PHOTO: SHUTTERSTOCK
PHOTO: SHUTTERSTOCK
PHOTO: KOOS GROENEWOLD
SOY ALTERNATIVES ▶▶▶
minerals, but supplemental calcium must be provided if this feed component is a significant proportion of the cattle diet. BSG has been found to be a suitable replacement for SBM or fishmeal in aquaculture diets. Specifically, scientists have found that this ingredient can replace up to 100% of SBM without a significant reduction in the growth of tilapia. Its high fibre content limits its use with broiler chickens, but it can be used with some success. The cost of BSG can fluctuate. BSG requires specialised han- dling and storage and is best fed to livestock soon after deliv- ery to avoid spoilage. In addition, its high moisture content of
Insect meals can contain up to about 80% pro- tein.
up to 80% water can result in high costs for transport over long distances. Because large amounts of BSG are available in summer when beer production peaks, but at a time when cattle are out at pasture, BSG can be dried or siloed so that it can be fed to cattle in winter when pasture is not available. This adds costs, but drying can be done in some areas using heat from the sun. BSG silage must be managed carefully in terms of temperature, pH and more.
5
Brewer’s spent grain is a high- ly-palatable, wet, low-cost protein feed in- gredient.
Single-cell protein (SCP) Single-cell protein (SCP) (growing yeast, bacteria or microalgae) are being actively investigated as a pro- tein feed ingredient as well as a source of fat for vari-
ous types of livestock, but there are currently concerns about costs. Large-scale production is also required. With recent com- mercialisation of SCP from yeast and bacteria, it has already been included in aquaculture feed, but as far back as the 1990s in Finland, it was commercialised (using forestry residues) for pig feed. SCP from yeast is being examined as a feed for dairy cattle, chickens and pigs – and in broilers, there is some evi- dence that certain species have the potential to replace in-feed antibiotics as well due to its antimicrobial properties. The fast growth rate of yeast and bacteria means that these organisms present a promising economical method for large- scale oil and protein production, but inputs of carbon chains are required. Similarly, heterotrophic microalgae are being grown on a limited commercial basis for both protein and oil for aquaculture feed. As with yeast and bacteria, the input of carbon is required, along with some trace minerals, for microalgae production, and the growth rate is slower. Some scientists have found that microalgae could be better incorporated in chicken diets by the use of carbohydrate-active enzymes that increase nu- trient bioavailability. Some studies have found that microal- gae can be used as a protein source for lactating dairy cows in intensive milk production systems, which makes them a suit- able substitution for SBM or faba beans. In the future, large- scale ‘autotrophic’ microalgae production (where the process
Single-cell pro- teins from grow- ing yeast, bacte- ria or microalgae are being active- ly investigated as a protein feed.
of photosynthesis is used by these organisms to capture CO2 from the air as a carbon source) may be possible. However, ensuring enough light reaches all algal cells as their density increases over time requires innovative tank design and/or lighting systems.
Other promising alternatives A percentage of SBM can also be replaced in cattle by maize by-products including distiller’s grains, corn-gluten feed and corn gluten. Protein concentrate from feed-grade bar- ley is also being actively commercialised in the US and Eu- rope as a feed ingredient for aquaculture species. Barley is a sustainable crop as it grows in areas where other food crops don’t fare well, needs little water and few inputs, is not ge- netically-modified and is relatively inexpensive.
20 ▶ ALL ABOUT FEED | Volume 29, No. 4, 2021
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