Parathyroid hormone response in treatment of subclinical hypocalcemia in postpartum dairy cows.

The aim of this study was to evaluate different treatments of postpartum subclinical hypocalcemia in dairy cows with emphasis on PTH response. Twenty four cows with subclinical hypocalcemia (Ca 1.4-2.0 mmol/L), out of 180 Holstein cows tested, were assigned in one of three equal groups: (1) CON received no Ca supplementation, (2) PO-Ca received 1000 mL of oral Ca suspension, immediately after establishing hypocalcemia, and 500 mL of the suspension 12 h after, (3) IV-Ca intravenously received 500 mL of Ca immediately after establishing hypocalcemia. The blood samples were taken up to 48 h after initial treatment for determination of Ca, iP, Mg and PTH concentrations. Urine pH was also evaluated up to 48 h after initial treatment. Compered to CON cows that were hypocalcemic up to the 48 h, Ca concentrations were significantly higher in PO-Ca up to hour 8 and IV-Ca up to hour 24. At first 2 h, PTH concentrations were significantly lower, compared to CON, only in IV-Ca, while at hour 4 PTH concentrations were significantly lower in both treated groups. At hours 24 and 48, PTH concentrations were significantly lower only in PO-Ca compared to CON group. Urine pH values in CON indicate alkalosis and were significantly lower both in PO-Ca and IV-Ca group, up to 12 h and 24 h respectively. In conclusion, both treatments mitigated hypocalcemia in cows, but with significantly different PTH response. Due to adequate PTH response, normocalcemia is established in CON and expected transient hypocalcemia is avoided in IV-Ca cows.

Effect of Peroral Administration of Chromium on Insulin Signaling Pathway in Skeletal Muscle Tissue of Holstein Calves.

The objective of this study was to investigate the effects of peroral administration of chromium-enriched yeast on glucose tolerance in Holstein calves, assessed by insulin signaling pathway molecule determination and intravenous glucose tolerance test (IVGTT). Twenty-four Holstein calves, aged 1 month, were chosen for the study and divided into two groups: the PoCr group (n = 12) that perorally received 0.04 mg of Cr/kg of body mass daily, for 70 days, and the NCr group (n = 12) that received no chromium supplementation. Skeletal tissue samples from each calf were obtained on day 0 and day 70 of the experiment. Chromium supplementation increased protein content of the insulin ß-subunit receptor, phosphorylation of insulin receptor substrate 1 at Tyrosine 632, phosphorylation of Akt at Serine 473, glucose transporter-4, and AMP-activated protein kinase in skeletal muscle tissue, while phosphorylation of insulin receptor substrate 1 at Serine 307 was not affected by chromium treatment. Results obtained during IVGTT, which was conducted on days 0, 30, 50, and 70, suggested an increased insulin sensitivity and, consequently, a better utilization of glucose in the PoCr group. Lower basal concentrations of glucose and insulin in the PoCr group on days 30 and 70 were also obtained. Our results indicate that chromium supplementation improves glucose utilization in calves by enhancing insulin intracellular signaling in the skeletal muscle tissue.