Inflammation is an innate process that occurs in response to physical or chemical damage in the body or invasion by an infectious agent or feed toxin. A prolonged subclinical inflammatory response in the animal leads to a continually reduced performance.
The effects of inflammation
Inflammatory processes reduce feed intake (anorexia), and energy is directed towards cellular defense mechanisms instead of being used for production, i.e., the accretion of muscle, production of milk or eggs.
An independent study was conducted to demonstrate the detrimental effects of a stimulated inflammation on piglet performance (Table 1). The piglets were challenged with an intraperitoneal Lipopolysaccharides (LPS) injection, which induces inflammatory response through the NF-κB pathway by the release of tumor necrosis factor-α (TNF-α) and Interleukin-1 β (IL-1β).
Blood parameters were analyzed and showed that Cortisol levels were elevated when fighting the inflammatory stimulus of LPS administration. This signified that a catabolic metabolism was taking place in order to provide the body with energy to fight the inflammation. Levels of IGF-1 (insulin-like growth factor 1), a factor which enhances the hypertrophy of muscle cells, were reduced. Decreased levels mean a reduced potential for muscle growth.
The negative effect on performance was reflected in reduced feed intake as well as a reduced weight gain of over 10 percent. The correlation between inflammatory processes and poor performance is frequently observed in practice. Particularly, during times of weaning or feed change, a reduction in feed consumption is indicative of inflammatory reactions in the gut.
All in all, underlying subclinical inflammation prevents the animal from reaching its full growth potential, therefore leading to lower profitability.
The necessity to take notice of inflammatory reactions was confirmed by Niewold, who stated that effective growth promoters should focus on inhibiting the intestinal inflammatory response.
Reducing inflammatory processes
One of the major mediators of inflammatory processes is the transcription factor NF-κB (nuclear factor κB), which is present in nearly all cells of the body. The activated form of NF-κB results in an increase in pro-inflammatory gene-expression.
On the contrary, Nrf2 (nuclear factor erythroid 2–related factor 2) is an antioxidant transcription factor involved in cell protection. The Nrf2 response pathway is the primary cellular defense against the cytotoxic effects of oxidative stress. Among other effects, Nrf2 increases the expression of several antioxidant enzymes. In general, the Nrf2 pathway acts as a defense against reactive oxygen species and reduces the susceptibility of cells to the harmful properties of pro-inflammatory cytokines.
To increase the efficiency of animal production, the pro-inflammatory NF-κB pathway should be constrained and the cytoprotective Nrf2 pathway stimulated.
Summing up, the aim is to reduce subclinical inflammatory processes in order to increase the availability of energy and nutrients for performance. By measuring the target genes of the NF-κB and the Nrf2 systems, the effect of a treatment on the health status of the animal can be measured at the cell level.