Dietary lipids and their relationship with pig immune function!

Dietary lipids play an important role in modulating the pig immune system. The gastrointestinal tract (GIT) is not only an important organ for digestion, absorption, and metabolism of dietary nutrients, but it is also the body’s largest immune organ and involves more than 70% of the body’s immune cells (Blikslager et al., 2007). Pigs face numerous pathogenic and non-pathogenic challenges after weaning, resulting in activation of the gastrointestinal immune system. While a healthy GIT is considered to be in a constant state of “controlled” inflammation, intestinal infections caused by pathogenic bacteria such as E. coli and Salmonella can dramatically amplify inflammatory responses.

However, weaning-related stress can also induce inflammation (Gresse et al., 2017).

During activation of the GIT immune system, several pro-inflammatory cytokines are produced. An overproduction of these cytokines results in intestinal injury and dysfunction. Fatty Acids (FAs) play a fundamental role as immune modulators. Contributing as:

• Main sources of energy
• Important components in cell membranes
• Metabolic substrates in many biochemical pathways and cell signaling molecules

  Focusing on the prevention of enteric diseases in pigs and broilers, Lauridsen (2019) described the influence of early nutrition with n-6 and n-3 dietary FAs on the synthesis of long-chain PUFA and eicosanoids. Including mechanisms for inflammatory responses and oxidative stress in these animals.

However, the optimal ratio between n-6 and n-3 FAs in terms of response parameters related specifically to immunity and pig gut health is still unknown.

   Conjugated linoleic acid (CLA) has been studied for its impact on intestinal immunity in growing and finishing pigs (Lauridsen et al., 2005;  Tous et al. , 2012). In addition, 2% CLA supplementation for sows from mid-gestation reduced intestinal inflammation of piglets compared to weaned piglets from control sows after exposure to piglets with  enterotoxigenic E. coli (Patterson et al., 2008).

• Therefore, in this study (Patterson et al., 2008), as well as in the study by  Lauridsen and Jensen (2007), a carryover effect was obtained. It was seen that the FA dietary treatment of sows influenced the lactating piglet through the fatty acid composition of the sow’s milk. The effect persisted in the form of enhanced immunity in the piglet after weaning.

Function of the intestinal epithelium Several conditions damage the intestinal epithelium and consequently cause poor absorption of nutrients. In general, E. coli infection  can:

• Decrease the height of the villi (villi atrophy)
• Increase crypt depth (crypt elongation)
• Exert detrimental effects on the relationship between the height of the villi and the depth of the crypts, the area of the villi and the volume of the villi, and can even destroy the villi.

In addition to a high cell turnover in the intestinal epithelium, oxidative stress and lipid oxidation products can also alter the barrier function of the epithelial monolayer.

• Fortunately, and even in case of overt inflammation, intestinal epithelium replacement is a process that occurs rapidly with cells proliferating in the crypts, maturing along the villi axis, and exfoliating from the tip of the villi. With a turnover rate of approximately 3 to 5 days (Potten et al. al.,  1997).

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