A. Subiyatno et al., METABOLITE AND HORMONAL RESPONSES TO GLUCOSE OR PROPIONATE INFUSIONS IN PERIPARTURIENT DAIRY-COWS SUPPLEMENTED WITH CHROMIUM, Journal of dairy science, 79(8), 1996, pp. 1436-1445
Two studies were conducted to evaluate the effects of Cr supplementati
on on blood metabolite and hormonal responses of Holstein cows to gluc
ose challenges during late pregnancy and early lactation and to propio
nate challenges during early lactation. Eight multiparous and 4 primip
arous 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 an
d 6 postpartum During glucose tolerance tests, Cr supplementation redu
ced 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 co
ws following glucose challenge. With supplemental Cr, insulin sensitiv
ity was reduced postpartum, particularly for primiparous cows, but ins
ulin sensitivity was increased prepartum. Results of this study sugges
ted that primiparous cows experienced Cr deficiency during late pregna
ncy and possibly during early lactation. Following propionate infusion
, Cr supplementation increased the serum glucose peak, increased the a
rea under the response curve for serum glucose, and tended to increase
IGF-I concentrations. Chromium supplementation tended to reduce the r
atio of insulin to glucagon. Supplementation might have enhanced gluco
neogenesis or glycogenolysis. Supplemental Cr also resulted in reduced
variability of most parameters during both experiments.