Off-campus UNL users: To download campus access dissertations, please use the following link to log into our proxy server with your NU ID and password. When you are done browsing please remember to return to this page and log out.
Non-UNL users: Please talk to your librarian about requesting this dissertation through interlibrary loan.
SIMULATED EFFECTS OF GENETIC CHANGE UPON LIFE-CYCLE PRODUCTION EFFICIENCY IN SWINE AND THE EFFECTS OF BODY COMPOSITION UPON ENERGY UTILIZATION IN THE GROWING PIG
Abstract
A mathematical, deterministic computer model was constructed to simulate the biological and economic inputs and outputs associated with pork production. Parameters used in the model were developed and verified from experimental results in the literature. The model was used to evaluate the effects of genetic change upon life-cycle production efficiency. Efficiency was defined 4 ways: Mcal/kg carcass lean marketed (H(,1)), Mcal/kg empty body weight marketed (H(,2)), $/100 kg carcass lean marketed (H(,3)), and $/100 kg liveweight marketed (H(,4)). Traits evaluated were increased growth rate (GR), lean growth rate (LGR), milk potential (MK), number born alive (NBA), viability (VIAB) and conception rate (CR) plus decreased percent fat at 100 kg (-%F), fat growth rate (-FGR) and age at puberty (-PUB). Responses in animal performance and efficiency were simulated for independent changes in each trait for several marketing and management systems. Relative weightings for each trait (b-values) were calculated as the change in efficiency per genetic standard deviation. For H(,1) and H(,2), growth traits were generally more important than maternal traits, but differences were much smaller for H(,2) than H(,1). For H(,3), when marketing was at constant weight, %F was most important with NBA, VIAB, LGR and -FGR intermediate and larger than GR, CR, -PUB and MK. When marketing was at constant age, b-values for GR and LGR increased substantially. For H(,4), maternal traits were most important under weight marketing, but GR was most important under age marketing. B-values for -%F and -FGR were negative for H(,4). In management systems which increased sow costs relative to pig costs, b-values of maternal traits increased relative to growth traits. When feed costs increased relative to non-feed costs, b-values of growth traits and -PUB increased relative to NBA and VIAB for H(,3) and b-values of -%F, -FGR and LGR decreased relative to other traits for H(,4). The effects of large genetic change and interactions among the traits were simulated and discussed. Ten sets of 3 littermate barrows from each of 3 lines (Beltsville Highfat and Lowfat composites plus a Large White x Hampshire cross) were used in a comparative slaughter experiment to investigate the effects of body composition upon energy utilization. At 10, 17 and 24 weeks of age fasting heat production (FHP) was measured on 1 pig from each set in an open-circuit calorimeter. Each pig was then slaughtered, frozen, and ground; then samples were analyzed for chemical composition. Pigs retained from 10 to 17 and 24 weeks were fed a 16% crude protein diet ad libitum. Regressions of FHP at each age on liveweight and on the chemical components of body weight indicated that FHP was determined by the weight of the non-fat component. Partial regressions on fat improved predictions only slightly and were negative at 10 and 17 weeks, suggesting a beneficial insulation effect of fat when pigs were cold. Five additional barrows from each line were used in metabolism trials at 12 and 19 weeks of age to determine the metabolizable energy value of the diet for each line and period. ME values were higher 19 weeks due to the improved digestion of fiber. ME values were not different among the lines when corrected to zero nitrogen balance. Regression estimates for energy costs of maintenance (ME(,m)), protein deposition (b(,P)) and fat deposition (b(,F)) were calculated by several methods. Comparisons among the different methods showed b(,P) to be very sensitive to prior estimates and/or assumptions relative to ME(,m). Results indicated that daily ME utilization for growing pigs was adequately described by the following model: ME intake = .116(lean,kg('.85)) + 11.0(protein deposited, kg) + 16.2(fat deposited, kg) R('2) = .98
Subject Area
Livestock
Recommended Citation
TESS, MICHAEL WALTER, "SIMULATED EFFECTS OF GENETIC CHANGE UPON LIFE-CYCLE PRODUCTION EFFICIENCY IN SWINE AND THE EFFECTS OF BODY COMPOSITION UPON ENERGY UTILIZATION IN THE GROWING PIG" (1981). ETD collection for University of Nebraska-Lincoln. AAI8118184.
https://digitalcommons.unl.edu/dissertations/AAI8118184