Assessment of bacteriological quality of raw camels’ milk in Ab -‘Ala, north eastern Ethiopia

Birhanu Hadush, Etsay Kebede and Hailay Kidanu

Faculty of Veterinary Sciences, Mekelle University P.O BOX 231, Mekelle, Ethiopia
bselam12@yahoo.com

Abstract

This study was aimed to determine the bacteriological quality of raw camels’ milk from udder and milking vessels through the assessment of standard plate count and identification of bacteria genera/species.

The bacterial isolates from the milking vessels were Escherichia coli (25 %), Rhodococcus equi (25 %), Alcaligens spps (12.5 %), Pasteurella haemolytica (10.71 %), Acinetobacter spps (10.71 %), pathogenic Staphylococcus aureus (7.14 %), Pseudomonas spps (5.35 %), non pathogenic Staphylococcus spps (1.79 %) and Bacillus spps (1.79 %). The isolates from udder were pathogenic Staphylococcus aureus (31.82%), Rhodococcus equi (22.73%), Acinetobacter spps (18.18%), non pathogenic Staphylococcus spp (9.09%), Pasteurella haemolytica (9.09%), Escherichia coli (4.54%) and Alcaligens spps (4.54%).  Species of Pseudomonas and Bacillus were isolated from the milking vessels only. Among 34 samples collected directly from the udder, 15 samples (44.12 %) were free of growth of mesophilic bacteria. The bacteriological quality of the 35 samples collected from the milking vessels was 2 (5.7%) very good, 9 (25.71%) good, 11 (31.43%) fair, 11 (31.43%) poor and 2(5.7%) very poor. On the other hand, out of 34 milk samples collected from the udder, 32 (94.12 %) were graded as very good and 2 (5.88%) fair. The difference in bacterial load among the two types of specimens was statistically significant (R²= 0.02, F= 0.49, P-value=0.002).

Key words: bacterial genera, bacterial species, bacterial isolates, bacterial load, bacteriological quality, milking vessels, udder

Introduction

Ethiopia's camel population is estimated to be one million head. This number ranks the country third in Africa after Somalia and the Sudan, and fourth in the world (India included) (Tezera and Kassa 2002). Because of its outstanding performance in the arid and semi-arid areas of eastern lowlands of Ethiopia where browse and water are limited, pastoralists rely mainly on camels for their livelihood. In these areas, camels are mainly kept for milk production and produce milk for a longer period of time even during the dry season when milk from cattle is scarce (Bekele et al 2002). The annual camel milk production in Ethiopia was estimated to be 75, 000 tones (Felleke 2003). In most pastoralists, camel milk is always consumed either fresh or in varying degrees of sourness in the raw state without heat treatment thus, can pose a health hazard to the consumer. Poor management and unhygienic milking practices prevalent in the traditional husbandry systems, which include tying the teats with soft barks to prevent the calf from suckling, tick infestations and cauterization of the udder and skin, are few of the factors responsible for contamination of milk (Abdurahman 1995, Almaw and Molla 2000, Obeid et al 1996, Woubit et al 2001). This study was therefore, aimed at determining the bacteriological quality of raw camels’ milk in Ab-‘Ala (formerly Shekhet), Afar regional state, North eastern Ethiopia

Materials and methods 

Collection of samples and handling procedures

About 15-20 ml of milk sample was collected either from the milking vessels or the last streak directly from the udder of lactating camel using sterile test tubes. During sampling, observation was made about the condition of the udder for the presence of lesions. A total of 69 samples; 35 from the milking vessels and 34 directly from the udder were collected.  Each specimen was labeled and placed in ice box till transported to the laboratory. These were put in a refrigerator at +4 ^OC and culturing was conducted with in 24 hours (Kebede 2005).

Bacteriological culturing and sub culturing

About 0.01 ml of milk from each specimen was streaked on nutrient agar and incubated for 48 hours at 37 ^OC (Quinn et al 2002). Isolated colonies were selected, transferred to nutrient Broth and incubated at 37 ^OC for 24 hours. Cultures were then grown on nutrient agar plates for further studies.

Biochemical tests

Individual colonies were picked  up  and cell morphology, Gram staining, catalase test, oxidase test, oxidation fermentation (O-F) test, presence or absence of   growth on mackonkay agar   were conducted (Rowland et al 1994). Further more, haemolysis on blood agar plate, citrate utilization, growth on manitol salt agar and fermentative activity of sugars on kligler Iron agar (KIA) were checked (Kebede 2005).

Standard plate count (SPC)

Serial ten fold dilutions using sterile 0.85% saline solution up to 10 X 10 ^-6 dilutions were prepared for each specimen.  Pour plate method was used to make viable count.  In this method, one ml inoculum was mixed thoroughly with molten plate count agar, previously held in water bath at 47°C. Four plates were inoculated with each dilution. The agar was allowed to set and then incubated at 37°C for 48 hours. Plates inoculated with a simple dilution that yielded between 30 and 300 colonies per plate were counted (Kebede 2005).  For each dilution, the viable counts in the four plates were counted and the mean was calculated. The result was compared with Indian bacteriological standards of raw milk stated as very good (< 2x10⁵ SPC/ml), good (2-10x10⁵ SPC/ml), fair (10-50x10⁵ SPC/ml), poor (> 50x10⁵ SPC/ml) and very poor (not specified) (Sherikar et al 2004).

Statistical analysis

For data entry and analysis SPSS version 12 was used.  Percentages were used to express the proportion of bacterial isolates. The difference in bacterial load between the milk samples from the udder and milking vessels was analyzed using Regression analysis.  The result was reported as significant if P-value was less than 5 %.

Results and discussion 

Bacterial isolates

Major bacterial isolate from udder was pathogenic S.aureus where as from milking vessels were Escherichia coli and Rhodococcus equi (Table 1).  

Staphylococcus aureus, Escherichia coli, Pseudomonas spps, Bacillus spps, and Alcaligens spps were reported as common microflora of raw milk (Sherikar et al 2004). Staphylococcus aureus, Pasteurella haemolytica and Escherichia coli have been reported to be responsible for mastitis in camel (Bekele and Molla 2001, Pascal 1994).  The isolation of species of Pseudomonas and Bacillus only from milking vessels samples may indicate that these were the common environmental contaminants.  The absence of growth of mesophilic bacteria in 15 (44.1%) cases was almost in agreement with previous reports (Pascal 1994).

Standard plate count (SPC)

The bacterial load (SPC/ml) and hygienic standard of the two types of samples is indicated in Table 2. The difference in bacterial load was statistically significant (R²= 0.02, F= 0.49, P-value=0.002). Majority of specimens from the milking vessels were more contaminated having grade of fair and poor while 94.12 % of the udder samples were having very good grade.

In the study area, pastoralists wash and smoke the milking vessels only once or twice per week and the personal hygiene of the milker is down graded by lack of awareness or  inaccessibility  to use soap  and insufficient clean water supply; all can contaminate the milk  after milking. On the other hand, the lesser bacterial load from the udder of the camel could be attributed to observation of few udder lesions and less tick infestation on camels’ udder.

Conclusions  

The results of this research had indicated that milk is getting contaminated by the handling of pastoralists. Thus, pastoralists should keep regular hygiene of personal, milking vessels and boil or sub boil the milk. Further more; they should avoid traditional beliefs such as branding of udder and professionals should work a lot on further study in identification and virulence of bacterial isolates and regular ecto-parasite control of livestock.

Acknowledgements 

The authors would like to acknowledge Mekelle University NORAD II project coordinators for approving and releasing the budget and the staffs of office of Ab-‘Ala Pastoral Agriculture and Rural Development for their unreserved endeavor in all activities.

References 

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Received 26 March 2008; Accepted 22 April 2008; Published 4 September 2008

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