A Comparison of the Growth Hormone Content of the Pituitary Glands from Dwarf and Normal Beef Calves

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Abstract
Pituitary glands from 30 dwarf and 30 nor-mal calves of comparable ages, sex, and breed were assayed in a series of 4 trials. Hypophysectomized, immature, female rats were used as the assay animal and the tibia test as the measure of re- sponse. Conventional least squares analysis was used to estimate the effects of source of hormone, preparation of material, sex and breed of calf, level of injection, reader difference, and differences in initial rat weight on the width of the epiphyseal cartilage. Trial means ranged from 90 to 105 micra for the controls, and from 136 to 183 and 174 to 187 micra for groups injected with glandular material from dwarf and normal calves, respectively. Three of the 4 trials indicated significantly less hormone, per unit of glandular powder, in the glands from dwarf calves (P<,01). Response from all treated groups was significantly greater (P<.01) than from the control groups. Air-dried and freeze-dried preparations were more potent than acetone-dried preparations. There was no signi-ficant difference due to sex of calf, or to breed of calf except in one trial. Cartilage width increased with level of injection from 0 to 800 micrograms (242 observations). Adjusting for minor differences in initial rat weight within trials had no significant effect on cartilage width.