Which of the following is a type of universal ear notching?

Universal ear notching is a technique used primarily in animal husbandry for identification purposes, particularly in pig farming. The correct answer, which is standardized shapes, refers to the system of utilizing specific, standardized notch shapes and placements in the ears of animals to categorize and identify them. This method is straightforward and universally recognized among farmers and veterinarians, allowing for consistent identification across herds.

Standardized shapes serve as a reliable form of communication about the animal's lineage, age, or health status, as each notch or combination of notches conveys distinct information. This system reduces confusion that could arise from personal or arbitrary tagging methods, ensuring that identification remains uniform across different farms and regions.

While other options, such as unique color patterns and proprietary identifiers, offer forms of identification, they do not conform to a universal system that is widely accepted and utilized. Numerical systems may refer to various identifiers but lack the specific visual and systematic clarity that standardized shapes provide in ear notching practices.