Randomized noninferiority clinical trial evaluating 3 commercial dry cow mastitis preparations: II. Cow health and performance in early lactation

The objective of this randomized noninferiority clinical trial was to compare the effect of treatment with 3 different dry cow therapy formulations at dry-off on cow-level health and production parameters in the first 100 d in milk (DIM) in the subsequent lactation, including 305-d mature-equivalent (305ME) milk production, linear score (LS), risk for the cow experiencing a clinical mastitis event, risk for culling or death, and risk for pregnancy by 100 DIM. A total of 1,091 cows from 6 commercial dairy herds in 4 states (California, Iowa, Minnesota, and Wisconsin) were randomly assigned at dry-off to receive treatment with 1 of 3 commercial products: Quartermaster (QT; Zoetis Animal Health, Madison, NJ), Spectramast DC (SP; Zoetis Animal Health) or ToMorrow Dry Cow (TM; Boehringer Ingelheim Vetmedica Inc., St Joseph, MO). All clinical mastitis, pregnancy, culling, and death events occurring in the first 100 DIM were recorded by farm staff using an on-farm electronic record-keeping system. Dairy Herd Improvement Association test-day records of milk production and milk component testing were retrieved electronically. Mixed linear regression analysis was used to describe the effect of treatment on 305ME milk production and LS recorded on the last Dairy Herd Improvement Association test day before 100 DIM. Cox proportional hazards regression analysis was used to describe the effect of treatment on risk for experiencing a case of clinical mastitis, risk for leaving the herd, and risk for pregnancy between calving and 100 DIM. Results showed no effect of treatment on adjusted mean 305ME milk production (QT = 11,759 kg, SP = 11,574 kg, and TM = 11,761 kg) or adjusted mean LS (QT = 1.8, SP = 1.9, and TM = 1.6) on the last test day before 100 DIM. Similarly, no effect of treatment was observed on risk for a clinical mastitis event (QT = 14.8%, SP = 12.7%, and TM = 15.0%), risk for leaving the herd (QT = 7.5%, SP = 9.2%, and TM = 10.3%), or risk for pregnancy (QT = 31.5%, SP = 26.1%, and TM = 26.9%) between calving and 100 DIM.