Relationship of Some Endocrine Measurements to Growth and Carcass Composition of Cattle

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Abstract
Concentrations of growth hormone (GH), insulin (I) and adrenal corticoids (C) in blood plasma, GH in the anterior pituitary and metabolic clearance (MCR) of injected GH were measured in 24 crossbred steers and correlated with body size, measurements of growth and carcass composition. The cattle were of Angus or Charolais sires and Angus × Hereford dams. Measurements were made at 110, 220, 360 and 500 kg live weight. Starting at 220 kg, half the cattle were full-fed a finishing diet, and half were limited-fed the same diet until slaughtered at 360 and 500 kilograms. Breed of sire had no effect on any of the endocrine measurements. An increase in plasma concentrations of C in the limited-fed animals was the only observed influence of level of feeding. Plasma concentrations of GH, pituitary GH/body weight, MCR of GH/body weight and secretion of GH/body weight decreased with increasing body size. Measurements of GH status were positively related to carcass muscle and RNA in muscle and were negatively related to carcass adipose. Concentrations of plasma C and I were positively correlated with carcass adipose and negatively correlated with carcass muscle. The differences between the younger small and older large animals suggest that the younger small cattle had more GH per unit of body weight and that with increasing size and feeding, there was relatively more I and C and less GH per unit of body tissue. Copyright © 1978. American Society of Animal Science . Copyright 1978 by American Society of Animal Science.