Epidemiology and diagnosis of subclinical iodine deficiency in crossbred cattle of Punjab

Objective To determine the prevalence of iodine deficiency in crossbred cow s (taurus x indicus) of Punjab and to assess the diagnostic value of the pl asma concentrations of thyroid hormones, total cholesterol and free fatty a cids in iodine deficiency. The efficacy of ethiodised oil, as a long-term s upplement of iodine, was also evaluated. Procedures Base-line survey of iodine status was conducted by measuring pla sma inorganic iodine (PII) concentration in 48 crossbred cows from 31 dairy units. Concentrations of plasma triiodothyronine (T-3), thyroxine (T-4), t otal cholesterol and free fatty acids were compared between iodine deficien t and normal cows. Circulating T-4 and T-3 concentrations were also determi ned before and after injection of ethiodised oil in cows with low PII level s. Results The mean prevalence of iodine deficiency was 35.9% and showed consi derable geographical variation from 0 to 86% within Punjab. Cardinal clinic al signs of iodine deficiency were absent and basal plasma T3 and T4 concen trations and their ratio did not differ between deficient and control cows. Activity of circulating T4 and T4:T3 ratio increased in response to ethiod ised oil injection and persisted beyond 70 days after injection. Conclusion Asymptomatic iodine deficiency is prevalent in crossbred cows of Punjab and response to iodine supplementation is the most reliable index o f thyroid dysfunction associated with iodine deprivation. The results of th is study also support the view that injection of 1 mL of 78% ethiodised oil can prevent iodine deficiency for more than 70 days.