Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Animal Science


A study comparing weaned spring born bull and steer calves was conducted at the Western Iowa Research Center near Castana over a three year period. The three trials commenced with the placement of cattle on test in November, 1982, October, 1983 and October, 1984. The first trial utilized 80 calves from Simbrah bulls mated to crossbred Charolais, Angus and Hereford cows. The second and third trials consisted of 87 and 90 Angus calves, respectively. Parameters evaluated in this study were total production costs, total feed dry matter consumption, feed cost by period, carcass and live values and total and net returns. The composition of the chuck and estimated percentages of boneless round, loin, rib and chuck were evaluated. Six to eight head of cattle were allotted to 12 pens by sex and weight. All steers were implanted with a growth stimulant at the start of each trial. Two dietary treatments were imposed within sex. One diet consisted of whole plant corn silage and the second consisted of shelled corn grain and whole plant corn silage. All cattle were weighed at 28-day intervals until removed from test when they were 16 to 17 months of age. Average lot final weights were 1150 lb in trial one, 1100 lb in trial two and 1130 lb in trial three. Bulls were found to have a greater total cost of production in trial one (P <.05). The total dry matter consumed per head was significantly lower for bulls than steers in trials two and three (P <.05). Feed costs per pound of gain were lower for bulls than steers during the entire test period of the first trial (P <.002). Net dollar returns were not significantly different for bulls and steers in any of the trials. Bulls in trial three produced chucks with the highest percent of muscle (P <.0004) and the lowest percent of fat (P <.0004). Bulls in trials one and two produced an estimated 60 lb (P <.0001) and 30 lb (P <.006) more retail product, respectively, per carcass than steers fed under like conditions. When trials two and three were combined, bulls produced 27 lb (P <.008) more retail product than steers.



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Brad Robert Harman



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165 pages