title: Effect of including canola meal and supplemental iodine in diets of dairy cows on short-term changes in iodine concentrations in milk.
abstract: 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 2.0mg 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 13d of receiving the treatment. Milk I concentration before the treatments started (cows fed 0.5mg/kg of I) averaged 272μg/L and increased within 22h after cows were first fed diets with 2mg/kg of I. As inclusion rate of canola meal increased, the concentration of I in milk decreased linearly. After 12d of supplementation, milk from cows fed 0.5mg/kg of I had 358, 289, and 169μg of I/L for the 0, 3.9%, and 13.9% canola-meal treatments. For cows fed 2.0mg/kg of I, milk I concentrations were 733, 524, and 408μg/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 2.0mg/kg of I. Feeding dairy cows diets with 13.9% canola meal maintained milk I concentrations below 500μg/L when diets were supplemented with 2mg/kg of I.
authors.affiliation: Department of Animal Sciences, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster 44691. Electronic address: Weiss.6@osu.edu.
authors.forename: W P
authors.initials: WP
authors.lastname: Weiss
authors.affiliation: Department of Animal Sciences, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster 44691.
authors.forename: D J
authors.initials: DJ
authors.lastname: Wyatt
authors.affiliation: Zinpro Corp., Eden Prairie, MN 55344.
authors.forename: D H
authors.initials: DH
authors.lastname: Kleinschmit
authors.affiliation: Zinpro Corp., Eden Prairie, MN 55344.
authors.forename: M T
authors.initials: MT
authors.lastname: Socha
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000818:Animals; D001937:Brassica / Q000737:chemistry*; D002417:Cattle / Q000378:metabolism*; D004032:Diet / Q000662:veterinary; D019587:Dietary Supplements / Q000032:analysis; D005260:Female; D007455:Iodine / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism*; D008892:Milk / Q000737:chemistry* / Q000187:drug effects; D013025:Glycine max / Q000737:chemistry
chemical_list: D007455:Iodine
keywords: canola meal; goitrogenic compound; iodine