

Assessment of quantitative parameters

Initial body weight (g), body length (cm), shank length (cm) and egg weight (g) were measured in each group separately. A total of 50 randomly selected eggs in each group were weighed.

NDV infection

Each bird received 1ml of the SUA 24/C NDV inoculum (Yongolo 1996) at 10⁶ ELD50. Inoculation was done as ocular and nasal drops, with one drop on each location on one side of the face, while the remainder of the inoculum was given orally. Observations for signs of Newcastle disease and mortality were made twice daily for a period of seven days.

S. gallinarum infection

Each of the twenty chickens was inoculated orally with 1 ml of overnight Muller Hinton broth culture of S. gallinarum (dose 5.2 x 10⁸ cfu). The S. gallinarum had previously been isolated from a field outbreak of Fowl typhoid in a Dar es Salaam chicken farm. The S. gallinarum used was shown to carry a heavy plasmid by plasmid profiling method (Mdegela et al 2000). The controls received 1 ml of the un-inoculated broth. The chickens were observed twice daily for clinical signs of fowl typhoid and for mortality for 14 days.

Statistical analysis

Descriptive statistics, analysis of variance and linear regression examining the effect of ecotype on the physical parameters were employed (Statistix ® version 4.1). The raw data used in the generation of the data set were for body length, shank length, and adult body weight.

 

Results

Overall variability in physical parameters

The overall variability in the physical variables studied is presented in Table 1.

 

Variability in physical parameters stratified by origin of the chickens

When each group was assessed separately for the physical parameters, the results obtained were either above or below the overall average values presented in Table 1 (Tables 2a and 2b). Chickens from Kuchi and Singamagazi ecotypes had mean values for all the four physical parameters measured that were above the overall averages. Chickens from other ecotypes had mean values below or close to the overall averages. Mean egg weights for the Kuchi and Singamagazi ecotypes, respectively, were also above the overall average. The average body weights for females for males from the Morogoro-medium group were below the overall mean values. The lowest values for body length, which were below the overall mean value, were seen in Mbeya females and Mbeya and Morogoro-medium males.  The shortest shanks were recorded in chickens of the Ching’wekwe ecotype.

 

 

Experimental infection with NDV and S. gallinarum

By day three after infection with NDV, six out of the 20 infected chickens showed clinical signs of ND, including depression, huddling, ruffling of feathers and reluctance to move. By day four after infection, all the infected chickens were sick and apart from the above symptoms, had greenish diarrhoea, oedema of the face and various degrees of nervous disorders. The facial oedema was visible only on the inoculated side. The nervous signs included torticolis, paresis of limbs, turning in circles and resting on the beak. Mortalities started from day five after infection and by day seven only one chicken was alive, but showed severe nervous signs. Although the remaining chicken survived the challenge it remained lame and was sacrificed on day fourteen after infection. At necropsy the dead birds appeared congested, oedematous (on the face), with haemorrhages on the larynx and the air sacs were cloudy. Other lesions included haemorrhages on the mucosal part of the intestinal tract and were visible on the serosa, cloaca and heavy muscles of the thighs and breast. In one bird the liver had greyish-white necrotic foci of various sizes. The sacrificed bird showed a similar necropsy picture to the birds that succumbed to infection but the intestinal haemorrhagic lesions were milder. None of the control birds showed any signs of the disease.

 

From the third day after infection most birds infected with S. gallinarum showed some clinical signs of fowl typhoid. The symptoms were depression, reluctance to move, and various degrees of inappetance, listlessness, yellowish diarrhoea and standing with closed eyes. The clinical signs were noted in the chickens of the light ecotypes (Ching’wekwe Morogoro-medium) and of the heavy ecotypes, Singamagazi but not Kuchi. Mortalities started on the seventh day after infection, when four chickens were found dead (two of the Singamagazi ecotype and one each from the Ching’wekwe and Morogoro-medium ecotypes). By day twelve after infection, thirteen chickens had died, while the remaining seven survived the challenge to the end. The survivors belonged to the Kuchi ecotype (all five), Morogoro-medium (one) and Ching’wekwe (one), while none of Singamagazi ecotype survived. At necropsy the picture was that of acute and sub-acute fowl typhoid. At post-mortem examination the carcasses were septicaemic, with congested subcutaneous blood vessels, enlarged liver and spleen, the skeletal muscles appeared congested and dark in colour. Out of the thirteen dead chickens examined, eight cases had livers with a coppery bronze sheen when exposed to light. Catarrhal enteritis of the small intestine was a consistent finding in all cases. The intestinal contents were invariably viscous and bile stained with a slimy consistency.

 

Attempts to re-isolate the organism from livers and spleens of the dead birds using Brilliant Green Agar (BGA) yielded pure colonies of S. gallinarum. However, re-isolation and determination of viable counts of S. gallinarum in the liver and spleen of the survivors 14 days after infection did not yield any bacteria. In spite of this, with pre-enrichment in peptone water before culturing in Selenite-F broth and BGA it was possible to isolate S. gallinarum from three out of the seven sacrificed birds.

 

Discussion

The results of the current study suggest a potential in both productivity and disease resistance traits in the free-ranging local chicken populations of Tanzania. Wide ranges were observed in adult body weight, egg weight, body length and shank length. When the studied chickens are taken as one group, the average values tended to mask the situation observed when each ecotype was considered separately. The average body weights of 1471g and 2261g for females and males, respectively, masks a range of 800 to 2300g (females) and 1000 to 3500g (males). Similarly, the average egg weight of 41.6 g from the range of 27 to 72g is hardly representative. Other parameters showed a similar pattern.

 

However, when these results are presented with respect to the ecotype of the chickens the differences became clearer and the ranges were less wide. Egg weights of local Tanzanian chickens averaging 41.4g (30 to 55g) reported by Minga (1989) are in agreement with the current average of 41.6g (27 to 72g). However, the ranges are not similar, which may be due to the inclusion in the current study of chickens from different ecological regions. French (1942) reported egg weights averaging 38g in most local chickens, but also that a few chickens produced eggs weighing 45 to 56g. Egg weight in Nigerian local chickens were reported to average 38.6g (Omeje and Nwonsu 1984). In Uganda, local chicken eggs weighed 35 to 45g (Trail 1963), while the Egyptian local chicken produced eggs averaging 40.1g (Abdou and Kolstad 1984). Values in the above reports are in broad agreement with the mean value (41.6g) from our current investigation. In comparing egg weights between local chickens and exotic egg and meat type chickens and their crosses, Katule (1988) reported significant differences between these genetic groups. Local chickens’ eggs weighed on average 38.2g, those from egg-type breeds 54.5g, those from meat-type breeds 57g and from a local x egg-type cross 46g. These results are all within the ranges obtained in the current study.

 

In terms of body weight, averages of 1471g (800 to 2300g) for females and 2261g (1000 to 3500g) for males were recorded in the current investigation. Previous reports have shown average weights of 1200g for hens and 2200g for cocks (Minga et al 1989), 1651g for hens (Katule 1988) and 1191g for hens (Abdou and Kolstad 1984). The results from these reports are comparable to some results in the current study, especially those of chickens from Mbeya and Morogoro. However, chickens from Kuchi and Singamagazi ecotypes had average weights well above those given in the above reports, and were higher than all the average weights reviewed by Gueye (1998).

 

There is a general consensus among many authors that the local chicken industries in the developing world should be developed as a sustainable alternative to the industrialised production (Sonaiya 1990; Bell, 1992; Mukherjee 1992; Gueye 1998). Still, it is important that before embarking on projects aimed at increasing the productivity of local chicken stocks, their current potential should be known (Lawrence 1998). French (1942) saw room for improvement in terms of egg production and other authors have expressed similar ideas (Minga et al 1989; Kabatange and Katule 1989; Katule 1990; Mwasha 1991; Mukherjee 1992). These views are supported by the variations observed in most of the parameters studied, suggesting that there is a possibility of increasing the mean values through breeding programmes (Lawrence 1998). There is no reason why the average egg weight should not be more than 50g if chickens producing eggs of this size are utilised in selective breeding programmes. Other characters can be improved in a similar manner.

 

The current investigation has provided insights into some of the differences within free- ranging local chickens in Tanzania from different geographical locations. This was somehow missing in previous studies and it is now more appropriate to utilise suggestions put forward by Katule (1988; 1990) on the improvement of productivity through crossbreeding. It can be argued that crossing heavy local ecotypes with meat types to achieve a meat-type cross will be more sensible than if a light local ecotype was used, and the same applies for improving egg weights and number. French (1942) saw room for improving the productivity of free-ranging local chickens in Tanzania way back in 1942; today, over fifty years later, we see that the potential is still there, and is probably greater, as more facts are known today about these chickens than at that time. Based on the results of the current investigation, crossbreeding can even be performed between the different local chicken ecotypes, owing to the clear differences observed between them.

 

In terms of natural disease resistance potential, our study indicates that the four free-ranging local chicken (SLC) ecotypes were all susceptible to Newcastle disease (ND). The clinical signs, mortality and necropsy picture presented by the infected birds confirmed this. These results agree with the study of Alexander (1997), who reported the lack of breed or genetically determined susceptibility to ND. The results of this study also concur with other authors who reported that ND was the number one killer of the free ranging local chickens in Africa (Minga et al 1989; Bell 1992; El Zubeir 1990; Sonaiya 1990; Musharaf 1990; Yongolo 1996). The one chicken ecotype from Tabora that had severe nervous symptoms, survived the challenge, which is in agreement with the literature that birds showing nervous signs have a tendency to recover (Cole and Hutt 1961; Bell 1992; Yongolo 1996).

 

The current investigation has shown that chickens of the Kuchi ecotype are resistant to Fowl typhoid, as all five chickens from this group survived the challenge without any visible clinical signs of the disease. The other two chickens (one each from Morogoro-medium and Ching’wekwe ecotypes) that also survived the challenge indicate that resistance to Fowl typhoid may be a trait among the free ranging local chicken ecotypes in Tanzania. These results are in agreement with work by Bumstead and Barrow (1993), who reported genetic resistance to Fowl typhoid in lines of White Leghorn chickens. It is likely that the differences observed in this experiment on resistance to Fowl typhoid between ecotypes are genetically determined.

 

The chicken Major Histocompatibility Complex (B complex) is one genetic system, which has been shown to control genetic disease resistance (Bacon 1987). Resistance to Marek’s disease by B21 haplotypes, Fowl cholera by B1haplotypes and coccidiosis by B3 haplotypes of White Leghorn chickens have been reported (Briles et al  1982; Bacon  1987; Lamont et al 1987; Caron et al 1997). However, according to Bumstead and Barrow (1993), genetic resistance to S. gallinarum is not associated with the B-complex. It has been suggested that genetic resistance to Salmonellosis is due to a better ability of the phagocytic system to contain infection during the initial phase of infection (Bumstead and Barrow 1993). Another mechanism, which influences the resistance of individuals to Salmonellosis, is the so-called Natural resistance-associated macrophage protein (NRAMP) (Cellier et al 1996; Gautier et al  1998). Studies have indicated that resistance to Salmonellosis in chickens is linked to NRAMP (JinXin et al 997). The basis and mechanisms by which the Kuchi ecotype has become resistant to Fowl typhoid is yet to be determined. However, it is possible that the NRAMP might have played a major role.

 

Further work is required in order to ascertain the basis and mechanisms behind the resistance of Kuchi ecotype to Fowl typhoid. Studies of the role of phagocytic cells in clearing Salmonellae infection can be expected to answer some of the questions. The role of NRAMP in the resistance can also provide part of the answers to the question. The possibility of transferring this trait to other chickens should also be considered. Further studies on the productivity, adaptability to different ecological zones and resistance to various diseases of the five identified ecotypes is required. However, the search for more ecotypes should continue. Genetic methods of characterisation such as MHC typing, microsatellite typing and identification of Quantitative Trait Loci (QTLs) should be applied.

 

The current investigation has revealed that free-ranging local chickens can attain reasonable body and egg weights under a zero input free ranging mode of nutrition. Tanzania is among the poorest countries in the world and is constantly threatened by famine (World Bank 1996). Shortages of maize, which is staple food for most Tanzanians, affect the production of commercial poultry feeds (maize being the major ingredient). The free-ranging local chicken sector can therefore provide a sustainable means of provision of much-needed animal protein at a minimum cost. Efforts to identify ecotypes showing high productivity and resistance to the major chicken diseases such as Newcastle disease should be encouraged. We are currently working on characterisation of the free-ranging local chicken ecotypes of Tanzania using microsatellite genetic markers. This we hope will enable us to gain more insights to the genetic diversity of the free-ranging local chickens in Tanzania.
 

Acknowledgements

DANIDA under the ENRECA project “Improving Health and Productivity of Rural Chickens in Africa” have supported this work. The authors are thankful for the support offered. Dr M G S Yongolo is thanked for providing the NDV inoculum. Messrs Andrew Kusilla, Elingao Uroki and James Mwesongo are thanked for their technical assistance.

 

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