The Role of Probiotics in Alleviating Postweaning Diarrhea in Piglets From the Perspective of Intestinal Barriers

Abstract

Early weaning of piglets is an important strategy for improving the production efficiency of sows in modern intensive farming systems. However, due to multiple stressors such as physiological, environmental and social challenges, postweaning syndrome in piglets often occurs during early weaning period, and postweaning diarrhea (PWD) is a serious threat to piglet health, resulting in high mortality. Early weaning disrupts the intestinal barrier function of piglets, disturbs the homeostasis of gut microbiota, and destroys the intestinal chemical, mechanical and immunological barriers, which is one of the main causes of PWD in piglets. The traditional method of preventing PWD is to supplement piglet diet with antibiotics. However, the long-term overuse of antibiotics led to bacterial resistance, and antibiotics residues in animal products, threatening human health while causing dysbiosis of gut microbiota and superinfection of piglets. Antibiotic supplementation in livestock diets is prohibited in many countries and regions. Regarding this context, finding antibiotic alternatives to maintain piglet health at the critical weaning period becomes a real emergency. More and more studies showed that probiotics can prevent and treat PWD by regulating the intestinal barriers in recent years. Here, we review the research status of PWD-preventing and treating probiotics and discuss its potential mechanisms from the perspective of intestinal barriers (the intestinal microbial barrier, the intestinal chemical barrier, the intestinal mechanical barrier and the intestinal immunological barrier) in piglets.

Weaning stress and intestinal health of piglets: A review

“…The reduction in VH and VCR means that intestinal mucosal function was impaired, and intestinal digestion and absorption capacity was reduced.In contrast, a higher VH and VCR, and a lower CD of the intestines indicated better intestinal function ( 25 , 26 ). As is well-known that alterations in the villus−crypt structure are universal in weaned animals, such as intestinal villus shedding, crypt hyperplasia, and intestinal mucosa atrophy, which further destroys intestinal mucosal barrier function and digestive and absorptive capacity ( 10 , 11 , 25 , 27 , 28 ). For example, a study by Bomba et al.…”

“…In modern intensive farming systems, early weaning techniques are often used to improve the productivity of sows, which can increase the annual litter size of sows, improve the utilization rate of breeding equipment, and bring more economic benefits for breeding enterprises ( 7 ). However, due to sudden separation from the sow, and the rapid changes in the diets, physical environments, and social environments, piglets may suffer from weaning stress, which jointly results in perturbation of intestinal microbiota, host physiological and biochemical functions, intestinal digestion and absorption capacity, and mucosal immune function ( 8 , 9 ), which eventually leads to decrease of feed intake, occurrence of post-weaning diarrhea (PWD), and growth restriction ( 10 , 11 ). That’s because, the intestinal development of the piglets is not mature, and the digestive system and immune system are not perfect at this stage, which leads to a poor ability of weaning piglets to adapt to the complex environment ( 11 ).…”

“…However, due to sudden separation from the sow, and the rapid changes in the diets, physical environments, and social environments, piglets may suffer from weaning stress, which jointly results in perturbation of intestinal microbiota, host physiological and biochemical functions, intestinal digestion and absorption capacity, and mucosal immune function ( 8 , 9 ), which eventually leads to decrease of feed intake, occurrence of post-weaning diarrhea (PWD), and growth restriction ( 10 , 11 ). That’s because, the intestinal development of the piglets is not mature, and the digestive system and immune system are not perfect at this stage, which leads to a poor ability of weaning piglets to adapt to the complex environment ( 11 ). Simultaneously, due to the insufficient secretion of digestive enzymes in the gastrointestinal tract, early-weaned piglets cannot digest solid food well, leading to the destruction of the intestinal physical barrier, including the destruction of the tight junctions (TJ), the reduction of mucins secretion, the increase of intestinal permeability and the un-balanced gut microbiota ( 12 – 14 ).…”

Prevention of gastrointestinal diseases in piglets at weaning using probiotics Bacillus coagylans and Bacillus megaterium

“…Many authors note that among many probiotics, Bacillus coagulans has become a key player in the field of probiotics in recent years. Many studies have demonstrated its activity in regulating the balance of intestinal microbiota, stimulating metabolism, improves the body's immune defence, B. Coagulans have a useful role as a feed additive [17,18].…”

Swine enteric colibacillosis: Current treatment avenues and future directions

“…As such, prebiotics, which are non-digestible feed ingredients positively affecting the host by stimulating the growth and/or the activity of a limited number of bacteria in the gastrointestinal microbiota ( 5 ), can be used to modulate the gut microbiota. Probiotics are defined as viable microorganisms that when ingested in sufficient amounts reach the intestine in an active state where they can exert positive effects on the host's health status ( 77 , 78 ). In last, synbiotics are defined as a mixture comprising live microorganisms (probiotics) and substrate(s) (prebiotics) selectively utilized by host microorganisms that confer a health benefit on the host ( 79 ).…”