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ABSTRACT. Maximum serum thyroxine (T 4 ) and triiodothyronine (T 3 ) levels of healthy calves were seen at 1 day after birth, and thereafter rapidly decreased until 5 days after birth. They stabilized until 2 weeks after birth, then gradually decreased until 4 weeks after birth. Serum T 4 levels of calves with endemic goiter tended to be lower than those of healthy ones, but showed similar levels to those of adult cows. T 3 levels of calves with goiter were similar to those of healthy ones, but showed higher variation. T 4 /T 3 ratio of calves with goiter were significantly lower than those of healthy ones and adult cows. While individual levels of serum T 4 and T 3 at just after birth could not be considered as a diagnostic index, the T 4 /T 3 ratio could be adopted as a diagnostic index of endemic goiter. The histopathological changes of an enlarged thyroid gland together with other evidence of hypothyroidism are necessary to diagnose endemic goiter in newborn calves [6,9,11]. However, since the energy metabolic rate is higher in newborn calves, thyroid hormone levels may be more variable just after birth. In this paper, the thyroid hormone levels of calves with goiter were compared with those of healthy calves and adult cows to investigate a possible diagnostic index of endemic goiter in calves.Six healthy Holstein calves were examined. Newborn Holstein calves with goiter (n=34) found at 3 farms in the Tokachi district in Hokkaido were also examined. The diagnosis of endemic goiter was based on histopathological findings of enlarged thyroid glands. The blood of healthy calves was collected from the jugular vein at the following times: just after birth, 1, 3, 5, 7 days after birth, 2, 3, 4 weeks after birth, and 2 months after birth. The blood of calves with endemic goiter was collected just after birth (n=13), 1 (n=8) and 3 (n=5) days after birth, and at 2 (n=4) and 4 (n=4) weeks after birth. As a control, the blood of healthy 18-21 month-old adult cows (n=6) was also examined. Serum was separated quickly from collected blood then frozen at -20°C until determination of the thyroid hormone levels.Serum thyroxine (T 4 ) and serum triiodothyronine (T 3 ) of healthy calves, calves with goiter and healthy adult cows were determined by the RIA method (SPAC T 4 RIA Kit and SPAC T 3 RIA Kit, Daiichi RI institute) and the T 4 /T 3 ratio was calculated. Differences of thyroid hormone levels among healthy calves, calves with goiter and healthy adult cows were considered significant if p values were <0.05 or <0.01 by Student's t test. Figure 1 shows the changes in serum levels of thyroxine (T 4 ), triiodothyronine (T 3 ) and the T 4 /T 3 ratio in healthy calves and calves with goiter. These were compared with those of adult cows. Serum T 4 levels of healthy calves until 7 days after birth were significantly (p<0.01) higher than those of adult cows, and showed the maximum levels at 1 day after birth. Thereafter, they decreased rapidly until 5 days after birth. The levels at 2 weeks after birth were significantly (p<0.05) ...

ABSTRACT. To determine the effects of ozone on the phagocytosis of bovine polymorphonuclear leukocytes (PMNs), ozone gas was administered in vitro on the blood and milk of healthy lactating cows, cows with acute mastitis, and cows with milk fever. In the blood of healthy dairy cattle, although there was no significant effect of ozone gas on the viability of the leukocytes, phagocytosis of PMNs significantly decreased. In contrast, ozone gas administration in vitro significantly increased phagocytosis of PMNs from the blood of cows with acute mastitis and milk fever, and from mastitic milk. These findings showed that ozone administration in vitro has positive and negative effects on bovine PMN phagocytosis, depending on the health status of the animal.