Make the marinade by stirring together the vegetable juice, garlic, onion, salt and pepper. Place the whole javelina shoulder in a large glass dish and pour the marinade over. Cover and allow to marinate in the refrigerator for 24 hours, turning occasionally.

Place the cumin seeds in a small skillet and toast over high heat, shaking constantly, until the seeds are lightly browned and fragrant. Set aside.

Heat oven to 300º.

In a heavy braising pot over medium-high heat, heat the oil until it just begins to shimmer and then add the onion, garlic, green and red bell peppers and jalapeños. Stir frequently and sauté until the vegetables are soft and the onion is translucent, about 5 minutes.

Drain the marinade from the meat and discard. Place the meat in the braising pot with the vegetables. Pour the beer over all. Add the oregano, chile powder, cayenne pepper, toasted cumin seeds, stewed tomatoes, salt and pepper. Bring the pot to a simmer, then cover with a tight-fitting lid and place in the oven.

Braise for 3–4 hours, until the meat falls from the bone. Remove the pot from the oven and remove the meat and vegetables from the pot with a slotted spoon and set aside. Shred the meat and discard the bone. Tent with foil to keep warm.

Place the pot over medium-high heat and boil until the sauce is reduced by half. Return the meat and vegetables to the pot and stir well until heated through.

Serve with hot cornbread or warm flour tortillas.