The objective of this study was to evaluate local molecular adaptations proposed to regulate protein synthesis in the mammary glands. It was hypothesized that AA and energy-yielding substrates independently regulate AA metabolism and protein synthesis in mammary glands by a combination of systemic and local mechanisms. Six primiparous mid-lactation Holstein cows with ruminal cannulas were randomly assigned to 4 treatment sequences in a replicated incomplete 4 x 4 Latin square design experiment. Treatments were abomasal infusions of casein and starch in a 2 x 2 factorial arrangement. All animals received the same basal diet (17.6% crude protein and 6.61 MJ of net energy for lactation/kg of DM) throughout the study. Cows were restricted to 70% of ad libitum intake and abomasally infused for 36 h with water, casein (0.86 kg/d), starch (2 kg/d), or a combination (2 kg/d starch+0.86 kg/d casein) using peristaltic pumps. Milk yields and composition were assessed throughout the study. Arterial and venous plasma samples were collected every 20 min during the last 8h of infusion to assess mammary uptake. Mammary biopsy samples were collected at the end of each infusion and assessed for the phosphorylation state of selected intracellular signaling molecules that regulate protein synthesis. Animals infused with casein had increased arterial concentrations of AA, increased mammary extraction of AA from plasma, either no change or a trend for reduced mammary AA clearance rates, and no change in milk protein yield. Animals infused with starch had increased milk and milk protein yields, increased mammary plasma flow, reduced arterial concentrations of AA, and increased mammary clearance rates and net uptake of some AA. Infusions of starch increased plasma concentrations of glucose, insulin, and insulin-like growth factor-I. Starch infusions increased phosphorylation of ribosomal protein S6 and endothelial nitric oxide synthase, consistent with changes in milk protein yields and plasma flow, respectively. Phosphorylation of the mammalian target of rapamycin was increased in response to starch only when casein was also infused. Thus, cell signaling molecules involved in the regulation of protein synthesis differentially responded to these nutritional stimuli. The hypothesized independent effects of casein and starch on animal metabolism and cell signaling were not observed, presumably because of the lack of a milk protein response to infused casein.

Insulin resistance is a phenomenon which accompanies the ongoing metabolic adaptation in cows during early lactation. The aim of our study was to determine the linear correlations of HOMA (Homeostatic Model Assessment), QUICKI (Quantitative Insulin Sensitivity Check Index) and RQUICKI (Revised Quantitative Insulin Sensitivity Check Index) indexes of insulin resistance with the metabolic status of cows (concentration of hormones, metabolites and body condition score). The experiment included 40 Holstein-Frisian cows in the fi rst week after calving. Indexes of insulin resistance valued: 18.68±5.43 (HOMA), 0.39±0.06 (QUICKI) and 0.45±0.06 (RQUICKI). Linear correlations were examined by testing the coeffi cient of correlation (r), determination (r 2 ,%) and regression parameter beta (b) in linear equation. A negative correlation was found between HOMA and IGF-I (insulin growth factor I) (r=-0.51, r²=25.0, b=-1.1257, p<0.01). HOMA showed a positive correlation with BHB (betahidroxybutyrate) (r=0.48, r²=23.2, b=0.0234, p<0.01). A positive correlation was found between QUICKI and IGF-I (r=0.30, r²=10.0 b=46.7900, p<0.05) and cholesterol (r=0.44, r²=18.3, b=1.9021, p<0.01). In contrast, QUICKI and BHB (r=0.51, r²=27.1, b=-1.7241, p<0.01), just like QUICKI and BCS (r=0.46, r²=20.9, b=-2.424, p<0.01), showed a negative correlation. RQUICKI showed positive correlations with IGF-I (r=0.48, r²=22.8, b=28.1230, p<0.01), T4 (r=0.47, r²=22.1, b=87.142, p<0.01) and triglycerides (r=0.36, r²=13, b=0.0407, p<0.05) but negative correlations with cortisol (r=-0.36, r²=13.0, b=-9.0332, p<0.05), STH (somatotropic hormone) (r=-0.42, r²=17.3, b=-5.4976, p<0.01), BHB (r=-0.62, r²=38.3, b=-1.1872, p<0.01), total bilirubin (r=-0.58, r²=33.7, b=-7.131, p<0.01) and BCS (body condition score) (r=-0.6, r²=36.4, b=-1.8347, p<0.01). In conclusion, indexes of insulin resistance may be used to evaluate the metabolic status of cows in early lactation. RQUICKI might be the most appropriate predictor of metabolic status due to its linear relationship with most of the parameters included in homeorhetic process.

No abstract

Cortisol levels were measured in hair, blood and milk in two different cattle breeds, kept under different breeding conditions and with different genetic merit for milk production. Cows and heifers of Holstein and Busha breeds were selected for the study. Cortisol concentration was determined by immunoassays. Cortisol accumulation was determined in proximal (close to the skin) and distal (far from the skin) segments of the hair shaft. The influence of hair colour and washing prior to extraction and analysis was also examined in order to establish additional factors that may have an impact on hair cortisol concentrations. Concentrations of cortisol determined in the proximal and distal segments of the shaft were significantly higher in Holstein than Busha cows and heifers (P<0.05 and P<0.01, respectively). In Holstein cows, no significant difference was found between concentrations in black and white hair. In hair washed with isopropanol, cortisol concentration was significantly lower compared to unwashed hair (P<0.01). Thus, cortisol concentration in hair varies with the technique of hair processing (washing), but not with colour in Holstein cows. Blood serum cortisol concentrations in Holstein cows and heifers were significantly higher than in Busha cows and heifers, (P<0.01 and P<0.05, respectively). Milk cortisol in Holstein cows was significantly higher than in Busha cows (P<0.05). The higher cortisol concentrations in Holstein cows are assumed to be the result of intensive breeding and physiological adaptation to high milk production.

The aim of this study was to examine the possibility of using results of metabolic profile test in the prediction and diagnosis of fatty liver in Holstein cows. Forty dry cows, 5 to 7 days before calving, were chosen from the commercial dairy herd and included in the study. Four blood samples were taken by jugular venipuncture from each animal: 5 to 7 days before expected calving (dry period), as well as on day 12, 30 and 60 of lactation. Concentrations of glucose, β-hydroxybutyrate (BHBA), total protein, albumin, urea, total bilirubin, calcium and phosphorus concentrations were measured in all blood samples. On day 12 after calving, liver percutaneous biopsies were obtained using a biopsy instrument. Liver tissue lipid content was determined by pathohistological determination. Cows were divided into two groups of equal size based on the degree of lipid accumulation in the liver: healthy cows (0.00 fat, n = 20) and cows with fatty liver syndrome (>20% fat, n = 20). Milking was measured each day from day 7 to day 60 of lactation. Results showed that 5 to 7 days before calving, as well as 12 days after calving, BHBA concentrations were significantly higher (p<0.001, respectively) in diseased cows than in healthy cows. Additionally, the concentration of glucose was significantly lower (p<0.01) and the concentration of total bilirubin significantly higher (p<0.001) in diseased compared to healthy cows, at day 12 of lactation. Thirty days after calving, concentrations of albumin, glucose, BHBA and Ca were significantly lower in diseased compared to healthy cows (p<0.05, p<0.01, p<0.01 and p<0.001, respectively). At day 60 after calving, concentrations of biochemical parameters did not differ between diseased and healthy cows. The lactation curve differed in diseased compared to healthy cows, starting from day 26 of lactation. Starting form that day until day 60 of lactation average daily milk production was significantly higher in healthy than in diseased cows, except on day 32 of lactation when the difference was not significant. Based on these results it can be concluded that the metabolic profile test may be a reliable tool for the prediction and diagnosis of fatty liver in Holstein cows

The aim of this study was to examine changes in some hormones concentrations in calves during the first 32 hours of neonatal life and to estimate their association with glycemia. Thyrty two Holstein breed calves were selected for the study. Blood samples were taken at 30, 60 and 90 minutes postnatal. Calves received pooled colostrum: primary colostum (1.5 L, 2 hours after birth), secondary colostrum (2 L, 14 hours after birth) and tertiary colostrum (2 L, 26 hours after birth). Blood samples were taken at hours 5, 20 and 32 of neonatal life. Concentrations of glucose, insulin, cortisol, thyroid hormones and IGF-I and abundance of IGFBP-1, IGFBP-2 and IGFBP-3 were determined in the blood serum. The T3/T4 ratio was also calculated. Calves were born hypoglycemic (glycemia was 2.56±1.05 mmol/L at birth). Thereafter, glycemia significantly increased (p<0.001) to 3.05±0.89 mmol/L at min 90. Glucose concentration showed a further increase after colostrum intake and was significantly higher than at the initial value in all examined periods (p<0.001). During the first 90 minutes of neonatal life insulinemia decreased significantly (p<0.001) compared to initial value (26.33±10.05 μIU/L) and it measured 18.66±5.56 μIU/L at min 90. Cortisolemia was highest at minute 30 (85.08±19.36 nmol/L) and than decreased until the end of the experiment (p<0.001) compared to initial values in samples obtained during the period of colostrum intake. A significantly high correlation was determined between glycemia and cortisolemia in all examined periods before the first colostrums intake (r2=0.854; p<0.01 at min 30; r2=0.742; p<0.01 at min 60 and r2=0.551; p<0.01 at min 90). T4 concentrations significantly increased during the first 2 hours, while T3 concentrations decreased, significantly from min 30 to min 90 postnatal (p<0.05). T3/T4 ratio significantly increased during the first 2 hours of neonatal life. After first colostrum intake, concentrations of both hormones rose significantly compared to the initial level, but T3/T4 ratio did not change and maintained the value determined at minute 90. IGF- 1 concentrations significantly decreased during the first 2 postnatal hours. A significant positive correlation was observed between IGF-1 concentration and insulinemia (r2=0.463; p<0.05 at min 30, r2=0.662; p<0.01 at min 60 and r2=0.583; p<0.01 at min 90). IGFBP-3 abundance significantly decreased, while IGFBP-1 significantly increased in this period. IGFBP-2 abundance was highest at birth. Results presented in this study indicate that the increase in glucose concentration during the first 2 hours of neonatal life, before the first colostrum intake is mainly the result of increased activity of the adrenal cortex in cortisol secretion and extrathyroidal tissue thus providing sufficient triiodothyronine. Immaturity of mechanisms responsible for insulin secretion provides the dominance of catabolic processes. Changes of the IGF system provide a rise of glucose concentration...

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 aim of this study was to assess the significance of body condition scoring and metabolic profile test for estimation of energy status of healthy high-yielding dairy cows. Twenty one healthy cows (primiparous and secundiparous) were divided into three groups: dry cows, early puerperal cows and early lactating cows. Cow's energy status was estimated by the analysis of blood samples for beta-hydroxybutirate (BHBA) and glucose. Additionally, urea, total bilirubine and total protein were measured in blood serum samples. According to body condition scores (BCS) results dry cows were overweight (4.03±0.29 points). Immediately after calving, cows lost their weight significantly, since BCS was 2.85±0.46 points at puerperal period and 3.12±0.33 points at day 60 of lactation (p<0.001 compared to dry period, respectively). Glucose concentration did not change significantly between dry and puerperal period, while BHBA increased significantly (0.46±0.14 mmol/l at dry period to 1.08±0.21 mmol/l at puerperal period; p<0.001). Urea concentration did not change significantly during examined period. Total bilirubin concentration significantly increased from dry (6.31±0.37 mmol/l) to puerperal period (7.63±2.52 mmol/l; p<0.001 compared to dry period) and remained high until day 60 of lactation (7.62±0.13 mmol/l; p<0.001 compared to dry period). Total protein concentration decreased from dry to puerperal period (69.59±6.14 g/l to 58.87±3.29 g/l; p<0.001). According to obtained results it can be concluded that cows were not in adequate energy status during transition period. Our results also indicate that, body condition scoring, BHBA and total bilirubin concentrations can be used as reliable indicators of cow's energy status even when there are not clinically visible health disorders.