How to improve sow annual productivity? A detailed guide to practical methods

Pig reproductive capacity is an important indicator affecting overall pig production. Many factors cause reproductive decline, resulting in serious economic losses. To achieve high-yield, high-quality, and efficient pig production, sow annual productivity must be improved.

1. Reproductive capacity and pig production

The main purpose of raising breeding pigs is to reproduce piglets and provide a source of pigs. Sow annual productivity refers to the number of weaned piglets provided by 1 sow within 1 year. Many factors constrain sow annual productivity, and the most important are litter size per farrowing and litters per year. Litters per year are constrained by the farrowing interval, which includes gestation, lactation, and the waiting-to-mate period (weaning to mating). Gestation is a constant component, the waiting-to-mate period is a basically constant component, and lactation is a variable component. It can be seen that early weaning of piglets is an important measure to shorten the farrowing interval and improve sow annual productivity. For example, if piglets are weaned at 3 weeks of age, 1 reproductive cycle is 143 days (gestation 115 days, lactation 21 d, waiting-to-mate period 7 d), with 2.55 litters per year; if piglets are weaned at 6 weeks of age, one reproductive cycle is 164 d, with 2.17 litters per year.

The number of weaned piglets per sow per year directly affects the level of pig production costs. The more weaned piglets produced throughout the year, the greater the spread of fixed costs, and the lower the cost. Improving sow reproductive capacity is a systematic project, and neglecting any aspect can prevent the expected goal from being achieved.

2. Factors affecting sow reproductive capacity

The reproductive process of pigs begins with the production of normal reproductive cells and goes through estrus, mating, fertilization, blastocyst implantation, gestation, farrowing, lactation, weaning, and other stages.

2.1. Main manifestations of sow reproductive disorders

(1) Anestrus: pathological anestrus (abnormal anestrus) caused by diseases of the ovaries and uterus;

(2) Fertilization disorders: death of the egg before sperm entry; structural or functional abnormalities of sperm and eggs; gametes unable to normally reach the site of fertilization, etc.;

(3) Prenatal death: early embryonic death, spontaneous abortion, mummification, fetal death at birth, etc.

2.2. Causes of reproductive disorders

2.2.1. Congenital factors: infantilism and malformation of the sow's reproductive organs, cryptorchidism or testicular hypoplasia in boars, etc.

2.2.2. Sow functional disorders: endocrine factors, ovarian dysfunction (ovarian hypofunction, atrophy or sclerosis, persistent corpus luteum, ovarian cysts), etc.

2.2.3. Boar functional disorders: lack of libido, difficulty mating, poor semen quality, etc.

2.2.4. Sow immune factors and the antigenicity of boar sperm.

2.2.5. Uterine capacity: embryo survival increasingly depends on the placenta, and placental development is affected by intrauterine space and blood vessel supply. Increasing the number of implantations reduces the blood vessel supply at each implantation site, limiting embryonic development. Small intrauterine space causes an increase in the number of embryonic and fetal deaths.

2.2.6. Chromosomal aberrations and other genetic factors: variation in chromosome structure and number, gene mutation, inbreeding, intrauterine environment, etc.

2.2.7. Reproductive organ diseases: endometritis, hydrometra, pyometra, hydrocele, orchitis, posthitis, etc.

2.2.8. Infectious diseases: all diseases affect pig reproduction. The highly harmful infectious diseases include parvovirus, swine fever, pseudorabies, Japanese encephalitis, reproductive and respiratory syndrome, etc.

2.2.9. Nutritional factors: lack of micronutrients, excessive energy levels, etc.

2.2.10. Improper management: insufficient exercise, poor mating disinfection, untimely mating, mechanical abortion, feeding toxic, spoiled, frozen, or moldy feed, etc.

2.2.11. Environmental factors: environmental temperature too low or too high, stocking density too high, poor ventilation and sanitation, strong noise, etc.

3. Ways to improve annual productivity

Improving sow annual productivity is an important topic, and comprehensive supporting measures should be adopted to tap the reproductive potential of breeding pigs.

3.1. Emphasize the genetic basis and strictly select and retain breeding pigs

As the saying goes: "A good boar benefits a whole slope," and "A strong sow makes fat piglets," which shows that breeding pigs have a certain influence on their offspring. Selection is a very complex task, and breeding farms all have a set of scientific selection methods. As a production pig farm, at minimum it should select piglets by looking at the mother, choose the best among the good, refer to the sow's previous farrowing performance, and select superior piglets from large litters. Weaning individual weight and weaning litter weight should be considered, and body conformation and appearance should also be noted. Selection should be made from the offspring of sows with relatively large body weight, long body, tall, sturdy, and broad limbs, many teats, and no genetic disorders in the whole litter. Long-bodied sows have a large abdominal space, allowing the placenta and fetuses to fully expand, which can reduce embryonic death and improve litter size and birth weight. According to data from Shanghai Yuejin Farm, for sows with a body length below 110 cm, the average piglet birth weight was 1.09 kg; for sows with a body length of 120-140 cm, piglet birth weight increased by 17.4%.

3.2. Strengthen the rearing of replacement pigs and manage the timing of first mating well

Replacement pigs are the basis for renewing the breeding herd, and the growth and development of replacement pigs have a certain impact on production performance. Although replacement pigs share many characteristics with growing-finishing pigs, the same nutritional supply, feeding methods, and management measures cannot be used. The nutritional level in the diet should vary according to the different growth stages of replacement pigs, paying attention to the ratio of energy to protein and fully meeting the supply of minerals, vitamins, and essential amino acids. A "open before, restricted after" feeding method can be adopted. Generally speaking, before body weight reaches 80 kg, feed freely, and it is expected that body weight can reach 80 kg at 5-6 months of age. After that, restricted feeding should be carried out. Before mating, the body condition required for mating must be reached; it must not be thin and weak, and even more so must not be overly fat. Management should be strengthened, and group housing is advisable. Body weight and body measurements should be measured at 6 months of age. Managers should frequently contact the pigs to achieve human-pig affinity, and do a good job in disinfection and cleaning of pens and in herd health care and immunization. The mating and utilization of replacement pigs should be determined by breed, feeding management level, climate, etc. Local breeds in China mature sexually early, while improved breeds and introduced breeds mature sexually later. Generally speaking, local breed sows are first mated at about eight months of age and a body weight of about seventy-five kilograms, while improved breed and introduced breed sows are first mated at about ten months of age and a body weight of about one hundred twenty kilograms. The body weight and age at which replacement boars begin mating should be higher than those of sows of the same breed. Mating replacement pigs too early or too late will cause adverse consequences.

3.3. Strengthen boar feeding and management to provide more sperm of high quality