Feeding Algae to Pigs: Really?

November 10, 2015

Lee Johnston and Rob Gardner

Algae is a casual term that has historically been used to classify organisms that live in water and perform photosynthesis.  Algae are a diverse classification, ranging from simple, single-cell microorganisms to complex large seaweeds.  There are an estimated 73,000 algal species worldwide.  Just like land plants, algae convert sunlight and carbon dioxide from the air into biomass.  But algae can make these conversions much faster than land plants.  Some algae can double their biomass in just a few hours.  This makes algae nature’s most efficient primary producers, and they account for more than 50% of global carbon fixation.

Commercial algae production races

Commercial algae production races (Photo credit: AgriLife Pecos Facility)

Because algae grow so fast, there is keen interest in using these efficient photosynthetic organisms to produce biofuels, specialty chemicals, food, and feed.  However, there are challenges associated with algae production.  The infrastructure needed to culture algae can be costly, not all algae make desired products so contamination of beneficial algae cultures with rogue strains is a problem, low fuel prices make it difficult for algal-based fuels to compete with fossil fuels, and algae use a lot of nitrogen and phosphorus.  Currently, industrial algal cultivation is becoming a reality as breakthroughs in technology are becoming realized.  One approach that algal biofuel producers are pursuing is to use oil-extracted biomass as a feed source for animals.  An important benefit of this approach includes selling a secondary product that has a higher value than biofuel which offsets high production costs of the algal-based biofuel.  Additionally, recycled nitrogen and phosphorus from wastewater can reduce some of the input costs of culturing algae.  Algae are very good at growing on wastewater.

The global demand for consumable proteins is increasing which is sequentially increasing the demand for high quality animal feedstocks.  Algae have the potential to increase the quality of animal feed by acting as a nutritional supplement that is high in desirable protein and other nutrients.  However, further evaluation of algae as a nutritional supplement must be conducted as different algal strains have different nutritional characteristics.  Here at the West Central Research and Outreach Center (WCROC), we recently completed an experiment to evaluate the efficacy of dried algae meal in diets for nursery pigs.  Basically, the algae meal we fed to pigs resulted from biomass after pretreatment for other purposes.  

We had two primary objectives in the experiment.  First, we wanted to know if the algae meal would act as a pre-biotic in the gut of newly-weaned pigs.  A pre-biotic is a compound that provides necessary nutrients to support the growth of beneficial bacteria in the gut.  Our thought was that some portions of the algae might help newly-weaned pigs transition from the milk diet they consumed while nursing to the dry diet provided to them after weaning.  The diet to test this objective included only 1% algae meal.  We monitored health of the pigs and growth performance.  In addition, we collected content samples from the pigs’ intestines, stomach, and digestive tract.  These data and samples will tell us how well the pigs adapted to their new diet after weaning.  

Newly weaned pigs

Newly weaned pigs (Photo credit: U of MN Extension)

Our second objective was to determine if the algae provided adequate nutrients to support normal growth of nursery pigs.  Maybe the algae is just another source of nutrients for pig growth just like corn, milk products, soybean meal, and other common swine feedstuffs.  To test this idea, we included 5, 10, or 20% algae meal in diets based on corn and soybean meal.  We monitored growth rate, feed intake, and efficiency of weight gain for the pigs over a 6-week period.  

What did we learn?  Pigs seemed to readily consume diets containing 1, 5, or 10% algae meal with no problems.  The highest level of algae meal (20%) seemed to be less desirable to pigs.  It appeared that this diet was very “sticky” and would cake on the feeders.  We suspect the pigs experienced an undesirable texture of this diet which reduced their feed intake.  The study just concluded so we still need to evaluate the samples collected to determine if algae meal acted as a pre-biotic.  Stay tuned for results as they become available!  We will continue to look for ways to capture nutrients from algae and other sources that will improve the sustainability of pork production.