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Descriptive and Analytical Epidemiology of Morbidity and Mortality on Calf Ranches

Walker, William Lindsey

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2012, Doctor of Philosophy, Ohio State University, Veterinary Preventive Medicine.

The proportion of dairy calves raised on specialized livestock operations, known colloquially as “calf ranches,” has increased over time. However, data about these operations, particularly regarding health and mortality, are lacking. Accordingly, the overall objectives of this body of work were: 1) to compile data on calf health, mortality, and health management practices for a sample of calf ranches across the United States using an established survey methodology and examine risk factors related to health outcomes in this population and 2) to examine calf health and mortality with a prospective observational longitudinal study on a single large calf ranch and examine risk factors associated with morbidity and mortality in this population.

The first study examined morbidity, mortality, antibiotic use, and biosecurity and biocontainment policies on a convenience sample of calf ranches in the United States. Calf ranches identified through a membership list, freely accessible websites, and personal contacts were surveyed according to a standard methodology. Herd-level health outcomes for calf ranches rearing preweaned heifer calves only or both preweaned heifer and bull calves were summarized and related to a number of potential risk factors with mixed-effects multivariable logistic regression. Multiple risk factors altered the odds of morbidity and mortality. Morbidity and mortality were generally similar to estimates from studies on US dairy operations.

The second study prospectively examined morbidity and mortality in relation to various risk factors for dairy heifer calves entering a single large calf ranch. Over eight months, morbidity, mortality, and demographic data were collected from the calf ranch’s record keeping system. Serum total protein concentration (TP) was determined from blood samples taken approximately 3 days post-arrival. The risk of morbidities and mortality in relation to source farm, month of arrival, TP, and antecedent morbidities were modeled for the calves with available morbidity data using multivariable Poisson regression with robust errors. The risks of morbidity and mortality were affected by source, season, TP, and other morbidities. Incidence of morbidities and mortality were generally similar to reports for dairy operations.

This body of work provides the first report of basic health metrics, antibiotic use, and biosecurity and biocontainment policies representing a larger sample of US calf ranches. In general, these industry-wide data suggest similar and occasionally slightly superior calf health when compared to dairy operations. Several policies were identified at the herd-level that could improve morbidity and mortality without significant barriers to implementation. For individual calves, reducing morbidity at an early age and improving TP could reduce the risk of subsequent morbidity and mortality. This work further demonstrates that analyses such as these can be used effectively to examine morbidity, mortality, and their risk factors on individual calf ranches.

Thomas E. Wittum, PhD (Advisor)
William B. Epperson, DVM, MS (Committee Member)
Linda K. Lord, DVM, PhD (Committee Member)
Päivi J. Rajala-Schultz, DVM, PhD (Committee Member)
Jeffrey Lakritz, DVM, PhD (Committee Member)
237 p.

Recommended Citations

Citations

  • Walker, W. L. (2012). Descriptive and Analytical Epidemiology of Morbidity and Mortality on Calf Ranches [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1354216604

    APA Style (7th edition)

  • Walker, William. Descriptive and Analytical Epidemiology of Morbidity and Mortality on Calf Ranches. 2012. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1354216604.

    MLA Style (8th edition)

  • Walker, William. "Descriptive and Analytical Epidemiology of Morbidity and Mortality on Calf Ranches." Doctoral dissertation, Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1354216604

    Chicago Manual of Style (17th edition)