Which of the following is a type of tag used for officially identifying swine?

USDA back tags are specifically designed for the official identification of swine. They are used in various situations, including tracking animals for health and regulatory purposes, as well as for ensuring that animals can be traced back to their source in the event of disease outbreaks. These tags are generally made from durable materials and are designed to withstand the conditions of farming environments.

In contrast, plastic clips, vinyl stickers, and rubber stamps are not typically employed for official animal identification purposes. Plastic clips may be used for temporary tagging, but they do not meet the requirements for formal identification needed for compliance with regulations. Vinyl stickers can also be used for various labeling needs but lack the official attributes and traceability requirements necessary for livestock identification. Rubber stamps do not provide a durable or reliable method for animal identification, making them unsuitable for this purpose. Therefore, USDA back tags are crucial as they fulfill the requirements set by regulatory bodies for animal tracking and health management.