Niacin, Metabolic Stress and Insulin Resistance in Dairy Cows

The periparturient period in cows is associated with metabolic stress and a state of negative energy balance, which are characterized by increased lipolysis, ketogenesis, hepatic steatosis, oxidative stress and insulin resistance. Such metabolic changes may exert adverse effects on the health and milk yield of lactating cows. The pharmacokinetics of niacin in ruminants is specific as rumen microorganisms facilitate both the synthesis of tryptophan and the degradation of niacin. Niacin administration to cows leads to an increase in the coenzyme activity, encompassing the activity of nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). These coenzymes are actively involved in the metabolism of lipids and carbohydrates, whereas NAD protects the organism from oxidative stress. In periparturient cows, the supplementation of niacin has been found to induce depressed lipolysis and a limited impact of nonesterified fatty acids on all metabolic processes. It also results in decreased lipid peroxidation regardless of the magnitude of lipolysis in the periparturient period. Furthermore, niacin reduces the concentration of ketone bodies, thus preventing the development of fatty lever disease and ketosis in cows. The anti-inflammatory effect of niacin is manifested in stimulating the secretion of adiponectin and inhibiting immune cells

Cure characteristics of recycled rubber powder filled styrene butadiene /chlorosulphonated polyethylene rubber blends

The effect of recycled rubber powder (RRP) on cure characteristics of styrene butadiene and chlorosulphonated polyethylene rubber blends (SBR/CSM) was investigated in the concentration range of 0 to 20 phr. Results indicate that the minimum torque and Mooney viscosity of the SBR/CSM rubber blends increase with increasing RRP loading whereas the scorch time and cure time exhibit a decreasing trend. Increasing RRP loading also gives SBR/CSM rubber compounds reduces the elongation at break but the tensile stress, M 200 (stress at 200% elongation) increases slightly.Physical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200

The influence of dual active fillers on curing characteristics of elastomers based on natural rubber and chlorosulphonated polyethylene rubber

The effects of two type active filler (carbon black and silica) on the characteristics of elastomers based on natural rubber and chlorosulphonated polyethylene rubber blend blend (NR/CSM) were investigated. For cure studies, torque-time curves were registered at different temperatures (150, 160 and 170°C). It was estimated that higher curing temperature cause decreas of the cure plateau torque and lead to higher crosslinking rate constant.Physical chemistry 2008 : 9th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 200

Polymer based nanocomposites

Dispersions consisting of spherical CdS and α-Fe2O3 particles in the nanometer and sub-micron size range, as well as β-FeOOH nanorods with three different aspect ratios were prepared using colloidal chemistry methods. After incorporation of filler particles into polystyrene and poly(methyl methacrylate) matrices influence of filler particles on the thermal stability and the glass transition temperature of polymer matrices was studied in details. Significant influence of content, size and shape of filler particles on thermal properties of polymer matrices was found.Physical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200

Blood Serum Stability Limit and Maximum Storage Time of Bovine Samples

Background: Measuring metabolic parameters in the blood has been an indispensable tool for assessing the productive and health status of dairy cows for more than 100 years. The values of laboratory parameters depend on various preanalytical, analytical and postanalytical factors. The most important preanalytical factors are sample transport time and temperature, hemolysis, anticoagulant type, and sample volume.Preanalytical factors can lead to reduced stability of the analyte in the sample, which changes their concentration. Loss of stability changes the time of storage and manipulation of the sample, which determines the criteria for its acceptance or rejection. The two stability indicators are stability limit and maximum permissible instability. A stability limit (SL) is defined as the period of time in which a property variation does not exceed a maximum permissible instability (MPI). The aim of this study was to determine the SL and MPI for each analyte in the blood serum of cows and to determine whether SL differs in the function of the presence of preanalytical errors in the blood sample.Materials, Methods & Results: Three hundred samples of dairy cow origin in different periods of lactation participated in this research. They were classified into 6 groups of 50 samples: according to the time from sampling to processing in the laboratory (0-4 h, 4-8 h and over 8 h; all transported on dry ice, protected from environmental factors, without preanalytical errors) and according to the presence of preanalytical errors (group with hemolysis, a group transported at ambient temperature and a group with a small sample volume). Each sample was aliquoted in two portions. One portion was left at +4°C and tested once a day for 6 days of sample storage, and the second portion, placed at -20 °C, was tested once a month for 6 months. The MPI had a value ranging from 1.55 to 8.4. Metabolic profile analytes with lower MPI values (1.51-3.22) were albumin (ALB), total protein (TPROT), UREA, glucose (GLU), calcium (Ca), and phosphorus (P). Higher MPI values (5.1-8.3) were found for nonesterified fatty acids (NEFA), beta-hydroxybutirate (BHB), cholesterol (CHOL), triglycerides (TGC), total bilirubin (TBIL) and aspartat aminotransferase (AST). For most parameters, we can conclude that their PD% changed faster in storage conditions at +4 °C compared to the regime of -20 °C. The largest number of biochemical analytes in bovine blood serum shows preserved stability in the first 6 days at +4°C or 6 months at -20°C if transported to the laboratory within 8 h after sampling in ideal conditions and without the action of preanalytical errors. Prolonged transport under ideal conditions or the existence of preanalytical errors such as transport at room temperature, hemolysis or small sample volume shorten the stability of the ALB, NEFA, GLU, UREA and P. Concentration of all analytesdecreasesduring the stability test except for UREA, NEFA, BHB and for CHOL and TGC in some groups. Variations in parameters such as BHB, NEFA, TBIL, AST, and Ca have shown potential clinical significance. At storage conditions at +4°C, clinically significant variations at at least one measurement point were found for AST (7.5% of samples), BHB (6.1% of samples), NEFA (9.9% of samples) and for TBIL (in 7% of samples).Discussion: This study can help define acceptable delay times and storage conditions for bovine blood samples, which is of great importance because in working with farm animals it is often not possible to take samples in a short time and deliver them to the laboratory, and samples are often burdened with certain preanalytical errors with limited possibilities of re-sampling

Relationship between the indexes of insulin resistance and metabolic status in dairy cows during early lactation

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 first 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 coefficient 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, r(2)=25.0, b=-1.1257, p<0.01). HOMA showed a positive correlation with BHB (beta-hidroxybutyrate) (r=0.48, r(2)=23.2, b=0.0234, p<0.01). A positive correlation was found between QUICKI and IGF-I (r=0.30, r(2)=10.0 b=46.7900, p<0.05) and cholesterol (r=0.44, r(2)=18.3, b=1.9021, p<0.01). In contrast, QUICKI and BHB (r=0.51, r(2)=27.1, b=-1.7241, p<0.01), just like QUICKI and BCS (r=0.46, r(2)=20.9, b=-2.424, p<0.01), showed a negative correlation. RQUICKI showed positive correlations with IGF-I (r=0.48, r(2)=22.8, b=28.1230, p<0.01), T4 (r=0.47, r(2)=22.1, b=87.142, p<0.01) and triglycerides (r=0.36, r(2)=13, b=0.0407, p<0.05) but negative correlations with cortisol (r=-0.36, r(2)=13.0, b=-9.0332, p<0.05), STH (somatotropic hormone) (r=-0.42, r(2)=17.3, b=-5.4976, p<0.01), BHB (r=-0.62, r(2)=38.3, b=-1.1872, p<0.01), total bilirubin (r=0.58, r(2)=33.7, b=-7.131, p<0.01) and BCS (body condition score) (r=-0.6, r(2)=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

Određivanje aktivnosti specifičnih enzima krvi u peripartalnom periodu i tokom pune laktacije

This study examined the activities of aspartate-aminotransferase (AST), gamma-glutamyl-transferase (GGT) and lactate-dehydrogenase (LDH) in the blood serum of 45 dairy Simmental cows divided into three groups according to production period. The first group (n=15) consisted of late pregnant dairy cows, the second group (n=15) cows in the early lactation, and the third group (n=15) cow in mid lactation. The significant higher activity (P (lt) 0.05) of AST, GGT and LDH were determined in the early lactation period than in dry period and during full lactation. Research results showed possibility of mild degree of hepatic lesions, probably due to fat infiltration in early lactation cows. Serum AST enzyme activities were significant correlated (P (lt) 0.05) with GGT and LDH activities and may be most sensitive indicator.U ovom radu je određivana aktivnost aspartat-aminotransferaze (AST), gama-glutamat-transferaze (GGT) i laktat dehidrogenaze (LDH) u krvnom serumu kod 45 simentalskih mlečnih krava, podeljenih u tri grupe u zavisnosti od produktivnog perioda. Prvu grupu (n=15) su činile visoko gravidne krave, drugu grupu (n=15) krave u ranoj laktaciji, a treću grupu (n=15) krave tokom pune laktacije. Statistički značajno veće aktivnosti AST (P (lt) 0.05),GGT (P (lt) 0.05) i LDH (P (lt) 0.05) u krvnom serumu su utvrđene kod krava u ranoj laktaciji u odnosu na aktivnosti ovih enzima u serumu kod zasušenih krava i krava u punoj laktaciji. Dobijeni rezultati ukazuju na mogućnost blagog stepena oštećenja ćelija jetre, odnosno masnu infiltraciju hepatocita kod krava na početku laktacije. Serumske aktivnosti AST su bile u značajnoj korelaciji (P (lt) 0.05) sa aktivnostima GGT i LDH u krvnom serumu pa se AST može smatrati pouzdanim indikatorom u tvrđivanju funkcionalnog stanja jetre kod mlečnih krava tokom peripartalnog perioda i pune laktacije

Thermal ageing and γ-radiation resistance of polyisoprene /chlorosulphonated polyethylene rubber blends

The effect of carbon black (average particle size 26nm) and wood flour (particle size from 300 to 400 μm) on thermal ageing and γ-radiation resistance of polyisoprene /chlorosulphonated polyethylene rubber blend (NR/CSM) was studied. The tensile strength of the aged samples was determined, after conditioning at 70°C during 72h. The radiation exposure of samples was performed at two doses: 212 and 400 kGy.Physical chemistry 2008 : 9th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 24-28 September 200

Influence of claw disorders on milk production in Simmental dairy cows

A study on claw disorders’ infl uence on milk production was performed during one year on 226 Simmental loose-reared cows. The first trial group included 42, the second 37, and the third 34 cows, with claw changes observed in the first hundred days of lactation, between days 101 and 200, between days 201 and 305, respectively. The control group included 113 cows with no observed changes. Lameness intensity was assessed once a week. Milk yield data were collected three weeks before, in the week of treatment of claws and three weeks afterwards. There were significantly more cows with lameness in the third group than in the other two groups, as well as the most cows with one aff ected limb in the first hundred days of the lactation (P<0.05). Significantly fewer cows with two aff ected limbs were present in the first group. In the second group, more cows were observed with two aff ected limbs than in the first group (P<0.05). In the third group, more cows with three or four aff ected limbs were noticed than in the other groups. The most common claw disorders were: solar ulcer, laminitis, dermatitis digitalis and overgrown claws. Cows whose claws were aff ected between days 101 and 200 of lactation period produced 231 kg less milk than those of the control group; cows whose claws were aff ected in the last third of lactation produced 26 kg less milk. Nevertheless, no significant diff erences were found between milk yields of the control and trial groups (P>0.05). Cows aff ected in the first third of lactation produced less milk (324 kg) than both healthy and cows with claw changes manifested in later stages of lactation. Obtained data confirm that claw disorders may aff ect dairy production

The influence of carbon black on curing kinetics and thermal aging of acrylonitrile–butadiene rubber

Elastomers based on a copolymer of butadiene and acrylonitrile (NBR) have excellent oil resistance but are very sensitive for degradation at very high temperatures. The aim of this applicative contribution was to determine the effect of high abrasion furnace carbon black with primary particle size 46 nm on aging properties of elastomeric materials based on NBR as network precursor. The curing kinetics was determined using the rheometer with an oscillating disk, in which the network formation process is registered by the torque variation during time. The vulcanizates were obtained in a hydraulic press at 150 °C. The mechanical properties of elastomeric composites were determined before and after thermal aging in an air circulating oven. The reinforcing effect of the filler particles was assessed according to mechanical properties before and after aging