Distillers grains, cottonseed meal and soybean meal are common examples of co-products used every day as ingredients in beef cattle rations.

In fact, one of the primary advantages of ruminant production systems is their ability to utilize low-value sources of nutrients, which contributes significantly to the sustainability of beef production systems.

A novel co-product of biofuel production from algae is currently being developed and evaluated as a potential feedstuff in beef systems.

Algae is posed as an ideal biofuel source because of its relatively high oil content and its ability to make use of land and water resources otherwise unsuitable for food or feed production.

One of the biggest challenges, however, remaining with the commercialization of algae as a biofuel source is capturing both economic and nutritive value from the residue post-oil extraction.

The remaining fraction, termed post-extraction algal residue – or in short, PEAR – has been observed to contain high levels of protein (18 to 38 percent) and high levels of ash (12 to 46 percent).

Nutrition and taste

We began investigating the use of the algae co-product in cattle consuming medium-quality and low-quality forage diets. In these projects, we focused on determining the palatability and nutrient availability of PEAR.

More recent research has involved the use of the algae co-product in concentrate or finishing rations of beef steers and its impact on carcass characteristics and beef quality and flavor.

Our initial work was completed using first-generation PEAR that contained 18 percent crude protein and 46 percent ash, not exactly an ideal feed ingredient.

Recent research has used second-generation PEAR, which benefits from improvements to the growing, harvesting and oil extraction processes used in algal biofuel production. The second-generation PEAR contained 34 percent crude protein, 12 percent ash and 4 percent crude fat – a more ideal feed ingredient compared to first-generation PEAR.

As further improvements and modifications are made to the oil extraction process, we expect processors to make additional gains in improving the nutritive value of PEAR and their ability to remove oil.

However, we expect variability in nutrient composition between sources of PEAR to be a long-term challenge for both nutritionists and producers. Hopefully, algal processors will see the value in producing a consistent co-product if algae emerges as a viable source of biofuel.

Mineral composition

An additional problem that will likely need to be addressed in the process of growing, harvesting and extracting the algae is its mineral composition. A number of PEAR samples have contained mineral imbalances or levels of concern that will create ration formulation challenges and toxicity concerns if not properly managed.

In our most recent study at Texas A&M, greater intake was observed for finishing steers consuming PEAR compared to control steers. However, dietary energy intake was similar among treatments, indicating reduced digestibility with PEAR inclusion.

Additionally, this observation is similar to that of our initial studies. This may be in part due to the high ash content of PEAR. The first-generation PEAR was nearly half ash, while the second generation was approximately 12 percent. However, in all of our projects, cattle have readily consumed PEAR provided they have the entire day to consume the diet.

In feeding form

One of the challenges we encountered with feeding PEAR is its physical form. In our work, PEAR has been provided as a dry powder, which has required various levels of processing prior to inclusion in different diets. We have experimented with pelleting PEAR and have produced pellets of excellent quality.

In complete rations, we have generally included the PEAR in powder form and have added moisture to decrease dust and to allow PEAR to stick to other ingredients.

Providing PEAR as a protein supplement to cattle consuming low-quality forage has generally resulted in responses similar to conventional protein supplements, increased intake and greater digestible energy consumption.

However, supplement consumption with PEAR inclusion was spread out across the entire day rather than as a bout of consumption lasting a few minutes as is commonly observed with conventional protein supplements. We attribute this difference to the high mineral content of PEAR.

Inclusion of PEAR in finishing rations of steers resulted in greater USDA marbling scores – and quality grades – than controls, while yield grades and carcass weights were not different. Exact mechanisms of improved carcass quality will require further research.

How’s the beef taste?

When purchasing animal protein, consumers have a variety of choices, and one of their primary motives when making a purchasing decision is flavor. Therefore, ensuring PEAR doesn’t negatively impact flavor is an essential component of our research. Variation in flavor can be the result of differences in fatty acid composition of beef.

Ultimately, differences in fatty acid composition are caused by the fatty acid composition of the diet consumed, such as in the case of grass-fed versus grain-fed beef.

The fatty acid composition of PEAR was intermediate to the finishing ration and hay used in our study, with similarities and differences to both the concentrate and forage, so we had reason to question the flavor properties of beef from PEAR-fed steers.

To investigate flavor differences caused by PEAR inclusion, a trained sensory panel evaluated strip steaks from steers fed PEAR and control diets. No off-flavors from the inclusion of PEAR in finishing rations were observed.

To answer additional questions related to beef flavor, a consumer sensory panel where consumers will sample ground beef from PEAR steers is set to take place in the near future. The upcoming consumer sensory panel will likely provide information on the ability of consumers to detect differences in beef flavor from steers fed PEAR.

There are many unanswered questions when it comes to the use of PEAR as a protein source for beef cattle and other livestock species. However, our current data suggest that beef production systems are a possible market for this novel co-product.  

PHOTOS
PHOTO 1: Unprocessed post-extraction algal residue on the left and pelleted PEAR on the right.

PHOTO 2: Kyle Weldon is feeding post-extraction algal residue to research cattle at a Texas A&M research facility in College Station, Texas. Photos courtesy of Texas A&M AgriLife Research