High somatic cell numbers in goat milk – influence on product quality (GoatMilkSCC)

The somatic cell count (SCC) in goat milk is too high by the end of summer. The somatic cells are a mixture of cells from the mammary glands and white blood cells (leukocytes). Goat milk normally has a higher content of SCC than cow milk since the milk excretion from the mammary gland differs. If the leukocytes, which are several different types of cells with different functions, identify harmful bacteria or viruses in the udder, they will signal to other leukocytes and immune cells that they must attack, thereby increasing the SCC in the milk. The leukocytes contain enzymes that may have a negative impact for milk and cheese quality. In 2019, almost 20 million litres of goat milk were produced in Norway. The production is based on rangeland pasture and mountain farming. The oestrous often coincides with the end of summer, and during this period the SCC increases, although the goat shows no signs of udder inflammation. High SCC results in reduced payment for the milk, which can lead to reduced use of rangeland pastures. GoatMilkSCC should give us more knowledge about the type of cells found in goat milk, why the cells increase in number and how this affects milk quality, cheese making properties and cheese quality. In the project, a new method using flowcytometry will be developed for mapping the types of cell in the goat milk and we will investigate how the SCC vary between different individuals, when let out on pasture, oustrus, etc. Furthermore, we will investigate how the SCC affect the composition of milk, the properties of cheese making, cheese yield and the quality of the cheese. Both milk from individual goats and tank milk will be examined, and milk from different herds will be analysed. Professionals with expertise in veterinary medicine, milk quality, microbiology, immunology and dairy technology, as well as professionals from TINE and NSG will be involved in the project. The project also has relevance and transfer value for cell counts in cow milk.

The Norwegian dairy industry observe that the somatic cell count (SCC) often increases when dairy goats are let out on rangeland pasture and during oestrus. However, in goats, a high SCC is also observed in milk without signs of clinical mastitis, There is limited knowledge on how the content and type of SCC in goat milk varies between individual goats and over the course of lactation, and also on how they are influenced by  pasture. Moreover, the effects of the SCC on product quality remain largely unknown. Therefore, knowledge of how, and to what extent SCC affects milk- and product quality especially during the pasture period, is of great importance for the future of the Norwegian goat milk production. The novelty of the project is the combination/integration of high-resolution characterization of the somatic cell types by flow cytometry and goat milk composition (chemical and microbial) and goat milk processing aimed towards the production of increased value dairy products from goat milk. Goat milk SCC aims at securing a sustainable goat milk production from healthy goats by providing novel insights on reasons for high number of somatic cell counts (SCC) in Norwegian goat milk and its influence on the yield and quality of goat milk products.