期刊
JOURNAL OF DAIRY SCIENCE
卷 98, 期 7, 页码 4841-4849出版社
ELSEVIER SCIENCE INC
DOI: 10.3168/jds.2014-9209
关键词
iodine; canola meal; goitrogenic compound
资金
- Ohio Agricultural Research and Development Center
- Zinpro Corp. Eden Prairie, Minnesota
- Ohio State University
The dietary requirement for iodine is based on thyroxine production, but data are becoming available showing potential improvements in hoof health when substantially greater amounts of I are fed. Feeding high amounts of I, however, can result in the milk having excessive concentrations of I. Canola meal contains goitrogenic compounds that reduce the transfer of I into milk. We hypothesized that including canola meal in diets would allow high supplementation rates of I without producing milk with unacceptable concentrations of I. Thirty midlactation Holstein cows were fed a diet with all supplemental protein from soybean meal (0% of diet dry matter as canola meal) or with all supplemental protein from canola meal (13.9% canola meal). A third treatment has a mix of soybean meal and canola meal (3.9% canola meal). Within canola-meal treatment, cows were fed 0.5 or 2.0 mg of supplemental I per kilogram of diet dry matter from ethylenediamine dihydroiodide. Cows were maintained on the canola treatment for the duration of the experiment but were changed from one I treatment to the other after 13 d of receiving the treatment. Milk I concentration before the treatments started (cows fed 0.5 mg/kg of I) averaged 272 mu g/L and increased within 22 h after cows were first fed diets with 2 mg/kg of I. As inclusion rate of canola meal increased, the concentration of I in milk decreased linearly. After 12 d of supplementation, milk from cows fed 0.5 mg/kg of I had 358, 289, and 169 mu g of I/L for the 0, 3.9%, and 13.9% canola-meal treatments. For cows fed 2.0 mg/kg of I, milk I concentrations were 733, 524, and 408 mu g/L, respectively. Concentrations of I in serum increased with increased I supplementation, but the effect of canola meal was opposite of what was observed for milk I. Cows fed the highest canola-meal diets had the highest serum I whether cows were fed 0.5 or 2.0 mg/kg of I. Feeding dairy cows diets with 13.9% canola meal maintained milk I concentrations below 500 mu g/L when diets were supplemented with 2 mg/kg of I.
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