A comparative study of farm management systems and influence on milk quality in Ngaka Modiri Molema District, North West Province, South Africa

Abstract

Dairy management is an important tool to improve animal health, productivity, quality of milk as well as to reduce the cost of production. The aim of this study was to assess different dairy management systems used by dairy farmers in the North West Province, South Africa and their impact on milk quality and occurrence of mastitis. To achieve this, seven (7) dairy farms were identified and selected using convenience sampling method in the North West Province, and a structured questionnaire used to assess the knowledge, attitudes, practices and management of the dairies with regard to mastitis in particular. In addition, milk samples were collected from individual animals and from the bulk tanks of each farm for the determination of mastitis. Milk samples (169), quarter (162) and bulk (7) were collected from 7 farms, and from 41 lactating cows and tested for sub-clinical mastitis (using California mastitis test) and cultured for bacterial isolation and identification. All milk samples were analysed for milk quality and content (fat; solids non-fats; lactose; solids and protein) using a speedy lab test machine, South Africa. Catalase and Indole tests were performed for identification of bacteria and biochemical identification. For confirmation, DNA was extracted, Polymerase chain reaction performed and gel electrophoresis run, followed by sequencing at INQABA. Data analysis was done using the Statistical Package for the Social Sciences (SPSS); Chi-square and Multivariate Analysis of Variance (MANOVA) test to analyse the relationship between results of quarter milk and different aspects of the dairy farm management. The analysis of data obtained from the questionnaires revealed that all three farming systems (intensive, extensive and semi-extensive) were applied by dairy farmers in the North West Province. There was a significant impact (p-value<0.05) mainly between the quantity of feed given to lactating cows, method used to clean the teats of the cows, and use of antibiotics and occurrence of mastitis, which was tested using the Chi-square test of association. The occurrence of mastitis, which was found using the CMT method, was confirmed through bacterial culture method to overrule false positive results. Biochemical testing separated the culture results between gram positive and gram negative bacteria using the gram staining testing method. However, the indole and catalase testing methods revealed more prevalence of gram positive bacteria. Results of the molecular test confirmed that Bacillus mainly Bacillus subtilis; Bacillus cereus; Bacillus spp. and Bacillus thuringiensis, Serratia (Serratia spp. and Serratia liquefaciens), Enterococcus (Enterococcus hirae and Enterococcus mundtti), Staphylococcus lentus and Clostridium spp. were the agents responsible for mastitis and that they were mostly environmental mastitis causing pathogens. In conclusion, it was observed that all farming systems had the potential of experiencing environmental mastitis; however, the study revealed that the best advice for management was for farmers to consider a lot of factors in the type of farming system and management they use such as, applying extensive farming system where daily hygiene cannot be prioritized (as cows will move around freely in a large environment instead of being crowded in a small area where they end up getting more contamination from faeces and concrete floors in some farms); routinely testing the herd for mastitis using CMT which is also inexpensive for small scale farmers, and will prevent misdiagnosis and overuse of antibiotics which could create drug resistance when overused; and preventing environmental mastitis by choosing an appropriate type of bedding which should be low in moisture content to prevent the provision of nutrients to bacteria (sawdust, straw and recycled manure are discouraged).