Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/14/1997
Publication Date: N/A
Citation: N/A Interpretive Summary: Endotoxins are lipopolysaccharides from Gram negative bacteria, which are released upon bacterial lysis. However, neutrophils contain an enzyme, acyloxyacyl hydrolase (AOAH), which detoxified the bacterial toxin and thus limit the severity of the inflammatory response. Because the prevalence and severity of mastitis due to Gram negative bacteria is high during the first weeks after calving, the objective of this experiment was to determine the relationship between AOAH activity in circulating neutrophils around the time of calving. Between 10 and 21 days after calving, activity of AOAH in neutrophils decreased approximately 20% below pre-calving values. These data are consistent with increased sensitivity and severity of coliform mastitis during this period and suggest that AOAH activity in neutrophils palsy a role in limiting the susceptibility of severity of coliform mastitis during early lactation.
Technical Abstract: Bovine neutrophils contain the enzyme acyloxyacyl hydrolase that hydrolyzes the acyloxyacyl linkage of the two nonhydroxylated fatty acyl chains to two 3-hydroxy fatty acids in the highly conserved lipid A part of endotoxins with high specificity. This decreases toxicity of lipid A, while the immune stimulatory capacity of endotoxins is largely maintained. We studied the activity of this enzyme in neutrophils isolated from the blood of 7 high-yielding dairy cows around parturition. Between 10 and 21 days after parturition, activity of acyloxyacyl hydrolase in neutrophils decreased approximately 20% below prepartum values. About two months after parturition, acyloxyacyl hydrolase activity in neutrophils shortly after parturition is a factor that increases susceptibility of dairy cows to coliform mastitis during early lactation.