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

Authors: ANTAYA, NICOLE - University Of New Hampshire; GHELICHKHAN, MOHAMMAD - University Of New Hampshire; PEREIRA, ANDRE - 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: 6/8/2019
Publication Date: 8/1/2019
Citation: Antaya, N., Ghelichkhan, M., Pereira, A., Soder, K.J., Brito, A. 2019. Production, milk iodine, and nutrient utilization in Jersey cows supplemented with the brown seaweed ascophyllum nodosum (kelp meal) during the grazing season. Journal of Dairy Science.102(9):8040-8058. https://doi.org/10.3168/jds.2019-16478.
DOI: https://doi.org/10.3168/jds.2019-16478

Interpretive Summary: Kelp meal is a livestock supplement made from the brown seaweed Ascophyllum nodosum, which is a rich source of minerals, especially iodine. Dairy producers use kelp as the main mineral source due to perceived health benefits for cattle. However, these anecdotal claims have not been substantiated by research. Our objective was to investigate the effects of kelp meal supplementation on milk production, milk iodine, and nutrient utilization in grazing dairy cows. Kelp supplementation did not improve milk production or nutrient digestibility, but did increase feed intake and milk iodine concentrations. These increased milk iodine levels may be of concern to human health and warrant further investigation.

Technical Abstract: Kelp meal (KM) is a supplement made from the brown seaweed Ascophyllum nodosum known to bioaccumulate iodine (I) and to be the richest source of phlorotannins, which can inhibit ruminal proteolysis and microbial growth. We aimed to investigate the effects of KM on production, milk I, concentrations of blood metabolites, apparent total-tract digestibility of nutrients, and CH4 emissions in grazing dairy cows. A second objective was to evaluate the impact of increased intake of partial total mixed ration (pTMR) at the expense of herbage as milk I may be affected by decreased glucosinolates consumption. Eight multiparous Jersey cows averaging (mean ± SD) 175 ± 60 days in milk and 12 primiparous Jersey cows averaging 142 ± 47 DIM in the beginning of the study were assigned to 0 g/d of KM (control diet = CTRL) or 113 g/d of KM (brown seaweed diet = BSW) in a randomized complete block design. Diets were formulated to yield a 70:30 forage-to-concentrate ratio and consisted of (dry matter basis): 48% cool-season perennial herbage and 52% pTMR. The study lasted 112 d with data and sample collection taking place on wk 4, 8, 12, and 16. Cows had approximately 16.5 h of access to pasture daily (~10 h in the last 28-d period). Data were analyzed using repeated measures. Herbage and total dry matter intake tended to increase in cows fed BSW versus the CTRL diet. Milk yield and concentrations and yields of milk components were not affected by diets. Similarly, blood concentrations of cortisol, glucose, fatty acids, and thyroxine did not change with feeding CTRL or BSW. However, a significant treatment by wk interaction was observed for milk I concentration; cows offered the BSW diet had greater milk I concentration during wk 4, 8, and 12, but the largest difference between BSW and CTRL was observed in wk 8 (+422%; 579 vs. 111 µg/L, respectively). Treatment by wk interactions were also found for serum triiodothyronine concentration, total-tract digestibilities of crude protein and acid detergent fiber, CH4 production, and urinary excretion of purine derivatives. An interaction for milk I concentration was detected with increasing pTMR intake comparing wk 4 versus 16; while the difference between treatments averages 238% in wk 4, it increased to 370% in wk 16, which is partially explained by decreased glucosinolates intake. Specifically, the increase in milk I concentration in cows fed the BSW diet averaged 126% from wk 4 (mean = 416 µg/L) to wk 16 (mean = 940 µg/L), thus well above the 500-µg/L threshold recommended for humans’ consumption. Overall, the lack of KM effects on milk yield and concentrations and yields of milk components indicate that producers should consider costs before making supplementation decisions for the grazing season. Future research is needed to evaluate the concentration of I in retail organic milk because of the high prevalence of KM supplementation in northeastern and midwestern U.S. organic dairies and possibly other regions of the country.