Abstract
PurposeIt is widely accepted that lipopolysaccharide and volatile fatty acids (VFA) accumulate in the digestive tract of ruminants fed diets containing high portions of grain. Compared to the ruminal epithelium, the hindgut epithelium is composed of a monolayer structure that is more “leaky” for lipopolysaccharide and susceptible to organic acid-induced damage. The aim of this study was to investigate changes in epithelial structure, apoptosis and inflammatory response in the hindgut of goats fed a high-concentrate diet for 6 weeks.Experimental DesignEight local Chinese goats with rumen cannulas were randomly assigned to two groups: one group was fed a high-concentrate diet (65% concentrate of dry matter, HC) and the other group was fed a low-concentrate diet (35% concentrate of dry matter, LC) for 6 wks. Ruminal fluid, plasma, and hindgut mucosa tissues were collected. Histological techniques, real-time PCR and western blotting were used to evaluate the tissues structure, cell apoptosis and local inflammation in the hindguts.ResultsFeeding HC diet for 6 wks resulted in a significant decrease of ruminal pH (p<0.01), and ruminal lipopolysaccharide concentrations were significantly increased in HC goats (p<0.05). Obvious damage was observed to mucosal epithelium of the hindgut and the intercellular tight junctions in HC, but not in LC, goats. The expression of MyD88 and caspase-8 mRNA was increased in colonic epithelium of HC goats compared to LC (p<0.05), and the expression of TLR-4 and caspase-3 showed a tendency to increase. In the cecum, interleukin-1β mRNA expression was decreased (p<0.05), and caspase-3 showed a potential increase (p = 0.07) in HC goats. The level of NF-κB protein was increased in colonic epithelium of HC goats. Caspase-3 activity was elevated in both colon and cecum, whereas caspase-8 activity was statistically increased only in colon.ConclusionsFeeding a high-concentrate diet to goats for 6 wks led to hindgut mucosal injuries via activating epithelial cells apoptosis and local inflammatory response.
Highlights
Current intensive production systems for ruminants feed large amounts of grain to animals to maximize energy intake and support high milk yields or rapid growth
Feeding HC diet for 6 wks resulted in a significant decrease of ruminal pH (p,0.01), and ruminal lipopolysaccharide concentrations were significantly increased in HC goats (p,0.05)
The expression of myeloid differentiating factor 88 (MyD88) and caspase-8 mRNA was increased in colonic epithelium of HC goats compared to LC (p,0.05), and the expression of Toll-like receptors (TLRs)-4 and caspase-3 showed a tendency to increase
Summary
Current intensive production systems for ruminants feed large amounts of grain to animals to maximize energy intake and support high milk yields or rapid growth. These feeding programs might be useful to lower the cost in the short term, the excessive amounts of non-structural carbohydrates and highly fermentable forages result in rapid fermentation and organic acids accumulation in rumen and hindgut [1,2]. Tight junctions (TJs) play an important role in maintaining the barrier function of epithelial cells, preventing the translocation of LPS and other toxic compounds from the intestinal tract into the circulatory system [10]. It’s reported that the disruption of intestinal TJs can increase the permeability of intestinal epithelia, the translocation of LPS and even cause systemic inflammation [14]
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