The presence of which substance in milk could indicate poor hygiene practices on a dairy farm?

The presence of antibiotics in milk is a strong indicator of poor hygiene practices on a dairy farm because it suggests that there may have been improper treatment of the cows or inadequate withdrawal periods after treatment. Dairy cows may be treated with antibiotics for various health issues, but if the milk is harvested too soon after treatment, it can contain residues. This is not only a violation of food safety regulations but also reflects a lack of diligence in maintaining the health standards necessary for a clean and safe milk supply.

In contrast, fat, cholesterol, and casein are natural components of milk and are expected to be present regardless of the hygiene practices. Their levels can fluctuate due to factors like the cow's diet and breed, but they do not serve as a direct indicator of cleanliness or the management practices employed on the dairy farm. Hence, the presence of antibiotics is a clear signal that hygiene and management protocols may be lacking, leading to potential contamination concerns.