The effect of fasting and refeeding on total antioxidant status (TAS), glutathione peroxidase (GSH-Px) activity and concentration of some non-enzymatic antioxidant compounds was studied in cockerels and pullets. Blood was collected before and after 48-h fasting and 24 h after refeeding. In cockerels, fasting resulted in a significant decrease of TAS and uric acid concentration. After refeeding, the concentration of TAS remained significantly lower as compared to the control level. At the same time, blood plasma level of total lipids increased in comparison to the control and post-fasting values. In pullets, fasting resulted in a significant decrease of whole blood haemolysate GSH-Px activity and blood plasma concentrations of albumin and uric acid. Simultaneously, a significant increase in total lipids and cholesterol was obtained. In pullets, refeeding resulted in a further decrease of TAS to undetectable values, a significant decrease of blood plasma cholesterol, and a significant increase of GSH-Px in the whole blood haemolysate and in blood plasma uric acid content. The results indicate that fasting has a negative impact on the antioxidant defence system of the blood, which leads to a reduced resistance to oxidative stress in both cockerels and pullets. However, pullets seem to be more susceptible to fasting-provoked oxidative stress than cockerels.Key words: Antioxidant system, cockerel, pullet, fasting, refeeding Reactive oxygen compounds are produced continuously in most living organisms as a consequence of normal metabolic processes. Aerobic organisms,

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e susceptibility of erythrocyte lipid to in vitro peroxidation as measured by TBARS (thiobarbituric acid-reactive substances) and concentration of reduced glutathione (GSH) in whole blood and erythrocyte suspension before and after incubation with hydrogen peroxide was assessed in ducks, chickens and pigs. A high susceptibility of erythrocytes to peroxidation in vitro was observed in all animals tested, but this susceptibility was of different intensity. Pig erythrocytes exhibited the lowest resistance to oxidative stress in vitro as compared with that in ducks (P < 0.01) and chickens (P < 0.02). A high level of GSH in the erythrocytes of ducks and chickens offers higher resistance to oxidative stress in comparison with that in the pig erythrocytes.

The milk composition and concentration of thiobarbituric acid reactive substances (TBARS) and superoxide dismutase (SOD) activity in fresh and refrigerated raw goat milk of Saanen and Alpine breed at the breeding period were investigated. Low average milk fat, SNF and lactose content were determined in both breeds with no significant differences between breeds regarding the milk yield and milk composition. The significantly higher somatic cell count (SCC) was detected in Saanen goats. The SOD activity and TBARS concentration were significantly higher 14 h after the collection and cold storage in both breeds of dairy goats with no difference between the breeds. In the Alpine goats the TBARS concentration was negatively correlated with urea concentration, and in the milk of the Saanen goats the TBARS was positively correlated with proteins and SCC. The higher SCC in the Saanen goats may have caused higher production of secondary oxidative products catalysed by the enzyme superoxide dismutase from polymorphonuclear granulocytes present in the udder, or by some other enzymes that participate in oxidation of the milk constituents. The energy shortage and protein surplus in the diet of the dairy goats may have induced the higher degree of lipid mobilisation and a consequent increase of polyunsaturated fatty acids (PUFA) that are easily prone to oxidation and formation of the secondary oxidative products.Keywords: goat, raw milk, milk components, peroxidation, quality Zusammenfassung Oxidative Stabilität und Qualität der Rohmilch von Saanen-und AlpenziegenUntersucht wurde die Milchzusammensetzung, die TBARS-Konzentration (Thiobarbitursäurereaktive Substanzen) und die SOD-Aktivität (Superoxiddismutase) in frischer und gekühlter Rohmilch von Saanen-und Alpenziegen während der Fortpflanzungszeit. Zwischen beiden Rassen bestanden keine signifikanten Unterschiede bei der Milchleistung und der Milchzusammensetzung, wobei ein relativ niedriger Fett-, Laktosegehalt und ein niedriger Wert für die Trockensubstanz nachgewiesen wurden. Bei den Saanenziegen ergab sich ein höherer somatischer Zellgehalt (SCC). 14 Stunden nach der Milchgewinnung und Kühlhaltung waren in der Milch die TBARS-Konzentration und die SOD-Aktivität signifikant höher, wobei zwischen den Rassen keine Unterschiede ermittelt wurden. Eine negative Beziehung fand sich zwischen dem TBARS-Wert und dem Harnstoffgehalt bei den MARENJAK et al.: Oxidative stability and quality of raw Saanen and Alpine goats milk 638 Alpenziegen, positiv war bei den Saanenziegen die Beziehung zwischen dem TBARS-Wert und dem Eiweiß-sowie SCC-Gehalt. Der höhere SCC-Gehalt war möglicherweise die Ursache für eine höhere Erzeugung von sekundären Oxidationsprodukten verursacht durch die Superoxiddismutase und den im Euter vorhandenen polymorphkernigen Granulozyten oder anderen Enzymen die an der Oxidation der Milchinhaltstoffe teilnehmen. Energiemangel und Eiweißüberschuss in der Ernährung von Milchziegen verursacht möglicherweise die höhere Lipidmobilisation und folglich die Erhöhun...

ZusammenfassungIn vorliegender Untersuchung sollten die Veränderungen der Kalzium-, Phosphor-und Changes of calcium, phosphorus and magnesium in the blood plasma of holstein mares during gravidity and early lactation High productivity in domestic animals, particularly gravidity, cause an additional metabolic encumbrance. During the gravidity, especially in its end and during the period of lactation, in the process of the change of substances there has been noticed an increased need for minerals both as building elements and the originators of a whole sequence of metabolic systems which are considered the parts of enzymes. The research has been made on six Holstein breed mares aging from 5 to 10 years. During the gravidity and in the early lactation the blood for analysis was taken for three times by venepuncture performed on the jugular vein with heparin as antikoagulant. The blood was taken on three occasions during the gravidity: within the first third of gravidity (till 15th week), the second third of gravidity (between 16th and 30th week) and the last trimestar (from 31st week till a foaling). The last sampling was during early lactation. The blood plasma was separated by centrifugation at 1500g for 15 minutes. The concentration of the minerals in blood plasma has been determined spectrophotometrically with a commercial set. Plasma calcium concentration decreased significantly (p<0,05) during second trimester of the gravidity in comparison with the first and third trimester. But, during the last third of the gravidity the concentration of calcium increased significantly (p<0,05) comparing to the results obtained in the first and fourth period of experiment. The concentration of phosphorus in blood plasma of the mares in the high stage of gravidity and in the beginning of lactation was significantly lower compared with the beginning of the gravidity (p<0,05), while during the second trimester significant increase of concentration was noticed (p<0,05) in comparison to third and fourth trimester. During the first trimester of gravidity, magnesium concentration was significantly higher than those measured at the early lactation period (p<0,05). Comparing to the previous observation, the last trimester was characterized by the significant increase, in consideration of the second and fourth experimental periods (p<0,05). According to the results of research the changes of the concentration of minerals in blood plasma during the period of gravidity and early lactation are closely connected with the metabolic processes which develop during the observation period and with their role in a metabolic process.