Influence of Amount Fed on Hormone Concentrations and Their Relationship to Mammary Growth in Heifers

Abstract

Concentrations in blood serum of growth hormones, prolactin, insulin, and glucocorticoids were investigated in 22 pre-or postpubertal heifers fed restricted or ad libitum amounts of a ration, Gains for the respective feeding regimens were 613 and 1218 g daily. Growth hormone was elevated for prepubertal heifers on restricted feed, whereas there was no difference from feeding for postpubertal heifers. Concentrations of prolactin, insulin, and glucocorticoids were higher for heifers fed ad libitum than for those restricted.