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Accounting for productive time lost in dairy cattle: disease adjusted lactation




McNeil, Ashleigh Ann, author
McConnel, Craig S., advisor
Garry, Franklyn B., committee member
Hadrich, Joleen C., committee member
Lombard, Jason E., committee member

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Dairy cow mortality, morbidity, and poor welfare have been of increased concern over the past several decades. Traditionally, dairy farm management has focused on singular costs associated with pathologies without thoroughly quantifying losses tied to disease and consequent death or culling. Within human epidemiology, the economic burden of time lost due to ill-health or early death is measured through the World Health Organization's disability adjusted life years (DALY). This project utilized the DALY concept to estimate time lost during a lactation due to disease and subsequent early removal of dairy cows. This was accomplished through the development of the disease adjusted lactation (DALact) metric. The DALact is calculated by combining days lost due to illness or injury (DLI) and days lost due to early death or removal (DLRD). The DLI reflects the number of cases during a certain period, multiplied by a disability weight and specific disease duration. The DLRD is comprised of two components: days lost due to death, and days lost due to culling from a given disease. Disability weights for 13 common dairy cow diseases were derived from an international expert opinion survey of dairy producers, managers and veterinarians. The selected disease states included: calving trauma, diarrhea, ketosis, lameness, left displaced abomasum, mastitis, metritis, milk fever, musculoskeletal injury, pneumonia, right displaced abomasum, and retained placenta. Survey participants were asked to estimate the impact of each disease on overall health and milk production. Diseases were classified from 0 (no adverse effects) to 10 (terminal). Validity and scope of participants' responses were assessed using a modified beta-Pert distribution and median points were used to provide disability weights for the DALact calculation. To support development of the DALact, collection of disease and removal data from three Kansas dairy farms representing 9,000 Holstein cows began January 1, 2014 and ended on May 26, 2015. A total of 7,233 cows were enrolled in the study across the three dairies. DALact measures were calculated using disease, culling and death data for each disease state while combining the disability weights, duration, and average days in milk at time of removal. Mastitis accounted for the largest category on all three dairies representing 29,779, 23,917, and 36,183 days lost for Dairies 1, 2, and 3, respectively. Conversely, prevalence of mastitis was largest on only Dairy 1 (33%). Lameness was the second largest DALact category for Dairies 2 (9,934) and 3 (29,912) but not for Dairy 1 (pneumonia, 13,571). Prevalence for lameness was largest (35%) for Dairies 2 and 3. The DALact method confirmed that mastitis and lameness are areas of focus, but also highlighted that pneumonia is a primary concern on Dairy 1. The DALact aims to provide an assessment of the complete impact of mortality and morbidity on time lost in dairy cattle. The end result will be to validate the effectiveness of dairy health oversight and to determine where to focus management to reduce the number and economic impact of preventable removals and diseases while increasing animal welfare.


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