Call number: LD2668 .T4 1986 S73 / Master of Science / Animal Sciences and Industry

Photocopy of typescript. / Digitized by Kansas Correctional Industries

Graduation date: 1995

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 172-181).

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The growth hormone receptor gene (GHR) has been previously documented to be a good candidate gene for detection of a quantitative trait locus (QTL) which influences milk production in Holstein cattle. In this study, the promoter region of the GHR gene and microsatellite markers AGAL29 and BM5004 were studied. Their effects on milk yield (MY), fat yield (FY), protein yield (PY), fat percentage (FP) and protein percentage (PP) were examined. DNA was isolated from 1746 used by the artificial insemination (AI) industry representing 26 half-sibling families. Three polymorphisms in the GHR gene were genotyped (GHRAlu, GHRAcc and GHR Stu) along with both microsatellites. The markers were analyzed in a cross-family analysis. The model included a population mean, a fixed grandsire effect, a fixed allele effect and a random residual error. The data was also analyzed using a nested model in a granddaughter design to investigate a possible consistency in the allelic effect in individual families. Lastly, the data was analyzed using the haplotypes of GHRAlu and GHR Acc, using the same model as the cross-family analysis. It included an analysis of a fixed haplotype effect instead of a fixed allele effect. (Abstract shortened by UMI.)

In dairy cattle, treatment with exogenous growth hormone (GH) affects growth and function of mammary gland. The actions of GH are mediated via interaction with GH receptors (GHR). The first step in signal transduction is homodimerization of two GHR molecules by GH. This step is critical since mutation in either GH or GHR can block dimerization and thus target cell activation. However, association between milk related traits and combination of GH and GHR variations are not known. Accordingly, DNA genotypes in the GH and GHR genes were investigated for association with milk, fat and protein lactation yields in Holsteins. The marker data were obtained on 873 progeny tested bulls by using PCR-RFLP and PCR-SSCP analysis. There were five markers in GH and three in GHR. Estimated breeding values (EBVs) were obtained from Canadian Dairy Network for milk, fat, and protein lactation yields for the 873 genotyped bulls. / There was significant difference among GH6.1 alleles (C-to-G transversion at position 2141) for the milk yield (P < 0.05) and protein yield (p < 0.05). There were significant differences in GHR AluI (A-to-T transversion at -1182) for milk (p < 0.05) and fat (p < 0.05), and GHR StuI (C-to-T transversion at -232) for fat (p < 0.0001) and protein (p < 0.05). Allele frequencies for GH6.1 (C), GHR AluI (A) and GHR StuI (C) alleles in bulls genotyped were 0.95, 0.63 and 0.95, respectively. Bulls with GH6.1 (C/G) genotype had higher milk EBV (p < 0.05) compared to C/C bulls. Bulls with GHR AluI (A/A) genotype had higher milk EBV (p < 0.01) and fat EBVs (p < 0.05). Bulls with StuI (C/C) genotype had higher fat EBV (p < 0.0001) and protein EBV (p < 0.05) compared to StuI (C/T). This study indicates that the combination of GH and GHR markers could serve as a tool to aid in selection for improving milk, fat, and protein production.

Three studies were conducted to determine the effects of roasting on ruminal degradability of sunflower seeds and the effects of feeding roasted sunflower seeds on ruminal fermentation, nutrient digestibility and milk yield and composition of dairy cows. Experimental treatments were a control diet with no added sunflower seed, a raw sunflower seed diet and a roasted sunflower seed diet. Sunflower seed diets contained 6% fat whereas the control diet contained 3% fat. In study one, two ruminally fistulated cows were used in a randomized complete block design to determine the effects of roasting on ruminal degradation of sunflower seeds. In the second study, three ruminally cannulated lactating Holstein cows were used in a 3 x 3 Latin square experiment to determine the effects of dietary treatments on ruminal fermentation and total tract nutrient utilization. In the last study, three primiparous and six multiparous Holstein cows were used in three 3 x 3 Latin squares to determine the effects of dietary treatments on milk yield and composition.