Location: Dairy Forage Research
Project Number: 5090-31000-027-014-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Jul 1, 2019
End Date: Oct 31, 2023
Objectives 1. Identify macroalgal species present off the California coast that may reduce the enteric production of methane when used as feed additives in ruminant diets. 2. Measure growth/nutrient uptake rates and suitability of candidate methane reducing macroalgae for aquaculture production systems. 3. Determine the in vivo digestibility and enteric methane production for dairy cows fed candidate macroalgae species displaying the best aquaculture potential and enteric methane reduction.
At least 20 species of readily available macroalgae species found in Californian coastal waters will be collected, freeze dried and then milled into a particulate. Macroalgal samples will be analyzed for biochemical parameters including proximate, elemental, tannin, and fatty acid composition. All 20 macroalgaes will be accessed for their impact on organic matter digestion by in vitro fermentation. Rumen fluid, along with an artificial saliva and a typical roughage that cattle normally consume, will be combined with a collected macroalgal sample in at least 6 replicated sterile bottles. The bottles will then be incubated at 39°C simulating bovine anaerobic digestion. Initial in vitro screening of seaweeds will assess nutrient organic matter digestibility at multiple inclusion rates of each seaweed species. Species and inclusion rates that do not significantly reduce rumen organic matter digestibility will then be assessed for gas production over a 24 h period. Gas chromatography will be used to measure the methane fraction of the total gas collected during the fermentation. To assess the effects of macroalgae supplementation on methane emission and energy loss to cattle, three of the most promising macroalgaes identified in the in vitro research will be fed to live dairy cows in controlled feed assays. Macroalgal feed additives at minimal inclusion rates will be compared to control diets without the feed additive. The methane and carbon dioxide emissions and oxygen consumption will be measured using both and advanced air-flow controlled chambers which permit total gaseous collection. Further, the effects of macroalgae supplementation on nutrient utilization, lactation yield and milk component quality will be determined.