Performance and intestinal health of broiler chickens supplemented with a protease and fed a standard diet or a low-density diet

Published: October 13, 2025

Source : M.L. DE MORAES 1, K.M. CARDINAL 2, I. ANDRETTA 2, E. SANTIN 3, J.C. BODIN 1,L. LAHAYE 1 and A.M.L. RIBEIRO 2 / 1 Jefo Nutrition Inc., Saint-Hyacinthe, Canada; 2 Federal University of Rio Grande do Sul, Porto Alegre, Brazil; 3 Federal University of Paraná, Curitiba, Brazil.

Summary

The effect of a protease on performance and intestinal health of broiler chickens was evaluated when supplemented on top of a standard diet or in a low-density diet. Male Cobb chicks (392; 1-42d) were reared in floor pens and allocated in a completely randomized design in a 2x2 factorial arrangement with 7 replicates. There were 2 feed formulations: a standard diet (STD) and a low-density diet (LDD), with 6% reduction in crude protein and main digestible amino acids. The 2 diets were either supplemented (+P) or not (-P) with a protease (Jefo Protease at 125 g/t). The performance was evaluated by feeding period (1-7, 7- 21, 21-35 and 35-42d). At day 28, samples of ileum of two bird/replicate were analyzed by a morphometric index for histological alterations. There was no interaction between factors and no differences between the treatments were observed for the first 7 days of age. In general, for all the other periods, birds fed the LDD-P were lighter and/or had poorer feed conversion ratio (FCR) when compared to all other treatments (P < 0.05). The supplementation of the LDD with protease increased body weight gain (BWG) and decreased FCR (P < 0.05), promoting a performance similar to birds fed the STD-P. At 42d, the birds on the STD+P were the heaviest (124g difference to STD-P, P = 0.1) and presented the same FCR as the STD-P and LDD+P groups while being 13 points lower (P < 0.001) than the LDD-P group. Regarding the gut health analysis, birds receiving the protease presented the best morphological index (P ≤ 0.06) mainly as a result of fewer alterations of lamina propria and epithelial thickness and enterocyte proliferation. In conclusion, the protease improved performance and intestinal health indicators of broiler chickens when added on top of a standard diet or with a low-density diet.

I. INTRODUCTION

Protease enzymes can improve the dietary protein utilization. Therefore, it is possible to decrease the level of dietary protein to save on feed cost while maintaining performance, reduce nitrogen excretion in the environment, and minimize the risk of enteric infections. The objective of this study was to evaluate the effect of a protease on performance and intestinal health of broiler chickens fed a standard diet or a low-density diet.

II. MATERIALS AND METHODS

A total of 392 day-old male broiler chickens (Cobb 500) was distributed in 4 treatments with 7 replicates over 42 days. The birds were reared on wood shavings in floor pens (14 birds/pen) and fed ad libitum. Each pen represented an experimental unit. Two diets were used: 1) a standard diet based on nutritional recommendations of the Brazilian Tables for Poultry and Swine (Rostagno et al., 2011) and 2) a low density diet, with 6% reduction in crude protein and digestible lysine (the ratio of the other essential amino acids to lysine was kept the same as in the Standard Diet). The two diets were either supplemented or not with protease (Jefo Protease, Jefo Nutrition Inc.; Table 1). A four-phase feeding program during the rearing period was used (1-7, 7-21, 21-35, and 35-42 days; Table 2).

Table 1 - Treatments distribution.

Table 2 - Composition of the experimental diets (as fed basis).

At d 28, a sample of ileum was collected from two birds per replicate and analyzed by the I See Inside Scoring System Methodology (ISI) according to Kraieski et al. (2017). In this methodology, an impact factor (IF) ranging from 1 to 3 is defined for each alteration in microscopic analysis according to the reduction of the organ’s functional capacity, where 3 is the most impactful. In addition, the intensity and extension of each alteration is evaluated and a score from 0 to 3 is assigned, with 0 being the absence of lesion. To reach the final value of the ISI® index, the IF of each alteration is multiplied by its respective score and the results of each individual alteration are summed. Therefore, a lower number of ISI index represents better result. Body weight (BW), feed intake (FI), body weight gain (BWG), and feed conversion ratio (FCR) were evaluated by feeding periods. Data were analyzed by ANOVA and Fischer LSD using the General Linear Model (GLM) procedure (SAS Inst. Inc., Cary, NC) in a completely randomized design with four treatments. A P ≤ 0.05 was used to indicate statistical significance and a P ≤ 0.1 was used to indicate tendency.

IV. RESULTS AND DISCUSSION

a) Intestinal health

Birds supplemented with the protease presented the best total ISI® morphological index (P ≤ 0.06) mainly as a result of the lower (P < 0.05) number of alterations regarding lamina propria, epithelial thickness and enterocytes proliferation (Table 3).

Table 3 - Histology analysis of the ileum / ISI® methodology.

b. Performance

Comparing both treatments without protease supplementation, birds fed the Standard Diet (T1) presented higher BW and better (P < 0.05) FCR at 21 (P < 0.05) and 42d (P < 0.10) compared to birds fed the low-density diet (T3), showing that the nutritional reduction applied was sufficient to reduce performance (Table 4). Protease supplementation on top of the standard diet (T2) tended to improve (P = 0.1) BW, in which treatment birds were 124 g heavier at 42 days than the ones fed the same diet formulation with no protease supplementation (T1); feed intake and FCR were not affected. Similar results were obtained by Lahaye et al. (2016) and Yu et al. (2007). Supplementation of the low-density diet (T4) with protease allowed the recovery of performance losses due to poor BWG and FCR, promoting an overall performance similar to the control treatment (T1). Because FI was not affected, these observations may be explained by a better efficiency of dietary protein use as previously shown by Wang et al. (2008), who demonstrated that protease supplementation could improve nutrient digestibility and FCR of broiler chickens.

Table 4 - Overall performance.

V. CONCLUSION

The protease studied can be used on top of a broiler standard diet to improve bird performance or with a low-density diet as a strategy to reduce feed cost while avoiding loss of performance. In both cases, the protease positively impacted intestinal health indicators.

Presented at the 29th Annual Australian Poultry Science Symposium 2018. For information on the latest and future editions, click here.

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