For producers to raise healthy pigs and to avoid the use of antibiotics, it is critical the piglet has optimal gastrointestinal functionality. However, around weaning there are significant challenges that make this goal difficult to achieve. Optimal gastrointestinal functionality is a situation where the welfare, health and performance of the pig is not constrained by intestinal dysfunction (Celi et al., 2017). To achieve optimal gastrointestinal functionality, there has to be effective digestion and absorption of the feed which requires a normal and stable microbiota, appropriate structure and function of the mucosa and a balanced immune system.
Supporting the piglet at weaning starts with supporting the gut. The gut provides three important functions: it regulates nutrient and fluid uptake, it plays a role in the immune system, and it provides a barrier to the external environment. In nature, the piglet is weaned over many weeks in a gradual, prolonged process which permits full development of these functions. However, in commercial production, the weaning process is an abrupt one-day event which brings many challenges to the three essential functions of the gut, culminating in the most commonly reported problem in weaned pigs globally of post-weaning diarrhea, sometimes resulting from leaky gut syndrome.
Leaky gut syndrome is characterized by hyper-permeability of the intestinal epithelium. A failure in tight-junction functionality results in an increase in paracellular transfer of deleterious compounds (such as bacteria and undigested nutrients) from the intestinal lumen. These deleterious compounds activate the NFkB pro-inflammatory cytokine cascade causing an increased production of reactive oxygen species such as peroxides to fight the microbes but which can also cause collateral damage to cells. Pathogens, such as enterotoxigenic E. coli (ETEC) are then able to adhere to the intestinal cells and produce toxins that induce a loss of water and electrolytes from the cells resulting in diarrhea (Gresse et al., 2017). In addition to diarrhea, the other outcomes of the enteric infection such as reduced feed intake, weight loss, fever, poor feed efficiency and lack of uniformity are easily seen by the producer. What is not easily seen though is the underlying increased production of pro-inflammatory cytokines and acute phase proteins that the enteric infection triggers. The production of these compounds significantly modifies qualitatively and quantitatively the requirement for specific nutrients such as amino acids, vitamins, minerals, antioxidants and lipids.
The severity of leaky gut syndrome is impacted by direct and indirect factors. The direct factors include allergens and antigens that activate the pro-inflammatory cytokine cascade that cause gut inflammation. Allergens can originate from feed and the most prevalent in piglet diets originate from soybean meal. Antigens can also originate from feed and include components such as mycotoxins, but can also originate in the gut lumen from cellular debris (peptidoglycans) originating from cell walls of dead gram-positive bacteria (McCormack et al., 2020).
The indirect factors contributing to the severity of leaky gut syndrome are the facilitators of a gut environment that supports the growth of pathogens both in terms of the substrates they need to grow and the environment in which they live in.
The dual strategy to reduce leaky gut syndrome are outlined in Figure 1.
Reducing the need for medications post-weaning relies on supporting the piglet gut that causes diarrhea and supporting optimum gastrointestinal functionality. The achievement of this objective requires a multifaceted approach that is not dependent on a single product strategy, but encompasses a comprehensive nutrition approach. In contrast, to tackle this challenge, success lies in the use of tailormade solutions that support a normal gut environment that is not favorable for pathogen growth.
18 July 2022
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