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Thesis (M.S.)--University of Nevada, Reno, 2008. / "December, 2008." Includes bibliographical references (leaves 27-31). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2009]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.

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Crossbreeding parameters (additive (a), dominance (d) and additive x additive (aa) epistatic effects for individual $ sp{ rm (I)}$ and for maternal $ sp{ rm (M)}$ performance) on body weight growth and first lactation performance traits of females from a crossbreeding experiment between Holstein (H) and Ayrshire (A) based lines were estimated by individual animal models, incorporating all known additive genetic relationships amongst animals, through restricted maximum likelihood and mixed-model methodologies. / The growth traits (asymptotic weight (A), rate parameter (k), inflection parameter (m), average lifetime absolute growth rate (AGR), average lifetime absolute maturing rate (AMR) and average lifetime relative growth rate (RGR)) were estimated by fitting the nonlinear equation, W$ sb1$ = A(1 $ pm$ be$ sp{ rm -kt}) sp{ rm M}$, to the observed weight-age data of 3076 individual females. / Results from the analyses of growth traits indicated that the H line exceeded the A line in addition genetic effects for individual performance (a$ sp{ rm I}$) for both A and AGR. The H line also exceeded the A line in additive effects for maternal performance (a$ sp{ rm M}$) in trait A. Both dominance (d) and additive x additive (aa) epistatic effects were statistically important in most cases. Individual heterosis (h$ sp{ rm I}$ = d$ sp{ rm I}$ $-$ 0.5aa$ sp{ rm I}$) was positive for traits A and AGR, whereas maternal heterosis (h$ sp{ rm M}$ = d$ sp{ rm M}$ $-$ 0.5aa$ sp{ rm M}$) was negative for A and positive for AMR. Total heterosis (TH = h$ sp{ rm I}$ + h$ sp{ rm M}$) had positive effects on AGR and AMR. For all growth traits, heterosis retained in advanced crossbred generations was statistically irrelevant. The overall conclusion was that crossbreeding systems designed to capitalize on TH would produce faster growing and earlier maturing animals. / The analyses of production traits found the additive effect of the H line for individual performance to be a major factor to increase yields of milk, protein and fat. On the other hand, line maternal and cytoplasmic source tended to favour the A line, but none reached statistical significance in any of the traits. Results indicate that two-line specific crosses or synthetic development would be sound breeding strategies for taking advantage of first cross heterosis or of line additive differences, respectively. / Estimates of crossbreeding parameters from mixed-model analyses, were found to be more reliable than those from ordinary least squares analyses. (Abstract shortened by UMI.)

Thesis (MSc (Veterinary Tropical Diseases, Veterinary Science))--University of Pretoria, 2008. / Includes bibliographical references. Also available in print format.

Thesis (M.Sc. Materials and Process Engineering)--University of Waikato, 2007. / Title from PDF cover (viewed May 8, 2008) Includes bibliographical references (p. 94-97)

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 104-114). Also available on the Internet.

Thesis (MSc (Agric)(Production Physiology)) -- University of Pretoria, 2007. / Includes bibliographical references.