Sow Management Plays an Essential Role in Pork Production

1.     Reproductive Management

1.1 Breeding Efficiency [1]: Proper management of sow reproduction ensures a consistent and healthy supply of piglets. It includes managing estrus cycles, artificial insemination, and ensuring successful pregnancies.

1.2 Heat Detection [2]: Identifying when a sow is in heat for optimal breeding.

2. Housing and Environment

2.1 Space and Comfort [3]: Managing gestation periods and farrowing (the process of giving birth) is critical. Sows need appropriate housing and care during gestation, and farrowing facilities must be designed to provide a safe and comfortable environment for both the sow and the piglets.

2.2 Temperature Control [4]: Maintaining appropriate temperature levels (21-25 ℃) at sows’ houses, especially during summer and winter.

3. Farrowing Management

3.1 Farrowing Assistance [5]: Monitoring sows during the farrowing process and providing assistance if needed. It should maintain accurate records of breeding, farrowing, and health events.

3.2 Piglet Survival Rate [6]: Ensuring the survival and well-being of piglets during and after birth. Analyzing data to make informed decisions for improving sow management practices. Sow management also includes post-farrowing care and ensuring a smooth transition of piglets from nursing to solid feed.

4. Genetic Selection

4.1  Breeding Traits [7]: Selecting breeding gilts and sows with desirable reproductive performances for improved productivity and efficiency.

4.2  Genetic Diversity [8]: Maintaining the genetic diversity of porcine herd to reduce the risk of inbreeding.

5 Health and Nutrition

5.1 Disease Prevention [9]: Sow health directly impacts the health of piglets. Adequate nutrition, vaccination, and disease prevention measures are essential to ensure healthy litters.

5.2 Nutritional Requirements [10]: Sow nutrient requirements must be put on the stages of pregnancy, colostrogenesis, lactation, and transition feeding. Be sure to provide adequate nutrition and functional feed to support healthy pregnancies and successful nursing.

The above-mentioned factors are all important factors for the production and management of sows, but the health of sows has an absolute influence on the production traits and health of their offspring. The correlation between sow health and piglet performance is significant and crucial for the overall success of swine production [7]. The health and well-being of the sow directly impact the growth, development, and survival rates of piglets. Here are some key aspects of the relationship between sow health and piglet performance:

1. Colostrum Quality [11]: Sow health influences the quality of colostrum produced. Colostrum is the first milk that the sow provides to piglets, and it contains essential nutrients and antibodies crucial for piglet immunity and growth. Healthy sows are more likely to produce high-quality colostrum, which positively affects piglet performance.

2. Milk Production [12,13]: The health of the sows is directly linked to her ability to produce adequate milk. Sows suffering from health issues produce less milk, reducing piglet nutrition. Proper nutrition is critical for piglet growth and development.

3. Maternal Care [14]: Healthy sows can better provide appropriate maternal care to piglets, such as protection and warmth. Maternal care is essential for the early survival and well-being of piglets.

4. Reproductive Performance [15]: The reproductive performance of sows, including fertility and the number of piglets born, can influence piglet performance. Healthy sows are more likely to have successful pregnancies and larger litters.

5. Genetic Factors [16]: Sow health is also related to the genetic potential of piglets. Well-managed breeding programs consider the health and genetic background of the sow to improve piglet performance.

6. Stress Impact [7]: Stress in sows can negatively affect piglet performance. Stressors such as overcrowding, inadequate nutrition, or poor environmental conditions can lead to lower birth weights, higher mortality rates, and slower piglet growth.

7. Disease Transmission [17]: Sick sows can transmit diseases to piglets during gestation or through contact after birth. This can negatively impact piglet health and performance.

Matrilineal transmission of intestinal flora in piglets involves the transfer of commensal bacteria from parents to offspring through various pathways, including germ cells, the placenta, the birth canal, and perinatal and postpartum milk transmission [18]. The microbial migration theory suggests that the microbiome of the sow is likely transferred to piglets, with potential sources being the placenta, birth canal, breast milk, and even sow feces after weaning [19]. This establishes the intestinal flora of the sow as a crucial source molding the intestinal flora of the piglets over multiple periods [20]. The maternal microbiome colonizes piglet intestines via the placenta, birth canal, and milk, resulting in a robust maternal origin of the offspring's intestinal microflora [18]. Nutritional measures based on maternal intestinal microflora affect piglet intestinal microflora structure [21]. The inseparable link between sow intestinal bacteria, piglet intestinal bacteria, and growth performance involves vertical, fecal, and indirect transmission, exposing piglets to pathogenic bacteria and potential health risks [22]. Widespread in mammals, vertical transmission relies on the combined action of maternal immune function and hormone levels, with the placenta, umbilical cord, and amniotic fluid facilitating material exchange during pregnancy, preparing for the vertical transmission of the beneficial bacteria flora to the offspring [23]. The maternal transmission pathway of the intestinal flora in piglets is shown in Figure 1.

Figure 1. The infections in the childbirth process [18].

The intestinal bacterial composition of sows significantly impacts the health and growth traits of piglets. Enteritis in sows, characterized by inflammation of the intestines, can be caused by various pathogenic bacteria. Different bacterial species result in similar symptoms, such as diarrhea and feed intake reduction [24,25]. Below are common symptoms and some pathogenic bacteria associated with enteritis in sows and also describe how it affects their descendants:

1. Escherichia coli (E. coli)

Certain strains of E. coli, such as enterotoxigenic E. coli (ETEC) and enteropathogenic E. coli (EPEC), can cause enteritis in sows [26]. Pathogenic E. coli also can affect piglets through sows, and various strains of E. coli can cause different diseases in piglets. The transmission of E. coli can occur through different routes, and it is essential to understand how it can impact piglet health [27]. The following are the pathways and effects of sows infected with this pathogen on piglets:

1.1  Colibacillosis [28]: Colibacillosis is a bacterial infection caused by certain strains of E. coli. Piglets are particularly susceptible to colibacillosis during the first few days of life. Sows, especially those with uterine or mammary gland infections, can shed pathogenic E. coli in their feces or milk, exposing piglets to the bacteria.

1.2  Fecal-Oral Transmission [9]: Piglets can become infected by ingesting contaminated materials, such as feces, contaminated bedding, or udders of infected sows. Contaminated environments, especially in farrowing areas, can contribute to the spread of E. coli.

1.3  Neonatal Diarrhea [29]: Pathogenic strains of E. coli can cause neonatal diarrhea in piglets. In severe cases, E. coli can lead to dehydration, weight loss, and increased mortality. The bacteria invade the intestinal lining, causing inflammation and disrupting normal digestive processes.

1.4  Systemic Infections [30]: Some E. coli strains can cause systemic infections in piglets, leading to conditions like septicemia. This occurs when the bacteria enter the bloodstream, spreading throughout the body and causing a systemic inflammatory response.

1.5  Endometritis [31]: Previous research speculated that E. coli is bound up with the onset of sow endometritis based on intestinal microbiota analysis in sows with endometritis, increasing the stillbirth rate of piglets, but the mechanism is still unclear.

1.6  Milk Production Reduction [32]: E. coli is widely recognized for reducing the milk yield of sows as well as diarrhea outbreaks in sows and newborn piglets. Coliform mastitis represents an economically very important disease complex in sows. Infected sows have swollen udders and piglets lie on their mammary glands, making affected sows feel painful to refuse piglets access to the teats, resulting in mortality and growth retardation in piglets.

2. Clostridium perfringens (C. perfringens)

C. perfringens is a bacterium that produces toxins and can cause pig enteric diseases [33]. This pathogenic bacterium has several types; the most toxic types are mainly A and C [34]. Reported presumptive cases of both type A and C occur during the first week of life in newborn piglets, and sows are considered the primary source of infection [35]. There are the critical points of C. perfringens can impact piglets through sows as listed below:

2.1 Types A and C Enteritis: C. perfringens Types A and C are commonly associated with piglet enteritis. Sows can carry this bacterium in their intestines [35]. Transmission of C. perfringens types A and C are mostly fecal-oral, and the source of infection for the piglets is the fecal material of sows in contaminated environments, especially during the farrowing process. Piglets ingest the bacteria, leading to enteric infections [36]. Besides, inhibition of beta-toxin degradation by trypsin inhibitors in the colostrum of sows and most likely initial damage to the small intestinal epithelial barrier [33].

2.2 Contamination of Farrowing Areas [33]: Sows shedding C. perfringens in their feces can contaminate farrowing areas. This bacterium can persist in the environment, and piglets are exposed through contact with contaminated surfaces or ingesting contaminated materials.

2.3 Neonatal Mortality [37]: Types A and C of C. perfringens are particularly concerning in neonatal piglets, and infection can result in severe enteritis and necrotizing inflammation of the small intestine. This can lead to high mortality rates in affected piglets.

2.4 Clinical Signs of infected piglets [38]: Piglets affected by C. perfringens enteritis show signs such as diarrhea, lethargy, dehydration, and abdominal discomfort. The disease can progress rapidly, and intervention is necessary to prevent further losses.

3. Lawsonia intracellular (L. intracellular)

L. intracellularis is a bacterium that can infect pigs, causing a disease known as porcine proliferative enteropathy (PPE) or ileitis [39]. The disease has different clinical forms and mainly affects the different age of the swine. The acute form, namely porcine intestinal adenomatosis (PIA), is observed with hemorrhagic diarrhea and sudden death in growing pigs, while the chronic form, namely proliferative hemorrhagic enteropathy (PHE), is observed with diarrhea, rough hair-coat, and retarded growth currently in fattening pigs and young gilts or sows [40]. Sows infected with L. intracellularis can shed the bacterium in their feces, contaminating the environment. L. intracellularis can be present for weeks or months in proliferating crypt cells of sows, but without reinfection, fecal shedding and seropositivity can cease four weeks after the challenge [41]. Piglets can then become infected by ingesting contaminated feed, water, or by direct contact with contaminated surfaces [42]. The following are the pathways and effects of sows infected with this pathogen on piglets:

3.1 Vertical Transmission [39]: Sows infected with L. intracellularis transmit the bacterium to their piglets during gestation or farrowing. While the exact mechanisms of vertical transmission are not fully understood, it is known that the bacterium can cross the placenta, infecting developing fetuses.

3.2 Contamination of the Environment [43]: Sows shedding L. intracellularis in their feces induces environmental contamination in the farrowing area. Piglets can contact contaminated surfaces, leading to oral ingestion of the bacterium.

3.3 Postnatal Transmission [44]: After birth, piglets can continue to be exposed to L. intracellularis through contact with contaminated feces, feed, or water. Postnatal exposure can result in the development of clinical signs associated with PPE.

3.4 Reproductive performance [45]: L. intracellularis infections negatively affect the gastrointestinal tract and influence the reproductive performance of young gilts and sows. In pregnant sows, acute PHE causes abortion within six days of the onset of clinical signs. Infected sows with L. intracellularis have a high correlation with low conception and farrowing rates. Besides, older sows have a greater tolerance of L. intracellularis.

3.5 Clinical Signs of infected piglets [46,47]: Lawsonia infection can lead to reduced growth rates, poor feed conversion, and, in severe cases, death.

4. Salmonella spp.

Salmonella infections in sows are frequently asymptomatic, even though fecal shedding can occur continuously or intermittently, even over long periods, regardless of clinical signs [48]. Breeding sows with Salmonella asymptomatic infection can transmit the pathogen to piglets. Many risk factors for a high Salmonella prevalence in pigs suggest different routes of porcine infection [48]. In some countries, most farms are single-site herds in which all production stages, from the sows (mating, gestation, and farrowing units) to the finishing pigs (nursery, growing, and finishing units), are located at the same site [49]. If sows are excreting Salmonella, the sow unit can be continuously contaminated with Salmonella. Thus, it be an essential source for direct or indirect transmission of Salmonella infections to piglets in the herd [50].

4.1 Vertical Transmission [51]: Sows infected with Salmonella transmit the bacteria to their offspring during gestation. The bacteria can cross the placenta and infect developing fetuses, resulting in piglets being born already infected.

4.2 Contaminated Feces and Environment [52]: Piglets can be exposed to Salmonella by contacting contaminated feces in the farrowing environment. Contaminated surfaces, feed, and water can serve as sources of infection.

4.3 Clinical Signs of Infected Piglets [48]: The symptoms of Salmonella infection in piglets are diarrhea, lethargy, dehydration, and, in severe cases, mortality.

5. Brachyspira hyodysenteriae (B. hyodysenteriae)

B. hyodysenteriae is a bacterium that is responsible for swine dysentery, a contagious and potentially severe disease in pigs [53]. Transmission of the bacterium can occur through fecal-oral contact, and sows can serve as carriers of B. hyodysenteriae [54]. There are the main points about how B. hyodysenteriae can impact piglets through sows:

5.1 Vertical Transmission [55]: Sows infected with B. hyodysenteriae can transmit the bacterium to their piglets during gestation. The bacteria cross the placenta, leading to infection in developing fetuses.

5.2 Contaminated Environment [56]: Sows shedding B. hyodysenteriae in their feces can contaminate the farrowing environment. Piglets can then be exposed to the bacterium through contact with contaminated surfaces, feed, or water.

5.3 Clinical Signs of Infected Piglets: Clinical signs of swine dysentery in piglets can include mucohemorrhagic diarrhea, dehydration, lethargy, and reduced growth [57]. Swine dysentery can cause significant economic losses in pig production due to increased mortality, decreased growth rates, and the cost of treatment [58].

Strategies to prevent pathogenic bacteria from sows to piglets

1. Biosecurity [59]: Implementing stringent biosecurity measures to prevent the introduction of pathogenic bacteria into the herd.

2. Sanitation [60]: Regularly clean and disinfect farrowing areas and other parts of the facility to reduce the environmental load of the bacterium.

3. Testing and Monitoring [61]: Regular herd testing for pathogenic bacteria, especially in high-risk areas like farrowing facilities, can help detect and manage infections early.

4. Regular Vaccinations: Regularly injecting relevant vaccines into sows can significantly reduce the chance of sows and piglets being infected with these pathogenic bacteria [62]. For instance, vaccination of pregnant sows with C. perfringens type C bacterins at 6 and 3 weeks, respectively, before parturition confers immunity to piglets at birth via colostrum. Sows who are so vaccinated are recommended to receive a booster vaccine three weeks before each farrowing [35].

5. Choose Good Quality Feed Additives [63]: The feed composition has great influence to the intestinal microbiome of sows. The balance and diversity of the gut microbiome can be modulated through feed containing phytobiotics, prebiotics, probiotics, or other feed additives. It is possible to increase the number of beneficial bacteria and repress pathogenic bacteria by adapting the feed. High-quality feed additives are necessary to prevent or control the spread of these pathogenic bacteria within the herd.

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