136 Reducing the incidence of postpartum bovine metritis by administration of mycobacterium cell wall fraction immunostimulant in a high-producing Holstein dairy herd

Metritis is a uterine disease that affects up to 40% of dairy cows and commonly develops when pathogenic bacteria infect the uterus after parturition. Research in the past few years suggests that metritis can be prevented when cows avoid, tolerate, and resist pathogenic bacteria. Innate and adaptative immunity are crucial for the resistance mechanisms. Mycobacterium cell wall fraction (MCWF) is an immunostimulant that has been shown to reduce bacterial load and alter aspects of the immune response in large animals. The administration of two doses of MCWF given before and near parturition was reported to decrease the incidence of metritis in dairy cows (Solano-Suarez et al. 2021 J. Anim. Sci. 99, skab191). The objective of this study was to determine if a single dose of MCWF given 7 days after parturition will decrease the incidence of metritis in dairy cows. To study this, adult cows that recently calved were assigned randomly to two groups: (1) MCWF (n = 184), an intramuscular dose of 5 mL of MCWF (Amplimune, NovaVive Inc.) given 7 days after parturition, and (2) control (n = 156), an intramuscular dose of 2 mL of oestradiol cypionate (4 mg, ECP, Zoetis, USA), used as standard prophylactic protocol at the farm, given 7 days after parturition. Metritis was defined as presence of a fetid watery red-brown uterine discharge, an abnormally enlarged uterus, associated with signs of systemic illness (decreased milk yield, dullness or other signs of toxemia), and fever >39.5°C, diagnosed within 25 days after calving. Data were analysed using chi-square. The MCWF treatment reduced (P < 0.05) metritis incidence compared with the control group (11.89% vs 19.87%, respectively). There was a 40% relative reduction of metritis incidence in MCWF-treated cows. In conclusion, a single treatment with MCWF 7 days after parturition shows potential as a preventive treatment to reduce the incidence of metritis in dairy cows. Further research is needed to investigate whether the treatment leads to improved reproduction.