Exploring the Role of Iodine and Thyroid Hormone in Abnormal Metestrus Bleeding Associated Repeat Breeding and Silent Estrus in Cows of the North Eastern State of Assam in India

Background: The present study documents the association of repeat breeding and silent estrus in cows with iodine deficiency, hypothyroidism and abnormal metestrus bleeding in high-producing Jersey and Holstein Friesian crossbred cows of Assam in India.Methods: The field based study was conducted involving 470 Holstein Friesian and Jersey crossbred cows in Assam of North East India during the period August, 2021 to July, 2022. Out of 470 crossbred cows investigated, 62 (13.00%) with repeat breeding and abnormal metestrus bleeding (Group-A), 18 (3.83%) were diagnosed as silent estrus (group-B) and 6 with normal breeding history (Group-C) without the signs of metestrus bleeding were randomly selected for the study. The cows belonging to all the 3 groups were subjected to serum T3, T4 and iodine estimation.Result: 42 (67.74%) crossbred cows in group A (n=62) and 13 (72.22%) in group B (n=18) were diagnosed to have hypothyroidism including Iodine deficiency. The overall incidence of hypothyroidism out of 470 cows was 11.70%. Group C showed significantly higher T3 and T4 levels than groups A and B. Thus, it concluded that iodine deficiency-induced hypothyroid condition might be attributed to the causes of abnormal metestrus bleeding associated with repeat breeding and silent estrus in high-producing crossbred cows of Assam in India.