Newborn calves are often deficient in iron and progressive reduction in blood iron concentration occurs over the first weeks of life. Some reports indicate the importance of interactions among iron and components of the insulin-like growth factor system. The aim of the study was to determine if there is a relationship between serum iron and insulin-like growth factor-I concentrations in neonatal calves. Blood samples were collected from 16 female Holstein-Friesian calves on day 10 of age. Erythrogram determination and measurements of serum iron, total protein, albumin, total iron binding capacity and serum insulin-like growth factor-I concentrations were performed. Haematological values were measured using an automatic analyzer, biochemical properties were determined spectrophotometrically, insulin-like growth factor-I concentration was measured by radioimmunoassay. Calves were divided into 2 groups according to iron concentrations; the first group of iron-deficient calves (n = 8, Fe < 10 μmol/l) and the second group of calves with optimal iron concentration (n = 8, Fe > 18 μmol/l). Blood indicators in all calves from the first group followed a pattern typically observed in anaemic calves. Insulin-like growth factor-I concentrations were significantly (P < 0.01) lower in the first group compared to the second group. However, insulin-like growth factor-I very strongly correlated with iron in calves from the second group compared to iron-deficient calves (r = 0.624; P < 0.01 and r = 0.478; P > 0.05, respectively). Based on our results, iron seems to have an important relationship to secretion of insulin-like growth factor-I in 10-day-old calves. This is the first report about such relationship in this age group of animals. Calf, haematology, IGF-I, iron deficiency

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 β-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.

Introduction. Neonatal calves are often deficient in iron. Accumulating evidence indicates that iron status is associated with disease pathologies including diarrhea. Our objective was to examine the association between iron status and gut function in neonatal calves with and without a history of calf diarrhea. Materials and Methods. Calves were divided into two groups based on their history of diarrhea; the first group were diarrheic calves (n=6) and the second group were nondiarrheic healthy calves (n=6). Blood samples (n=12) were collected at day 12 of age and erythrogram determination and measurements of serum iron and total iron binding capacity were performed. Hematological values were measured using an automatic analyzer, and biochemical properties were determined spectrophotometrically. Fecal samples were obtained from all calves and pH measured using semi quantitative test strips as well as being examined by bacterial cultivation for enterotoxigenic Escherichia coli, Salmonella spp. and Clostridium perfringens, by RT-PCR for the presence of bovine rotavirus, bovine coronavirus and bovine viral diarrhea virus, and by microscopy for the presence of Cryptosporidium parvum. Results and Conclusions. There were significant iron-related changes for most hematological indices in diarrheic calves; and iron (Fe) deficiency and microcytic, hypochromic anemia were diagnosed. The pH of the feces was significantly higher in diarrheic calves than in the non-diarrheic healthy group (P<0.01). All fecal samples were negative for the analyzed enteric pathogens. According to the results obtained, calves experiencing iron

Season may affect calves' thermal comfort and behavior, but the data related to the overall influence of seasonal variations on dams' colostrum and postnatal adaptive capability of calves are limited. The aim of this study was to measure the effects of a 49-day-long low air temperature (LAT) season (5.20 ± 0.46 °C mean air temperature) and a 53-day-long high air temperature (HAT) season (27.40 ± 0.39 °C mean air temperature) on dams' colostrum quality and physiological, biochemical, hormonal, and oxidative stress parameters of their calves during the first 7 days of life. The dams' colostrum was sampled at 2, 14, and 26 h after calving, before feeding of their calves. Calves' blood samples were taken before the first colostrum intake and on days 1, 2, 3, and 7 of life. Calves' physiological parameters were measured on days 0 and 7. HAT season significantly reduced the quality of dams' colostrum. The ingestion of the low-quality colostrum, combined with the thermal discomfort during HAT season, probably provoked impaired physiological, biochemical, hormonal, and oxidative stress parameters in samples taken from the post-colostral calves. Additionally, intravenous glucose tolerance test was performed on day 7, which suggested an enhanced insulin response in HAT season calves. This study highlights the importance of adequate supporting strategies for the care of the late gestation cows and postnatal calves during the HAT season.

SummaryThirty days before expected time of parturition, 20 Holstein cows were divided into ÀCr and +Cr groups. From day 25 before parturition (BP) up to day 30 after parturition (AP), +Cr cows received 10 mg of Cr (chromiumenriched yeast) daily. Muscle and adipose tissue samples were taken at days À30, À10, +7 and +10 related to parturition, when body condition score (BCS) was also determined. Hepatic tissue samples were taken at days À10 and +7. Tissue samples were used for determination of the insulin signalling pathway protein expressions. Intravenous glucose tolerance test (IVGTT) was performed at days À28, À7, +10 and +30. Milk yield was recorded during first 14 weeks AP. Milk composition was obtained at days 7 and 28 AP. At day 10 BP, protein content of b-subunit of insulin receptor (IRb) was significantly higher (p ˂ 0.05) in muscle, and phosphorylation of insulin receptor substrate 1 at serine 307 (pIRS-1 Ser 307 ) was significantly lower (p ˂ 0.05) in hepatic tissue of +Cr group. After parturition, pIRS-1 Ser 307 was significantly lower in muscle tissue at days 7 and 28 (p ˂ 0.05 and p ˂ 0.001, respectively), while phosphorylation of Akt at serine 473 (pAkt Ser 473 ) was significantly higher (p ˂ 0.01) in hepatic tissue at day 7 AP in +Cr group. Chromium had opposite effect on insulin kinetics during IVGTTs obtained BP and AP. Insulin secretion was significantly reduced at day 7 BP and significantly enhanced at day 10 AP, when NEFA concentration was also significantly increased. Milk yield and ECM value were depressed in +Cr group. DMI and BCS were significantly enhanced in +Cr group at day 7 BP. In conclusion, chromium modulates insulin signalling pathway in dairy cows, but targeted signalling molecules are different in antepartal then post-partal period, probably due to duration of exposure to chromium and different energy status between those periods.