Maine organic dairy producers’ receptiveness to seaweed supplementation and effect of Chondrus crispus on enteric methane emissions in lactating cows

INTRODUCTION: There is a growing interest in utilizing seaweed in ruminant diets for mitigating enteric methane (CH(4)) emissions while improving animal health. Chondrus crispus is a red seaweed that grows in the Gulf of Maine (United States) and has shown to suppress CH(4) production in vitro. Organic dairy producers in Maine are currently feeding seaweed due to herd health promoting benefits. However, large-scale adoption depends on technical and financial factors, as well as validation from pilot studies. METHODS: A survey was developed to identify barriers and drivers towards the adoption of CH(4)-reducing algal-based feeds. Concurrently, a randomized complete block design study was conducted to investigate the effect of C. crispus on enteric CH(4) emissions and milk production in a typical Maine organic dairy farm. Twenty-two organically certified Holstein and Jersey cows averaging 29 ± 6.8 kg of milk/d and 150 ± 69 days in milk, were blocked and randomly assigned to a control diet without C. crispus (0CC), or with 6% [dry matter (DM) basis] C. crispus (6CC). Samples were collected on the last week of the 2-wk covariate period, and wk 3, 5, 8, and 10 after initiation of treatments for a total of 12 weeks. Gaseous emissions were measured using a GreenFeed unit. Data were analyzed using the MIXED procedure of SAS with repeated measures over time. RESULTS: All survey respondents (n = 35; 54% response rate) were familiar with seaweeds as feed, and 34% were already users. Producers who were willing to pay 0.64 USD/cow/d on average for a CH(4)-reducing algal-based feed, also stated the need for co-benefits in terms of cattle health and performance as a requirement for adoption. Feeding 6CC decreased enteric CH(4) production by 13.9% compared with 0CC (401 vs. 466 g/d). Further, milk yield (mean = 27.1 kg/d), CH(4) intensity (mean = 15.2 g of CH(4)/kg of energy corrected milk), and concentrations and yields of milk fat and true protein were not affected by treatments. DISCUSSION: Producer receptiveness to CH(4)-reducing algal-based feeds will not only be dependent on purchase price, but also on co-benefits and simplicity of integration into existing feed practices. Feeding C. crispus at 6% of the diet DM decreased CH(4) production in dairy cows by 13.9% without negative effects on milk yield and composition. Identifying the bioactive compounds in C. crispus is critical to understand the effect of this red seaweed on mitigating enteric CH(4) emissions in dairy cows.