L-Lysine

Industrial amino acid makers ferment sugars to make lysine for animal feed, then purify the broth into a stable additive. A kibble formulator buys it to correct a recipe's amino acid balance.^4,6,7

1. 01 // Source Fermentable sugars Sugars from molasses or processed starch feed the production culture.
2. 02 // Process Bacterial fermentation Corynebacterium glutamicum converts the sugars into L-lysine in a controlled fermentation.
3. 03 // Process Lysine separated Ion exchange resins separate charged lysine from the fermentation broth.
4. 04 // Output L-lysine powder One form is a dry hydrochloride powder; tested batches contained 79.7% lysine on a dry matter basis.

1. 01

   Closes a lysine gap

   Dogs cannot make lysine. Adding it separately lets formulators adjust dietary lysine without changing every protein ingredient, while the finished food still needs the other essential amino acids.^1,4

2. 02

   Balances processed protein

   Heat processing can bind lysine and reduce its availability. Supplemental lysine gives formulators another way to set a target, although the pet food survey did not test supplemented recipes.^2,4

3. 03

   Buys one nutrient

   Industrial fermentation makes feed amino acids at large scale. Manufacturers can buy lysine separately instead of adding whole protein solely to correct a lysine shortfall; recipe costs are unpublished.^1,6

How much In a 13-dog trial, top-dressed lysine hydrochloride lifted a deficient 0.36% lysine diet to as much as 0.62% as fed.¹

1. Brands say

   Added lysine corrects a dietary shortfall

   Evidence

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

   A 13-dog study raised lysine in a deficient test diet and measured a breath tracer response. It supports correcting a shortfall, but did not test extra lysine in dogs already eating enough.^1,4

2. Owners say

   Lysine alone makes a low protein recipe complete

   Outruns the evidence

   Evidence

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

   The 13-dog experiment adjusted lysine while controlling the other amino acids. EFSA says supplementation requires an appropriate amino acid balance. One isolated amino acid cannot replace missing protein or supply the others a dog needs.^1,5

3. Owners say

   Extra lysine cannot hurt a puppy

   Outruns the evidence

   Evidence

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

   A nutrition guideline summarizes a puppy experiment: 4% added lysine reduced weight gain, while 2% did not. Those were deliberately high test doses, so the finding does not implicate ordinary complete kibble.³

4. Brands say

   Added lysine restores heat-damaged protein

   Outruns the evidence

   Evidence

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

   An analysis of 53 pet foods and treats found less reactive lysine in dry foods than wet foods. It did not test supplementation. Adding one amino acid cannot repair protein already damaged by processing.^2,4