- Glycine and serine can become growth-limiting for 1 to 21 days old broilers in feed containing less than 20 % crude protein.
- Glycine and serine should be assessed together using the glycine equivalent rather than the simple sum of glycerine+serine.
- The requirement for glycine equivalent depends on other nutrients such as threonine, choline, and cysteine. Reversely, the requirement for threonine and choline is not constant, and the optimal ratio between methionine and cysteine depends on the glycine equivalent concentration.
- Adequate glycine equivalent concentrations enable reducing the crude protein concentration in feed for broilers from 1 to 21 days to about 16 % without undesirable effects on growth and feed efficiency.
- Adequate glycine equivalent concentrations in low crude protein feed can only be achieved with using animal proteins and/or free glycine or l-serine.