Died, euthanised, slaughtered or alive? outcomes for 10 023 Ayrshire and Holstein cows and associations between veterinary treatments and mortality

Animal welfare and disease prevention are important considerations for the modern dairy industry that strives for sustainability and responsibility. Diseases negatively impact cow welfare, lifespan, milk yield and lifetime productivity, and through those, farm economy, and resources needed in producing dairy foods for human consumption. Unassisted deaths and euthanasia represent cows that have suffered from an illness or trauma and leave the herd too early and without deliberate planning. The objectives of our study were to describe different ways cows exit the herd and farmer-reported reasons for culling, and to compare characteristics and veterinary treatment history of cows that either died unassisted or were euthanised on-farm. We studied data from the Finnish national Dairy Herd Improvement database and followed 10 023 cows in 76 herds in Finland, for 305 days. Based on a farmer-reported way for a cow exiting the herd, we grouped the cows into four categories based on their status at the end of the follow-up period: died unassisted (DIED), were euthanised (EUT) on farm, were sent to slaughter, or stayed alive in a herd, which accounted for 2, 4, 17, and 77% of the study population, respectively. We analysed cow characteristics and veterinary treatments (VET) the cows had received and explored their associations with on-farm deaths using generalised linear mixed models. Overall, the survival of Ayrshire and Holstein (HOL) cows was similar, but HOL cows died on farm more often. The median time from calving to exit was 26 days for DIED and 38 days for EUT cows. Compared to EUT cows, a smaller proportion of DIED cows had been treated by a veterinarian, but for a wider range of diseases. Having a VET for calving difficulty and digestive tract disease increased the odds of being a DIED cow, and VETs for milk fever, digestive tract or claw and leg diseases increased the odds of being an EUT cow, compared to not having the VET recorded. To gain more knowledge which could help to reduce mortality in the future, we suggest (1) separating the groups of DIED and EUT cows in forthcoming studies on culling and mortality, and (2) including the way dairy cows exit a herd into routinely monitored and reported statistics within the dairy industry and more detailed herd specific analyses into farmers' and advisors' tools for benchmarking and problem-solving at individual herd level.