J. Appl. Poult. Res.
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J APPL POULT RES 2006. 15:544-550
© 2006 Poultry Science Association
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Research Reports

Beneficial Effects of Versazyme, a Keratinase Feed Additive, on Body Weight, Feed Conversion, and Breast Yield of Broiler Chickens

J. J. Wang*,1, J. D. Garlich{dagger} and J. C. H. Shih{dagger}

* BioResource International Inc., Morrisville, NC 27560; {dagger} Department of Poultry Science, North Carolina State University, Raleigh 27695

1 Corresponding author: jwang{at}briworldwide.com


   SUMMARY
TOP
 SUMMARY
DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Versazyme (VZ) is a keratinase-based feed additive. Broiler diets were formulated with low (95%), medium (100%), or high (105%) CP and amino acid levels relative to US Poultry Industry Reporting Service averages (2003). In each diet, amino acid minimums were maintained relative to the percentage of CP. The protein levels were as follows: starter—21, 22, 23%; grower—19, 20, 21%; finisher—17, 18, 19%; and withdrawal—16, 17, 18%. Mixed sex broilers 0 to 48 d of age were fed the 3 protein levels with and without VZ (0.10%) in a 3 x 2 factorial experiment. Statistical main effects indicated 48-d BW was greater on the high protein diets (2.42 kg) compared with low protein (2.36 kg), with the medium protein diet being intermediate (2.40 kg). Overall, VZ significantly (P < 0.01) improved 48-d BW 2.54% (from 2.36 to 2.42 kg, P < 0.01), feed conversion ratio 1.62% (from 1.912 to 1.881, P < 0.01), and breast meat yield 1.68% (from 31.57 to 32.10%, P < 0.01). The improvements in BW and feed conversion ratio by VZ were greatest with the low protein diets. However, VZ produced the greatest improvement in breast meat yield at the medium and high protein levels. This enzyme feed additive apparently improves the utilization of amino acids by broilers fed diets formulated to commercial specifications.

Key Words: broiler • breast meat • dietary protein • protease • keratinase


   DESCRIPTION OF PROBLEM
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Commercial poultry diets are formulated on a least-cost basis and may contain protein from numerous ingredients that can vary greatly in the bioavailability of their amino acids. For example, the average true digestibility coefficients for Cys, Lys, and Thr, respectively, are for soybean meal (82, 91, and 88%), corn (85, 81, and 84%), meat meal (58, 79, and 79%), and feather meal (59, 66, and 73%) [1]. There are variations among sources of each ingredient, especially the animal byproducts. Obviously, dietary proteins are not completely utilized by chickens. There is potential to improve amino acid utilization by supplementation of broiler diets with a proteolytic enzyme that has appropriate properties such as activity, stability, and low cost for feed applications.

Studies using multiple enzyme preparations containing proteases in poultry diets have sometimes produced inconsistent results [2, 3, 4]. Recently, supplementation of broiler starter feed with protease- or keratinase-containing products have produced significant improvements in growth [5, 6]. Versazyme (VZ), produced by the natural thermophillic Bacillus licheniformis PWD-1 grown at 50°C, has especially high keratinolytic activity and hydrolyzes a broad range of protein substrates [7, 8, 9]. The VZ added to low protein corn-soybean meal-based starter diets significantly improved the market weight of broilers [10]. The VZ addition to broiler starter diets containing corn, soybean meal, and cottonseed meal significantly improved BW, feed conversion ratio (FCR), and protein digestibility [11]. The objectives of this study were to determine the main effects on live performance and carcass yield and interactions of 3 protein levels (95, 100, and 105% of industry average) with 2 levels of VZ (0 and 0.10%) fed for 7 wk to broilers grown in litter floor pens.


   MATERIALS AND METHODS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Broiler Management
The experiment was conducted on a commercial research farm. The care of chickens used in this trial conformed to the Guide for the Care and Use of Agricultural Animals in Agricultural Research and Teaching [12]. A total of 5,088 mixed-sex 1-d-old broiler chicks of a commercial strain [13] were placed on new litter in an environmentally controlled (23L:1D), curtain-sided, commercial-style broiler house. The house was divided into forty-eight 8 x 10 ft floor pens providing 0.75 ft2/ bird. In each pen, 106 (53 male and 53 female) broiler chicks were placed and reared from 1 to 50 d of age.

Feed Formulation
A corn-soy basal diet was formulated to meet the nutrient profile of US Poultry Industry Reporting Service [14] "all company average" for broilers grown to 2.00 to 2.72 kg (2003). This profile is herein called the medium CP (MP) diet. The MP diet served as the control treatment and represented 100% of the US Poultry Industry Reporting Service averages. Two other diets were formulated to be approximately 5% lower and 5% higher in CP and amino acids than the MP diet. The low CP (LP), MP, and high CP (HP) diets for the 4 growth phases were as follows: starter—21, 22, and 23% CP; grower—19, 20, and 21% CP; finisher—17, 18, and 19% CP; and withdrawal—16, 17, and 18% CP. In each diet, amino acid minimum levels were maintained constant relative to the percentage of CP (Table 1Go). Except for CP and amino acid contents, these diets were approximately isonutritive and either met or exceeded the NRC [1] nutrient requirements for broiler chicks. The respective LP, MP, and HP diets were fed with or without VZ [15] through all growth phases. Diets were fed ad libitum as either crumbles (0 to 18 d) or pellets (19 to 50 d). Versazyme, which is heat stable, was added to the mixer. The mixed feed was pelleted at approximately 180°F. Samples of the diets were analyzed for keratinase activity, CP, and gross energy (by bomb calorimetry). All diets contained approximately the target levels of protein formulated (Table 2Go).


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  		Table 1. Calculated CP and available amino acid levels in experimental diets
 

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  		Table 2. Calculated apparent ME (AME) and CP, and analyzed gross energy and CP, of experimental diets
 
Enzyme
Versazyme was manufactured as recommended by Wang and Shih [16]. In brief, VZ was prepared by growing B. licheniformis PWD-1 in 6,000-L commercial fermentors. The cells were removed by centrifugation. The collected supernatant containing keratinase was de-watered by spray-drying. The enzyme product was added in the dry form to the feed at an inclusion rate of 0.10%, providing 300,000 units/kg of feed of protease activity based on azocasein assay [17]. No other enzymes were present.

Data Collection
The 4 growth phases were as follows: starter (0 to 18 d), grower (19 to 28 d), finisher (29 to 42 d), and withdrawal (42 to 50 d). Body weight and feed consumption were determined at 28 and 48 d of age. Dead birds were recorded daily to calculate mortality. The BW gain was calculated, and FCR and FCR (2.381 kg) adjusted to a constant weight of 2.381 kg (5.25 lb) were calculated (Table 3Go). Feed conversion ratio was adjusted for mortality. Uniformity of BW was determined at 49 d of age by randomly selecting 2 pens per treatment and weighing all birds in these pens. Standard deviation and CV served as indicators of uniformity.


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  		Table 3. Treatment main effects for 48-d BW gain, adjusted feed conversion ratio [FCR (2.381 kg)], and mortality
 
Cut-up yields were determined at 49 and 50 d by taking 100 birds from 1 randomly selected pen per treatment (half at 49 d and half at 50 d). Yields of the following parts were calculated as a percentage of live weight: ready-to-cook carcass without giblets (WOG), leaf fat, breast, leg, back, and wings. The yields of breast fillet, breast tenders, breast bone, and breast skin were calculated as a percentage of whole breast.

Experimental Design and Data Analysis
The experimental design was a randomized complete block with a 2 x 3 factorial arrangement of the 6 treatments (VZ at 0.0 and 0.10% levels; CP at 95, 100, and 105% of control diet). The blocks were based on locations within the house. There were 8 randomized complete blocks. The experimental unit was a pen of 106 broilers. There were 8 replicate pens per treatment. Performance parameters of BW, FCR, mortality, and carcass yields were analyzed using the ANOVA GLM procedure [18] and Tukey’s procedure to separate means. Significance was set at P ≤ 0.05.


   RESULTS AND DISCUSSION
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
No blocking effect was observed for location of pens within the house (data not shown). Mortality through 48 d ranged from 6.5 to 8.3% among treatments and was not significantly affected by dietary CP level or VZ (Tables 3Go and 4Go).


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  		Table 4. Treatment interaction effects on BW gain (BWG), feed conversion ratio (FCR), and mortality
 
As CP levels increased, 48-d BW increased (P = 0.04; Table 3Go). Broilers fed HP diets gained significantly more than those fed LP diets, and the BW gain on MP diets was intermediate. Similarly, FCR was significantly lower (P = 0.02) on the HP diets than on the LP diets, with MP diets being intermediate. The FCR standardized to 2.381 kg (5.25 lb) was significantly (P < 0.01) lower for MP and HP diets than for LP diets. A growth response to increasing dietary CP and amino acid density is well established in the literature [19, 20].

The VZ significantly (P < 0.01) improved 48-d BW by =59 g, FCR by –0.031, and FCR (2.381 kg) by –0.037 when averaged across the 3 CP levels (Table 3Go).

Treatment interaction effects on live performance are presented in Table 4Go. The VZ made the greatest improvement in BW gain and FCR on the LP (95% of "all company average, 2003" [14]), with lesser but still numerically positive values at the MP (100%) and HP (105%) levels. This was true for the 0- to 28-d and 0- to 48-d periods. Versazyme was fed for 50 d. The improvements in BW gain and FCR seen in the first 28 d continued in the 28- to 48-d period. The VZ produced the greatest improvement in BW gain and FCR with the LP diet. These results confirmed our previous studies [6, 10] and indicate the benefits of extending the application of VZ through 7 wk of age.

Carcass component weight as a percentage of live weight is shown in Figure 1Go. The results show clearly that VZ significantly (P < 0.05) improved WOG and breast yield at the HP level, with numerical improvements at the MP and LP levels. Breast fillet and tenders are shown in Table 5Go. The HP = VZ diets significantly increased (P = 0.03) the breast fillet component of breast yield compared with the MP diets.


Figure 1
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  		Figure 1. Carcass components of mixed sex broiler chickens at 49 and 50 d of age; WOG = the dressed, ready-to-cook carcass without giblets; LP = low CP; MP = medium CP; HP = high CP. For both WOG and breast yield, there was a significant improvement by Versazyme (VZ) [15] (P < 0.01) at HP level.

 

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  		Table 5. Breast parts (cut-up) yield as a percentage of whole breast
 
The sensitivity of growth assays can be increased by formulating broiler diets with lower ME or CP than NRC [1] recommendations to better evaluate the efficacy of enzyme supplementation [21, 22, 23]. Thus, as dietary CP is marginal or deficient, there is a greater potential for a response as the proteolytic enzyme releases more amino acids in the digestive tract to meet the bird’s requirements.

It may be inferred from the results of the present study that greater amounts of dietary amino acids were being made more available by VZ. Importantly, WOG and breast meat yield were more responsive to VZ in the HP diets and MP diets than the LP diets. This result probably relates to the higher overall amino acid requirements for optimizing breast meat yield compared with BW in general [24, 25].

Mortality, which ranged from 6.50 to 8.30% among the 6 treatments in 48 d, was not significantly affected by dietary VZ (Table 4Go). Although in theory more protein digestibility may improve immune function and disease resistance, there was no evidence to suggest any such effect in these healthy broilers that were started on fresh litter.

Uniformity of BW is described by SD and CV (Table 6Go). When VZ was added to the diet, the mean SD and CV were numerically lower at LP and significantly and near significantly reduced at MP (P < 0.001) and HP (P = 0.07), respectively. Overall, uniformity of BW is significantly improved with VZ supplementation (P < 0.01). Improvements in BW, FCR, or both have been reported with several types of feed additives (e.g., synthetic amino acids, antibiotics, enzymes, and probiotics). Often these improvements are associated with greater uniformity of BW [26, 27]. This effect has been interpreted to mean that the otherwise smaller, slower growing birds benefit the most by the enhanced nutrition, gut health, or both.


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  		Table 6. Body weight (kg) uniformity of mixed sex broiler chickens at 49 d of age
 

   CONCLUSIONS AND APPLICATIONS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
REFERENCES AND NOTES
 
  1. Versazyme, a commercially available thermostable keratinase with high protease activity, fed till 50 d of age, apparently improves amino acid bioavailability, as evidenced by improvement in BW, FCR and yield of WOG, and breast meat.
  2. Versazyme improved market BW and FCR when added to commercial-type diets varying in protein and amino acids from 95 to 105% of the US Poultry Industry Reporting Service industry average (2003). The relative improvements in BW and FCR were greatest at the low protein level.
  3. Versazyme significantly improved yields of WOG and breast meat at the high protein level.
  4. Versazyme is recommended for addition to commercial broiler diets to improve live performance and carcass yield. The effects would be particularly beneficial when diets are formulated to be marginal in essential amino acids or in total protein to minimize waste N excretion.


   ACKNOWLEDGMENTS
 
This research was supported by the Small Business Innovation Research (SBIR) program of the USDA (2003-33610-13334).


   REFERENCES AND NOTES
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 

  1. National Research Council. 1994. Nutrient Requirements of Poultry. 9th rev. ed. Natl. Acad. Sci., Washington, DC.
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  11. Wang, H. Y., Y. M. Guo, and J. C. H. Shih. 2006. Effects of keratinase supplementation on growth performance, nutrient digestibility, and intestinal development of broiler chickens fed diets with soybean meal and cottonseed meal as protein sources. Anim. Feed Sci. Technol. (In press)
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  15. BioResource International Inc., Raleigh, NC.
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