How concentrate feeding affects glucoregulatory hormones in ruminants: implications in bovine ketosis

Twenty-four feedlot steers and four sheep were fed roughage or grain rations while three other sheep received intraduodenal infusions of amino acids, glucose, volatile fatty acids, and proteins to determine whether the release of plasma glucagon-like immunoreactivity is influenced by dietary factors and the composition of duodenal chyme. Plasma glucagon-like immunoreactivity rose in both cattle and sheep as the proportion of grain in their rations was increased. In response to intraduodenal infusions, only glucose stimulated glucagon-like immunoreactivity release. These experiments demonstrate that plasma glucagon-like immunoreactivity concentrations change in cattle and sheep in response to the amount of grain consumed and that glucagon-like immunoreactivity release is triggered by glucose in intestinal chyme.