title: Short communication: Iodine concentrations in serum, milk, and tears after feeding Ascophyllum nodosum to dairy cows-A pilot study.
abstract: Kelp (Ascophyllum nodosum) is rich in iodine and often fed by organic dairy producers as a mineral supplement to support animal health. A commonly held belief is that kelp supplementation decreases susceptibility to infectious bovine keratoconjunctivitis due to increased iodine concentrations in tears. Whereas serum and milk iodine concentrations are positively correlated and modulated by oral iodine supplementation, nothing is known about the iodine concentration of tears. Therefore, the 3 objectives of this pilot study were to determine (1) the iodine content of tears, milk, and serum of cows after being fed kelp for 30d; (2) the trace mineral and thyroid status of cows before (d 0) and after being fed kelp for 30d; and (3) the in vitro growth rate of bacteria in tears (Moraxella bovis) or milk (Staphylococcus aureus, Escherichia coli, Streptococcus uberis) collected from cows fed no kelp (d 0) or kelp (d 30). Cows (n=3/treatment) were individually fed 56g of kelp per day (n=3/treatment) or not (n=3/no treatment) for 30 d. Daily feed intake of the TMR was recorded and weekly TMR, kelp, milk, blood and tear samples were collected and analyzed for iodine. The feed samples were pooled and further analyzed for other minerals. On d 0 and 30, liver biopsies and blood samples were collected and analyzed for mineral content and thyroid hormone concentrations, respectively. An inhibition test used milk and tear-soaked plates from kelp-fed cows (d 0 and 30) as well as 1 and 7.5% iodine as positive and distilled water as negative control. As expected, serum iodine concentrations were positively correlated with milk and tear iodine concentrations. Whereas the iodine concentrations in serum increased significantly in the kelp-fed cows during the 30-d study, milk and tear iodine concentrations increased only numerically in these cows compared with the control group. Liver mineral profiles were comparable between groups and generally did not change over the course of the study. Thyroid hormones remained overall within the reference range throughout the trial. Neither milk nor tears from kelp-fed cows inhibited in vitro growth of any of the plated bacteria. In summary, serum iodine concentration was correlated with the iodine concentration in milk and tears and feeding kelp increased only the serum iodine levels of cows in this trial. Bacterial growth was not inhibited in milk and tears of kelp-fed cattle in vitro, and prevention of infectious bovine keratoconjunctivitis would not be based solely on increased iodine concentrations in tears.
authors.affiliation: Department of Veterinary Population Medicine, University of Minnesota, Saint Paul 55108. Electronic address: sorge@umn.edu.
authors.forename: U S
authors.initials: US
authors.lastname: Sorge
authors.affiliation: Department of Veterinary Clinical Sciences, University of Minnesota, Saint Paul 55108.
authors.forename: M
authors.initials: M
authors.lastname: Henriksen
authors.affiliation: Faculty of Veterinary Medicine, Department of Obstetrics and Gynaecology, Ankara University, Ankara, Turkey.
authors.forename: A
authors.initials: A
authors.lastname: Bastan
authors.affiliation: Veterinary Diagnostic Laboratory, University of Minnesota, Saint Paul 55108.
authors.forename: N
authors.initials: N
authors.lastname: Cremers
authors.affiliation: Veterinary Diagnostic Laboratory, University of Minnesota, Saint Paul 55108.
authors.forename: K
authors.initials: K
authors.lastname: Olsen
authors.affiliation: Department of Animal Science, University of Minnesota, Saint Paul 55108.
authors.forename: B A
authors.initials: BA
authors.lastname: Crooker
mesh_terms: D000821:Animal Feed / Q000032:analysis*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D044646:Ascophyllum; D002417:Cattle; D004032:Diet / Q000662:veterinary*; D004926:Escherichia coli / Q000302:isolation & purification; D005260:Female; D007455:Iodine / Q000032:analysis / Q000097:blood*; D008892:Milk / Q000737:chemistry* / Q000382:microbiology; D016955:Moraxella bovis / Q000302:isolation & purification; D010865:Pilot Projects; D013211:Staphylococcus aureus / Q000302:isolation & purification; D013291:Streptococcus / Q000302:isolation & purification; D013666:Tears / Q000737:chemistry* / Q000382:microbiology
chemical_list: D007455:Iodine
keywords: Ascophyllum nodosum; infectious bovine keratoconjunctivitis; iodine; kelp; tears