Plasma Growth Hormone Levels and Thyroid Secretion Rates during Compensatory Growth in Beef Cattle

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Abstract
Plasma growth hormone levels and thyroid secretion rates were measured at different live weights in uncatheterized and catheterized steers fed two different energy levels continuously (controls) or following a period of restriction (compensatory). Growth hormone levels varied between the control and compensatory steers and with energy level in the ration. In all but two treatment groups in both uncatheterized and catheterized steers, the compensatory steers had lower plasma growth hormone levels than controls. Thus, there was a negative relationship between rate of protein deposition and plasma growth hormone level. Compensatory steers had lower thyroid secretion rates during the period of restriction and during the first part of the full feeding period in most treatment groups. Thyroid secretion rates increased to or above the level of controls as the full feeding period progressed. These changes in thyroid secretion rates suggest that there was a lower energy requirement for maintenance during the period of energy restriction and the first part of the full feeding period, thus contributing to the ability of the cattle to utilize energy and protein more efficiently when placed on full feed. Copyright © 1974. American Society of Animal Science . Copyright 1974 by American Society of Animal Science.

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