Enzymes in Poultry Feed

Abstract

Since the use of non-traditional feedstuffs has become more popular in poultry production, the use of exogenous enzymes has become more crucial. In order to lower the cost of ration formulation, low protein diets and unconventional feedstuffs are now being used. Therefore, enzyme supplementation or fermented feedstuffs could release certain nutrients and increase their availability. In conclusion, the supplementation of exogenous enzymes may introduce a positive development in terms of poultry nutrition. For instance, it has been discovered that phytase supplementation may release phosphorus from phytate and reduce phosphorus excretion in broiler manure. In addition, fiber-degrading enzymes have been proven to improve broiler performance and reduce intestinal viscosity. Likewise, protein-degrading enzymes are beneficial in low-protein diets, as they decrease anti-nutritional factors in soybean meal, increase crude protein, amino acids digestibility and reduce nitrogen excretion and ammonia emission in broiler manure, which positively impacts the environment. The supplementation of mixed exogenous enzymes to broiler feed may lead to better utilization of the nutrients on behalf of the chickens. This chapter discusses the most common enzymes in the field of poultry production, such as β-glucanase, xylanase, mannanase, phytase, and protease.

1. Introduction

Soybean meal (SBM), which is a major source of protein, and yellow corn, which is a major source of energy, are the two feed components that are most frequently utilized in animal rations. However, the global demand of poultry products (meat and eggs) is rising, particularly in developing countries to cover the gap of protein shortage [1, 2]. In addition, the global population is expected to reach 9.1 billion habitants by the year 2050, and the current trend nowadays is to produce biofuel from feed ingredients, which can create a serious food security threat, especially in the developing regions [1].

As a result, there is considerable interest in incorporating non-traditional feed ingredients in poultry rations to substitute some of the SBM and yellow corn [1] or in using some medicinal plants in poultry diets [3, 4]. Natural alternatives to sub-therapeutic antimicrobials are increasingly being used to improve the performance and safety of broiler products. Many feed additives, like enzymes, as a result, that can reduce the risk of digestive diseases while also improving performance are valuable tools for poultry nutritionists. Nevertheless, the non-traditional feedstuffs have anti-nutritional factors (ANF) or significant amounts of insoluble fiber (cellulose) and non-starch polysaccharides (NSP) as soluble fiber in poultry feed [5]. The low portions of dietary fibers and NSP in poultry diets could be beneficial in terms of gut health [6]. However, high levels of NSP may cause excreta to become more viscous and reduce nutrient availability. Thus, the formulation of poultry feed is constrained by these ANF [5, 7, 8]. Enzymes, by definition, are chemicals or catalysts released by cells to speed up specific chemical reactions. This definition accounts for enzymes released in the digestive tract to aid in the digestion of food. Today, these same enzymes can be effectively manufactured and added to animal feeds. Three classes of enzymes (phytases, carbohydrases, and proteases) are typically considered for use in poultry feeds [9]. Therefore, the supplementation of enzymes in poultry feed could be essential to enhancing digestion and nutrient availability, particularly for young birds. Based on the fact provided above, this chapter discusses the concept of enzyme supplementation to poultry feed and their effects on productive efficiency. Supplementing broiler diets with combinations of xylanase, amylase, and protease has been extensively researched. They have been shown to improve nutrient digestibility and growth performance [10, 11, 12, 13, 14]. A combination of amylase, xylanase, and protease enzymes could effectively act together to cleave various bond types in indigestible portions of feed ingredients, leading to increased levels of energy available for growth and/or egg production. The supplementation of these three enzymes to the diet in combination at 500 mg/ton typically increases energy availability to the birds by 3 to 5% [15]. Supplementation of 300 or 600 g/kg diet of such enzymes to broiler or turkey-fed wheat-distillers’ dried grains with soluble-based diet showed improvement in metabolizable energy of up to 203 kcal/kg dry matter [10].

2. The significant impact of enzyme supplementation to poultry feed

Because of the increasing consideration in using non-traditional feedstuffs in poultry diets and their limitation in monogastrics, the significance of enzyme supplementation was considerable for researchers. Besides, attention has been paid to the solid-state fermentation by fiber-degrading microbes [16, 17, 18, 19, 20].

The increasing price of SBM and yellow corn, which are the main feed ingredients in poultry diets, prompted researchers to consider alternative feed ingredients to face the shortage of the aforementioned feedstuffs. The limitation of using the local feedstuffs or agro-industrial waste in poultry feed is a barrier due to their content of ANF, fibers, and NSP [21]. Hereby, the significance of enzyme supplementation becomes apparent in order to alleviate the negative effect of ANF and to increase the nutrient availability to birds. As a result, the supplementation of enzymes allows the feed manufacturer to be more flexible in using a variety of local raw materials. Moreover, a decrease in the excretion of phosphorus and nitrogen to the field has positive effects on the environment and its elements [22].

The type of enzyme that can be used in poultry feed depends on the substrates or the chemical component of the non-traditional feed material that is used as an alternative to yellow corn. There are many types of enzymes that can be utilized in poultry feed. For instance, if palm kernel cake (PKC) is utilized as chicken feed, β-mannosidase [23], β-mannanase, xylanase, and β-glucanase would be included in the feed [5, 17, 20]. On the other hand, if barley or wheat is utilized as chicken feed, xylanase can break down the arabinoxylans in wheat, and β-glucanase can hydrolyze the β-glucosidic bonds of β-glucans in barley [24]. A research study carried out on broiler fed with diet containing 1% prilled palm fat with lyso-lecethin showed significant enhancement in nutrient digestibility, BWG, and FCR during the experiment [25]. Another important point to consider is that wheat and barley can be fed to young birds up to 40 and 30%, respectively, with the supplementation of enzymes [26].

About 80% of birds’ diets are made up of ingredients from plant origin containing non-starch polysaccharides (NSP) in the plant’s cell wall. Among NSP, β-mannans can be considered as the leading molecules and are the most prevalent in a wide variety of feed ingredients including soybean meal, which is the major protein source in feeds produced around the world [27]. In practice, poultry diet supplementation with exogenous enzymes is a universal strategy to improve nutrient utilization and growth performance, thus reducing feed cost [28]. In energy-deficient diets (less than 80 kcal/kg from basal diet), the supplementation of β-mannanase enzyme at 250 or 300 g/ton improved growth performance (P < 0.05) in broiler from 3 to 5 weeks of age. Accordingly, β-mannanase enzyme supplementation should be considered when low-energy diets are formulated in broiler [29].

3. Fiber-degrading enzymes in broiler feed

Supplementation of enzymes to poultry feed, nowadays, is more considerable by nutritionists to improve the nutritional value to the agro-industrial waste. Thus, it can replace a reasonable portion of yellow corn and SBM in poultry diets.

Numerous studies have been done on broiler chickens to determine the influence of enzyme supplementation on productive efficiency. A study carried out by Kocher et al. [30] showed a significant (P < 0.05) improvement in apparent metabolizable energy (AME) and protein digestibility in broilers supplemented with endo-1,3(4)-β –glucanase, hemicellulose, and pectinase at 365 g/kg to their yellow corn and SBM-based diet.

Ng and Chong [31] pointed that fish fed with 40% PKC-based diet and supplemented by exogenous enzyme exhibited improvement in dry matter and energy digestibility. Similar outcomes were reported by Iyayi and Davies [32], who mentioned that supplementation of 0.01% avozyme® in broiler fed with 30% PKC-based diet, led to a significant (P < 0.05) increase in feed intake and body weight gain (BWG) during the starter phase. In addition, substantial increase (P < 0.05) was observed in apparent digestibility of crude protein, fiber, and fat. However, the carcass characteristics and internal organs were not affected by the supplementation of enzyme.

It was reported that gamanase inclusion (hemicell mannanase from Bacillus lentus and mannanase from Aspergillus niger) improved the BWG of broiler fed with diet containing PKC [33]. Furthermore, β-mannanase, β-mannosidase, and β-glucanase are the main enzymes that may degrade the mannan molecule [23]. Additional enzymes were suggested by Moreira and Filho [23] to aid the process of degrading mannan such as acetyl mannan esterase and α-galactosidase to cleave the side chain that may be attached to the mannan.

The fiber content in PKC fermented by cellulolytic and hemicellulolytic bacteria showed significant decrease (P < 0.05) in neutral detergent fiber (NDF), acid detergent fiber (ADF), crude fiber, cellulose, and hemicellulose [17]. In a digestibility trial conducted by Alshelmani et al. [34] on broiler chickens, the amino acid content and availability of PKC fermented by Paenibacillus polymyxa ATCC842 and P. curdlanolyticus DSMZ 10248 were significantly (P < 0.05) increased (Tables 1 and 2).

Nutrient (g/kg)	PKC	FPKCa1	FPKCb2	SEM3	P-values
Crude protein	164.3^b	168.0^a	166.8^a	0.04	0.0003
Dry matter	914.2	926.2	924.4	0.38	0.5228
Ash	47.4	46.7	48.0	0.13	0.2201
Crude fiber	169.6^a	140.9^b	142.9^b	0.19	<0.0001
Neutral detergent fiber (NDF)	822.9^a	717.0^b	735.4^b	0.52	<0.0001
Acid detergent fiber (ADF)	514.8^a	472.7^b	474.5^b	0.58	0.0003
Hemicellulose	308.1^a	244.3^b	264.2^b	0.75	0.0010
Cellulose	355.5^a	318.5^b	314.1^ab	0.62	0.0010
In dispensable amino acids
Lysine	3.7	4.1	3.8	0.02	0.1325
Leucine	8.9	9.4	9.5	0.02	0.0551
Isoleucine	5.0^b	5.9^a	5.3^a	0.02	0.0239
Valine	6.9	7.8	7.2	0.03	0.1433
Phenyl alanine	5.7^b	6.6^a	6.3^ab	0.02	0.0192
Threonine	4.1^b	5.1^a	4.6^ab	0.02	0.0118
Histidine	2.3^b	2.9^a	2.4^ab	0.02	0.0150
Methionine	2.2^b	2.7^a	2.6^a	0.01	0.0003
Arginine	16.0^b	17.6^a	16.9^ab	0.04	0.0312
Glycine	6.0^b	7.8^a	7.1^ab	0.04	0.0489
Dispensable amino acids
Aspartic acid	11.2^b	12.7^a	12.3^ab	0.03	0.0155
Glutamic acid	24.8^b	28.0^a	27.6^a	0.08	0.0033
Proline	4.4^b	5.9^a	5.2^ab	0.02	0.0018
Serine	5.6^b	6.9^a	6.6^ab	0.04	0.0150
Tyrosine	2.5	2.4	2.4	0.01	0.4435
Cysteine	2.0	2.2	2.1	0.01	0.3632
Alanine	6.2	7.0	7.1	0.06	0.3892

Table 1.

Nutrient content of palm kernel cake and fermented palm kernel cake by cellulolytic bacteria (dry matter basis)*^A.

¹

FPKCa; fermented palm kernel cake by P. polymyxa ATCC 842.

²

FPKCb; fermented palm kernel cake by P. curdlanolyticus DSMZ 10248.

³

Pooled standard error of means.

^*a,bMeans ± SEM. Means with different superscripts in the same row are differ significantly (P < 0.05).

n = 6 (6 replicates per treatment with 2 birds per replicate).

A = Adapted from Alshelmani et al. [34].

Nutrient (%)	PKC	FPKCa1	FPKCb2	SEM3	P-values
Crude protein	57.92^b	61.83^a	60.88^a	0.63	0.0014
In dispensable amino acids
Lysine	65.94	69.57	70.63	2.12	0.1479
Leucine	65.47	68.04	63.89	1.39	0.1375
Isoleucine	69.59	70.47	66.39	2.58	0.5152
Valine	62.89^b	70.42^a	65.08^b	1.26	0.0022
Phenyl alanine	68.77	70.76	68.51	1.96	0.6802
Threonine	61.38	64.98	61.69	1.73	0.2935
Histidine	56.99^b	71.50^a	64.83^ab	2.77	0.0076
Methionine	61.67^b	71.92^a	69.20^a	0.90	<0.0001
Arginine	75.75^b	81.15^a	76.30^b	0.95	0.0019
Glycine	47.44	45.52	52.96	4.16	0.4424
Dispensable amino acids
Aspartic acid	56.87^b	64.30^a	61.74^a	1.20	0.0018
Glutamic acid	62.64^b	72.37^a	65.45^b	0.91	<0.0001
Proline	53.76	58.73	51.20	3.06	0.2401
Serine	65.76	69.78	67.58	2.10	0.4186
Tyrosine	59.04^b	67.58^a	61.93^ab	1.84	0.0155
Cysteine	33.34^b	41.45^a	37.46^ab	2.01	0.0393
Alanine	52.07^b	66.87^a	59.84^ab	2.49	0.0029

Table 2.

Amino acid and crude protein digestibility of palm kernel cake and fermented palm kernel cake by cellulolytic bacteria (dry matter basis)*^A.

¹

FPKCa; fermented palm kernel cake by P. polymyxa ATCC 842.

²

FPKCb; fermented palm kernel cake by P. curdlanolyticus DSMZ 10248.

³

Pooled standard error of means.

*^a,bMeans ± SEM. Means with different superscripts in the same row differ significantly (P < 0.05).

n = 6 (6 replicates per treatment with 2 birds per replicate).

A = Adapted from Alshelmani et al. [34].

A feeding trial conducted by Soltan [35] on broiler chickens found that supplementation of enzyme improved the BWG and feed conversion ratio (FCR) in the group fed with 20% PKC-based diet compared to the control group. The supplementation of 0.015% roxazyme® to broiler feed increased BWG and final body weight. Moreover, the supplementation of such enzyme to the PKC led to a significant (P < 0.05) increase in crude protein from 12 to 17.8%. On the other hand, the crude fiber was significantly (P < 0.05) decreased from 20.2 to 17.3% [36].

The nutritional value of the PKC treated with enzyme [36] or fermented by cellulolytic bacteria [7, 17, 34] improved when compared against untreated PKC. It has been found that fungal growth on lignocellulosic fibers during solid state fermentation decreased NDF, ADF, and hemicellulose. In addition, the ANF (phytate and tannins) declined in some agro-industrial waste as a result of microbial fermentation [37]. Regarding the ANF in animal feed ingredients, it has been found that NSP has been reported to be the main reason affecting nutrient digestibility and increase intestinal viscosity. Therefore, the immunity status and gut microflora will be adversely affected as a result of decreasing nutrient absorption and utilization by the animal [5, 7, 20, 38]. The research demonstrated that supplementation of β-mannanase [38] or solid-state fermentation technique by cellulolytic microorganisms [5, 7, 20, 34] to β-mannan-rich diets may increase nutrient digestibility, enhance immunity status of the bird, increase beneficial microflora in small intestines, and improve the productivity of poultry.

In vitro trial conducted by Zamani et al. [39] showed that P. polymyxa ATCC842 and P. curdlanolyticus DSMZ 10248 were capable of producing cellulase, xylanase, and mannanase in PKC, rice bran, and wheat pollard. On the other hand, the supplementation of glucanase and xylanase in broiler fed with wheat-based diet improved the gut microflora [40]. The BWG and FCR improved in broiler chickens fed with diet containing 15% barley and supplemented with β-glucanase [41].

4. Keratin-degrading enzymes

The increase in production of poultry around the world resulted in massive waste output. The most poultry waste resulting from poultry processing in slaughterhouses are feathers. Several million tons of such industrial by-products have been recorded [42, 43]. It is reported that feather constitutes about 8% of the adult bird [44] and contains about 85% crude protein [1]. The feather’s protein is keratin, and the degradable protein is difficult. Feather meal contains 5% cysteine and 3000 kcal/Kg metabolizable energy. The digestible cysteine is about 60% based on the processing conditions [1].

4.1 Degradation of feather meal

The biological value of a feather meal is low because of its nutrient availability to the animal. However, the fermentation process by microorganisms or using keratinolytic enzyme could improve the nutritional value of such a product [1, 44]. Several keratinases were generated from Bacillus spp., B. licheniformis, B. pumilus [44] B. subtilis, and Aspergillus fumigatus [1]. It was observed that keratinase supplementation increased amino acid digestibility in raw feather meal from 30 to 66% [44].

The incubation of keratinase from B. pumilus A1 at 45 to 60°C for 6 h led to the successful degradation of the feather meal. Therefore, the treated feather meal or even the fermented one can be utilized as an animal feed ingredient [44, 45]. Additionally, fermentation with B. licheniformis at 50°C for 5 days may produce a fermented feather meal comparable to that of SBM [1, 46].

As can be seen, the inclusion of feather meal in poultry rations is about 2–3%. Nevertheless, the fermented product by keratin-degrading microbes or keratinase supplementation may provide additional value to such a product, lowering the cost of poultry feed (Table 3) [1].

Reference	Method	Inclusion of feather meal	Output
Adejumo and Adetunji [47]	Feather meal was fermented by B. subtilis to produce microbial biodegraded feather meal.	6%	Improved growth performance
Xu et al. [48]	Supplementation of 200,000 U/kg of keratinase on broiler diet	4%	Improved growth performance, meat quality, and nutrient digestibility
Lee et al. [49]	Feather meal was mixed with soybean meal and fermented by B. amylolequefaciens CU33	5%	Improve duodenal morphology and promote digestion and absorption

Table 3.

Effect of keratinase supplementation or fermented feather meal on broiler performance.

5. Enzyme supplementation on plant protein meals

The most protein-rich source in poultry nutrition is SBM. Raw SBM contains some ANF, such as trypsin inhibitors [46] and lectins [50]. Fortunately, these ANF can be minimized by heating. However, excessive heat leads to decreased lysine availability because lysine is very sensitive to Maillard reaction so that the reducing sugars (raffinose and stachyose) react with the epsilon amino group of lysine and become unavailable [51].

There is a tendency to use low-protein diet in poultry production [46]. The benefits behind that are to reduce nitrogen excretion and ammonia emission from poultry manure to the environment. Additionally, it decreases the cost of feed, increasing the revenue from the production of broilers [52]. Therefore, enzyme supplementation or fermentation processes are being used to break down plant protein for monogastrics. It is recommended to supply protease and phytase to SBM to improve amino acid availability [53] and release more phosphorus from phytate [54].

Phytate molecules can reduce amino acid digestibility by binding dietary amino acids. Therefore, the supplementation of phytase to the chickens increases the availability of phosphorus and amino acids as well [52]. At the same time, it can play an important role in reducing the release of phosphorus into the soil [46]. Other minerals can be increased along with phosphorus as a result of phytase supplementation, so that the availability of other elements, such as zinc, from yellow corn and SBM increases up to 10% [46].

In a feeding trial conducted by Maqsood et al. [55], broiler chickens (Ross 308) fed with low-protein diets (20% of crude protein less than standard allowances) and supplemented with protease at 200 g/ton led to improved growth performance, intestinal health, and carcass characteristics. Similar findings were observed by Tajudeen et al. [56] when birds were fed low-protein diets and administered with 0.022% protease; the birds exhibited an improvement in BWG, crude protein digestibility, and gut morphology. McCafferty et al. [57] reported that protease supplementation in broiler diets improved their growth performance.

Encouraging results were observed among laying hens fed with corn and SBM-based diets and supplemented with protease. A study conducted by Poudel et al. [58] showed that protease supplementation considerably improved crude protein digestibility and increased egg production in laying hens. Wealleans et al. [59] claimed that multi-protease enzyme supplementation to broiler chicken-fed low-protein diets led to enhanced FCR, carcass yield, and gut health. It is suggested that phytase and protease supplementation to low-protein diets can improve crude protein and majority-of-amino acid digestibility [52].

The beneficial impact of protease supplementation on SBM could be attributed to the reduction of ANF, such as trypsin and chymotrypsin inhibitors [56]. The mechanism can occurred via the release of more peptides from ANF that exist in SBM (Table 4) [58].

Supplemented enzyme	Influence	Reference
Protease at 200 g/ton to low-protein diet (20% reduction of protein from standard requirements of Ross 308).	Improved growth performance, gut health, and carcass traits	Maqsood et al. [55]
Protease at 0.022% to low-protein diet (0.75% lower than standard requirements).	Optimum findings in BWG and nutrient digestibility	Tajudeen et al. [56]
Phytase, xylanase, and protease at 2000 U/kg, 200 U/kg, and 15,000 U/kg, respectively.	Improved broiler performance	McCafferty et al. [57]
Protease at 60 g/ton of feed.	Increased egg income and return on investment.	Poudel et al. [58]
Multi protease at 300 mg/kg diet to low protein diet (3.5% lower than standard requirements of Ross 308).	Improved FCR, carcass weight and yield, breast yield, and gut health and morphology.	Wealleans et al. [59]

Table 4.

Effect of diet supplemented with protease and phytase on broiler performance.

6. Conclusion

• In conclusion, the supplementation of exogenous enzymes to poultry feed may introduce a positive development in terms of poultry nutrition. For instance, it has been discovered that phytase supplementation to broiler diets may release phosphorus from phytate and reduce phosphorus excretion in broiler manure.

• In addition, fiber-degrading enzymes have also been proven to improve broiler performance and reduce intestinal viscosity. Likewise, protein-degrading enzymes are also beneficial in low-protein diets, so that it decreases ANF in SBM, releases amino acids, increases crude protein and most-amino-acid digestibility, and reduces nitrogen excretion and ammonia emission in broiler manure, which positively impacts the environment.

• The supplementation of mixed exogenous enzymes to broiler feed may lead to better utilization of the nutrients on behalf of the chickens.

• The dosage of enzyme in poultry feed depends on the enzyme activity and the manufacturer recommendation.