Thesis (Ph.D.)--University of Nebraska-Lincoln, 2008. / Title from title screen (site viewed Mar. 5, 2009). PDF text: 205 p. : col. ill. ; 5 Mb. UMI publication number: AAT 3336551. Includes bibliographical references. Also available in microfilm and microfiche formats.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1962. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 111-118).

Thesis (M. Agr. Sc.) -- Lincoln University, 2008. / Also available via the World Wide Web.

Thesis--University of Florida. / Description based on print version record. Typescript. Vita. Includes bibliographical references (leaves 134-140).

Thesis (M.S.)--University of Wisconsin--Madison, 1963. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 80-89).

Typescript, etc.

This dissertation investigates the process of genetic-based technical change in the Canadian beef cattle industry. Specifically, I analyze the effect of market forces on three processes necessary for genetic-based technological change: expansion of the genetic pool, inbreeding of divergent genetic strains to increase the probability of desired heritable properties in a pure breeding strain, and crossing of pure breeding strains to take advantage of hybrid vigour. This is accomplished through two studies. The first study, examines the expansion of the genetic pool through the establishment of purebred breeders of cattle breeds imported since 1965. A model is developed to explain the location of breeders within a time framework. The model was tested across breeds and over time. The process of breeder location appears consistent for the various breeds and can help explain the dates of availability of new breeds of cattle in different areas of the country. The second study examines the ongoing process of genetic technical change through the improvement and sale of breeding stock. A model is developed explicitly using the "characteristics" approach to production with the phenotypic characteristics of breeding bulls as arguments in a production function. Prices of individual bulls and values for the characteristics were collected at bull sales and shadow values for the characteristics estimated. These shadow values were used to predict characteristics which should be emphasized in herd improvement, and the prediction was compared to observed practices. The use of the characteristic: approach led to the identification of a different production function for the traditional straightbred technology and the new crossbred technology. Market forces seem to regulate the process of technological change and promote breed improvement. The major constraint to availability appears to be the limitation on imports and the biological limits to increasing the stock of purebred females. / Arts, Faculty of / Vancouver School of Economics / Graduate

The body weight of beef cows (cow weights) on nine ranches and farms located in the province of British Columbia were recorded each fall and spring for three years. Cow weights were also recorded on two additional occasions during the winter in the largest of these herds. The cows in these herds were all straightbred Hereford or Angus cows, or crossbreds of one or other of these breeds. During the summer five of the herds used rangeland, and four used pasture. Each herd calved in the spring after overwintering on conserved forage. The influence of breedtype, year, age, season and herd on the spring and fall weight records were determined by a least-squares analysis as outlined by Harvey (1975). Season was found to have a major influence on cow weight. Each weight change (considered as a percentage of the mean weight during the period) was included as a dependent variable in separate analyses. In addition to the parameters already mentioned, calf sex, calf age, calf weaning weight, previous weight change and the interval from calving to weighing in the spring were included where appropriate in the models for these analyses. The two mid-winter weights were included in a similar statistical analysis to determine the influence of pregnancy per se on cow weight in this herd. The parameters fitted in this model were age, year, age x year, days pregnant (DP), DP² and DP³. Age, season and herd were found to be significant sources of variation in the cow weight records; bat, within each herd, genetically different breedtypes normally had similar weights. The cows on summer rangeland were on average 119.0 lb. lighter than those on summer pasture. The increase in weight over age and the seasonal fluctuations around this mean growth curve also varied significantly between herds. However, in all but one of the herds there was a weight loss each winter and a weight gain each summer. The mean spring/fall weight difference was 114.2 lb. The mean mature age of the cows was six, and the mean mature weight was 1083.9 lb. The summer change in weight of a cow depended on age and herd, but not on breedtype. Younger cows gained more weight through the summer than older cows; the influence of herd on cow weight was not correlated with any single factor. Summer weight change was not influenced by the calf the cow suckled during the summer, but cows which lost the most weight during the previous winter gained the most the following summer. The winter weight change of a cow was not the same for all ages and breedtypes, but differed from herd to herd according to the level of winter feeding in each herd. Again there was a close correlation between this weight change and that in the previous period. The winter weight loss was found to continue through the interval from calving to weighing. The average weight loss during this period was around 0.7 lb. per day. A mean weight increase of 101.4 lb. was recorded between the 90th and 260th days of pregnancy. There was then a 6.8 lb. weight loss in the remaining 25 days through to parturition. The weight loss at parturition was 80.0 lb. or 7.3% of the cow's pre-partum weight. / Land and Food Systems, Faculty of / Graduate

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 56-61). Also available on the World Wide Web.

Thesis--Auburn University, 2010. / Abstract. Includes bibliographic references (p.82-90).