Influence of medium‐chain fatty acids and short‐chain organic acids on jejunal morphology and intra‐epithelial immune cells in weaned piglets
Weaning is a challenge for the piglet including separation from the mother, environmental and nutritional changes. This may set the scene for digestive disorders, reduced performance and even increased mortality (Campbell et al., 2013). Feed composition is an important driving factor for feed intake, energy and nutrient supply to enterocytes and subsequently affects epithelial structure and integrity (Le Dividich and Sève, 2000; Lallès et al., 2004, 2007; Zabielski et al., 2008). In addition, nutritional factors and changes in the gut microbial ecosystem may affect the local immune response in the piglet gut during the weaning period (Le Dividich and Sève, 2000; Lallès et al., 2004, 2007; Zabielski et al., 2008). Transient changes in intestinal morphology and function (e.g. reduction of villus length and enzyme activity) within the first 5 days following weaning may therefore result from the complex interaction between diet, intestinal microbiota and the local immune system (Pluske et al., 1997; Stokes et al., 2004). The mucosa‐associated immune system is an important factor determining the balance between tolerance against food antigens or autochthonous intestinal bacteria or local defence reactions against putative pathogens or other antigens. Local intestinal immune response is mainly driven by complex interactions between innate and acquired mechanisms of the intestinal associated local immune system (Pabst and Rothkötter, 1999; Vega‐Lopez et al., 2001; Stokes et al., 2004). Intra‐epithelial lymphocytes (IEL) as part of the gut‐associated immune system are located between the enterocytes, and in pigs, they are relatively equally distributed along the villus axis (Vega‐Lopez et al., 2001). Based on the close proximity to the intestinal lumen, it is hypothesized that IEL may play an important role within the local immune defence (Pabst, 1987). Maintaining the intestinal physiological and intestinal barrier function in weaning piglets is of high importance for the prevention of digestive disorders.
Medium‐chain fatty acids (MCFA) and short‐chain organic acids (SOA) constitute rapidly available energy sources for intestinal and extra‐intestinal tissues and could be useful particularly in feeding weaned piglets (Lueck, 1980; Borum, 1992; Heo et al., 2002). MCFA and SOA can be utilized by enterocytes as energy source and can attenuate negative effects of weaning on villus length and crypt depth in piglets (Dierick et al., 2002a,b, 2003; Lee et al., 2007). Additionally, previous studies suggest that MCFA or SOA can modulate the number of intra‐epithelial lymphocytes (IEL), the lymphocyte proliferation rate and jejunal cytokine expression (Dierick et al., 2002a,b, 2003; Lee et al., 2007; Kuang et al., 2015).
The focus of this study was to investigate the effect of SOA and the combination of SOA with MCFA on gut morphology and IEL populations in weaned piglets, with focus on synergistic effects of both feed additives.