Research and educational approaches to guide dairy farmer decisions about kelp meal supplementation in the Northeast

Final Report for GNE15-101

Project Type: Graduate Student
Funds awarded in 2015: $14,666.00
Projected End Date: 12/31/2016
Grant Recipient: University of New Hampshire
Region: Northeast
State: New Hampshire
Graduate Student:
Faculty Advisor:
Dr. Andre Brito
University of New Hampshire
Faculty Advisor:
Simone Frotas
University of New Hampshire
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Project Information


The objective if this study was to evaluate the impact of feeding incremental amounts of kelp meal (Ascophyllum nodosum) and a single dose of the ionophore monensin on rumen microbiota and fermentation, markers of animal health, and iodine metabolism in lactating Jersey cows. We also compared the effects of kelp meal vs. monensin on performance traits, urinary N excretion, and apparent total-tract digestibility of nutrients. Five lactating Jersey cows fitted with ruminal cannulas were used in a 5 × 5 Latin square design. Cows were fed a total mixed ration containing (dry matter basis) a 65:35 forage-to-concentrate ratio and 1 of 5 dietary treatments: 1) 0 g/d, 2) 57 g/d, 3) 113 g/d, 4) 170 g/d of kelp meal or 5) 300 mg of monensin. Results showed that kelp meal supplementation did not change dry matter intake; however, changes were observed for milk yield, and concentration and yield of milk fat and true protein, which were all quadratically affected by kelp meal supplementation. Cows fed monensin had greater concentration and yield of milk fat, and milk concentrations of true protein compared with those supplemented with 170 g of kelp meal. Urinary excretions of all metabolites did not differ across dietary levels of kelp meal. Apparent total-tract digestibility of organic matter increased linearly with increasing kelp meal supplementation, but no effects were observed for digestibility of fiber in cows supplemented with kelp meal. Overall, monensin supplementation did not affect digestibility of nutrients. Concentration of serum cortisol decreased linearly decreased with incremental amounts of kelp meal, but no other effects were observed for blood metabolites. No treatment effects were observed for rumen fermentation profile, but the population of the methanogen Methanobrevibacter sp decreased linearly. Incremental levels of kelp meal linearly increased iodine on milk, feces, urinary, and serum.


Macroalgae (commonly known as seaweed) have been used as feed supplements, soil conditioners, and as source of minerals, particularly iodine, for plants and animals since antiquity (Allen et al., 2001). Ascophyllum nodosum, commercialized throughout the Northeast as kelp meal, is undoubtedly the macroalga species most used and researched in agricultural systems (Allen et al., 2001). In addition to the high concentration of macro and microminerals, kelp meal is known to contain a wide spectrum of nutritional compounds, including polyunsaturated fatty acids, polyphenols, bioactive peptides, and vitamins (Antaya et al., 2015). Specifically, kelp meal is rich in polyphenolic compounds such as phlorotannins, which are similar to terrestrial tannins in the ability to bind proteins and carbohydrates and to inhibit bacterial growth (Wang et al., 2008, 2009). Moreover, kelp meal contains significant concentrations of antioxidants, which may improve animal health (Allen et al., 2001).

Hardie et al. (2014) used surveys to demonstrate that 49% of Wisconsin organic dairy farmers feed kelp meal to lactating dairy cows. We also showed via a survey funded by NE SARE (award# G12-049) that 58% of organic dairy farmers in the Northeast feed kelp meal to the milking herd for the following reasons: (1) it improves body condition and overall animal appearance; (2) it decreases milk somatic cells count and the incidence of reproductive problems and pinkeye; and (3) it helps to control nuisance flies. Although these anecdotal claims seem to justify the use of kelp meal, there is limited scientific evidence to support its remarkable popularity among organic dairy farmers. In fact, research conducted at the University of New Hampshire (UNH) showed no improvement in milk production, milk composition, and feed efficiency in organic Jersey cows supplemented with kelp meal during the grazing and winter seasons (Antaya et al., 2013, 2015).

Antaya et al. (2015) fed incremental amounts of kelp meal to organic Jersey cows and observed a quadratic response for digestibility of acid detergent fiber, suggesting that kelp meal supplementation may stimulate or inhibit growth of ruminal cellulolytic bacteria in a dose-dependent fashion. Phlorotannins extracted from kelp meal exhibited antimicrobial activity against ruminal bacteria and methanogens (i.e., archaea; Wang et al., 2008), and pathogens such as Escherichia coli O157:H7 in vitro (Wang et al., 2009). Moreover, kelp meal phlorotannins decreased in vitro ruminal proteolysis of casein and deamination of amino acids, indicating inhibitory effects against proteolytic and hyper ammonia-producing bacteria (Wang et al., 2008). Reduced ruminal ammonia concentration has been associated with less urinary nitrogen excretion by dairy cows and more environmentally-friendly dairy farms.

We are not aware of any study to date that has investigated the shifts in rumen microbial population as a result of kelp meal supplementation for lactating dairy cows. It is unknown whether the quadratic responses observed for fiber digestibility and urinary nitrogen excretion in our previous study (Antaya et al., 2015) were caused by shifts in the populations of ruminal microbes that ferment fiber (e.g., cellulolytic bacteria) and protein (e.g., proteolytic bacteria). There is no scientific information about the impact of kelp meal on the population of microorganisms that produce methane, a potent greenhouse gas. Information is also lacking on the effects of kelp meal on animal health. These critical knowledge gaps were addressed by the current project.

Project Objectives:

Objective 1: Identify and quantify ruminal microorganisms (e.g., bacteria, protozoa, and methanogens) in response to incremental amounts of kelp meal fed to lactating dairy cows.

Objective 2: Develop a Kelp Meal Feeding Guide to help dairy farmers and supporting industry to make educated decisions about the use of kelp meal in the Northeast region.


Click linked name(s) to expand
  • Andre Brito
  • Simone Frotas


Materials and methods:


Five ruminally-cannulated lactating Jersey cows (mean ± standard deviation) averaging 27.2 ± 2.8 kg of milk yield/d, 102 ± 15 days in milk, and 450 ± 33 kg of body weight were used in our project. Cows were randomly assigned to treatments in a 5 × 5 Latin square design. Each experimental period lasted 28 d within 21 d for diet adaptation and 7 d for data and sample collection. Cows were fed a total mixed ration containing (dry matter basis) a 65:35 forage-to-concentrate ratio and 1 of 5 dietary treatments: 1) 0 g/d (negative control), 2) 57 g/d, 3) 113 g/d, 4) 170 g/d of kelp meal or 5) 300 mg of monensin (positive control). The ionophore monensin was used because of its well established effect on shifting the rumen microbial population and modifying fermentation profile. Treatments were administered directly in the rumen via the cannula after the morning feeding. Figure 1 (Figure-1-Calan-gate-system) shows the Calan gate system that individualizes feed intake, and Figure 2 (Figure-2-Ruminally-cannulated-cows) shows the ruminally-cannulated cows.

Cows were milked twice a day (0530 a.m. and 0530 p.m.) with milk production recorded at each milking throughout the experiment. Milk samples were collected for 4 consecutive milkings during the first 3 d of each sampling period, preserved in tubes containing 2-bromo-2-nitropropan-1,3 diol, pooled by cow according to a.m. and p.m. milk weights, refrigerated at 4°C, and analyzed for fat, protein, lactose, and milk urea N (MUN) by mid-infrared spectroscopy (Dairy One Cooperative, Inc., Ithaca, NY).

Blood samples were taken for 2 consecutive days (d 27-28 of each period) approximately 4 h after the morning feeding via the coccygeal vein into 10-mL tubes (Monoject Covidien, Mansfield, MA) containing EDTA and serum separator. Tubes were placed immediately on ice and centrifuged (Eppendorf Centrifuge model 5810; Eppendorf, Hamburg, Germany) at 2,155 × g for 20 min at 4°C. Plasma and serum were collected and stored in cryovials at -20°C and -80°C for further analysis including hormones, iodine, glucose, non-esterified fatty acids, urea, and antioxidant enzymes using commercial available kits.

Urinary spot samples were collected for 3 consecutive days of each period at 0600 a.m. (d 22), noon (d 23), and 0600 p.m. (d 24) by stimulating of the pudendal nerve massaging the area below the vulva. Samples were analyzed for allantoin, uric acid, creatinine, NH3-N, and total N. Fecal grab samples were collected concurrently with urinary spot samples, placed on disposable aluminum foil pans, and dried in a forced-air oven at 55°C (VWR Scientific, Radnor, PA) for 72-96 h. Fecal samples were ground to pass through a 1-mm screen and analyzed for dry matter, ash, total N, and neutral and acid detergent fiber (Dairy One Forage Testing Laboratory, Ithaca, NY) to estimate apparent total-tract digestibility.

Rumen digesta samples (about 400 g) were collected at 0 h (just before feeding) and 3 h after morning feeding for 3 consecutive days (d 23-25). Samples were taken from different sites in the rumen, strained through 2 layers of cheesecloth into volumetric flasks to a final volume of approximately 400 mL. Rumen pH was immediately measured using a Thermo Orion A214 meter (Thermo Fischer Scientific, Waltham, MA). Rumen fluid samples from each time point and day (free of diluent) were stored at -80°C into 2 mL cryovials and sent to Molecular Research DNA laboratory (Shallowater, TX) for DNA extraction, qPCR, PCR amplification and sequence analysis. Rumen digesta samples were also collected, as described above, at 0, 1, 2, 4, 6, and 8 h after feeding on d 27 of each period for diurnal pH measurements, and volatile fatty acids and NH3-N analyses.          

Mineral concentrations, including iodine, on feeds, refusals, dietary treatments, feces, serum, milk and urine were analyzed by inductively coupled plasma mass spectrometry with alkaline dilution or digestion using tetramethylammonium hydroxide (Trace Element Laboratory, Hanover, NH). A complete nutritional analysis of feeds was done and is presented in Table 1.

All data were analyzed using the MIXED procedure of SAS (SAS version 9.4; SAS Inst. Inc., Cary, NC) for a 5 × 5 replicated Latin square with cow considered as random variable. Contrasts were used for all variables (with and without repeated measures) to compare treatments effects. Degrees of freedom for treatments were partitioned as follow: linear, quadratic, kelp meal vs. monensin, and 170 g kelp meal vs. monensin.


We developed the Kelp Meal Feeding Guide (Kelp-Meal-Feeding-Guide) based on data from the current project and previous research. A final version of the guide will be produced by incorporating when microbiota data of our project are finalized. Microbiota analysis is very complex and we are still fine tuning the statistical analysis and double-checking the massive dataset including archaea, bacteria, and protozoa.


Research results and discussion:

The nutritional composition of the feeds, including kelp meal, is presented in Table 1 (Table-1-Feed-nutritional-composition), and the ingredient and nutritional composition of Table 2 (Table-2-Ingredient-and-nutritional-composition-of-the-diet). As expected the iodine concentration of kelp meal was much greater compared with all remaining feedstuffs (Table 1). However, the iodine concentration of the kelp meal used in this project was about 2-fold lower than that from a kelp meal source used in our previous research (Antaya et al., 2015). This indicates a large variation in iodine concentration across kelp meal sources. Even though the arsenic concentration in kelp meal was much greater than that of the remaining feedstuffs (Table 1), it is not concerning to animal or human health.

The animal production performance and milk composition results are presented in Table 3 (Table-3-Production-performance). No treatment effects were observed for dry matter intake. A quadratic effect (P = 0.005) was observed for milk yield; cows fed 0 or 170 g/d of kelp meal produced more milk than those fed 56 or 113 g/d. A quadratic effect (P = 0.001) was observed for the concentration of milk fat with cows fed 113 g/d of kelp meal having the greatest content. Milk fat yield also responded quadratically (P = 0.04) with cows no kelp meal resulting in the greatest value. Quadratic effects were observed for the concentration (P = 0.004) and yield (P = 0.05) of milk protein; cows fed 0 or 170 g/d kelp meal had the lowest milk protein content, and those fed 113 g/d kelp meal the lowest milk protein yield. The concentration of milk lactose was not affected by treatments. However, milk lactose responded quadratically (P = 0.01) to kelp meal supplementation, with cows fed 0 or 170 g/d kelp resulting in the greatest lactose yield in milk. MUN concentration was also affected quadratically in response to kelp meal supplementation; cows fed 57 g/d kelp had the lowest MUN.

Compared with kelp meal fed cows, those fed monensin had greater concentration (P < 0.001) and yield (P = 0.002) of milk fat (Table 3). Similarly, milk fat concentration (P < 0.001) and yield (P = 0.02) was greater in cows fed monensin that in those fed the greatest dose of kelp meal (i.e., 170 g/d; Table 3). The concentration of milk protein was greater in cows fed monensin than kelp meal (P = 0.01), and it was also greater (P < 0.001) when comparing monensin with 170 g/d of kelp meal (Table 3). In contrast, MUN was lower in cows fed kelp meal than monensin (P < 0.001), and it was also lower (P = 0.01) when comparing 170 g/d of kelp meal vs. monensin (Table 3).

Overall, the observed quadratic responses for milk yield and milk composition is response to incremental amount of kelp meal may be attributed to bioactive compounds present in kelp meal, as well as changes in rumen microbiota. However, production performance and milk composition data should be interpreted cautiously due to the low number of cows used in this study.

The urinary excretion of nitrogenous metabolites and apparent total-tract digestibility of nutrients are presented in Table 3. No treatment differences were observed for the urinary excretion of total N, allantoin, uric acid, and total purine derivatives (allantoin + uric acid). Purine derivatives are used as intrinsic markers to estimate microbial protein synthesis. Apparent total-tract digestibility of organic matter increased linearly (P < 0.001) in cows fed incremental amounts of kelp meal, which is consistent with linear positive trend (P = 0.06) in crude protein digestibility (Table 3). No other treatment effects were observed for total-tract nutrient digestibility (Table 3).

The concentration of blood metabolites is presented in Table 4 (Table-4-Blood-metabolites). No treatment differences were observed for the blood hormones aldosterone and insulin, as well as the antioxidant enzymes superoxide dismutase, glutathione peroxidase, and catalase. Similarly, no treatment effects were found for the markers of liver health bovine serum albumin and aspartate aminotransferase. The blood concentrations of both non-esterified fatty acids and β-hydroxybutyric acid, which are metabolites associated with mobilization of fat from the adipose tissue, did not differ significantly across treatments. In contrast, blood concentration of cortisol decreased linearly when feeding increasing amounts of kelp meal, suggesting a reduction in animal stress. The blood concentration of glucose was greater in cows fed monensin vs. kelp meal, and also greater when comparing monensin against the greatest dose of kelp meal. Monensin has been shown to improve energy utilization in dairy cows, thus increased blood glucose is consistent with the role of monensin on energy use efficiency.

The rumen metabolism and volatile fatty acid profile is presented in Table 5 (Table-5-Rumen-metabolism). No treatment differences were observed for the rumen pH, as well as for the rumen concentrations of ammonia-N and total volatile fatty acids. The iodine balance is presented in Table 6 (Table-6-Iodine-metabolism1). As expected, intake of iodine, as well as iodine output in milk, urine, and feces increased linearly (P < 0.001) in cows fed incremental amounts of kelp meal. Similarly, the concentration of iodine in serum increased linearly (P < 0.001). Increased iodine secretion in milk, and excretion in feces and urine are explained by increased iodine intake as a result of the high concentration of iodine in kelp meal. No treatment differences were observed for the serum concentration of the thyroid stimulating hormone, triiodothyronine (T3), and thyroxin (T4).

Table 7 shows the rumen microbiota results (Table-7-Rumen-microbiota). The rumen archaea/methanogen Methanobrevibacter sp. decreased linearly (P = 0.04) in cows fed incremental amounts of kelp meal. Compared with monensin, cows fed kelp meal had lower proportion Methanobrevibacter sp. The greatest dose of kelp meal (170 g/d) also resulted in decreased proportion of Methanobrevibacter sp. in the rumen when compared with monensin. Decreased Methanobrevibacter sp. population implies reduction in methane emissions. No other major changes were observed in the rumen microbiota except Clostridium spp. that increased linearly (P = 0.01).





Research conclusions:

The major impact of this project is that a comprehensive study about iodine balance and the potential implications to human and animal health was conducted. This project and our previous research confirm that kelp meal supplementation has minimal impact on milk production and composition. As dairy farmers are paid based on milk components, feeding kelp meal as a way to improve milk production or milk composition is probably not justified. Based on our collective data and analyses to date (results from 3 studies conducted at UNH and literature reports), kelp meal can be replaced by cheaper mineral sources without negatively impacting milk production or milk composition. On the other hand, kelp meal decreased the serum concentration of cortisol (a stress hormone) in the current project, which confirm our previous findings (Antaya et al., 2015). However, this reduction in cortisol did not improve milk production or milk composition. Therefore, our research provide key information to guide farmers’ decision about the use of kelp meal, which is an expensive feed supplement. As related to milk iodine, results from the current project corroborate our previous research (Antaya et al., 2015; Antaya, 2016) that kelp meal significantly increases iodine levels in milk that can be potentially concerning for human health, particularly children. Data from the current project can be used by extension educators and milk processors to inform farmers and the general public about the potential health concern of consuming milk from cows fed kelp meal. We also discovered that supplementation with kelp decreased the population of microbes that produce methane in the rumen, indicating that kelp meal may be used as an strategy to mitigate methane emissions in dairy systems. Overall, extension educators, nutritionists, and veterinaries can also use project research to guide farmers about the tradeoffs between lack of effect on milk production, but decreased cortisol and methane-producing microbes when feeding kelp meal. We are also finalizing the Kelp Meal Feeding Guide (Objective 2) and will distribute via UNH social media, UNH dairy tours, and UNH field days, and farmer-oriented conferences in the region (e.g., VT Organic Dairy Conference, NOFA-NY Organic Dairy Conference, and NODPA annual field day and conference, etc.).

Participation Summary

Education & Outreach Activities and Participation Summary

Participation Summary

Education/outreach description:

Results of the project were presented during the 2016 Joint Annual Animal-Dairy Science Meeting (JAM) held in Salt Lake City, Utah. This annual meeting is the largest livestock scientific gathering in the United States with over 3,000 attendees. An abstract highlighting project results was published in the conference proceedings (see reference below and link) and the poster presented can be seen in Figure 3 (Figure-3-NE-SARE-Kelp-meal-project). We also presented project results at the UNH field days and farm tours typically attended for over 60 people including farmers, students, and extension and industry personnel. We expect to submit our findings to the Journal of Dairy Science in the next couple of months, as well as writing a farmer-oriented article to be published by NODPA News. The Kelp Meal Feeding Guide (Objective 2) will be distributed via UNH social media, UNH dairy tours, and UNH field days, and farmer-oriented conferences in the region (e.g., VT Organic Dairy Conference, NOFA-NY Dairy and Field Crop Conference, NODPA annual field day and conference, etc.). See

Reis, S. F., A. F. Brito, C. P. Ghedini, D. C. Moura, and A. S. Oliveira. 2016. Effects of Ascophyllum nodosum meal and monensin on performance and iodine metabolism in lactating dairy cows. J. Dairy Sci. 99 (E-Suppl. 1):645.

Project Outcomes

Project outcomes:

According to a Northeast survey conducted by our laboratory (Pereira et al., 2013), organic dairies in the region are characterized by herd sizes averaging 58 lactating cows per farm. We also learned that the amount of kelp meal supplementation in the Northeast ranges from less than 1 oz to 7 oz per cow daily (NE SARE; award# G12-049). Using the mean dose of 3 oz per cow recommended by companies such as North American Kelp and Thorvin, kelp meal supplementation would represent additional $5,081 in feed costs per farm (3 oz at $0.08/oz × 58 cows/farm × 365 days). As our data showed no positive impact of kelp meal supplementation on milk production or milk composition, farmers may need to rethink the use of kelp meal in their farms as a generic mineral mix is generally less expensive than kelp. It is well known that many farmers feed kelp meal due to its high concentration of minerals.

Farmer Adoption

Although we did not directly involve farmers in this project, our results can be used by farmers to make informed decisions about kelp meal use in their dairy enterprises. For instance, kelp meal did not improve milk production or milk composition, but it seems to reduce stress in lactating dairy cows. Thus, farmers have the option to decide whether or not kelp meal fit in their farm economic budget. Kelp meal is an expensive supplement and our current and previous results do not support kelp supplementation if farmers’ goals are to improve milk production, milk composition, and feed efficiency. In addition, extension educators, nutritionists, and veterinarians can also make informed decisions, and educate farmers about the pros and cons of feeding kelp meal.

Assessment of Project Approach and Areas of Further Study:

Areas needing additional study

Past and recent survey research revealed that up to 80% of organic dairy farmers in the Northeast and Midwest feed kelp meal. Our laboratory showed some evidence that kelp meal seems to be involved in decreasing animal stress and microorganisms in the rumen associated with methane production. In addition, there is some indication that kelp meal supplementation improves milk quality by reducing milk somatic cells count. Thurs, future research should address the potential role of kelp meal on mitigating methane emissions, as well as its potential effect on improving milk quality and udder health.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.