Iodine supplementation restores fertility of sheep exposed to iodine deficiency.

The aims of the study were to monitor sheep iodine intake in different sheep breeding farms in Abruzzo and to evaluate the effects of iodine supplementation on ovine fertility. The urinary iodine concentrations (UIC) in animals of 8 out of the 11 breeding farms analyzed were borderline (UIC 100-150 microg/l) or very low (UIC < or = 50 microg/l). Only animals bred in 3 farms showed an adequate iodine intake with a mean UIC > or = 300 microg/l. Animals with very low iodine intake had lower T4 and T3 (p < 0.01) serum levels, compared to those with adequate iodine intake. To investigate the effects of iodine supplementation on ovine fertility, 32 ewes and 20 rams, characterized by low UIC, were randomly divided into 2 groups. One group (16 ewes and 10 rams) received a sc injection of 1 ml of Lipiodol, containing 480 mg of iodine, while the remaining animals were employed as control. This treatment was able to maintain UIC above 300 microg/l for 3 months and to increase T4 and T3 serum levels (p < 0.01). After 9 months, the fertility of control and treated animals was assessed by monitoring the rate of successful matings by ultrasonography. The results showed that 100% of treated ewes mated with treated rams were pregnant vs 37% of the control ewes mated with control rams (p = 0.007). The iodine content was 4-fold higher in milk from treated ewes (2393 +/- 453 microg/l), compared to controls (675 +/- 154 microg/l). The results demonstrated that iodine supplementation restores fertility of sheep living in iodine deficient areas and may represent a means to achieve a silent iodine prophylaxis of local populations.