Supplementation of soybean meal and canola meal with ethylenediamine dihydroiodide and Ascophyllum nodosum on iodine metabolism, production performance, and nutrient utilization in dairy cows

Authors: GHELICHKHAN, MOHAMMAD - University Of New Hampshire; SILVA, LUIS - University Of New Hampshire; Soder, Kathy; BRITO, ANDRE - University Of New Hampshire

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/21/2025
Publication Date: 3/1/2026
Citation: Ghelichkhan, M., Silva, L.H., Soder, K.J., Brito, A.F. 2026. Supplementation of soybean meal and canola meal with ethylenediamine dihydroiodide and Ascophyllum nodosum on iodine metabolism, production performance, and nutrient utilization in dairy cows. Journal of Dairy Science. 109:2549-2563. https://doi.org/10.3168/jds.2025-27399.
DOI: https://doi.org/10.3168/jds.2025-27399

Interpretive Summary: Lactating dairy cows can be fed brown seaweed (BSW) as a good source of readily-available minerals, but this can result in milk iodine concentrations above the recommended levels considered healthy for human consumption. Canola meal comes from a brassica forage that contains secondary compounds (glucosinolates) that may inhibit the transfer of iodine into the milk, but has not been thoroughly tested. In this study, lactating dairy cows were fed a base diet with one of the following supplements: 1) soybean meal + BSW; 2) soybean meal + iodine supplement; 3) canola meal + BSW; or 4) canola meal + iodine supplement. Results showed that lactating dairy cows fed canola meal + BSW had reduced milk iodine concentrations and yields compared to the other diets. This suggests that feeding brassicas to lactating dairy cows may be a viable management strategy to mitigate the negative effects of BSW, which otherwise is a natural, highly-absorbable source of minerals.

Technical Abstract: Previous research showed that feeding the brown seaweed Ascophyllum nodosum (ASCO) resulted in milk I concentration above the threshold considered healthy for human consumption. Canola meal (CM) contains glucosinolates, which are metabolites known to inhibit the transfer of I from feed to milk. Therefore, we aimed to compare the effects of diets containing soybean meal (SBM) or CM, each supplemented with ethylenediamine dihydroiodide (EDDI) and ASCO meal, on I metabolism, production performance, and nutrient utilization in dairy cows. Sixteen multiparous Jersey cows averaging (mean ± SD) 138 ± 58 DIM and 456 ± 62.1 kg of BW in the beginning of the study were used in a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments. Each experimental period lasted 21 d, with 14 d for diets adaptation and 7 d for data and samples collection. Diets were formulated to yield similar concentrations of CP and I. Cows were fed the following experimental diets (DM basis): 1) 10% SBM plus 110 mg/d of EDDI (SB+I), 2) 10% SBM plus 113 g/d of the brown seaweed ASCO (SB+SWD), 3) 12.5% CM plus 110 mg/d of EDDI (CAN+I), and 4) 12.5% CM plus 113 g/d of the brown seaweed ASCO (CAN+SWD). We observed a protein source by I source interaction for milk I concentration, which was similar between diets containing EDDI (SB+I and CAN+I), but it decreased by 27.8% when comparing SB+SWD versus CAN+SWD. In addition, milk I yield, the transfer efficiency of I from feed to milk, and the serum concentrations of thyroid stimulating hormone and total triiodothyronine were lower in diets containing CM than SBM. Contrarily, the serum concentration of I and the urinary excretion of I increased in cows receiving CAN+I and CAN+SWD versus SB+I and SB+SWD. We also detected a protein source by I source interaction for the serum concentration of free thyroxin, with cows fed CAN+I showing a tendency to have greater free thyroxin levels than those fed SB+I. Iodine intake, milk I yield, serum I concentration, and urinary excretion of I were lower in cows fed CAN+SWD and CAN+SWD than SB+I and CAN+I. Intake of DM and total glucosinolates were greater with feeding CAN+I and CAN+SWD versus SB+I and SB+SWD. In contrast, milk yield, milk N efficiency, and feed efficiency were lower in cows offered CAN+I and CAN+SWD compared with SB+I and SB+SWD. Furthermore, MUN and BUN concentrations, apparent total-tract digestibilities of DM, OM, NDF, ADF, and CP, and urinary and fecal excretion of N were lower in CAN+I and CAN+SWD than SB+I and SB+SWD diets, with these responses associated with the greater contents of neutral detergent insoluble CP and acid detergent insoluble CP in CM versus SBM. In brief, our results revealed that feeding CM reduced milk I concentration, milk I yield, and the feed-to-milk I transfer efficiency, particularly when supplemented with ASCO meal.