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Time lost to disease in dairy cattle: associations between two consecutive lactations




Bacigalupo Sanguesa, Paola, author
Garry, Franklyn B., advisor
McConnel, Craig S., advisor
Lombard, Jason E., committee member
Pinedo, Pablo, committee member

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In the dairy industry, individual diseases and their effects are normally studied independently. However, in many cases the diseases are all related. The diverse effects of these diseases provide the foundation for creating a measure that incorporates morbidity and removal (death or culling) measures and evaluates the impact diseases can have during lactation. This summary health measure is called the disease-adjusted lactation (DALact) and it represents time lost due to disease and injury. The DALact is a time-based summary measure that represents a new approach to assess the impact of diseases in a lactation. The objective of this study was to evaluate the association between time lost due to specific diseases and total time lost due to diseases in two consecutive lactations using the DALact. Health and removal (culling and death) data were obtained from a Colorado dairy with approximately 1,400 lactating cows. A total of 803 cows in their second or greater lactation that calved, were sold, or died from July 1, 2015, through June 30, 2016, were selected. Health data were collected from Dairy Comp 305 for each most recently completed lactation and from the previous lactation. Health events included calving injury, displaced abomasum, diarrhea, hypocalcemia, ketosis, lameness, mastitis, metritis, musculoskeletal injuries, pneumonia, and retained placenta. All cow-level data were imported into SAS® for validation, calculation of DALact and modeling. The DALact was calculated by adding the Days Lost due to Premature Death or Culling (DLRD) and the Days Lost due to Illness (DLI). DLRD was calculated as the difference between the average completed lactation days in milk for that herd and the days in milk at culling or death. The DLI was the product of the number of cases multiplied by previously established disability weights and estimated disease durations (days) for a specific disease. The PROC GLM procedure was used to model the association of DALacts between the 2 consecutive lactations. A p-value of ≤0.05 was considered significant. Positive significant associations (P<0.001) were found between the DALact of the previous lactation and the current lactation for lameness and mastitis. The total DALact of the previous lactation was significantly associated (P<0.001) with the total DALact of the current lactation. Significant associations (P<0.001) were also found between the mastitis and lameness DALact of the precious lactation with the total DALact of the current lactation. Identification of diseases and reasons for removal that significantly affect time lost during two consecutive lactations will help producers focus management and preventive measures on diseases having the greatest impact on future productivity and wellbeing.


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