Diet-induced bacterial immunogens in the gastrointestinal tract of dairy cows: Impacts on immunity and metabolism

Abstract

Dairy cows are often fed high grain diets to meet the energy demand for high milk production or simply due to a lack of forages at times. As a result, ruminal acidosis, especially subacute ruminal acidosis (SARA), occurs frequently in practical dairy production. When SARA occurs, bacterial endotoxin (or lipopolysaccharide, LPS) is released in the rumen and the large intestine in a large amount. Many other bacterial immunogens may also be released in the digestive tract following feeding dairy cows diets containing high proportions of grain. LPS can be translocated into the bloodstream across the epithelium of the digestive tract, especially the lower tract, due to possible alterations of permeability and injuries of the epithelial tissue. As a result, the concentration of blood LPS increases. Immune responses are subsequently caused by circulating LPS, and the systemic effects include increases in concentrations of neutrophils and the acute phase proteins such as serum amyloid-A (SAA), haptoglobin (Hp), LPS binding protein (LBP), and C-reactive protein (CRP) in blood. Entry of LPS into blood can also result in metabolic alterations. Blood glucose and nonesterified fatty acid concentrations are enhanced accompanying an increase of blood LPS after increasing the amount of grain in the diet, which adversely affects feed intake of dairy cows. As the proportions of grain in the diet increase, patterns of plasma β-hydoxybutyric acid, cholesterol, and minerals (Ca, Fe, and Zn) are also perturbed. The bacterial immunogens can also lead to reduced supply of nutrients for synthesis of milk components and depressed functions of the epithelial cells in the mammary gland. The immune responses and metabolic alterations caused by circulating bacterial immunogens will exert an effect on milk production. It has been demonstrated that increases in concentrations of ruminal LPS and plasma acute phase proteins (CRP, SAA, and LBP) are associated with declines in milk fat content, milk fat yield, 3.5% fat-corrected milk yield, as well as milk energy efficiency.

Changes in milk performance and hepatic metabolism in mid-lactating dairy goats after being fed a high concentrate diet for 10 weeks

“…As a consequence, the ruminant microbial ecology and systemic metabolic state will change because of the rapid fermentation and subsequent excessive organic acids accumulation, and such animals are likely to suffer metabolic disorders such as acidosis, fatty liver, laminitis and even systemic inflammation (Alegre et al, 1988;Kleen et al, 2003;Plaizier et al, 2008;Dong et al, 2011;Tao et al, 2014). Our previous studies also showed that long-term feeding of a 65% high concentrate (HC) diet to lactating dairy goats led to subacute ruminal acidosis (SARA) and disruptions of mucosal barrier in the hindgut (Dong et al, 2013;Tao et al, 2014).…”

Effects of dietary supplementation of glutamine and mannan oligosaccharides on plasma endotoxin and acute phase protein concentrations and nutrient digestibility in finishing steers

“…It is well recognized that high grain diets will result in increased release of LPS in the rumen as well as in the intestine (Gozho et al 2006;Khafipour et al 2009;Plaizier et al 2009;Dong et al 2011;Plaizier et al 2012). A recent study by Steele et al (2011) showed that the structural integrity of the rumen epithelium was compromised during high grain feeding, which can result in translocation of LPS into the circulation across the rumen epithelium.…”

“…When cattle are fed high-concentrate diets, ruminal acidosis, especially subacute ruminal acidosis (SARA), may occur in practical beef production. As a result, the harmful and toxic substances, such as lactate (particularly the D-isomer), ethanol, histamine, tyramine, tryptamine, and bacterial endotoxin (or lipopolysaccharide, LPS), are released in the rumen in a large amount (Dong et al 2011). Among those substances, LPS has received a lot of attention because it potentially causes systemic immune responses and metabolic changes in the body Dong et al 2011).…”

“…As a result, the harmful and toxic substances, such as lactate (particularly the D-isomer), ethanol, histamine, tyramine, tryptamine, and bacterial endotoxin (or lipopolysaccharide, LPS), are released in the rumen in a large amount (Dong et al 2011). Among those substances, LPS has received a lot of attention because it potentially causes systemic immune responses and metabolic changes in the body Dong et al 2011). During grain-based SARA, the barrier function of the rumen and the intestines are compromised, and LPS can substantially translocate into the bloodstream across epithelium of the digestive tract (Dong et al 2011;Plaizier et al 2012).…”

“…Among those substances, LPS has received a lot of attention because it potentially causes systemic immune responses and metabolic changes in the body Dong et al 2011). During grain-based SARA, the barrier function of the rumen and the intestines are compromised, and LPS can substantially translocate into the bloodstream across epithelium of the digestive tract (Dong et al 2011;Plaizier et al 2012). Immune responses are subsequently caused by translocation of LPS into the systemic circulation, which can activate immune cells, and this process ends up with the release of proinflammatory cytokines and acute phase response (Khafipour et al 2009;Zebeli & Metzler-Zebeli 2012).…”