Effect of Changes in Forage Ration on the Thyroidal I131 Release Rates of Young Dairy Animals
Thyroidal I131 release rates of Holstein heifers were sigrtificantly higher shortly after they were changed to legume-grass silage than when they were fed alfalfa hay. They were also significantly higher when the heifers were fed legume-grass silage from a plastic-covered stack or mixed grass- clover-alfalfa hay than when they were fed legume-grass silage from a tower silo. When the forage Was changed from alfalfa hay to legume-grass silage, during the time I131 release rate was being determined, 3 of 5 calves exhibited an increased release rate, whereas their controls showed do change. When neutrilization of iodine was blocked with thiouracil, the 2 calves switched to silage showed a significant increase in I131 release rate, whereas 1 control calf exhibited a decrease and the other an increase. The changes in I131 release rate indicated that some as yet unidentified factor(s) in certain forages exerts an influence on the thyroid activity, so that an adjustment in thyroid activity of the animal is induced when a sudden change in forage rations is made. This may explain the sharp decline in milk production caused by ration changes noted previously. (H.H.D.)
- Research Organization:
- Ohio Agricultural Experiment Station, Wooster
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-17-005723
- OSTI ID:
- 4755428
- Journal Information:
- Journal of Dairy Science, Journal Name: Journal of Dairy Science Journal Issue: 2 Vol. 45; ISSN 0022-0302
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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