What component in milk may decrease in levels when cows have high somatic cell counts?

The correct response highlights the connection between somatic cell counts and casein levels in milk. When cows experience high somatic cell counts, which typically indicate a response to infection or inflammation, their overall milk quality can be negatively impacted. Elevated somatic cells can lead to disruptions in the milk's composition, primarily affecting protein content.

Casein is a key protein in milk that makes up a significant portion of its total protein content. High somatic cell counts can compromise the cow's ability to produce casein effectively, ultimately leading to a decrease in its concentration in the milk. This change is detrimental to milk quality, particularly for cheese production, where casein plays a vital role in curd formation.

While lactose, fat, and vitamin D levels may also be affected under certain conditions, the direct correlation between high somatic cell counts and a reduction in casein is well-established. Casein's reduction illustrates the physiological implications of mastitis or other infections reflected by high somatic cell counts, making it the most relevant component to highlight in this context.