(1) Judging from estrus cycle: The estrus cycle of a pig is about 3 weeks. If it stops estrus after breeding for 3 weeks, it can be inferred that it is pregnant, especially for sows with normal estrus cycle before breeding.

(2) Judging from the external characteristics and behavior: anyone who is quiet after mating, can eat and sleep, recovers quickly, has a gentle temperament, bright fur and clings to the body, acts steadily, gradually increases the abdominal circumference, closes or contracts the vulva joint, and has obvious upturning may be pregnant.

(3) Judging from the change of nipples: After Yorkshire sows are mated, the nipples turn black after 3 days, and the nipples are slightly elongated. If the nipples show a dark purple halo at the base, it can be judged that they are pregnant. However, this method is not suitable for pregnancy diagnosis of Landrace pigs.

(4) Urine test: Take about 1 ml of morning urine of sows 5-1 days after mating, put it in a test tube to measure the specific gravity (which should be between 1.1 and 1.25). If it is too thick, add water to dilute it to the above specific gravity, then drop 1 ml of 5%-7% iodine, and heat it on an alcohol lamp. When it reaches the boiling point, the color will change. If the sow is pregnant, the urine will turn red from top to bottom; If you are not pregnant, the urine is yellowish or brownish green, and the color will disappear after cooling.