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.

Effect of Dietary Seaweed Supplementation in Cows on Milk Macrominerals, Trace Elements and Heavy Metal Concentrations

“…In the current study, seaweed supplementation in dairy cow diets increased I concentrations in milk, which is in line with the findings from previous work that investigated the effect of feeding A. nodosum [10,52,57] and kelp powder or Thallus laminariae to dairy cows on milk I concentration [58]. Concentrations of I in raw milk are primarily influenced by diet I concentrations, but in-feed goitrogenic compounds, husbandry practices, and mammary gland hygiene management (teat-dipping) are also determinant factors [10,59,60].…”

Production, milk iodine, and nutrient utilization in Jersey cows supplemented with the brown seaweed Ascophyllum nodosum (kelp meal) during the grazing season

“…Variations in serum concentrations of T 3 and T 4 are driven by differences in environmental temperature, DIM, milk yield, and dietary goitrogens, among other factors (Aceves et al, 1987;Pezzi et al, 2003;Anderson et al, 2007). Sorge et al (2016b) reported serum concentrations of T 3 (mean = 1.27 ng/mL) and T 4 (mean = 33.2 ng/mL) in lactating Holstein cows fed KM that were greater and lower, respectively, than those measured herein. Even though serum T 4 concentrations (mean = 40.3 ng/mL) in cows used in the present study were within healthy limits (29.5 to 44.3 ng/mL) based on data from Holstein, that of serum T 3 (mean = 0.86 ng/mL) was not inside the normal range of 0.98 to 1.37-ng/mL (Kafi et al, 2012).…”

“…Chaves Lopez et al (2016) demonstrated a 113% increase in milk I concentration with feeding (% of the diet DM) 2.3% of KM incorporated in a ground corn-based concentrate blend. In contrast, Sorge et al (2016b) reported no effect of KM supplementation (56 g/d) on milk I concentration. According to Sorge et al (2016b), this lack of response was possibly caused by a baseline serum I concentration already above the reference range of 50 to 120 ng/ mL in their cows and an unexpected high I content in the TMR.…”

“…In contrast, Sorge et al (2016b) reported no effect of KM supplementation (56 g/d) on milk I concentration. According to Sorge et al (2016b), this lack of response was possibly caused by a baseline serum I concentration already above the reference range of 50 to 120 ng/ mL in their cows and an unexpected high I content in the TMR.…”

Assessing the potential of milk iodine intake to mitigate iodine deficiency in pregnant women of the United States via supplementation of Ascophyllum nodosum meal to dairy cows: A sensitivity analysis

“…Nonlinear regression models between iodine intake from cows fed various amounts of Ascophyllum nodosum meal (0, 57, 113, or 176 g/d) and milk iodine yield (A) or milk iodine concentration (B) using data from study 1 (Antaya et al, 2015), study 2 (Antaya et al, 2019), study 3 (A. F. Brito, unpublished), and study 4 (A. F. Brito, unpublished). uptake of I − from seawater (Baily and Kelly, 1955;Küpper et al, 1998;Muramatsu and Wedepohl, 1998;Fuge and Johnson, 2015), which can be transferred into milk via ASCO supplementation (Antaya et al, 2015(Antaya et al, , 2019Chaves Lopez et al, 2016;Sorge et al, 2016b). A large variation in milk I concentration was observed within and across experiments, reflecting differences in content and bioavailability of I present in A. nodosum used to produce ASCO, the amount of ASCO fed, ingredient composition of the basal diet, and management system (grazing vs. confinement).…”