(1) Select breeding pigs according to their body shape and appearance. Each breed has its standard body shape and appearance. The appearance characteristics of pigs are closely related to their production performance. The selection criteria of general sow body appearance are: handsome head and face, good upper lip anastomosis; Shoulder width and flat back, smooth hair, large abdomen without sagging; Full legs and hips, strong limbs and high tail root position; The whole body structure is symmetrical; The vulva develops normally, the number of effective nipples is more than 7 pairs, and the nipples are arranged neatly, well developed, gentle and maternal.
(2) Selection of breeding pigs according to growth and production performance Although the appearance characteristics of pigs are related to their production performance, they are not absolute. When selecting sows, individuals of the same age with rapid growth and development, high feed utilization rate, newborn weight and significant weaning should be selected as breeding pigs on the basis of meeting the requirements in appearance.
(3) Selecting breeding pigs according to the quality of parents. If conditions permit, when selecting breeding pigs, we should also review the production performance of the selected individuals in the last three generations (with emphasis on their parents) and their offspring, so as to know whether the excellent traits of breeding pigs can be stably passed on to the next generation. If the production performance of the last three generations is good and the production performance of their offspring is excellent, then the production performance of the selected breeding pigs is more reliable. Generally speaking, sows should choose piglets produced by mature sows with large litter size, strong motherhood and sufficient milk.