Influence of feeding and diet on diurnal patterns of plasma growth hormone and insulin in calves

Plasma GH concentrations were lower after feeding than before (newborn calves, P < 0.05; steers, P < 0.01). Calves fed concentrate had higher plasma insulin concentrations than those fed hay (P < 0.01). Meal feeding milk or concentrate, but not hay, elevated plasma insulin (P < 0.05). Diet type and feeding time relative to sampling time must be considered when measuring GH and insulin. Key words: Diurnal patterns, growth hormone, GH, insulin, calves