SEASONAL-VARIATION IN THE CONCENTRATION OF VITAMIN-A AND VITAMIN-E INTHE BLOOD-PLASMA OF FAT-TAILED SHEEP

Six non-pregnant ewes and 6 rams (age: 3-4 years) of an Iranian fat-ta iled sheep breed (Shall were used. Blood samples were collected monthl y for 12 months, and the concentrations of retinol and alpha-tocophero l were determined by high-performance liquid chromatography (HPLC). A limited ration of standard composition was fed throughout the year. Th e ration was supplemented with 25-32 IU alpha-tocopherol/animal/day. V itamin A concentrations in the blood plasma of ewes were lower in the spring (442 +/- 9 mu g/L) and summer (452 +/- 7 mu g/L) and higher in the autumn (467 +/- 5 mu g/L). In the rams, the plasma concentration o f vitamin A was the lowest in the spring (436 +/- 6 mu g/L) and the hi ghest in the summer (471 +/- 5 mu g/L). A seasonal comparison did not show statistical differences between consecutive seasons for the ewes (P > 0.05). The differences were significant between winter and spring (P < 0.05) and spring and summer (P < 0.001) for the rams. The blood plasma concentration of vitamin E was 1.21 +/- 0.05, 1.04 +/- 0.05, 1. 24 +/- 0.05 and 1.24 +/- 0.08 mg/L in spring, summer, autumn and winte r, respectively, for the ewes and 1.24 +/- 0.05, 1.11 +/- 0.06, 1.09 /- 0.04 and 1.38 +/- 0.07 mg/L in spring, summer, autumn and winter, r espectively, for the rams. The values were significantly different bet ween spring and summer (P < 0.05) and summer and autumn (P < 0.01) for the ewes. In rams, the values obtained in autumn also showed a signif icant difference (P < 0.001) from those found in winter. Differences b etween values found in other seasons were not significant (P > 0.05). The retinol and alpha-tocopherol concentrations of the blood plasma we re highly similar in the two sexes. The concentrations of retinol in t he summer (P < 0.01) and alpha-tocopherol in the autumn (P < 0.05) sho wed significant differences between the two sexes. The results show th at the concentrations of vitamins A and E are relatively constant in t he blood plasma of fat-tailed sheep kept on a standardised feed. Howev er, some differences due to the influence of season and sex were obser ved.