Microbiological quality of goat's milk obtained under different production systems

Abstract

In order to determine the safety of milk produced by smallholder dairy goat farms, a farm-based research study was conducted on commercial dairy goat farms to compare the microbiological quality of milk produced using 3 different types of dairy goat production systems (intensive, semi-intensive and extensive). A survey of dairy goat farms in and around Pretoria carried out by means of a questionnaire revealed that most of the smallholder dairy goat farms surveyed used an extensive type of production system. The method of milking varied with the type of production system, i.e. machine milking; bucket system machine milking and hand-milking, respectively. Udder half milk samples (n=270) were analysed, of which 31.1 % were infected with bacteria. The lowest intra-mammary infection was found amongst goats in the herd under the extensive system (13.3 %), compared with 43.3 % and 36.7 % infection rates under the intensive and semi-intensive production systems, respectively. Staphylococcus intermedius (coagulase positive), Staphylococcus epidermidis and Staphylococcus simulans (both coagulase negative), were the most common cause of intramammary infection with a prevalence of 85.7 % of the infected udder halves. The remaining 14.3 % of the infection was due to Staphylococcus aureus. Bacteriology of bulk milk samples on the other hand, showed that raw milk obtained by the bucket system milking machine had the lowest total bacterial count (16 450 colony forming units (CFU)/mℓ) compared to that by pipeline milking machine (36 300 CFU/mℓ) or handmilking (48 000 CFU/mℓ). No significant relationship was found between the somatic cell counts (SCC) and presence of bacterial infection in goat milk. In comparison with the herds under the other 2 production systems, it was shown that dairy goat farming under the extensive production system, where hand-milking was used, can be adequate for the production of safe raw goat milk.