Which of the following breeds is double muscled?

The Piedmontese breed is known for its distinctive double muscling trait, which results from a genetic mutation. This trait is characterized by an increased muscle mass and a more robust physique compared to typical cattle. The double muscling effect in Piedmontese cattle leads to higher muscle yields and can be particularly advantageous in terms of meat production, providing leaner cuts with less fat.

This breed's unique muscle development is due to the myostatin gene mutation, which inhibits muscle growth regulation, allowing for greater muscle accumulation. This genetic characteristic is specifically prominent in Piedmontese, setting it apart from other cattle breeds listed in the multiple-choice question.

Red Angus, Watusi, and Polled Hereford do not exhibit the double muscling feature associated with Piedmontese. Instead, these breeds are recognized for different attributes, such as meat quality, adaptability, and certain production traits that do not include the genetic makeup leading to double muscling.