Date of Graduation

8-2016

Document Type

Thesis

Degree Name

Master of Science in Animal Science (MS)

Degree Level

Graduate

Department

Animal Science

Advisor

Charles F. Rosenkrans

Committee Member

Jeremy Powell

Second Committee Member

Sami Dridi

Third Committee Member

Michael Looper

Fourth Committee Member

Bryan Kutz

Keywords

Biological sciences; Beef cattle; Dopamine D2 receptor; Genetics; Melatonin receptor; 1A; Polymorphism; Prolactin

Abstract

Calving rate is a qualitative trait regulated by several genes and is strongly affected by the environment. With the development of biotechnology and gene identification, scientists are able to determine which genes affect these productivity traits to improve accurate selection decisions. Prolactin (PRL) has been associated with reproductive traits, melatonin receptor 1a (MTNR1A) has been associated with meat quality traits, and the dopamine receptor D2 (DRD2) gene has been associated with hair coat score (HCS) in cattle. Our objective was to determine associations between mutations in the PRL, MTNR1A, and DRD2 genes and cow-calf profitability traits. Genomic DNA was extracted from buffy coat samples of Angus-based crossbred cows (n = 170). Relationships were determined using mixed model ANOVA with genotype, year, and cow age group as main affects. When F-tests were significant, means were separated using multiple t-tests and Tukey’s adjustment. We identified three single nucleotide polymorphism (SNP) sites in the PRL gene of cattle (C1286T, A1128T, G8398A), five SNP sites in MTNR1A (A541G, G575A, A583G, T679C, C721T) and one SNP site in DRD2 (A534G). Three years (2012 - 2014) of performance data were used to determine relationships to SNP genotypes. Mutation site C1286T, in the PRL gene, affected (P = 0.038) both calving rate and cow efficiency. Calf weaning weight and adjusted 205-d weight tended (P < 0.10) to be different for the C1286T SNP site. The SNP site A1134T affected (P < 0.05) calf birth weight, adjusted 205-day weight, and cow efficiency; and tended to affect (P < 0.10) calf weaning weight. Cows that were homozygous minor allele at MTNR1A SNP site, A583G, had increased hair coat scores (HCS) and calving rate. The DRD2 gene SNP site tended (P = 0.10) to affect HCS. These results suggest that PRL, MTNR1A, and DRD2 genes could be used as molecular markers for selection in cattle.

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