Date of Graduation

5-2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Animal Science (PhD)

Degree Level

Graduate

Department

Animal Science

Advisor/Mentor

Charles Rosenkrans

Committee Member

Michael Looper

Second Committee Member

Jeremy Powell

Third Committee Member

Nick Anthony

Fourth Committee Member

Don Coover

Keywords

Beef Heifers, Cattle, Disease, Genetics, Heat Shock Proteins, Reproduction

Abstract

Reproductive performance is crucial for sustained financial success in the beef cattle industry. This dissertation includes a population study that quantified the incidence of Neospora caninum infections in the central region of the United States and tested its relationship with reproductive performance in beef cattle. Trial one of that study concluded that 6.9% of open, replacement heifers (n = 1306) tested seropositive. The second trial in that project found that 9.6% of the breeding age females (n = 500) tested were seropositive for Neospora caninum; and that state in which the cattle lived and age impacted (P < 0.05) infection rate. Breed composition, number of farm dogs on the ranch, and use of total mixed rations were not associated (P > 0.1) with seropositive tests. Fewer (P < 0.05) seropositive females were pregnant in Oklahoma, but overall infection rate was not associated (P > 0.1) with non-pregnant females. The second study, tested for a relationship between heat shock protein 70 (Hsp70) genotypes and reproductive characteristics. Blood samples were collected from beef heifers (n = 165) being developed for replacements and Hsp70 genotypes (A1125C, C895D, G1851A, G2033C) were determined using a commercial laboratory (Neogen Corporation; Lincoln, NE). There was an association (P = 0.04) between C895D genotype and the percentage of lymphocytes in circulation. Pelvic area, reproductive tract score, pregnancy rate, and white blood cell concentrations were affected by (P < 0.05) genotype at G2033C. Cows with heterozygous genotype for G2033C had a lower (P = 0.02) pregnancy rate; conversely, those same cows had larger (P = 0.02) PA. No associations were detected between A1125C or G1851A and the traits evaluated. While more research is needed in this area, these projects indicate that identifying Neospora caninum infected cattle and Hsp70 genotypes could be useful tools for selecting beef cattle.

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