This study assessed the changes of plasma vitamin A, E, and C and the lipid peroxidation status of sheep during breeding and pregnancy under drought conditions. The study was conducted on 105 cross-bred fat tailed ewes, 3-5 years old with body condition scores (BCS) of 2.5 to 3.5. The ewes were grazing on medium-to-low quality forages during summer and low quality forages within the succeeding months and had ad libitum access to a mixture of alfalfa hay (40%) and wheat straw (60%) in the afternoons. From 3 weeks before breeding till 1 month after the introduction of rams, 300 g of barley grain/head/day was offered to the ewes and then the supplemental grain was reduced to 100 g/head/day. For better synchronization of estrus cycles in ewes, they were isolated from the rams for at least 2 months and then kept in close proximity of the rams for 1 week before the introduction of the rams to the ewe flock. Then, whole blood samples were collected on days 1, 7, 21, and 120 after ram introduction. Vitamins A, E, and C were measured in plasma. Malondialdehyde (MDA) was measured in the hemolysate as a biomarker of lipid peroxidation. Plasma progesterone (P4) was measured in the samples of day 120 for assessing pregnancy status of the ewes. Vitamins A and C showed continuous and significant declines (P < 0.05) through days 1 to 120. Vitamin E declined only during the first 21 days of the study and remained almost constant till day 120. MDA concentration increased significantly at day 21. An elevated concentration of MDA was also detected at day 120. The difference between days 21 and 120 was not significant (P > 0.05). A positive correlation between vitamins E and C was detected at day 120 (r = 0.349, P < 0.01). Age and BCS did not affect the patterns of changes. Assuming that the ewes with P4 concentrations ≥2.5 ng/ml were pregnant, 95 out of 105 ewes (90.5%) were pregnant at day 120 of the study. Under the conditions of the present study with medium-to-low quality pastures as the main sources of feed, ewes of various ages and body conditions may suffer from oxidative stress during breeding and pregnancy.

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Serum concentrations of very low-density lipoproteins (VLDL), low-density lipoproteins (LDL), high-density lipoproteins (HDL), triglycerides, cholesterol, and total lipids of a group of monensin-treated cows (n = 7) were compared with those of a control group (n = 6) from about 10 days before calving to 45 days postpartum. Monensin was fed in the diet from about 20 days before predicted calving date to 45 days after parturition. Blood samples were obtained on days 20 and 10 before predicted calving, and on days 4, 15, 25 (phase I), and days 35 and 45 (phase II) post calving. Cholesterol (p = 0.046) and total lipids (p = 0.003) were lower in the treatment group 10 days before calving. Concentrations of serum triglycerides and VLDL (p = 0.017), and that of LDL (p = 0.032) were significantly higher in the treatment group in phase I postpartum. No significant difference was detected between groups during phase II. Comparison of the entire length of the trial showed higher concentrations of triglycerides and VLDL in the treatment group (p = 0.009). It is concluded that monensin is effective in increasing secretion of triglyceride-rich lipoproteins from the liver during the postpartum transition period of dairy cows. This may be effective in reducing the intensity of hepatic lipidosis and the incidence of periparturient diseases resulting from disturbances in energy metabolism.

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