Merck Once PMH SQ is a cattle vaccine featuring avirulent live cultures of Mannheimia haemolytica and Pasteurella multocida. Formulated as a powder for solution (kit), it is designed for subcutaneous administration to cattle. Available in 20 ml and 100 ml vial sizes, this livestock health product supports efficient herd vaccination with a convenient 2 mL per dose. Ideal for producers and veterinarians building a proactive herd health program and seeking a reliable bovine vaccine.