Which nutrient, when excessive, can lead to animal health issues due to its uptake regardless of plant needs?

When considering which nutrient can lead to animal health issues when present in excess, particularly through uptake irrespective of plant needs, potassium is the correct choice. While potassium is an essential nutrient for plant growth and function, excessive levels can cause problems. High potassium levels can lead to a range of health issues in livestock, including interference with the absorption of other critical nutrients such as calcium and magnesium, potentially resulting in deficiencies and imbalances.

Unlike nitrogen, phosphorus, and calcium, which have specific uptake mechanisms in relation to plant needs and can cause their own set of problems when imbalances occur, potassium's impact can often stem from its higher mobility in soil solutions. This mobility allows for greater potential for accumulation in feed, surpassing the requirements of the plants being consumed by livestock. Thus, when the nutrient intake exceeds what the animal physiologically requires, adverse health outcomes can arise, highlighting the importance of monitoring potassium levels closely in nutrient management practices.