What is a simple rule to prevent excess blood collection in an animal?

The guideline for blood collection in animals is rooted in ensuring the well-being and health of the animal subjects. Collecting no more than 1% of body weight is generally recommended to minimize stress and avoid potential adverse effects, such as hypovolemia or discomfort. This amount is conservative and helps ensure that the animal can recover quickly without negative consequences.

In contrast, recommendations to collect larger percentages, such as 2%, 5%, or even 10% of body weight, can pose significant risks to the animal's health. While some species or specific circumstances might allow for slightly higher volumes, the standard practice prioritizes animal welfare by adhering to the more cautious approach of limiting blood collection to around 1%. This minimizes the potential for complications and supports ethical research practices.