Stillbirth/perinatal weak calf syndrome: a study of calves with an abnormal thyroid gland

Data collected from 365 calves dead from stillbirth/perinatal weak calf syndrome were analysed to determine the predictive value of thyroid gland weight as an indicator of abnormality of the thyroid gland, and to examine the relationships between abnormality of the thyroid gland and other findings in the calves and also the parity of the dam. There was a significant relationship (P < 0.001) between the thyroid gland weight and bodyweight for the calves with a histologically normal thyroid gland, but there was no such relationship for calves with an abnormal thyroid gland. Only 1.1 per cent of the histologically normal thyroid glands weighed more than 30 g, indicating that there is a very high probability that glands weighing more than 30 g are abnormal. However, 76.0 per cent of moderately to severely affected glands weighed less than 30 g. The following significant differences between calves with an abnormal and those with a normal thyroid gland were established. Abnormal thyroid glands were significantly heavier (P < 0.01), constituted a significantly greater percentage of the calf's bodyweight (P < 0.01) and had a significantly lower iodine concentration (P < 0.001). A significantly higher proportion of calves with an abnormal thyroid gland had uninflated lungs (P < 0.01), and a significantly higher proportion had pneumonia (P < 0.01). Abnormal thyroid glands were associated with a low selenium concentration in the kidneys. There were no associations between abnormalities of the thyroid gland and the parity of the dam, the presence of skeletal fractures, the weight or sex of the calf, infection with leptospira, Salmonella dublin, Bacillus species, Actinomyces pyogenes or Aspergillus species, the quantities of hepatic iron pigment, liver vitamin E concentration or serum cholesterol concentration.