Date of Award
Doctor of Philosophy
Weights, heights and compositional data were collected on cattle resulting from a four breed diallel crossbreeding study. Breeds involved were: Angus, Hereford, Holstein, and Brown Swiss. Cattle were raised and maintained at two Iowa State University Research farms;Objectives of the study were: to examine the growth pattern of a population of cows differing widely in productive characteristics and size, to examine the relative tissue growth of steers from the same population, and hypothesize about the effect of size and composition differences in the cow population and the subsequent effect on production efficiency;Growth pattern was quantified through nonlinear regression of cow weights from birth through six years of age;Asymptotic mature weight was significantly affected by breed of sire, breed of dam, and calfhood management. Crossbred cows were 3.4% heavier at maturity than straightbred cows. Cows with dairy dams and beef sires were 2.7% heavier at maturity than the reciprocal cross. Rate of maturing was 3.7% greater for crossbred cows than straightbred cows. Cows with beef sires and dairy dams matured 3.9% more rapidly than the reciprocal cross. Correlation of maturing rate and mature size was -.60;Large breed differences were evident in height measurements. Heterosis for height at birth, 180 days, 365 days and maturity was 0.0%, 0.8%, 1.2% and 0.3%, respectively;Large breed and management differences were evident in the tissue composition of steers. Leaner breed combinations were generally associated with larger mature cow size;The study indicates that differences in mass of metabolically active tissue are greater than would be indicated by mature cow weight alone. Maintenance mass of larger cows of dairy breeding appear underestimated relative to the smaller, fatter beef breeds.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Michael James McInerney
McInerney, Michael James, "Maintenance mass of mature beef cows " (1984). Retrospective Theses and Dissertations. 9009.