Yes, tannin-free sorghum exists.
Sorghum has a reputation of high tannin levels. This is an image handicap, as the presence of tannin in animal feed is a significant anti-nutritional factor for monogastrics. Indeed, it was prove than even 1% tannin lowered by 7% the energy value of sorghum with pigs and 11% with poultry.
But European sorghum do not have this handicap.
Why are the French and EU sorghum varieties tannin-free?
Because in these countries the « Tannin contents <0.3 » criterion is required to register new varieties. In practice, this means “tannin-free” as its presence is so weak that it has no impact on the quality of cattle feed.
What are tannins ?
Tannins (condensed) are polyphenols of vegetal origin. They precipitate proteins, forming enzyme-resistant complexes, that plant use as a chemical defence solution against pathogen germs and herbivores.
For the past 30 years, European sorghum has been tannin-free, as shown in the graph here under:
On this graph, each dot represents an European variety (in blue from 1980-1982, in red from 1989-1991 and in green, from 2010). Two teachings can be drawn from the data:
- There is a significant correlation between tannin-content and the energy value of the finished product
- Since the end of the 1980s, European varieties are tanning-free