Clinical response after chitosan microparticle administration and preliminary assessment of efficacy in preventing metritis in lactating dairy cows

The objectives were to evaluate the clinical response to intrauterine administration of chitosan microparticles (CM) and to assess efficacy for preventing metritis in dairy cows. Holstein cows (n = 104; 40 primiparous and 64 multiparous) at increased risk for metritis (cows that had abortion, dystocia, twins, stillbirth, or retained placenta) were randomly assigned to 1 of 2 treatments at 1 d in milk (DIM; 24 h postpartum): CM group (n = 52), daily intrauterine infusion of 8 g of CM dissolved in 40 mL of sterile water for 5 d; control (CON) group (n = 52), daily intrauterine infusion of 40 mL of sterile water for 5 d. Clinical response was assessed by evaluation of parameters associated with inflammation (rectal temperature and plasma haptoglobin concentration) and metabolism [plasma nonesterified fatty acid (NEFA) and β-hydroxybutyrate (BHB) concentrations] up to 14 DIM, and daily milk yield up to 30 DIM. Uterine discharge pH was evaluated at 4, 7, 10, and 14 DIM as an indicator of bacterial load and acid byproduct production. The cumulative incidence of metritis was evaluated up to 4, 7, 10, and 14 DIM. Continuous and dichotomous outcomes were evaluated with mixed linear and logistic regression analysis, respectively. Treatment with CM did not affect rectal temperature (39.17 ± 0.04 vs. 39.14 ± 0.04°C), haptoglobin (1.10 ± 0.05 vs. 1.07 ± 0.05 mg/mL), NEFA (0.64 ± 0.04 vs. 0.63 ± 0.04 mmol/L), BHB (0.61 ± 0.03 vs. 0.57 ± 0.03 mmol/L), or milk yield (30.3 ± 0.92 vs. 30.1 ± 0.97 kg/d) compared with CON. An interaction between treatment and time showed that NEFA concentrations were lower for CM than CON at 10 DIM (0.46 ± 0.06 vs. 0.64 ± 0.06 mmol/L). Treatment with CM resulted in greater uterine discharge pH than CON (6.91 ± 0.03 vs. 6.83 ± 0.02). Cows that developed metritis had increased concentrations of haptoglobin and BHB, and decreased uterine discharge pH and milk yield. Treatment with CM resulted in decreased incidence of metritis up to 7 DIM compared with CON (46.2 vs. 65.4%); however, no differences were found at 4 (11.5 vs. 17.3%), 10 (61.5 vs. 73.1%), and 14 DIM (63.5 vs. 73.1%) for CM versus CON, respectively. In conclusion, CM did not alter clinical parameters of cows at risk for metritis, and may merit further investigation for prevention of metritis. However, the duration of treatment may have to be extended to effectively reduce the incidence of metritis during the high-risk period.