Metabolite and hormonal responses to glucose or propionate infusions in periparturient dairy cows supplemented with chromium.

Two studies were conducted to evaluate the effects of Cr supplementation on blood metabolite and hormonal responses of Holstein cows to glucose challenges during late pregnancy and early lactation and to propionate challenges during early lactation. Eight multiparous and 4 primiparous cows (Experiment 1) and 12 primiparous cows (Experiment 2) were assigned to one of two treatments: control and 0.5 ppm of supplemental Cr. The glucose challenges were performed at 2 wk prepartum and at 2 wk postpartum, and the propionate challenges were conducted at wk 2 and 6 postpartum. During glucose tolerance tests, Cr supplementation reduced the ratio of insulin to glucose and reduced plasma concentrations of insulin and triglycerides of primiparous cows during the prepartum period. Chromium supplementation decreased plasma Cr of primiparous cows following glucose challenge. With supplemental Cr, insulin sensitivity was reduced postpartum, particularly for primiparous cows, but insulin sensitivity was increased prepartum. Results of this study suggested that primiparous cows experienced Cr deficiency during late pregnancy and possibly during early lactation. Following propionate infusion, Cr supplementation increased the serum glucose peak, increased the area under the response curve for serum glucose, and tended to increase IGF-I concentrations. Chromium supplementation tended to reduce the ratio of insulin to glucagon. Supplementation might have enhanced gluconeogenesis or glycogenolysis. Supplemental Cr also resulted in reduced variability of most parameters during both experiments.