A Study on How Vitamins Enhance Sow Fertility

The factors that influence the reproductive performance of sows primarily include genetics, nutrition, disease prevention, environment, and management. In recent years, with the rapid advancement of nutritional science and technology, research aimed at improving sow reproductive performance through nutritional regulation has begun to yield promising results. Both domestic and international studies have found that nearly all vitamins significantly affect the reproductive performance of breeding pigs. The main vitamins that influence sow reproductive performance are as follows:

　　Vitamin E: Vitamin E is closely associated with reproductive function. It promotes the production of thyroid-stimulating hormone (TH), adrenocorticotropic hormone (ACTH), and gonadotropins, thereby enhancing ovarian function and increasing the number of luteal cells in follicles. Supplementing the sows’ diet with vitamin E not only improves conception rates and reduces fetal mortality but also increases litter size. Moreover, it enhances piglets’ stress resistance, reduces pre-weaning mortality, shortens the interval between weaning and estrus in sows, and improves semen quality in boars. Studies have shown that sows fed high levels of vitamin E have higher litter sizes and more live piglets per litter, as well as lower incidence of Mastitis-Metritis-Agalactia (MMA) syndrome. When sows are deficient in vitamin E, ovarian function declines, the estrous cycle becomes irregular, fertilization becomes impossible, and embryonic development may be abnormal or result in stillbirths.

　　Folic acid plays an important role in maintaining the reproductive performance of sows and promoting early fetal development. Its primary function is as a coenzyme in various enzymatic systems, participating in purine synthesis and thus being crucial for the synthesis of DNA and RNA. In terms of sustaining stable reproductive function in breeding sows, folic acid can increase the number of piglets per litter and help maintain good lactation performance, preventing lactation disorders. Studies have shown (Lindemann et al., 1989) that adding folic acid to the sow’s diet can improve embryo survival rates and consistently increase the number of piglets born per litter.

　　Beta-carotene: Supplementing sow diets with beta-carotene can improve litter size, correct silent estrus and delayed ovulation in sows, and enhance embryonic survival rates. Beta-carotene is also involved in progesterone synthesis; insufficient progesterone levels can lead to pregnancy termination. Recent studies have further shown that adding beta-carotene to boar diets can promote testicular development and improve semen quality. Vitamin A and carotenoids are prone to oxidative degradation, especially under conditions of high humidity and heat, as well as when exposed to trace elements and rancid fats.

　　Vitamin A: Appropriately increasing the dietary level of vitamin A can enhance both the number of piglets born per litter and the number of weaned piglets (Antipas, 2003). When sows are deficient in vitamin A, their conception rates decline, and they may exhibit abnormal estrus cycles, dystocia, abortion, stillbirths, weak piglets, congenitally malformed piglets, and retained placenta. Piglets born with blindness and limb paralysis are prone to pneumonia, diarrhea, and other diseases. In young gilts, delayed estrus can impair ovarian development and lead to a high embryo mortality rate.

　　Biotin: Its primary function is to maintain the health of sows’ hooves, preventing hoof cracks, lameness, and paralysis. At the same time, biotin promotes fetal growth and development, reduces fetal mortality, enhances lactation, increases ovulation rates and conception rates in sows, and shortens the interval between weaning and estrus in sows. If the dietary biotin content falls below 330 μg, it can lead to an increase in stillbirths and impaired growth and development in nursing piglets due to insufficient milk supply from the sow. Studies have shown that supplementing with biotin can increase the length of the sow’s uterine horns by 20%, thereby expanding the space available for the fetus within the uterus—a factor of great significance for fetal growth and survival.

　　Studies have shown that adding 300 mg of biotin per ton of complete sow feed significantly increases the average number of weaned piglets per litter at 21 days of age compared to the control group that received no biotin supplementation. Supplementing sows’ diets with biotin can prevent cracked hooves in sows during winter and markedly reduce the incidence of foot problems and lameness in the pig herd.

　　Vitamin C plays an important role in various redox reactions within living cells, participates in the synthesis of corticosteroids in the adrenal cortex, helps alleviate stress, and counteracts the adverse effects of high temperatures on semen quality. After boars are supplemented with vitamin C, their sperm quality improves; in sows, the conception rate increases. Particularly during summer’s high temperatures or when sows experience environmental or physiological stress around farrowing, vitamin C exhibits strong anti-stress effects, thereby improving sow reproductive performance by alleviating stress. Breast milk is the sole source of vitamin C for piglets up to one week of age. During pregnancy and lactation, supplementing sows with vitamin C can reduce the mortality rate of piglets before weaning.

　　Vitamin B2 (riboflavin): Studies have shown that feeding 100 mg of riboflavin per day from 4 to 7 days after mating can increase the number of viable embryos, embryo survival rate, farrowing rate, and the number of live piglets born per litter in sows. Tilton (1991) confirmed in his study that supplementing sows with 90–100 mg of riboflavin per day during early pregnancy can significantly improve their farrowing rate.

　　Vitamin K: Adding 100 mg/kg of vitamin K3 to the diet of pregnant sows increased the number of piglets born by 5.66%. Adding 100 mg/kg of vitamin K3 to the diet of lactating sows improved piglet weight gain by 7.78% and increased piglet survival rate by 3.81%.

　　Vitamin B6: Adding 15 mg/kg of vitamin B6 to the diet of gestating sows (compared to 1 mg/kg in the control group) can reduce the interval between weaning and estrus by 1.1 days.

Niacin: Add 33 mg/kg to the diet during sow pregnancy and lactation periods. Niacin reduces the incidence of metritis-mastitis-agalactia syndrome in sows by 30%.

Vitamins are the most vulnerable nutrients to degradation. Environmental factors such as high temperature, high humidity, exposure to light, trace elements, choline chloride, table salt, and pH levels can all reduce vitamin activity. Although complete feeds and concentrated feeds are fortified with vitamins, various trace elements present in the feed can accelerate vitamin oxidation during feed processing, storage, transportation, and preservation—especially during summer when temperatures are high and humidity is elevated. Fat in feed is the most susceptible to oxidation; the resulting peroxides can accelerate the degradation of fat-soluble vitamins. Moreover, the high temperatures and humidity of summer can induce stress in pigs. Under stressful conditions, all pigs—including sows—have increased vitamin requirements, making vitamin deficiency symptoms particularly pronounced in pigs.

The supplementation of vitamins for sows accounts for only 2% of the cost of the complete feed. —3%, yet it can still yield excellent economic benefits. To prevent vitamin deficiencies from affecting the reproductive performance of sows, additional vitamins can be incorporated into their feed during periods of empty gestation, mating, and pregnancy. Experts recommend that sows receive an extra 250–500 grams per ton of high-quality multivitamin supplements, which can significantly enhance their reproductive performance.