How to select a backup boar

To select back-up boars, one is to cultivate excellent breeds such as Landrace, Landrace and Duroc. Second, the variety should be pure. Third, the appearance should have the characteristics of varieties. The waist is long and the limbs are strong, the shoulders are wide and the back is wide, the buttocks are round, the testicles are even and strong, and the nipples should be more than 6 pairs. The saying of folk jingle is: a pair of eyes are bright, lively and heroic; the head is small, the face is wide, the face is short, the forechest is developed and the buttocks are round; the belly is not public, the two testicles are long, and the sows are sexually active.