Thesis (Ph. D.)--Washington State University, May 2008. / Includes bibliographical references.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Typescript, etc.

Typescript. / Digitized by Kansas State University Libraries

Call number: LD2668 .T4 1957 W48 / Master of Science

Typescript (photocopy). / Digitized by Kansas Correctional Industries

A deterministic beef cattle computer simulation was used to estimate effect of genetic change in mature size (WMA), maximum daily milk production (PMA) and 60-d conception rate (CP) on costs per 100 kg slaughter weight (COST) and costs per 100 kg weaned weight (WNCOST) both adjusted for cull cow sales. Genetic inputs were defined as peak values for mature cows in an unrestricted environment and ranged from 400 to 800 kg WMA, 6 to 30 kg/d for PMA and 75 to 95% for CP. Two planes of nutrition for wintering cows, high and low and two economic schemes, high. versus low cow herd costs, were simulated. In all four systems, WMA and CP had quadratic effects (R² > .99) on cost over the range simulated. PMA effects were also curvilinear but could not be described by a simple quadratic curve (R² < .63). PMA appears to have a feasible range within which COST and WNCOST are little changed by changes in PMA. PMA levels below the lower end of the range were associated with increased costs due to increased calf death losses. Levels above the upper limit increased costs due to increased lactational stress and lower reproductive rates. The width of this range was reduced by lowering the plane of nutrition for wintering cows. The phenotypic manifestations of these three traits were also investigated, weaning rate (WRATE), weaning weight of an average 7 mos old steer (W117) and mature size (WMA). The results for these traits are similar to the genetic variables. The worth of a phenotypic standard deviation change in each trait (ah²) predict that a change in PMA or W117 is worth the most when outside the feasible range, followed by WMA and then CP or WRATE when COST is the measure. When WNCOST is the economic measure, PMA or W117 is again the most important of the traits but is now followed by CP or WRATE and then WMA. / M.S.

Data for this study was collected over a six-year period (1970 through 1975) on 217 bulls and 211 steers at the Bland Correctional Center, Bland, Virginia. Animals of this study were primarily cross-breds of Angus, Charolais, Hereford, Holstein and Simmental breeds. The objective of this study was to compare bulls and steers for growth and carcass traits. Bulls (220, 310, 449 kg) weighed more than did steers (204, 273, 381 kg) at weaning, 12 and 18 months of age, respectively, (P < .05), and scored higher on condition at weaning and 18 months of age (P< .05). Bulls (501, 281, 0.48 kg) were also heavier than steers (414, 219, 0.39 kg) for live slaughter weight, carcass weight, and carcass weight per day of age, respectively, (P< .05). Bulls and steers did not differ in ribeye area per 100 kg of carcass weight, backfat thickness, and marbling scores. Percent kidney and kidney fat per carcass weight was less in bulls (1.59%) than steers (2.58%) (P < .05). Bull carcasses graded low good whereas steer carcasses graded low to middle good. Armour tenderometer measurements were 8.25 kg and 7.09 kg for bulls and steers, respectively, (P < .05) , with any reading below 8.2 kg being of acceptable tenderness. Carcass yield grades were 1.29 and 1.90 for bulls and steers, respectively, (P < .05). The superior growth rate of bulls and the minimal sex differences in carcass quality renders the present market bias against bull beef questionable. / Master of Science

These studies were conducted to define calf body shape, to test for relationships between calf shape and sire expected progeny differences for birth weight (BWTEPD) and first-calf calving ease (CEEPD) and to evaluate the efficacy of calf shape as a selection criterion for reduction of calving difficulty. Birth weight (BW), head circumference (HC), hip width (HW), shoulder width, body length (BL), cannon circumference (CC), cannon length (CL) and heart girth (HG) were measured at birth on 1,016 calves sired by Angus, Polled Hereford and Simmental bulls. In the Angus- and Polled Hereford-sired calves, sire effects were present for BW-adjusted residuals of CC. Additionally, HW, BL and HG residuals differed among half-sib groups for the Polled Hereford-sired calves. Thus, calf body measure differences independent of BW were in part attributable to sire. Multivariate factor analysis was used to identify underlying skeletal width and frame dimensions of calf shape in both breeds. After adjustment of body measures for differences in BW, a positive relationship of BWTEPD with HC and CC and a negative relationship between CEEPD and CC existed. Further adjustment for BWTEPD removed effects of CEEPD on CC. Thus, BWTEPD influenced calf shape independent of BW, but shape was not related to CEEPD independent of BWTEPD. Simmental bulls were divergently selected on CEEPD relative to BWTEPD so that body measures of calves from sires whose progeny tended to be born with more or with less dystocia than expected from BWTEPD could be obtained. Differences in CL and CC at constant BW were in part attributable to sire. Underlying shape factors were similar to those of the other breeds. Sire BWTEPD was positively related to CC and HC independent of BW. However, a relationship between body measures and CEEPD existed only at constant BW and BWTEPD. Calf shape independent of BW was also not different among calves born unassisted and assisted. Estimates of heritability, repeatability and birth to weaning relationships for each BW-residual body measure were generally not significant. Overall, sire BWTEPD was related to calf shape independent of BW. However, increases in skeletal dimensions were not related to either observed calving difficulty nor sire CEEPD independent of BW. Selection for reduced calving difficulty should not be based on calf body shape. / Ph. D.

Thesis (M.Sc.) (Agriculture) --University of Limpopo, 2007 / The objectives of this study were to evaluate the effect of pre-weaning selection on estimates of genetic parameters for post-weaning average daily gain in Phases C (ADG-C) and D (ADG-D) and to estimate genetic relationships between average daily gain in the two phases. Performance records of the South African Angus cattle breed was used in the analysis. (Co)variance components and genetic parameters for weaning (WWT), AGD-C and ADG-D were estimated by REML procedures fitting three different models (Models 1, 2 and 3) that differed in how they integrated sequential selection in the analysis of post-weaning traits. Model 1 was a univariate model of WWT, ADG-C and ADG-D. Model 2 was a two trait model of WWT and either ADG-C or ADG-D. Model 3 was a three trait model of WWT, ADG-C and ADG-D. Estimates of heritability for ADG-C were 0.39±0.08, 0.42±0.06 and 0.44±0.01 from Model 1, 2 and 3 respectively. Corresponding estimates of heritability for ADG-D were 0.18±0.021, 0.19±0.021 and 0.21±0.02 respectively. An estimate of genetic correlation between ADG-C and ADG-D was 0.58± and it suggested that the two traits may not necessarily be under the same genetic control. Rank correlations for all bulls based on ADG-C estimated breeding values (EBV’s) were 0.92, 0.83 and 0.94 for Model 1 vs. Model 2, Model 1 vs. Model 3 and Model 2 vs. Model 3 respectively. Corresponding ADG-D EBV’s rank correlations were 0.88, 0.84 and 0.93. Rank correlations for top and bottom 1%, 5% and 10% were lower than those for all bulls in both ADG-C and ADG-D. Low rank correlations showed that the difference in magnitude of genetic parameters from different models was enough to alter bull rankings based on EBV’s of ADG-C and ADG-D. Hence it was concluded that inclusion of pre-weaning information in genetic analysis for post-weaning average daily gain is necessary to account for selection at weaning. / the THRIP (Technology and Human Resource for Industry Project) and NRF (National Research Foundation).