L-Threonine

Feed makers buy L-threonine made in fermentation tanks from carbohydrate feedstocks. Researchers have also studied whey left from cheese making as a feedstock. A dog food label does not reveal which substrate its supplier used.^5,6,11

1. 01 // Source Carbohydrate feedstock Fermentation plants use carbohydrate sources; cheese whey has also been studied as a possible source.
2. 02 // Process Fermented Production bacteria turn the feedstock into L-threonine in a fermentation tank.
3. 03 // Process Recovered and dried For purified grades, processors clarify the broth, isolate the threonine, crystallize it and dry it.
4. 04 // Output Dry L-threonine Purified powder or a dried fermentation product arrives at the kibble plant for measured addition.

1. 01

   Fills a threonine gap

   A formulator adds it when the other ingredients do not supply enough threonine. The needed amount depends on the diet's existing amino acids and the dog's life stage.^1,6,7

2. 02

   Controls protein costs

   In livestock feed, isolated amino acids let formulators use less intact protein when a specific amino acid is short. That approach can save money, but published dog food savings are unavailable.¹⁰

3. 03

   Adjusts one nutrient

   Purified L-threonine raises threonine without bringing along the fat, fiber and other amino acids in a larger serving of a whole protein ingredient.⁵

How much A study in 13 adult dogs tested total dietary threonine from 0.23 to 0.83% as fed; it did not report a typical commercial addition.¹

1. Vets say

   Dogs need threonine in their food

   Evidence

   1. Strong
   2. Some
   3. Thin
   4. None

   Young dogs fed diets without threonine lost weight and had negative nitrogen balance. A separate study in 13 adult dogs measured a dietary requirement. Those findings support meeting the need, not feeding extra.^1,3

2. Brands say

   Adding threonine supports growth when a diet is short

   Evidence

   1. Strong
   2. Some
   3. Thin
   4. None

   In growing Beagles fed purified amino acid diets, 0.52% or more dietary threonine met the study's growth and nitrogen-retention measures. Correcting a shortfall matters; this does not show a benefit from extra threonine in an adequate puppy food.^2,7

3. Brands say

   Extra threonine strengthens every dog's gut

   Outruns the evidence

   Evidence

   1. Strong
   2. Some
   3. Thin
   4. None

   Threonine contributes to intestinal mucus. In a mouse colitis experiment with 5 mice per group, supplementation begun with inflammation delayed recovery. No dog trial shows that extra threonine improves digestion when the diet already supplies enough.⁴

4. Brands say

   Added threonine makes a low-meat food complete

   Outruns the evidence

   Evidence

   1. Strong
   2. Some
   3. Thin
   4. None

   A purified feed material is listed at 99.5% threonine on a dry matter basis. AAFCO's dog food profile requires other amino acids too. This ingredient adjusts one nutrient; it cannot rescue an otherwise deficient recipe.^5,7

5. Owners say

   Fermented L-threonine is unsafe for dogs

   Outruns the evidence

   Evidence

   1. Strong
   2. Some
   3. Thin
   4. None

   An EFSA panel found no viable production cells in the fermentation product it evaluated and judged use at appropriate nutritional amounts safe for target animals. Its assessment covers that product, not every supplier or an excessive dose.⁶