Abstract :
[en] Iodine (I) deficiency is commonly reported in cattle around the world and is often associated with clinical or sub-clinical diseases. As most of clinical signs are not pathognomonic, diagnosis has to be confirmed by biochemical analyses such as plasmatic inorganic iodine (PII) or urinary I. Different oral mineral forms of I are available in Europe for cattle. The aim of the study was to compare the kinetic of I in blood and urine in non-lactating cows, following oral administration of different forms of I.
Five groups of 6 non-lactating cows (aged 6 ± 2 years, weight 604 ± 89 kg), receiving the same ration (11 kg dry matter) and housed in the same conditions (tied-stall and straw) underwent a double-blinded trial during 2 months. Excepting in Group A (Control), all cows received a daily oral supplementation of I equal to 5 ppm, in the form of Ca(IO3)2 (Group B), KI (Group C), organic form of I 1 (Group D) and organic form of I 2 (Group E). Formulas of the organic forms of I are not public and coverable by patent. Supplementation was stopped at T45. Blood and urine samples were taken at T0, T15, T30 and T60. Thyroxine (T4) was measured at T0, T30 and T60 while PII and urinary I were measured at the 4 times of the trial. Student-t test and multiple comparisons of means (mix crossed model) were used to compare I and T4 concentrations between groups and times.
All characteristics about the cows and I levels in blood or urine were not significantly different at T0 (p>0.1). There was no significant difference (p>0.1) between groups B, C, D, E at the different times of the trial. PII and urinary I in Group A were significantly lower than in other groups (p<0.01) at T15 and T30. Highest concentrations of I (PII up to 242 ± 30 µg/L and urinary I up to 2326 ± 439 µg/L) were reached at T15 for groups B, D and E. At T60, PII (19 ± 4 µg/L) and urinary I (110 ± 29 µg/L) of all groups reached the basal level. A good correlation was found between PII and urinary I (r² = 0.77). No significant differences were found about T4 (67 ± 10 nmol/L) in all groups and times (p>0.1).
PII and urinary I are good markers to assess I nutritional status. No difference was found between either inorganic or organic forms of I, nor between them. Concerning the mineral forms of I, Ca(IO3)2 might be preferably used because of its higher stability in the mineral complexes.
