# Effects of protease supplementation on the ileal digestibility of amino acids for protein ingredients in broiler chickens

## TL;DR

This study found that adding protease to chicken feed improved amino acid digestion in some protein sources but not others.

## Contribution

The study reveals that protease supplementation enhances amino acid digestibility in specific protein sources like soybean meal and high-protein DDGS in broiler chickens.

## Key findings

- Protease improved amino acid digestibility in soybean meal and high-protein DDGS.
- No improvement was observed in expeller-extruded soybean meal, canola meal, and corn DDGS.
- The effectiveness of protease varied based on the physiochemical properties of the protein sources.

## Abstract

This study aimed to evaluate the effects of dietary protease supplementation on the apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of amino acids (AA) in five protein feedstuffs fed to broilers. A total of 504 one-day-old male broiler chickens (Cobb 500) were randomly assigned to 84 cages in Petersime battery cages (6 birds/cage). From days 0 to 14, all birds were fed a commercial starter diet. From day 14 onward, birds were randomly assigned to one of ten dietary treatments in a 5 × 2 factorial design (8 replicates/treatment), consisting of five protein sources, including soybean meal (SBM), expeller-extruded SBM (ESBM), canola meal (CM), corn dried distillers grains with solubles (DDGS), and high-protein DDGS (HP-DDGS), and two protease dosages (0 and 250 mg/kg). Experimental diets were provided from days 14 to 21. Additionally, four cages were fed N-free diets with or without protease. On day 21, ileal digesta samples were collected after euthanasia. Data were analyzed using two-way ANOVA with the MIXED procedure of SAS to evaluate the main effects of protein source, protease dosage, and their interactions. In the present study, there were interactive effects (P < 0.05) between ingredient and protease on AID and SID of His, Ile, Leu, Phe, Thr, Val, and nonessential AA. Specifically, dietary protease improved (P < 0.05) the AID and SID of these AA for SBM and HP-DDGS. However, broilers fed ESBM, CM and DDGS diets supplemented with protease had no improvement in the AID and SID of these AA. In conclusion, protease supplementation could enhance the SID of AA in SBM and HP-DDGS in broilers, but its effects were less pronounced in ESBM, CM and DDGS. The lack of improvement in AA digestibility for ESBM, CM and DDGS may be attributed to their physiochemical properties, including the complexity and composition of the protein-fiber matrix, and antinutritional factors compared to other protein sources.