Protease is an exogenous enzyme added to broiler feed to improve protein digestion, but its value extends far beyond simply breaking down dietary protein. It is a strategic tool used to enhance nutrient efficiency, reduce metabolism costs, support gut health, and lower both feed costs and environmental impact.
Adding exogenous protease to broiler chicken diets could increase ileal digestibility of crude protein (CP) by 3-8%by hydrolysing complex proteins into absorbable peptides and amino acids; degrade trypsin inhibitors, lectins, and antigenic proteins such as glycinin and β-conglycinin, allowing to reduce immune activation and gut inflammation; reduce pancreatic endogenous amino acids losses by preventing pancreatic hypertrophy and reducing excessive enzyme output; reduce undigested protein in the hindgut to limit substrate for pathogenic bacteria like Clostridium perfringens.
Because protease spares significant amounts of endogenous amino acids, this spare effect contributes directly to the “matrix values” used in feed formulation. Based on the ideal amino acids profile, the modern broiler chicken performance is mainly driven by the dietary digestible lysine levels. Compared with the Aviagen recommendation, increasing 3% of standardized ileal digestible (SID) Lysine level will usually increase chicken body weight by 175 grams in 42 days of post hatching period and reduce feed conversion ratio (FCR) by 2 points. On the other hand, increasing 3% of SID lysine level will increase feed cost by 12 AUD/MT. Based on the study conducted in the University of Sydney, after adding phytase, xylanase to wheat-soybean meal- canola meal diet, VTR’s protease supplementation could spare 2.7% of SID lysine level or save the feed cost about 10 AUD /MT but will not improve the chicken performance. However, if this protease tops up the current feed formulation, it will increase chicken body weight gain by 158 grams and improve FCR by 1.8 points.
It is noteworthy that in the feed formulation with protease supplementation, the ideal amino acids profile must ensure that SID lysine is the first limiting amino acid and any other single amino acid deficiency will depress chicken performance (Figure 1). Adding protease to diets with unbalanced amino acids profile has no benefits on chicken performance. Interestingly, when dietary SID tryptophan to lysine ratio increased from 0.16 (ideal amino acid profile) to 0.22, it significantly improved FCR (Figure 2).
In addition, dietary SID cysteine (Cys) proportion in SID sulphur amino acids (Met+Cys) also influence the effect of protease supplementation. When the chicken diet contains the higher meat and bone meal, it will result in the lower proportion of SID Cys in SID Met+Cys. Adding Protease to this diet may improve chicken immunity but no obvious effect on chicken performance. However, when the chicken diet contains the higher feather meal, it will result in the higher proportion of SID Cys in SID Met+Cys. Adding protease to this diet will significantly improve the chicken performance.
Figure 1. The effect of single amino acids deficiency on chicken body weight gain (g/birds, 15-35 days of age).
Figure 2. The effect of higher dietary tryptophan level on chicken FCR (15-35 days of age)
A study compiled by our Redox Animal Nutritionists.