Causes of losses in free range local chickens following control of Newcastle disease in three villages in Morogoro, Tanzania

B Alfred, P L M Msoffe, F F Kajuna, D Bunn, A P Muhairwa and C J Cardona*

Faculty of Veterinary Medicine, Sokoine University of Agriculture, P. O. Box 3017, Morogoro, Tanzania
* University of Minnesota, USA
bentemba@yahoo.com

Abstract

A one year study was conducted to determine the causes of chick losses in free range backyard chicken flocks in three villages in Morogoro, Tanzania. A weekly data sheet was used to collect information from chicken keepers on chick losses from hatching to six weeks of age. A total of 4197 chicks were recruited and were followed for a six weeks period.

The parameters under observation were general and cause specific losses of chicks in the flocks. It was found that total chick losses in the first six weeks of age were 53%. The main causative factors for chick losses  were predation (55%), illness other than ectoparasites (30%), ectoparasites (5%), management factors (6%) and unidentified causes (5%). Losses due to predation were significantly higher (p<0.05) when compared to the other identified causes. It was concluded that losses in free range chicken is high in early days of life and that predation is the leading cause. Further studies linking ill health and predation are required.

Key words: Ectoparasites, housing, management, predation, supplementation

Introduction

Traditional chicken keeping involving local and uncharacterized chicken ecotypes constitutes a greater percentage of chicken kept in developing countries, especially in Africa and Asia(Kitalyi, 1998). The local chicken constitute up to 80% of the total poultry population in Africa (Gueye 1998; Simaingaet al 2011) and are characterized by small body size, slow growth rate, low egg production and late maturity in comparison to the commercial hybrids. Despite these drawbacks these birds are apparently are more suitable to the production system in the villages where there are limited resources,poor infrastructure and deficient veterinary services. Consequently, many efforts have been done in facilitating Tanzania villagers in improving free-range chicken production as a way to alleviate poverty and supplement family protein intake.

In various studies diseases have been identified as the major constraint to free range local chickens subsector (Mingaet al 1989; Awanet al 1994; Gueye 1998; Dontwiet al 2011). Studies by Perminet al(1997) and Magwishaet al (2002) showed high prevalence of intestinal helminths and ectoparasites in free range chicken in Tanzania. Parallel investigation done in the same place established that low nutritional status and predation add to the morbidity and losses experienced by the farmers (Mwalusanyaet al 1998). A study on the losses of chicks in naturally brood flocks showed that up to 50% of chicks are lost during the first 8 weeks (Swaiet al 2007). Thus, despite the multiple causes of losses encountered in free range local chickens quantitative study of the causes and their contribution to losses in the flocks have not been established. Wickramenratne et al (1994) found that predators accounted for up to 88 percent of mortality and that coloured birds had a higher survival rate than white birds.

Chicken losses have been reduced significantly in areas where disease identification and control strategies have been communicated to chicken keepers as compared to areas were no extension measures have been put forward (Msoffe et al 2010). Knowing that most losses occur in chicks has been of crucial importance to establish the different causes, their magnitude and contributing factors. This will give a direction on where greater efforts should be. This study was therefore aimed at studying the causes of chick losses at household level after Newcastle disease vaccination, which will help in formulating a disease control package ideal for village free-range chickens.

Materials and methods

Study area

Chick data were collected from three neighbouring villages (Sangasanga, Vikenge, and Changarawe) in Mzumbe ward which is at 6° 56' (6.933333°) South, 37° 34' (37.566667°) East with elevation of 600 meters above the sea level located at Mvomero District in Morogoro region, Tanzania. Human premises are closely located; most houses are made of bricks and mud. The villages are partially urbanized as there is a tarmac road passing and connecting the three villages. Electricity (to those who can afford), tap water, schools, small eating places, small open air markets and shopping points are also available. Vegetation is mainly trees planted around the houses and village pathways giving a forest look. Farming is the main bread earning activity and is performed by the families in small-holdings. The main crops grown are millet, maize and rice. In addition, several households rear animals (primarily poultry but also pigs, goats and cattle). The climate is tropical, and characterized most of the year by moderate to high temperatures. There are two distinct seasons: a rainy season from February to June (with a mean annual rainfall between 1200 and 1800mm) and a dry season from July to November. Short rains are normally experienced between December and January. The survey was conducted from 1^st March 2010 to 28^th  February 2011.

Study population

The study population comprised of free ranging local chickens (Gallus gallus). In most of the households the chickens are let free during the daytime to scavenge around the homestead for food from the surroundings and kept indoors during the night in small poultry shelters or within the family accommodation. Chicks are hatched from natural incubation by the hens and are reared by their dams until when they are two to three months of age. Feeds may be occasionally supplemented by provision of household table scraps and grains or grain bran.

Sampling frame

It was revealed from the ward government statistics that an average of 140 households kept local chicken in each of the three villages. The records also showed that an average of 5 – 15 adult chickens was kept by the families at each point in time. From this sampling frame, 20 households per village were randomly selected for the study. Because the three villages are bordered to each other and no geographic or geological differences exist, the chickens were considered as one population.

Cohorts of chicks

The total number of chicks recruited in the three villages was 4197 (Table 1) giving the average of 69 chicks per household in the 61 households involved. In Sangasanga and Vikenge villages, 1592 and 1520 chicks were respectively  recruited giving an average of 76 chicks per household, as compared to Changarawe village where 1085 chicks that were about 54 chicks per household.

Data collection

A data sheet was developed to record weekly flock dynamics and the number of losses observed since the previous visit. Data collected included the number of chicks recruited (hatched), number of chicks weaned (attain more that six weeks of age) and number of chicks that were lost and the causes of the loss. Chicken keepers were also asked to categorize chick losses by cause. Five categories of causes of loss were mentioned, considering the scope of understanding of each farmer. These included predation, illness (excluding external parasites), external parasites (mainly fleas), mismanagement (accidents, cold weather) and unknown (sudden death or disappearance). Three field workers (one in each village) were trained to conduct face-to face interviews with the chicken keepers and conduct thorough observations. Interviews were conducted in Kiswahili and answers recorded in the same language into the questionnaire but translated to English during data handling and analysis. Each household was visited weekly over a period of 12 months, from March 2010 until February 2011. Before the enrolment of the chicken keepers, verbal consent was sought from the head of the household and chicken keepers were free to leave the study at any time if they so wished.

Data handling and statistical analysis

The chick losses data were entered into Excel ® spread sheet separately by cause of loss. General causes of losses were established by determining the proportion of the chicks that were lost over the total number recruited. Cause-specific losses were established by determining the proportion of chicks that were lost due to determined cause, which is mortality over the total number of chicks recruited in the study. Comparison between the losses caused by different factors and between the three villages was carried out. Statview® computer program was used for computation of descriptive statistics and comparison of means.

Results

Routine management activities for chicks

Chicken keepers were interviewed for basic management of chicks including disease control, feeding and housing. It was found that all except one chicken keeper provide ND vaccination to their chicken. As can be seen in Table 1 below, provision of disease treatment, de-worming and supplementary feeding were done in varying proportions of the chicken keepers interviewed. The Table shows also the type of brooding and housing provided to the chicks.

Survival of chicks to six weeks of age

The total number of chicks that survived in the flock to six weeks of age was 1986 which is about 47%, thus 53% of the chicks were lost before six weeks of age. Vikenge had the highest losses at 64% followed by Sangasanga (58.7%) and Changarawe (28%) (Figure 1). Sangasanga and Vikenge villages started with an average of 76 chicks per household but an average of 31 and 27 chicks per household respectively survived to six weeks ofage. In Changarawe village, an average of 54 chicks per household started, and at the end an average of 39 chicks survived to six weeks in each household. This was a better survival rate compared to the other two villages (Table 2).

Figure1. Percentage representation of the chicks that survived and died in the three study villages. The N values are the chicks studied in the respective village and n values are the number of chicks died and weaned in each village.

Cause-specific losses

Predation and illnesses were found to be the most common causes of death when compared with external parasites, mismanagement and unknown causes (Figure 2). On average, for the three villages it was found that predation causes 55% of all deaths while illness caused 30%. Deaths due to external parasites were 5% and 6% were due to management factors. It was also found that 5% of the deaths were not identified by the chicken keepers. Figure 2 below indicates contribution of each factor to the recorded deaths in each village. Predation was the leading cause of losses in the two villages of Sangasanga and Vikenge, but the second to illness in Changarawe village.

Figure 2. Percentage distribution of deaths to the specific causes of mortality in the three villages. The n values are number of chicks that died for each village and deaths due to the major causes; predation and diseases in each village.

The number of chicks lost through predators (Table 3) is significantly higher compared to the ones lost through illnesses (p=0.0049), and was higher than all causes (other than diseases) combined together (p <0.0001). Diseases also caused significantly more losses compared to all other remaining causes combined (p<0.0001). However, most chicken keepers perceived diseases as their number one chicken enemy.

Frequently observed clinical signs of diseases

In the current study identification of diseases responsible for chick deaths was done by interviewing the chicken keepers. Farmers were able to identify various clinical signs, but as can be seen in Table 3, diarrhoea, head nodules, dark red faeces, swelling and closure of the eyes and nasal discharges were frequently observed in chicks that died.

Discussion

Free range local chickens suffer from various calamities leading to a general situation of low productivity. Among the major causes of low productivity in free range local chickens are physical losses that occur at various stages in their lives particularly during first eight weeks. Several studies have revealed high mortality as one of the causes of losses (Matthewman et al 1977; Wilson et al 1987, Minga et al 1989; Ainiet al 1990, Bell et al 1992). For instance in Nigeria and Mali, mortality was shown to be in the ranges of 80-90% in the first year of life (Matthewman et al 1977; Wilson et al 1987) while in Burkina Faso, almost 32% of losses in chicks were attributed to mortality (Kondombo et al 2003). Kondombo and others (2003) attributed 83% of the mortality to illness while a paltry 10% was due to predation. Most of the mortality in free range local chickens has been blamed on periodic outbreaks of Newcastle Disease (Tran 2002; Muchadeyi et al 2005; Henning et al 2007). However, during the current study no outbreaks of ND were reported in any of the participating households. This was most likely due to a vaccination programme that covered all the study participants. Predation and exposure to extreme weather conditions have also been named as another important cause of losses particularly among the youngest age group of chickens (Minga et al 1989,Ainiet al 1990, Bell et al 1992). One study found that about over 40% of mortalities were attributed to predation, while disease accounted for 30% of deaths over a 12-month observation period in Zimbabwe (Mapiye and Sibanda 2005).

While the current findings are in line with those of Botswana and Zimbabwe that found predation to be the leading cause of losses (Sibanda and Mapiye 2005) dissecting between illness and predator related losses is by no means easy.This probably is because the two are rarely mutually exclusive under a free range management system. Studies that reported disease related mortality as the main cause of chick losses, mostly based on dead chicks that were available for post-mortem examination or presence of sick chicks in the flocks which then disappeared. It can however been argued that the disappearance is most probably linked to predation. We further assert that, with the disease burden so high under the free range management system, predation offers a narrow window for the sick chicks to recover naturally or even to receive treatment because sick chicks lack the physical strength to escape or fight the predators so they are incapacitated to defend themselves against predators.

Although the current study shows that in free ranging chicks predation causes more losses than any other problem, still chicken keepers were justifiably more concerned about the illnesses than predation. The values of chickens to the farmer grow with the age of the chickens and since predation is less common in adult chicken, then diseases are more alarming. Although illnesses might kill more chicks than adults, still chicken keepers observe more diseases in valuable adults than due to predation or any other cause of loss.

In the current study identification of diseases responsible for chick deaths was done by interviewing the chicken keepers. Chicken keepers were asked to explain clinical signs they could note before the chick died. Clinical presentations that were commonly noted by chicken keepers included diarrhoea, drooping wings, dark red faeces, skin nodules on the head parts, swelling and/or closure of the years, nasal discharges and paralysis. It was however not easy for the chicken keepers to pinpoint on a specific disease. Swellings of the eyes described as conjunctivitis suspected to be caused by infectious coryza or vitamin A deficiency was shown to be among the important causes of mortality of free range chickens in Tanzania (Muhairwa et al 1999; 2001). However, further investigations are needed to ascertain the diagnosis of the condition and its importance in free range chickens.

External parasites were also mentioned as common cause of losses in chicks of free range chicken. Often chicken keepers noticed a mass of stick-tight fleas all around the eyes of the chicks. The burden of the infestation may be high enough to impair the opening of the eye and at this stage the chick will not be able to feed. Parasites contribute substantially to poor growth and production in infested chickens (Dube et al 2010). Although the condition may be accompanied by other sort of infections, at the end when the chick dies the farmer will definitely point the parasites as the cause. Stress from parasites can affect the blood picture and cause anorexia (Permin et al 1997; Horning et al 2003).

Some recorded losses of chicks were due to mismanagement issues. In this case, carelessness either due to ignorance or negligence predisposed the chicks. The young birds suffered from extremes of weather in particular coldness. Lack of good care also results in  chicks being attacked by older chicken and sometimes being denied access to food. The issue of good care in chicken in some households becomes questionable due to the fact that chicken keepers leave the task to the young children. Although this may have a positive effect of training the children to provide care to animals, still the chicken succumbed to various risks due to lack of experience and concentration from the carers. This therefore calls for constant supervision from more skilled adults.

Although chicken keepers could tell the causes of majority of losses in their chicken, still some cases occurred unnoticed or due to unidentifiable causes. In the current study we found that 5% of chicks that died were due to unknown causes. In these cases the chicks may have just disappeared without any indication that they were predated, or may have been found dead without any suspected cause. Again this may be due to negligence by the chicken keepers. However, cases of sporadic acute cases of infection, some accidents or some predation and attacks probably account for larger part of unknown causes of deaths although adult birds can be lost due to theft (Henning et al 2007).

From this study, it is evident that chick losses under the free range management system in the study area could be reduced significantly if chicken keepers would pay attention in protecting chicks from predators in addition to controlling Newcastle disease. Any attempts to shelter young chicks during their first few weeks of age will prevent them from being preyed on and may also provide an opportunity to better attend to any health problems that they might have. The use of early chick shelters such as the hay box brooder and other such equipment may assist in reducing preventable chick losses. Furthermore, identification of specific causes of illnesses in chicks in the free range management system is vital to any improvement program. 

Acknowledgement

Financial support was provided by the Newcastle Disease – Avian Influenza control project under generous support from GL-CRSP at UC Davis. The authors are thankful for the support. Thanks also to the field officers and chicken keepers who participated in the study.  

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Received 13 December 2011; Accepted 11 June 2012; Published 1 July 2012

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