The inclusion of phenolic compounds enhanced growth performance, decreased lipid oxidation, decreased cholesterol value and increased beneficial fatty acids content. Positive effects varied depending on phenolic compound used and, therefore, it would be interesting to further investigate synergistic effects of investigated phenolic compound.

Abstract. Transition dairy cows often enter a stage of negative energy balance during which the utilization of energy reserves is reflected in the milk fatty acid (FA) composition. In this study, metabolic status was evaluated by measuring milk FA, ruminal short-chain FA (RSCFA), and serum biochemical parameters in Holstein cows. Samples (milk, rumen contents, and blood) were collected around days 30 (early) and 150 (middle) of lactation, and rumen contents and blood samples were collected 30 days before calving (dry). Fatty acids were extracted and FA composition was determined. Glucose, triacylglycerols, total cholesterol, low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C), beta-hydroxybutyric acid (BHB), and non-esterified fatty acid (NEFA) concentrations were determined in serum samples. Lower percentages of saturated FA in milk and higher percentages of monounsaturated FA, polyunsaturated FA, and C18:1n-9 were observed in early lactation compared to mid-lactation. In rumen higher concentrations of propionic acid were determined at mid-lactation compared to early lactation. Acetic and butyric acid concentrations showed no significant differences between sampling intervals. In serum higher glucose concentrations were observed during the dry period and mid-lactation than during early lactation. Lower BHB and higher NEFA concentrations were noted during early lactation compared to mid-lactation and the dry period. Total cholesterol, LDL-C, HDL-C and triacylglycerols showed no significant differences between sampling intervals. The results of the present study suggest that determination of milk FA is a potential indicator of energy status in dairy cows.

A feeding trial was conducted to evaluate the influence of live yeast culture (Saccharomyces cerevisiae) on milk production, composition, and blood biochemistry of dairy ewes during the machine milking period.The control group (CD) was fed a concentrate mixture and hay and grazed twice daily, while the second (YS3) and third (YS6) groups were fed the same diet supplemented with 3 or 6 g of live yeast culture (Yea Sacc 1026 ), respectively. The treated groups had significantly higher values (p < 0.05) for fat corrected milk (FCM) (1221, 1116 and 940 g/day, for YS6, YS3 and CD group, respectively) and fat-protein corrected milk (FPCM) (1204, 1103 and 931 g/day, for YS6, YS3 and CD group, respectively), while the values for milk yield, fat yield and lactose yield were higher (p < 0.05) only in the YS6 group compared to the CD group. Milk yield values were constantly higher in the YS6 group than in the control group while the values for the YS3 group were more variable during milking. Milk composition was not significantly affected by yeast supplementation with the exception of urea values which were lower (p < 0.05) in the YC6 group. Yeast administration influenced β-hydroxy-butyrate (BHB) values, which were higher (p < 0.05) in the treated groups; and non-esterified fatty acids (NEFA) values, which were higher (p < 0.05) only in the YS6 group compared to the control group. Other blood biochemistry values were not influenced by the treatments.We conclude that supplementation with live yeast culture, under the conditions of our experiment, had a significant effect on the performance and metabolism of grazing dairy ewes during the machine milking period. Based on more constant results, we could recommend the inclusion of live yeast culture (Yea Sacc 1026 ) at 6g/animal/day as appropriate for field conditions.

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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,