Effects of intramammary infusion of cis-urocanic acid on mastitis-associated inflammation and tissue injury in dairy cow

Abstract

Objective - To evaluate the effects of cis-urocanic acid (cis-UCA) on mammary gland (MG) inflammation and injury associated with Escherichia coli-induced mastitis in dairy cows. Animals - 12 lactating dairy cows (36 MGs). Procedures - At 7-week intervals, a different MG in each cow was experimentally inoculated with E coli. At 6-hour intervals from 6 to 36 hours after inoculation, the inoculated MG in each cow was infused with 40 mL of saline (0.9% NaCl) solution, 12.5mM cis-UCA, or 25mM cis-UCA (4 cows/group); ultimately, each cow received each treatment. Immediately prior to and at various time points after inoculation and treatment, milk samples were collected. Bacterial CFUs, somatic cell counts (SCCs), N-acetyl-beta-D-glucosaminidase (NAGase) and lactate dehydrogenase (LDH) activities, and concentrations of bovine serum albumin, tumor necrosis factor-α, and cis-UCA were quantified in each milk sample. Results - Compared with findings in saline solution-treated MGs, NAGase and LDH activities in milk samples from cis-UCA-treated MGs were lower. Cis-UCA had no effect on milk SCCs and milk concentrations of bovine serum albumin and tumor necrosis factor-α. Furthermore, cis-UCA had no adverse effect on bacterial clearance; CFUs of E coli in MGs treated with saline solution or cis-UCA were equivalent. Conclusions and Clinical Relevance - In cows, milk NAGase and LDH activities were both lower in E coli-infected MGs infused with cis-UCA than in those infused with saline solution, which suggests that cis-UCA reduced mastitis-associated tissue damage. Furthermore, these data indicated that therapeutic concentrations of cis-UCA in milk can be achieved via intramammary infusion.