Final answer:
Cattle heading to feedlots should be vaccinated against less common diseases such as Anthrax, Tuberculosis, and Clostridial toxicoses to prevent outbreaks and ensure both animal and public health.
Step-by-step explanation:
Among diseases to consider when vaccinating cattle heading to a feedlot, three less common but important ones include Anthrax, Tuberculosis (TB), and Clostridial toxicoses. Anthrax, caused by Bacillus anthracis, can be contracted through contact with infected animals or contaminated soil. Tuberculosis, particularly caused by Mycobacterium bovis, can spread among cattle and also poses a zoonotic risk to humans, thereby making the BCG vaccine a crucial preventive measure. Lastly, clostridial toxicoses caused by various Clostridium species result in diseases such as blackleg and enterotoxemia, making vaccination a critical step in protecting cattle health.