Microbial content and quality of raw bovine milk from selected farmers in Namwala district of Zambia

Abstract

Contamination of milk by pathogenic microbes may be a hazard to human health. Worldwide, pathogenic microbes contribute to numerous cases of diarrheal diseases and outbreaks. This study set out to determine microbial content, nutrient quality and associated risk factors regarding contamination of raw bovine milk in Namwala district of Zambia. A cross sectional study was conducted in March, 2017 among small scale dairy farmers. Total enumeration of three milk collection centres (MCCs) was carried out. A simple random sampling method was employed to select study participants. Probability proportion to size was considered in selecting the sample size per MCC. A total of seventy (70) farmers were included in the study. Laboratory forms were used to collect data on the laboratory outcomes (microbial content and milk quality) and questionnaire was used to collect data on the probable risk factors to contamination. Observation checklist was also used to record hygiene practices during milking. The microbial content and quality of raw milk was determined by comparing Total Bacteria Count (TBC) and Total Coliforms Count (TCC) against the requirements by the Zambian Bureau of Standards (ZABS) and the Food and Drugs Act (FDA). Bacterial speciation was determined through isolation of microbes of public health importance such as E. coli and S. aureus while milk compositional quality was determined by comparing the levels of added water in milk, nutrients such as butter fat content, solid nonfat, density and protein. Data were analyzed using STATA version 13.0. Multiple logistic regression was used after which Step wise regression model (machine led) was adopted to establish association between the dependent and independent variables adjusting for confounding factors. A total of 70 farmers participated in the study out of which 16 (22.8%) were from Namwala central, 24 (34.3%) from Nchole and 30 (42.9%) from Mungaila dairy farmers cooperatives. Total bacterial count (TBC) of raw milk from 32 (45.7%) farms was above the maximum legally accepted limits in Zambia. Total Coliforms Count (TCC) from 19 (27.1%) farms did not conform to recommended Zambian standards. Nchole had the highest contamination of S. aureus (41.8%) with Namwala central having the lowest (19%). The overall prevalence of pathogenic E.coli (0157:H7) was at 21% with Namwala central having the highest (10%) contamination among the MCCs in Namwala district. Milk samples from Namwala did not conform to only Zambian standards but also to regional and international standards. Water adulteration was detected in 50% of the samples. About 56% and 47% samples were below standards for butter fat (BF) and solid nonfat content, respectively. The milk density was below the recommended standards for all samples. Microbial content as defined by Total Bacterial Count (TBC) was found to be an average of 2.8 x 106± 9.8 x 105cfu at producer level. Total coliform count (TCC) values for farmers in Namwala district averaged of 3.7 x 105± 6.3 x 105 cfu. Based on milk composition quality, about 50% of farmers practiced water adulteration. Factors associated with contamination of the milk in Namwala district included use of family members in milking 1.26 (p=0.50, 95% Cl 0.64-2.50) and age 1.47 (p=0.31, 95% Cl 0.69-3.09). About 83% (n=58) of the farmers in Namwala district did not follow good hygienic practice of hand washing when milking.The study found that milk in Namwala district was of poor quality with high water adulteration. This suggests the need for a milk processing facility and active surveillance in the area to improve hygienic practices to safeguard public health. Keywords: Raw bovine milk, quality, microbial content, dairy farmers, risk factors,contamination.