Thesis (M. Com. (Agr.)) -- Lincoln University, 2009. / Also available via the World Wide Web.

Thesis (doctoral)--Swedish University of Agricultural Sciences, 2000. / Includes bibliographical references.

Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

Thesis (M.S.)--University of Wisconsin, 1963. / Typescript (carbon copy). eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 41-43).

Thesis (M.S.) University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 21, 2007) Vita. Includes bibliographical references.

Please read the abstract (Summary) in the section 00front of this document / Thesis (D Phil (Information Science))--University of Pretoria, 2007. / Information Science / unrestricted

Lameness is a painful disorder that decreases performance and is highly recognized as one of the most important health and welfare concerns for dairy cattle. Visual gait scoring is the most common way to detect gait change in dairy cattle. However, this is not only subjective, but is also time consuming and costly. A need to remove the subjective assessment of human observation exists. Therefore, automatic gait change detection for continuous monitoring by precision dairy monitoring technologies may be beneficial. The first objective of this research was to characterize behavior and production variables as cow gait changed to evaluate potential usefulness in gait change detection across two different studies. Weighted gait score was a significant (P < 0.05) predictor of rumination time for study 1. Rumination time decreased as weighted gait score increased. However, for study 2, numbers of steps and feeding time were significant predictors (P < 0.05). Number of steps increased as weighted gait score increased. Time at the feedbunk and feedbunk visits decreased as cows weighted gait score increased. The second objective was to compare behavior and production variables for each individual gait aspect in increasing gait scores to evaluate potential usefulness in gait change detection across two different studies. For study 1, milk yield, rumination, and neck activity decreased as cows as tracking score increased. For study 2, lying time decreased as cow’s general symmetry score increased. Feedbunk visits decreased as cows tracking score increased. Number of steps increased as cow’s spine curvature score increased. Time active increased as cows head bobbing score increased. Activity increased as cows speed score increased. Lying time decreased as cow’s abduction/adduction score increased. The third objective was to detect gait change utilizing multiple precision dairy monitoring technologies in two different studies. For study 1, 56% of predicted gait scores were within 0.25 points of the actual weighted gait score and for study 2, 41% of predicted gait scores were within 0.25 points of the actual weighted gait score. Pearson Correlation for study 1 and 2 was 0.43 and 0.46, respectively. For both studies, the Pearson Correlation yielded results in the low category, when evaluating goodness of fit.

Corpus luteum (CL) dysfunction has been implicated among various factors predisposing early embryonic mortality in cattle. Two experiments were conducted to evaluate the efficacy of using human chorionic gonadotropin (hCG) given either at the time of breeding (day 0) , day 7 or 14 post breeding, in reducing that component of early embryonic mortality caused by CL dysfunction. The aims of experiment 1 were to investigate the effectiveness of using hCG, in inducing the development of accessory CL, their formation and growth, and the effect of such treatments on the function of both the induced and spontaneous CL. Thirty-four lactating Holstein cows were randomly assigned to one of four treatments. A single intramuscular injection of 1000 IU of hCG was given either at the time of breeding (day 0, n=8), day 7 (n=9) or 14 (n=9) post breeding or no hCG given (control, n=8). A real-time ultrasound machine was used to study follicular dynamics and CL growth. The CL and antral follicle diameter was determined using a built-in system of calibrated callipers. Ultrasound scanning was carried out on days 7, 9, 11, 14, 16, 18, 21, 28, 35 and 42 post breeding. Blood and milk samples, for progesterone (P₄) determination using radioimmunoassay, were collected on days coincident with ultrasonography. Diameter of the CL is presented as the sum of the diameter of all luteal tissue in each animal. Differences in CL diameter, milk and plasma P₄ were analyzed using the General Linear Models Procedures while pregnancy data were analyzed using Chi-Square analysis in Statistical Analysis Systems (SAS, version 6.3). Based on the day 7 ultrasound scanning, the incidence of twin ovulations was higher among cows treated on day 0 (3/8) compared to control cows (1/8) and day 7 (1/9). Accessory CL were detected in 7/9 of the day 7-treated cows compared to 4/9 among the day-14 treated cows. Least squares means (LSMeans) for CL diameter were significantly higher (P<0.001) among cows treated with hCG compared to control cows starting at day 7 continually until day 42. Plasma P₄ profiles were significantly higher (P<0.05), at days 18, 35 and 42, in cows treated on day 7 or 14 compared to control cows. The first detectable differences (P<0.05) between hCG treated and control cows, in milk P₄ occurred at day 21 and persisted until day 42. Pregnancy rates were highest among cows treated with hCG on day 7 where 6 of the 9 cows were diagnosed pregnant. Corresponding pregnancy rates for day 0, 14 or control cows, were 4/8, 5/9 and 3/8, respectively. In the second experiment, two trials were conducted at two different farms to investigate the efficacy of using hCG to increase milk P₄ and pregnancy rates. In trial one, 79 lactating Holstein cows were exposed to the treatment protocol described in experiment 1. In addition to the milk sample collection schedule given in experiment 1, a sample was collected on day 0. Milk samples were stored at 4°C and later transported to the UBC laboratories for P₄ analysis. LSMeans for milk P₄ concentrations were different only at days 16 and 18 post breeding. Pregnancy rates were improved (P<0.01) by hCG treatments. The respective pregnancy rates for cows receiving hCG on day 0 (n=20), 7 (n=20), 14 (n=20) or control (n=19) were 25, 35, 35 and 21 %. In the second trial, 121 lactating Holstein cows were randomly assigned to treatments as described earlier. Weekly milk samples were collected from each animal and assayed for P₄ as described above. LSMeans for milk P₄ were significantly different (P<0.05) among groups starting at day 14 until day 42 post breeding. hCG increased pregnancy rates over control cows. The pregnancy rates for cows treated on day 0, 7, 14 and control were 31, 50, 41 and 26 %, respectively. In conclusion, this study revealed that treatment with hCG induced accessory CL development, increased P₄ production and improved pregnancy rates. It is evident, too, that treatment with hCG on day 7 post breeding may have greater potential for improving pregnancy rates not only in dairy and beef cattle but equally beneficial to the embryo transfer programmes. Increased pregnancy rates confirm the hypothesis that CL dysfunction does cost the livestock industry appreciable losses in embryos. / Land and Food Systems, Faculty of / Graduate

Production of dairy cows is influenced by many factors, among which are: genetics, nutrition, management, disease and age. Most of these factors can be modified to maintain a high level of production. Age, however, is beyond the influence of mankind; therefore, it is important to understand the effect of age on milk and butter-fat production.