Document Type

Dissertation - Open Access

Award Date

1971

Degree Name

Doctor of Philosophy (PhD)

Department / School

Animal Science

First Advisor

C.A. Dinkel

Abstract

During 1968, 29 Hereford steers were individually fed and marketed at one of seven constant weight classes from approximately 386 to 522 kg at intervals of 22.7 kg. During 1970, 21 Angus and Hereford crossbred steers were individually fed and marketed at one of four constant weight classes from approximately 386 to 522 kg at intervals of approximately 45.0 kg. The amounts of edible portion, trimmed fat, removed bone and the summation of the kidney, pelvic, and cod fat were determined on the steers of both years. In 1970 two experiments examined the usefulness of an analog computer for calculation of heat loss of individually fed steers raised in a near normal or conventional environment. The instrument was equipped with eight skin leads, a rectal and an ambient probe. The computer used combinations of sensed temperature and manually set factors to calculate heat production. Experiment one utilized six Angus and Hereford crossbred steers to evaluate sources of variation associated with the temperature computer measurements. Experiment two included measurements taken during the five day period prior to slaughter before and after feeding on each of the 21 steers assigned to weight classes. Combinations of production and calculated heat losses were used to partition the theoretical energy utilization during the intervals between weight classes. The edible portion growth of the steers of both years was characterized by a plateau or reduction near the middle of the weight range and an increased amount of edible portion after the plateau. Lower feed consumption and slower gains appeared to be associated with the plateau or reduction of edible portion. The results of the 1970 trial suggested a reduction of feed consumption and production of less edible portion and more fat and bone during the middle interval as compared to the other intervals. Ambient temperature significantly affected the temperature computer measurements in both experiments. After adjustment for ambient temperature effects, no differences were observed for measurement period within the same day. No important differences were observed for weight classes or breed of sire. Calculated metabolizable energy intake and temperature computer measurements of heat loss were utilized to compare the theoretical partition of energy utilization between weight class intervals of the 1970 trial. The average metabolizable energy intake was considerably lower for the middle interval. The apparent available energy above that accounted for by the temperature computer heat loss was also considerably lower for the middle interval than for either the first or third interval. The apparent reduction of energy intake during the same interval as the reduction in edible portion occurred was suggested as a possible cause of the plateau. Alterations in protein metabolism and deposition similar to those which occur during semi-starvation studies were theorized as possible explanations for the occurrence of the edible portion plateau. Data from all steers suggested that considerable variations and reductions in feed consumption and performance occurred during the interval between weight classes 3 and 5.

Library of Congress Subject Headings

Beef cattle -- Weight

Format

application/pdf

Number of Pages

109

Publisher

South Dakota State University

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