What are the evaluation indicators for pig reproductive performance?

  The reproductive performance indicators of pigs mainly include the following seven:

  (1) Litter size. Litter size has two indicators: total number born and number born alive. Total number born refers to the total number of piglets in the same litter within 24 hours of birth, including stillborn fetuses, mummified fetuses and deformed pigs; number born alive refers to the number of live piglets in the same litter within 24 hours of birth, including weak piglets. Litter size is a low-heritability trait and also a composite trait, composed of three parts: ovulation number, fertilization rate and embryo survival rate.

  (2) Birth individual weight and birth litter weight. Birth individual weight refers to the individual weight of a piglet weighed within 12 hours after birth; birth litter weight refers to the sum of the birth individual weights of the piglets (live piglets) in the same litter. The birth individual weight of piglets is a very important indicator in production. The birth individual weight is related to breed; generally, the birth individual weight of local pig breeds in China is generally lower than that of piglets of introduced foreign breeds.

  (3) Lactation ability. Lactation ability is generally expressed by the litter weight of piglets at 21 days of age (including fostered piglets). Because the weight gain of piglets before 21 days of age mainly depends on breast milk, lactation ability is a very important production performance indicator.

  (4) Nursing rate. Nursing rate refers to the ability of a sow to nurse piglets, also called rearing rate. Its calculation formula is as follows:

  (5) Weaning weight. This includes weaning individual weight and weaning litter weight. The former refers to the individual body weight of a piglet at weaning, and the latter refers to the total body weight of all piglets in the litter (including fostered piglets) at weaning. Weaning is generally based on 28 days of age, and its formula is as follows:

  28-day-old weight = actual weight at a certain age x correction coefficient for that age (r)

  (6) Farrowing interval. The number of days between the farrowing dates of two consecutive litters of a sow.

  (7) Age at first farrowing. The age in days of a sow at the time of farrowing her first litter.