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J APPL POULT RES 2007. 16:1-12
© 2007 Poultry Science Association
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Research Reports

The Effects of Nonstarch Polysaccharide Enzyme Addition and Dietary Energy Restriction on Performance and Carcass Quality of Organic Broiler Chickens

N. P. Buchanan*, L. B. Kimbler*, A. S. Parsons*, G. E. Seidel{dagger}, W. B. Bryan{ddagger}, E. E. D. Felton* and J. S. Moritz*,1

* Division of Animal and Nutritional Sciences, {dagger} Department of Statistics, and {ddagger} Division of Plant and Soil Sciences, West Virginia University, Morgantown 26506

Correspondence: 1 Corresponding author: Joe.Moritz{at}mail.wvu.edu


   SUMMARY
TOP
 SUMMARY
DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Feed constitutes a substantial cost in organic production. Organic poultry may have access to pasture, a nutrient source that has the potential to curtail feed costs. Past research has demonstrated that feed restriction will motivate broilers to forage. Incorporating a nonstarch polysaccharide (NSP) enzyme may enable broilers to better utilize nutrients found in forage. The objective of this study was to examine ways to decrease feed costs by increasing forage intake through dietary energy dilution (7%) and increasing forage digestibility through the incorporation of an exogenous NSP enzyme. The experiment was conducted during the 3-to-8-wk growing phase in spring and summer months on broilers with and without access to pasture. Dietary energy dilution did not result in increased broiler forage intake. During the spring months, NSP enzyme inclusion enhanced performance only when broilers were given access to pasture. Feeding a low-energy diet with NSP enzyme did not enable broilers to overcome a 7% energy dilution. Decreasing energy and subsequent feed cost in organic broiler diets may be possible with energy dilutions less than 7%, depending on forage intake and quality.

Key Words: nonstarch polysaccharide • forage utilization • broiler production • organic production • energy variation


   DESCRIPTION OF PROBLEM
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Segments of the American public have become increasingly concerned with management practices and the composition of diets fed to production animals. In accordance with the demand for an increase in organic foods, organic poultry production has become a fast-growing segment of American agriculture. Organic poultry production provides consumers a product derived from organically certified grain that is free of antimicrobial additives. Organic poultry producers supply only 1% of the poultry market in the United States, yet the demand for organic poultry products exceeds the supply [1].

Organic poultry production offers an economic opportunity for integrated companies looking for a niche market and family farms looking to supplement existing income. Land and husbandry costs are a small investment, but feed is a substantial cost in production. The price of organic feed may be twice that of conventional feed due to the premiums required for organically certified grain.

Little is known about the nutrient requirements of broilers fed organic diets. Requirements may be affected by organic production methods. Current diets are formulated to meet or exceed NRC [2] recommendations for poultry that are reared in a conventional setting. However, organic broilers may have access to pasture, which is a nutrient source that has had little evaluation for use in poultry production. Thus, it may be plausible to address consumer concern over management practices and reduce feed costs by maximizing the use of pasture.

In some free-range and organic production settings, birds may seldom leave the house [3]. This becomes a concern because the birds do not properly utilize outdoor enclosures, leading to a false consumer perception that birds spend much time outdoors. Past research has reported that fast-growing commercial strains of birds given access to the outdoors will not take full advantage of pasture access due to natural behavior or a rapid growth rate and the subsequent correlation to impaired mobility [4, 5]. To maximize pasture use, it is imperative that birds be motivated to spend time outdoors. A commercial strain of broilers restricted to 50% intake of an ad libitum pair-fed group has been shown to consume significantly more forage [6]. Thus, by providing a limited amount of feed, or perhaps reducing nutrient density, a producer may have the ability to motivate broilers to maximize forage intake.

Feed costs may be offset by increasing forage intake and improving forage digestibility. Nutrient availability of forage may be increased through the incorporation of feed enzymes. Forage is a fiber-based energy source consisting of assorted nonstarch polysaccharides (NSP). However, NSP levels vary depending on forage type, stage of growth, and season [7]. Monogastrics have a limited ability to utilize NSP as a nutrient source [8, 9, 10]. In addition, NSP may play an antinutritive role, adversely affecting digestion of other nutrients by imbibing water and causing feed to form a bolus that may reduce exposure to digestive enzymes [9, 11]. Increased consumption of NSP has been linked to management problems involving increased stickiness of excreta and increased litter moisture [8, 12].

Broiler chickens do not produce endogenous enzymes that aid in NSP digestion. Thus, they rely on acid digestion in the proventriculus and microbial degradation in the ceca and large intestine [11]. Digestion of NSP can range from 13% in lupin diets to 21.9% in wheat diets without enzyme supplementation [13]. The effectiveness of exogenous NSP enzymes in monogastric diets has been controversial. Past research has shown that enzyme inclusion in a variety of poultry rations has no effect on performance or digestibility variables [8, 14, 15]. However, other studies report improved performance and digestibility [10, 16, 17, 18]. Research on NSP enzyme supplementation associated with forage digestibility in poultry does not exist. The objectives of this study were to reduce feed costs by increasing forage consumption via the use of a low-energy diet and to increase nutrient digestibility of forage through the incorporation of an exogenous enzyme cocktail containing ß-glucanase, pentosanase, and hemicellulase hydrolyzing activities.


   MATERIALS AND METHODS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Experiment 1
Five hundred 1-d-old Ross 308 x 344 broilers [19] of mixed sex were obtained from a commercial hatchery. All broilers were reared during the 0- to 3-wk period in floor pens in a cross-ventilated negative-pressure house using forced-air brooders. Broilers were provided with feed and water, supplied through feed pans and nipple drinkers, ad libitum. The temperature of the room was maintained at 35°C (95°F) and decreased to 22°C (71.6°F) during the 0- to 2-wk period. One week before outdoor placement (2- to 3-wk period), temperature was decreased so that indoor temperature was comparable to outdoor temperature to acclimate broilers (Table 1Go). Broilers were fed a certified organic starter diet during the 0- to 3-wk period (Table 2Go). The diet met or exceeded NRC recommendations [2].


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  		Table 1. Outside environment conditions and feed and forage nutrient content
 

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  		Table 2. Diet formulations and nutrient parameters for organic diets
 
At 21 d of age, 300 birds were randomly selected and transported to the West Virginia University Organic Farm [20]. Birds were assigned at random to 1 of 5 poultry houses, 3.05 x 3.05 m (10 x 10 ft), utilizing natural ventilation. Each poultry house comprised 1 block and was divided into 4 equally sized pens that contained 15 birds at a stocking density of 0.14 m2/bird (1.5 ft2/bird). Each pen was equipped with fresh wood shavings, a Kuhl feed pan and hopper, and a 5-gal water fountain. All 4 pens within a single house had access to 2 individual 6.10 x 9.15 m (20 x 30 ft) outdoor paddocks and unlimited forage, including Kentucky bluegrass, white clover, red clover, and tall fescue. Each pasture paddock contained an enclosed area to allow for estimation of forage growth. One pasture paddock was utilized for the 21- to 38-d period and the second pasture paddock for the 38- to 56-d period. This rotation was utilized to provide access to new forage growth and clean pasture. Pasture height of enclosures not in use by broilers was maintained by grazing sheep. Broilers had access to pasture throughout all daylight hours (0800 to 2000 h) and were confined in the house throughout the night.

An energy level x NSP enzyme inclusion factorial design was utilized to provide a total of 4 dietary treatments [normal energy-no enzyme (NOR-NE), normal energy-enzyme (NOR-E), low energy-no enzyme (LOW-NE), and low energy-enzyme (LOW-E); Table 2Go]. The normal-energy (NOR) diet consisted of an organically certified grower diet that met NRC 3- to 6-wk nutritional recommendations [2], with the exception of Met. Past research has shown that birds given access to pasture may, in part, compensate for small deficiencies in Met through pasture access [6]. Hence, diets excluded synthetic Met and were slightly deficient in Met according to NRC recommendations. The low-energy (LOW) diet was similarly formulated, with the exception of a 7% energy reduction obtained by the addition of washed builder’s sand [21] (Table 2Go). Treatments consisted of the 2 aforementioned diets with or without the addition of a commercially available NSP enzyme cocktail at an inclusion level of 1 kg/ton. The enzyme cocktail was derived from the fermentation of Aspergillus aculeatus and contained ß-glucanase, pentosanase, and hemicellulase hydrolysis activities [22]. Broilers fed LOW diets were pair-fed according to the previous day ad libitum consumption of broilers fed NOR energy diets. Pair feeding was performed daily to standardize feed intake (FI) and to conclude that treatment differences were due to the variation in dietary energy.

Broilers without pasture access (negative control) were reared in floor pens at the West Virginia University poultry farm. The negative control broilers were fed the same dietary treatments as broilers with pasture access. Water was provided ad libitum through nipple drinkers and pair-feeding was utilized. Each negative control treatment was blocked by location in the room and replicated in 5 pens containing 10 birds/ pen [0.14 m2/bird (1.5 ft2/bird)]. Lighting and temperature were controlled within the constraints of management equipment to mimic outdoor conditions.

Live weight gain (LWG), FI, feed efficiency (FE), forage intake, and percentage of mortality were determined from 21 to 38 d, 38 to 56 d, and the entire 21- to 56-d experimental period. Forage intake was calculated by measuring sward height and using regression analysis to estimate herbage mass. An enclosed area in each paddock was used to estimate forage growth. The disappearance of herbage mass in the pasture paddock compared with the enclosed area was equated to the forage intake [23]. Grass samples were collected in each paddock using the procedure outlined by Rayburn and Rayburn [23]. Feed and grass samples were freeze-dried [24], ground to 1 mm [25], and analyzed for gross energy [26], N [27], amino acid content [28], NDF [29], and acid detergent fiber [30] (Table 1Go).

On d 57, all broilers were processed at the West Virginia University pilot processing plant. Four broilers (2 males and 2 females) were selected from each pen within all houses and from each pen in the negative control room. Broilers were selected based on their representation of the mean pen weight. Hot carcass weight (HCW), hot gizzard weight, chilled carcass weight (CCW), chilled breast weight, and hot fat pad weight data were obtained. The study was conducted in spring months and then repeated in summer months to assess season effects. All birds were reared according to protocols established by the West Virginia University Animal Care and Use Committee (03-0302).

Experiment 2
A feed passage time study was performed to assess possible passage time variation in diets that differed in energy and composition. Sixty 1-d-old Ross 308 x 344 broilers [19] of mixed sex were obtained from a commercial hatchery. All broilers were reared during the 0- to 3-wk period in a manner similar to experiment 1, with the exception of brooding temperature. Over a 3-wk period, temperature was regulated thermostatically by beginning chicks at 35°C (95°F) and decreasing the temperature to 22°C (71.6°F). On d 21, broilers were transferred to 30.48 x 50.80 cm (12 x 20 in.) raised wire cages in a cross-ventilated negative-pressure room. Three broilers were placed in each cage that contained nipple drinkers and an external feed trough.

The organic grower diets (Table 2Go) utilized in experiment 1 were randomly assigned to cages within each of 4 blocks. Feed and water were provided ad libitum during a 7-d adaptation period, and fecal samples were collected to determine percentage of acid insoluble ash (AIA) from diets without added AIA. Concluding the adaptation period (d 28), feed was restricted for 24 h. Broilers were then fed 100 g/cage of the same experimental diet with the addition of 5.0% AIA in the form of celite [31]. Diets containing celite were provided for 2 h. After the 2-h period, any remaining feed was removed and weighed to determine feed intake. The experimental diet with no celite was fed upon removal of the diet containing celite. Water was provided ad libitum throughout the experiment. Fecal collection began 4 h after broilers were given celite-containing diets and continued every 2 h for the following 14 h, then again at 24 h. Excreta samples were weighed, freeze-dried [24], and ground to 1 mm [25]. Dry matter and AIA were determined according to Vogtmann et al. [32], and feed passage time was calculated.

Statistical Analysis
In experiment 1, a season x energy x enzyme factorial split-plot design was used to explore main effects and interactions of all treatments on performance and carcass characteristics. Pasture access was designated as the main plot. Season, energy, and enzyme constituted the subplots. Treatments were blocked by organic house for broilers given outdoor access. For broilers given no outdoor access, treatments were blocked by location in the room. A male:female was used as a covariate for performance. All possible linear contrasts were performed to explain significant interactions (data not compiled in a table). Orthogonal contrasts were used to answer specific interactions between treatments. A second analysis, consisting of a randomized complete block design, was used to analyze forage intake and feed passage time. A male:female and a legume:grass were used as covariates for forage intake. Fisher’s least significant difference test was used for multiple comparisons between mean values for forage intake. Duncan’s new multiple range test was used for multiple comparisons between mean values within each collection time for feed passage time. All statistical analyses were performed using the GLM procedure of SAS Institute [33], and {alpha} was designated as 0.05.


   RESULTS AND DISCUSSION
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Environmental Conditions
The environmental conditions during spring and summer months are described in Table 1Go. Broilers reared in spring months were exposed to lower temperature and humidity, as well as a shorter photoperiod, compared with broilers reared in summer months. Precipitation values were similar among study periods. Environmental conditions are presented as descriptive data to support season effects.

Organic Broiler Performance and Carcass Characteristics
Table 3Go contains all performance data for the 21- to 38-d, 38- to 56-d, and 21- to 56-d period. Only the 21- to 56-d period will be discussed, unless more specific periods are needed to support overall observations. Table 4Go describes the carcass characteristics of broilers processed on d 56. To negate the effects of varying LWG, gizzard weight (GRH) and fat pad weight (FRH) are recorded as a ratio to HCW, and breast weight is recorded as a percentage of CCW. All data were statistically analyzed; however, only ratio and percentage weights will be discussed.


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  		Table 3. Influence of enzyme inclusion and dietary energy restriction 3- to 8-wk performance in spring and summer months
 

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  		Table 4. Influence of enzyme inclusion and dietary energy restriction on 3- to 8-wk broiler carcass characteristics in spring and summer months at d 56
 
Broilers fed LOW diets, despite pair-feeding, consumed significantly less than broilers fed NOR diets (P = 0.0001). This result was thought to be due, in part, to variation in digestive transit time in the intestine of broilers fed the LOW diet that included washed builder’s sand. Feed passage time data (experiment 2) is described in Table 5Go. Only broilers fed the LOWE diet had increased feed passage time (P = 0.0047 and P = 0.0307) at 6 and 8 h postfeeding, respectively. Danicke et al. [34, 35] and Lazaro et al. [36] found that enzyme addition reduced digesta viscosity and increased feed passage time of markers in the digestive tract, resulting in an increase in feed intake. In the current study, FI was decreased. Therefore, a reduction in FI for broilers fed LOW diets is likely due to energy restriction during the growing period. Energy restriction has been shown to reduce the probability of a bird meeting optimal growth, causing a subsequent decrease in FI [37, 38, 39].


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  		Table 5. Influence of enzyme inclusion and dietary energy restriction on passage time as determined by percentage of acid insoluble ash1 (AIA)
 
An energy x access interaction was observed (Table 4Go) for HCW (P = 0.0223), CCW (P = 0.0429), and GRH (P = 0.0330). Broilers fed LOW diets and given access to pasture had smaller HCW and CCW compared with all other broilers. However, pastured broilers fed LOW diets had larger GRH than pastured broilers fed NOR diets or broilers fed either diet and given no access to pasture. An energy x enzyme x access interaction was observed for FRH (P = 0.0455). Only when broilers were fed the LOW-NE diet and given access to pasture was FRH significantly reduced. An increase in GRH and a decrease in FRH suggest that broilers fed LOW diets were attempting to compensate for dietary energy restriction through increased foraging activity; however, forage intake was not significantly different (Table 6Go). This observation is consistent with Moritz et al. [6].


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  		Table 6. Forage intake in treatment paddocks for spring and summer months
 
An energy x enzyme x access interaction was observed for LWG (P = 0.0064; Table 3Go). Withholding pasture access resulted in increased LWG compared with broilers given pasture access. In addition, consumption of NOR diets improved LWG compared with LOW diets for broilers within pasture access groups. However, enzyme inclusion improved LWG only when broilers were fed NOR diets and given access to pasture. These data suggest that a NSP enzyme may be more beneficial when feeding a balanced ration to broilers given access to pasture.

An enzyme x season interaction was also observed for LWG (P = 0.001; Table 3Go). Feeding diets with enzyme resulted in increased LWG compared with feeding diets with no enzyme only in spring months. Feed intake was also affected by season (P = 0.0428). Broilers reared in spring months consumed less feed than broilers reared in summer months and had significantly higher FE (P = 0.0009). A shorter photo-period during the spring months as compared with the summer months (13.58 vs. 14.92 h) may have influenced FI. However, the fact that broilers in spring had larger LWG but consumed less feed suggests that they were able to compensate for decreased feed consumption by more efficiently utilizing feed and forage for growth. Broilers reared in spring months had smaller GRH than broilers reared in summer months (P = 0.0001), suggesting that broilers reared in summer months may have consumed a more fibrous forage (Table 4Go). Forage intake did not differ between treatments (P > 0.05) or between seasons (P > 0.05; Table 6Go). Therefore, these data corroborate forage analysis, illustrating that forage utilized in summer months had a more fibrous consistency and a decreased nutrient value (Table 1Go).

The level of NSP in grains and forages fluctuates depending on season [40, 41]. Nutrient values for forage utilized in this study were superior in spring (Table 1Go). Nutrient value in forage has been documented to decline as the plant matures. Plant maturation results in an increase in acid detergent fiber and NDF and a decrease in crude protein concentration [7]. Bach-Knudsen [40] reported that the principal polymer of grass meal is cellulose, constituting 48% of total CF. However, CF composition varies depending on season. First-cut grass has been shown to have a total NSP content of 37% compared with 43% NSP content in second-cut grass [40]. Perhaps enzyme inclusion more easily degraded early-growth forage in the spring, leading to more efficient nutrient utilization. Broilers reared in spring months and supplemented with enzyme had a larger CCW and smaller FRH than broilers reared in summer months (P = 0.0193 and P = 0.0235, respectively; Table 4Go). In addition, an enzyme x season x access effect was observed for HCW (P = 0.0489). Pastured broilers fed diets containing enzyme in spring months had larger HCW than pastured broilers fed diets containing no enzyme in spring months or pastured broilers fed either diet in summer months. These data support the theory that the capacity of a NSP enzyme to aid in the degradation of plant cell wall components is accentuated in early-growth forage in spring months. Mortality was not affected by dietary treatment, enzyme inclusion, pasture access, or season (P > 0.05; Table 4Go).

Enzyme and Feed Restriction Feasibility
To determine if there is an economic benefit associated with enzyme incorporation in an organic production system, pastured broilers fed NOR-NE were compared with pastured broilers fed LOW-E. For the 21- to 56-d period broilers fed NOR-NE had larger LWG (P = 0.0349 and P = 0.0001; Table 3Go), HCW (P = 0.0015 and P = 0.0001; Table 4Go), CCW (P = 0.0019 and P = 0.0001; Table 4Go), and improved FE (P = 0.0114 and P = 0.0064; Table 3Go) compared with broilers fed LOW-E in spring and summer months, respectively. However, in spring months, LWG and FE were not significantly different during the 38- to 56-d period, suggesting compensatory growth of broilers fed the LOW-E diet. Forage intake did not differ among treatments (Table 6Go). However, forage intake values did increase during the 38- to 56-d period compared with the 21- to 38-d period for all treatments. Therefore, it may be plausible that broilers given LOW-E were able to digest more forage in spring months to compensate for decreased growth in the 21-to 38-d period. Broilers fed LOW-E had greater GRH (P = 0.0001) and a lesser FRH (P = 0.015) than broilers fed NOR-NE in summer months. This was not observed in spring months. Broilers fed LOW-E and reared in summer months consumed a more fibrous forage (Table 1Go) that likely contributed to a larger GRH. Feeding a LOWE diet did not enable broilers to overcome a 7% energy dilution. Decreasing energy and subsequent feed cost in organic broiler diets may be possible with energy dilutions less than 7%, depending on forage intake and quality.


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

  1. Feed restriction did not result in increased forage intake for broilers fed low-energy diets or broilers supplemented with an NSP enzyme.
  2. In spring months, NSP enzyme inclusion enhanced performance only when broilers were given access to pasture.
  3. Reducing dietary energy by 7% and incorporating an exogenous NSP enzyme is not a viable means for reducing organic feed cost.


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

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  4. Weeks, C. A., C. J. Nichol, C. M. Sherwin, and S. C. Kestin. 1994. Comparison of the behaviour of broiler chickens in indoor and free-range environments. Anim. Welf. 3:179–192.
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  6. Moritz, J. S., A. S. Parsons, N. P. Buchanan, N. J. Baker, J. Jaczynski, O. J. Gekara, and W. B. Bryan. 2005. Synthetic methionine and feed restriction effects on performance and meat quality of organically reared broiler chickens. J. Appl. Poult. Res. 14:521–535.[Abstract/Free Full Text]
  7. Barnes, R. F., D. A. Miller, and C. J. Nelson. 1995. Hay and silage management. Pages 158–159 in Forages: An Introduction to Grassland Agriculture, Iowa State Univ. Press, Ames.
  8. Kocher, A., M. Choct, R. J. Hughes, and J. Broz. 2000. Effects of food enzymes on utilization of lupin carbohydrates by broilers. Br. Poult. Sci. 41:75–82.[Web of Science][Medline]
  9. Choct, M., R. J. Hughes, J. Wang, M. R. Bedford, A. J. Morgan, and G. Annison. 1996. Increased small intestinal fermentation is partly responsible for the anti-nutritive activity of non-starch polysaccharides in chickens. Br. Poult. Sci. 37:609–621.[Web of Science][Medline]
  10. Fengler, A. I., and R. R. Marquardt. 1988. Water-soluble pentosans from rye II. Effects on rate of dialysis and on the retention of nutrients by the chick. Cereal Chem. 65:298–302.
  11. Leeson, S., and J. D. Summers. 2001. Digestion and nutrient availability. Page 5 in Scott’s Nutrition of the Chicken. Univ. Books, Guelph, Ontario, Canada.
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  14. Kocher, A., J. Broz, M. D. Porter, and M. Choct. 2002. Effects of feed enzymes on nutritive value of soyabean meal fed to broilers. Br. Poult. Sci. 43:54–63.[Web of Science][Medline]
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  19. Aviagen Inc., Huntsville, AL.
  20. Ohio Ecological Food and Farm Association, Columbus, OH.
  21. Energy reduction (7%) was based on an extrapolation of data using ME values for alfalfa (NRC) and forage intake data from previous studies at West Virginia University [6]. Average forage intake of restricted-fed broilers (50% intake of ad libitum pair-fed group) was 164.7 g of DM/paddock per day or 10.98 g of DM/bird per day. The NRC MEn value for alfalfa is 1,200 kcal/kg (as-fed basis). Assuming a forage intake value of 10.98 g of DM/bird per day and an estimated MEn value of 2,000 kcal/kg (DM basis) for alfalfa, birds with access to pasture may obtain approximately 7% of their energy requirement from forage.
    Forage Inclusion Level
    Forage intake of restrictive-fed broilers
    Average forage intake (kg/d) x MEn of alfalfa (DM basis) = kcal of forage/d
    0.01098 kg/d x 2,000 kcal/kg = 21.96 kcal of forage/d
    FI of restrictive-fed broilers
    Average FI (kg/d) x ME of feed (DM basis) = kcal of feed/d
    0.082 kg/d x 3,636.36 kcal/kg = 298.18 kcal of feed/d
    Total intake of restrictive-fed broilers
    21.96 kcal of forage/d + 298.18 kcal of feed/d = 320.14 kcal of feed/d
    Formula
    x = 6.86%
  22. Ronozyme VP (CT), DSM Nutritional Products, Basel, Switzerland.
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