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Title: BACTERIOLOGICAL QUALITY OF BOVINE MILK IN SMALL HOLLDER DAIRY FARMS IN DEBRE ZEIT ETHIOPIA
Authors: WUBETE, ALEHEGNE
Advisors: Dr. Bayleyegn Molla
Keywords: Milk
TAPC
Coliform counts
MPN
Raw
Pasteurized Critical points
CMT
Copyright: 2004
Date Added: 15-Apr-2008
Publisher: Addis Ababa University
Abstract: The critical control points in milk handling, determination of bacterial load of milk at each critical control points and farm water, isolation and identification of bacterial pathogens in milk were determined from September 2003 to March 2004. A total of 178 raw milk samples from various critical points, and 77 farm water samples were taken three times from 27 small holder dairy farms of Adaa-Liben district dairy and dairy products producers and marketing co-operative society. Pasteurized milk samples (n=100) were taken from Mama milk processing plant. Specific gravity, alcohol and Californian mastitis tests were used as screening tests, and total aerobic plate counts (TAPC) and coliform counts from milk and the most probable number (MPN) of coliform counts from farm water were conducted. Isolation and identification of the bacteria in the milk was conducted following standard methods. The specific gravity values of milk from the dairy owner’s were in the range of 1.025 to 1.029. The normal range being 1.026 to 1.032 at 20 oC. Nine percent of the samples had values below 1.026, an indication of some adultration with addition of water. All the milk samples tested were alcohol test negative. Pooled milk was taken from 25 dairy farms and the CMT results showed that 76 % of the total samples were CMT negative and the remaining 24 % were positive for CMT, indicating the presence of mastitis. The mean total aerobic plate counts of raw milk samples analyzed were 2.10x105 (udder), 1.58x107 (bucket), 1.50x108 (storage container), and 5.67x109 cfu/ml upon arrival at processing plant. The mean coliform counts were 4.84x103 (udder), 1.37x105 (bucket), 1.67x106 (storage container), and 1.26x107 cfu/ml upon arrival at processing plant. The increment of the TAPC and coliform counts at each critical control points were observed statistically significant (P < 0.001) for both counts. There was no significant variation between milk collection centers and the interactions between milk collection centers and critical control points for TAPC and coliform counts (P > 0.1). According to international standards of raw milk quality both the TAPC and coliform counts have values above the upper limits set. These include 10.4% of the raw milk samples from udder, 45.4% of raw milk samples from milking bucket and 100% of raw milk samples from storage containers and X upon arrival at processing plant for TAPC.and 37.7% of the raw milk samples from udder, 96.1% of raw milk samples from milking bucket and 100% of raw milk from storage container and upon arrival at processing plant for coliform counts. Analysis of water samples from the farms revealed that 54.6% were poor (non potable) quality. Pasteurized milk in this study had TAPC and coliform counts ranging from 2.65x103 to 7.2x105 and 0 to 7.5x103 cfu/ml, respectively. Based on the international standards, 7% and 27% of pasteurized milk fall below the standards set for TAPC and coliform counts, respectively. In the course of this study the frequent bacterial pathogens isolated from raw milk samples taken from the udder include: Staphylococcus aureus, Staphylococcus intermidus, Staphylococcus epidermidus, Staphylococcus chromogenes, Streptococcus agalactae, Streptococcus uberis, Streptococcus bovis, Corynebacterium bovis, Corynebacterium ulcerans and Pseudomonas aeroginosa. Similarly, samples from milking bucket, storage container and upon arrival at processing plant were additionally contaminated with bacterial pathogens such as Micrococcus, Rhodococcus spp, Enterococcus fecalis, Bacillus spp, Escherchia coli, Pseudomonas aeroginosa, Enterobacter aerogenes, Enterobacter aglomerans, Klebsiella pneumonia and Citrobacter freundi. Streptococcus pyogenes and Enterobacter aerogenes. Bacteria of public health significance isolated were Staphylococcus aureus, Streptococcus agalactae, Corynebacterium ulcerans, Corynebacterium haemolyticum, Streptococcus pyogenes and Escherichia. coli. Bacterial pathogens such as Staphylococcus intermidus, Staphylococcus epidermidus, Staphylococcus chromogenes, Streptococcus pyogenes Enterococcus faecium, Corynebacterium haemolyticum, Corynebacterium ulcerans and Klebsiella oxytoca which are normally eliminated by efficient pasteurization, were still present in the pasteurized milk samples. The present study showed that: TAPC and coliform counts of raw milk were increased at all critical points from udder to upon arrival at processing plant significantly. However, the counts decreased to lower level after pasteurization. Most probable number (MPN) of coliform counts from farm water samples showed 55.6% were of non-potable quality XI The number and types of isolated bacteria increased after the milk left the udder to upon arrival at processing plant due to exogenous contamination sources. The health of dairy herd, milking and storage conditions, unclean milk equipment, frequent transferring of milk into different containers and sieves, contaminated water were some of the basic determinants of milk quality. Furthermore, the milk was also subjected to more contamination as it was transported long distances to the processing plant under high ambient temperature and without cold chain facility and using materials which were not airtight. The high level of counts and isolate numbers and types found in the milk represent a poor keeping quality and public health risk to the consumer and this suggests the need for improved hygiene practice at all levels in the dairy.
Description: A Thesis Submitted to the Faculty of Veterinary Medicine, Addis Ababa University in Partial Fulfillment of the Requirement of the Degree of Master of Science in Tropical Veterinary Medicine
URI: http://hdl.handle.net/123456789/472
Appears in:Thesis - Tropical Veterinary Medicine

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