Effect of vaccination with a Mannheimia haemolyticasubunit vaccine on milk yield in lactating dairy cows
Vaccination of adult lactating dairy cattle can have a negative impact on milk production. Decreased milk production may occur from a combination of the cow’s immune response, endotoxin level in the vaccine, and the impact of cattle handling. A randomized clinical trial utilized 3 treatment groups to examine changes in milk production following vaccination with a Mannheimia haemolytica subunit vaccine (MHSV; Nuplura PH, Elanco Animal Health) using 972 lactating dairy cows on a single Midwestern dairy: a vaccinated group (MHSV, n=315); a placebo-treated control (saline, n=342); and a negative control group (no injections, n=315). The decline in milk across a 3 d post-treatment period for the saline group was 0.5 lb (0.2 kg) greater than the negative control cows, but the difference was not significant (P=0.57). The decline in milk during the same time period for cows in the MHSV group was 1.5 lb (0.7 kg) more than the negative control, (P=0.02). The declines between the saline group (0.5 lb; 0.2 kg) and the MHSV group (1.5 lb; 0.7 kg) were not significantly different (P=0.17).