Key Technical Points and Precautions for Maintaining Pregnancy in Pregnant Sows

Introduction: Raising pregnant sows is a major part of the production process in modernpig farms. The quality of the feeding and management of pregnant sows not only tests the success or failure of sow mating, but also serves as preparation for farrowing and lactation. This production stage, which bridges what comes before and what follows, plays a key role in enablingpig farmsto achieve sustained economic benefits; therefore, implementing safe and effective pregnancy-maintenancetechniquesand improving the reproductive capacity of pregnant sows should receive great attention from pig farming enterprises.

The growth and development of the fetus and the state of the sow's physique and body condition are closely related to pregnancy-maintenancetechniquesfor pregnant sows. Implementing pregnancy-maintenancetechniquesmeans, according to the patterns of fetal growth and development and changes in the sow's condition, strengthening feeding management and disease prevention and control to ensure that fertilized eggs, embryos and fetuses develop normally in the sow's body, reducing embryonic death and sow miscarriage; at the same time, the sow must be ensured to have good body condition and enter lactation smoothly.

After a sow becomes pregnant, its anabolism increases significantly, and body weight can increase by 25-35 kg over the entire gestation period. The feed nutrient utilization rate of pregnant sows can increase by 9.2%-18.1% compared with non-pregnant sows.

Studies show that during the first 40 days after a sow becomes pregnant, fetal weight gain is only equivalent to 1% of its birth weight; from day 41 to 80 after pregnancy, fetal weight gain is 20% of its birth weight; from day 81 to 114 after pregnancy, fetal weight gain exceeds 60%-70% of its birth weight.

It can be seen that the pattern of weight gain of the sow's uterine contents is higher in late pregnancy than in early pregnancy, but the sow's own body weight gain is higher in early pregnancy than in late pregnancy.

To achieve pregnancy maintenance and obtain a relatively high birth weight, attention must be focused on the quality management of the sow's feed in early pregnancy, especially meeting the sow's needs for digestible amino acids, vitamins and trace elements.

Essential amino acids such as lysine, methionine, tryptophan and threonine in the feed must be supplied adequately; at the same time, conditionally essential amino acids for pregnant sows such as arginine and histidine must not be lacking, as they can improve the sow's reproductive efficiency and promote fetal growth and development.

Vitamins A, E, B2, B6, B11, biotin and the trace elements zinc, manganese, selenium and iodine can all maintain the normal reproductive function of pregnant sows and ensure fetal growth and development.

If they are lacking in the feed for a long time, it will cause reproductive dysfunction in pregnant sows, resulting in stillbirths, weak piglets or miscarriage.

Because pigs absorb only 20%-30% of vitamin D, sows have a very high requirement for vitamin D.

A lack of vitamin D in the feed will likewise cause a decline in reproductive capacity and lead to miscarriage;

also, because black pigs' tolerance to vitamin D deficiency in feed is only 25% of that of white pigs, pregnant sows of black pig breeds in China must be supplied with more vitamin D, and the vitamin D content in their diet during gestation must not be lower than 200 IU/kg.

After a sow becomes pregnant, different feeding patterns should be implemented according to its age and physical condition to maintain pregnancy.

For first-parity sows, the feeding level is increased as gestation days increase, reaching its highest peak one month before farrowing, so that both the sow itself and the fetus can grow and develop well.

For multiparous sows, they can be divided into two types according to body condition: good body condition and poor body condition. Visual observation of the fat deposition and fullness at the tail root, rump end, spine and ribs of the sow can fairly accurately identify the sow's body condition.

For multiparous sows in good body condition, in early pregnancy it is only necessary to feed high-quality green and coarse feed and compound feed with lower energy and protein content to meet the nutritional needs of the dam and fetus;

in late pregnancy, the feed quality should then be improved to ensure the needs of rapid fetal growth and development.

For multiparous sows in poor body condition, good feed must be supplied in early pregnancy, especially with adequate supply of vitamins and trace elements. In addition to ensuring fetal growth and development, this can also help the sow recover strength as quickly as possible and increase body condition, ensuring the sow's health so as to better maintain pregnancy; in mid-pregnancy, because the sow's body condition has improved and the fetus does not yet need many nutrients, more green and coarse feed can be given; in late pregnancy, fetal growth and development accelerate, so more high-qualityconcentrate feedshould be added, and feed that is too bulky and difficult to digest should not be fed, so as to avoid the sow's digestive organs pressing on the uterus and causing miscarriage.

If a pregnant sow is too fat, it will affect fetal survival and reproductive performance in subsequent parities. Therefore, for pregnant sows that are too fat, under conditions of nutritional balance, nutrient intake can be controlled through various methods such as shortening feeding time, restricting feeding quantity and lowering feed quality.

The average daily feed intake of pregnant sows is preferably 2.0-2.5 kg/head. In addition to the sow's body condition and parity, it should also be appropriately adjusted according to pen type and environment, feeding method, health level, production performance level and management standards, so that after restricted feeding, pregnant sows can reduce farrowing difficulty and increase embryo survival rate, thereby achieving the purpose of effective pregnancy maintenance.

The feed for pregnant sows must be kept clean and fresh. Feeding moldy, spoiled, rotten, frozen or strongly irritating feed is prohibited, to prevent embryonic resorption, weak fetuses, stillbirths and miscarriage;

in order to maintain pregnancy, feed should not be changed frequently during gestation. If replacement is truly necessary, the feed should be gradually transitioned over 1 week so that the sow can fully adapt.

The most suitable environmental temperature for pregnant sows is 15-21°C and humidity is 45%-65%. Attention should be paid to cold protection and heat protection; good ventilation equipment should be provided to ensure fresh air inside the pig house; the pen floor should be flat, dry and clean, and kept warm in winter and cool in summer; manure should be cleaned up promptly, manure storage pits should be shallow, and the slope going up and down the pits should not be too steep; the pen should be kept quiet.

Keepers should be gentle and patient with pregnant sows, and should observe the sow's feeding, drinking, lying down, feces and urine, and mental state every day; the sow's body should be brushed frequently to keep its skin clean, and the abdomen can be touched frequently to help maintain pregnancy; sows should be prevented from crowding, slipping and falling, and frightening and beating are strictly prohibited to prevent mechanical miscarriage.

In the middle and late stages of pregnancy, sows should exercise appropriately to strengthen their physique and ensure fetal growth and development. Exercise should stop 1 week before farrowing.

1. Prevent infectious diseases

Infectious diseases have the characteristics of complex causes, variable clinical symptoms, difficulty in diagnosis and serious harm. Viral infectious diseases are currently the main cause of reproductive disorders in pregnant sows, especially swine fever virus, pseudorabies virus, parvovirus, Japanese encephalitis virus, circovirus, and the recently discovered highly pathogenic porcine reproductive and respiratory syndrome virus. Single or mixed infections can all cause reproductive disorder symptoms in pregnant sows such as premature birth, silent miscarriage, stillbirth, mummified fetuses, weak piglets and fetal malformations;

Some bacterial infectious diseases such as brucellosis, salmonellosis, leptospirosis, listeriosis, chlamydiosis and Mycoplasma suis can also cause similar symptoms. These infectious diseases pose great harm to pregnant sows and are the main targets for prevention and control in pig production.

2. Preventparasitic diseases　

Toxoplasma gondii and Schistosoma japonicum (blood fluke) are typical multi-host internal parasites and are among the most serious parasites harming pregnant sows. They can cause miscarriage, weak fetuses and stillbirths in sows. Toxoplasmosis in particular spreads quickly, has an acute onset and a high mortality rate, and its clinical symptoms resemble swine fever, while also directly affecting human health.

Skin surface parasites such as Sarcoptes scabiei var. suis and pig lice feed on pig tissues and lymph or suck blood. Infection with these parasites makes pregnant sows appear depressed, itchy and restless, frequently rubbing themselves, and have reduced appetite. They often become thin and weak due to malnutrition and are prone to miscarriage.

3. Prevent common diseases

Once a sow is confirmed pregnant, strict preventive measures must also be taken against common and frequently occurring diseases to ensure pregnancy safety. In addition to reproductive system diseases such as oophoritis and vaginitis that can cause miscarriage, colds, feed poisoning and stress can also cause miscarriage;

In particular, when adding distillers' grains, cottonseed cake, rapeseed cake and other feeds to prevent pregnant sows from becoming too fat during gestation, poisoning caused by improper feeding or excessive intake must be avoided, as this can cause miscarriage or even death in sows.

Green feed is best fed fresh and raw. If it is cooked and fed, a small amount of vinegar should be added, which can both sterilize and decompose nitrite, avoiding premature birth, weak fetuses or stillbirths in pregnant sows caused by nitrite poisoning.

4. Use drugs correctly

During pregnancy in sows, drugs must be used with great caution. The following drugs are strictly prohibited:

First, drugs that can directly excite uterine smooth muscle, such as ergot preparations, posterior pituitary extract, oxytocin, quinine, etc. (except when used for induced labor and postpartum hemostasis);

Second, drugs that can indirectly excite uterine smooth muscle (strong purgatives), such as magnesium sulfate, sodium sulfate, castor oil, etc. After use, they can produce mechanical or chemical stimulation of the digestive tract and can reflexively excite the uterus and induce miscarriage.

Third, drugs that can affect fetal growth or cause fetal malformations, such as salicylates, nicotinamide, pilocarpine, physostigmine, etc. In addition, in early pregnancy, drugs that may produce adverse consequences such as cortisone, sex hormones and long-acting sulfonamides should be avoided;

Fourth, Chinese herbal medicines with the effects of breaking blood stasis, activating blood circulation and regulating qi, such as peach kernel, safflower, sparganium, zedoary, Leonurus japonicus, Dryopteris crassirhizoma, Euphorbia pekinensis, Wikstroemia, Kansui, pokeweed, Pharbitis nil, rhubarb, Gleditsia sinensis, bitter orange, Corydalis yanhusuo, trogopterus dung, musk, leech, as well as Chinese patent medicines such as Huoluo Dan and Dieda Wan, will all cause serious harm to sow pregnancy maintenance and may even lead to miscarriage.

First, establish a scientific disease diagnosis and detectiontechnologysystem. Strengthen disease monitoring, formulate and implement reasonable immunization programs, and promptly cull and purify pigs with infectious diseases that are highly harmful, incurable ortreatmentcosts are too high;

Second, implement self-breeding and self-raising, and strictly prevent external sources of disease. Whenbreeding pigsmust be introduced, they may be mixed into the herd only after isolation and quarantine prove that they are free of disease;

Third, strengthen daily feeding management, improve environmental conditions and enhance the disease resistance of sows;

Fourth, the production method is best based on all-in, all-out, and thoroughly do a good job in farm area hygiene and disinfection. Within 5 m around the gestation pen, weeds must not be overgrown; mosquitoes, flies and rodents should be frequently driven out and killed; aborted fetuses, fetal membranes, stillborn fetuses and contaminants should be harmlessly treated at centralized designated points;

Fifth, pigs must not be raised together with cattle, sheep, chickens, ducks, etc., and pets such as dogs and cats must not be raised either. Pregnant sows should be dewormed regularly, and when sows become ill, they should promptly receivetreatmentand handling, strictly preventing the expansion of the disease and secondary infection.