et al.

Influence of Enzymes on Performance and Digestive Parameters of Broilers Fed Rye-Based Diets R. La´zaro, M. Garcıá, P. Medel, and G. G. Mateos1 Departamento de Produccioń Animal, ETSI Agrońomos, Universidad Politećnica de Madrid, 28040 Madrid, Spain d (P < 0.001). Among rye diets the greatest feed intake and weight gain were obtained with Petkus variety, which also produced the lowest intestinal viscosity. Enzyme addition reduced the time needed to recover 1% (0.78 vs. 0.98 h; P < 0.05) and 50% (4.2 vs. 6.5 h; P < 0.01) of the marker in feces and reduced the mean retention time of marker in the gastrointestinal tract (17.1 vs. 18.8 h; P < 0.05). Also, ES reduced intestinal viscosity (P < 0.001) and improved feed intake, daily gain, and feed conversion of birds from 4 to 25 d (P < 0.01) but did not modify volatile fatty acid concentration in ceca. We concluded that ES added to rye diets decreased intestinal viscosity and accelerated digestive transit, improving productive performance of broilers.

ABSTRACT An experiment was conducted to study the influence of enzyme supplementation (ES) to rye-based diets on rate of food passage through the digestive tract, viscosity of jejunum content, volatile fatty acid concentration in ceca, and performance of broilers. There were seven treatments; six diets arranged factorially with three varieties of rye (Petkus, Prima, and Saratov V) and two levels of ES (0 or 500 ppm of an enzyme complex containing 858 IU of β-glucanase and 864 IU of xylanase/ g) and an additional control diet based on corn. Each treatment was replicated seven times (12 chicks caged together), and the trial lasted 25 d. Rye feeding increased intestinal viscosity and impaired bird performance at 25

(Key words: broiler, enzyme, rye, transit time, volatile fatty acid) 2003 Poultry Science 82:132–140

performance of birds (Frigard et al., 1994; Langhout et al., 1997). However, the mode of action of enzyme supplementation (ES) is not completely understood. Enzymes, as they break water-soluble NSP of rye into oligo and monosaccharides, reduce viscosity of intestinal content (Pawlik et al., 1990; Bedford and Classen, 1992) and might reduce time for passage of digesta through the gastrointestinal tract (Da¨nicke et al., 1997a, 1999). A change in transit time because of ES added to NSP-enriched diets might influence the growth of microflora in the small and large intestines, modifying volatile fatty acid (VFA) production. However, data on end products of flora fermentation by different authors are contradictory (Viveros et al., 1994; Choct et al., 1996, 1999; Vahjen et al., 1998). The present experiment was conducted to study the effects of ES to rye-based diets on intestinal viscosity, rate of digesta passage through the gastrointestinal tract, and VFA concentration in ceca of broilers, as an indication of pattern of flora growth, in order to elucidate the mechanism of action of enzymes. In addition, performance of birds fed rye with or without ES was also determined and compared to birds fed a typical corn-soybean meal diet.

INTRODUCTION The use of rye in poultry diets is limited because of its negative effects on bird performance (Misir and Mar˚ man, 1988; Ragaee et al., quardt, 1978; Pettersson and A 2001a). The reduction of productivity is related, at least in part, to the high viscosity of digesta content produced by rye feeding, which reduces the probability of endogenous enzymes meeting the substrate, impairing digestibility of dietary nutrients (Campbell et al., 1983; Ward and Marquardt, 1987) and increasing the incidence of sticky droppings (Jami et al., 1980; Pettersson, 1987). The increase of intestinal viscosity is due to the presence of water-soluble nonstarch polysaccharides (NSP) (Fernańdez et al., 1973; Fengler and Marquardt, 1988). Scoles et al. (1993) and Ragaee et al. (2001b) in studies in vitro and Bedford et al. (1991) in studies in vivo have demonstrated that with rye the increase in viscosity is due to the high molecular weight fraction of soluble NSP. Xylanase and β-glucanase addition to rye-based diets reduces the incidence of pasting vents and improves litter quality (Pettersson et al., 1990; Garcıá et al., 1997) and

2003 Poultry Science Association, Inc. Received for publication April 30, 2002. Accepted for publication September 23, 2002. 1 To whom correspondence should be addressed: ggmateos@pan. etsia.upm.es.

Abbreviation Key: cP = centipoises; ES = enzyme supplementation; MRT = mean retention time; NSP = nonstarch polysaccharides; VFA = volatile fatty acids.

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MATERIALS AND METHODS Birds, Housing, and Diets Six hundred thirty-seven 1-d-old male broiler chicks (Cobb 500) were obtained from a commercial supplier2 and housed in battery brooders. At 4 d of age, 588 of the birds were selected according to body weight (111 ± 1.5 g) and allocated to the 49 experimental units. The temperature under the brooder was maintained at 32 C for the first 3 d of age, and room temperature was decreased gradually from 30 C at Day 1 to 24 C at 15 d of age and then kept constant until 25 d of age. The experimental design was completely randomized with seven treatments: a control diet based on 50% corn and six diets arranged factorially, with 50% of three varieties of rye (Petkus, Prima, and Saratov V) and two doses of an enzyme complex (0 and 500 ppm). Petkus variety was originally from Germany and grown in Spain (Navarra), whereas Prima and Saratov V were originally from Canada and Russia, respectively, and grown in Canada (Saskatoon, Saskatchewan). The commercial enzyme preparation used was obtained from Aspergillus niger and contained 858 IU of β-glucanase (EC 3.2.1.6.) and 864 IU of xylanase (EC 3.2.1.8.) per gram.3 Diets were formulated to meet or exceed requirements by the National Research Council (1994) for broilers of this age and were offered in mash form (Table 1). Chemical analyses, including composition of the total NSP of the rye varieties, are shown in Table 2. Each treatment was replicated seven times, and the experimental unit consisted of 12 chicks caged together (1.0 × 0.4 m/ cage). All birds were fed the control diet based on corn during the first 4 d of life and then were fed their respective experimental diets. The incidence of pasting vents was recorded at 11 d, and birds and feeds were weighed at 11, 18, and 25 d. At 18 d, two chicks of each replicate of the treatments based on Prima rye (with and without ES) were removed from the trial. They were placed in groups of two in metabolism cages (0.50 × 0.35 m), fed the same experimental diets that they received previously, and used to carry out a transit time study from 20 to 22 d. The Prima variety was chosen because it produced the highest intestinal viscosity values of all ryes. The routine animal care and experimental procedures used in this study conformed to regulations and guidelines of Spanish Royal Decree 223/88 (1988).

Intestinal Viscosity At 11 and 25 d of age, two birds per replicate were killed by cervical dislocation and digesta content collected from the end of the duodenum to the Meckel’s diverticu-

2

Cobb, Alcala´ de Henares, Spain. Endofeed, GNC Bioferm Inc., Saskatoon, Saskatchewan, Canada. 4 Brookfield Engineering Laboratories, Stoughton, MA. 5 Thermo Jarrell Ash Corporation, MA. 6 Hewlett Packard Espanõla, S.A., Madrid, Spain. 3

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lum was pooled and homogenized. Two Eppendorf tubes were filled with 1.5 g of sample and centrifuged at 17,500 × g for 3 min, and the viscosity of the supernatant (0.5 mL), expressed as centipoises (cP), was immediately measured with a Brookfield digital viscometer4 (Model DV-III).

Digestive Transit Time Study At 20 d of age, feed from birds housed in the metabolic cages was withheld for 8 h. Each chick then received a gelatin capsule containing 50 mg of chromic oxide, and the time of marker administration for each replicate was recorded. Afterward, all birds had access to their corresponding experimental diets ad libitum, and all the feces produced were collected hourly for the first 8 h and then at 10, 12, 24, 36, and 48 h. Excreta was placed in plastic bags and frozen at −20 C until determination of chromium content.

Volatile Fatty Acid Concentration in Cecum At 25 d of age, one of the two birds housed in each metabolic cage was killed by cervical dislocation, and cecal content was collected to determine concentration of acetic, propionic, and butyric acids. Cecal content was diluted with an equal weight of distilled water (Sudo and Duke, 1980) and centrifuged at 25,500 × g at 0 C for 20 min. A solution of 5% orthophosphoric acid (vol/vol) plus 1% mercury chloride (wt/vol) was added (0.1 mL/ mL) to the supernatant (Garcıá et al., 2000); the mixture was then frozen and stored at −20 C until VFA determination.

Chemical Analyses Samples of rye and feeds were analyzed (Association of Official Analytical Chemists, 1995) to determine dry matter by the oven drying method (934.01), ash (942.05), crude protein by the Kjeldahl method (954.01), ether extract by Soxhlet fat analysis (920.39), calcium by the dry ash method (927.02), and phosphorus by the photometric method (965.17). Total NSP of rye was determined according to the method described by Theander et al. (1995), and activity of the commercial enzyme complex was determined by the reducing sugar method described by Miller (1959), at pH 4 and 30 C, and with incubation for 5 and 10 min. Chromium contents of feed and excreta were analyzed by atomic absorption spectrometry (Smith-Hieftje 22),5 following the procedure described by Garcıá et al. (1999), and using predosed samples of feces to prepare common-matrix standards. Previously, samples were ashed at 550 C for 6 h and then digested by boiling with a solution of nitric acid (1.5 M HNO3) and potassium chloride (3.81 g/L KCl). Cecal VFA concentration was determined following the procedure described by Garcıá et al. (2000) by using a Hewlett-Packard gas chromatograph6 (5710 A) with a flame ionization detector and a Hewlett-Packard recorder integrator6 (3390 A).

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TABLE 1. Experimental diets Ingredients

Control (%)

Corn Rye Lard Extruded soybean Soybean meal (47%) Sunflower meal (36%) Calcium carbonate Dicalcium phosphate Sodium chloride DL-Methionine L-Lysine HCl (78%) Vitamin-mineral premix2 Calculated analysis3,4 AMEn, kcal/kg Crude protein, % Total lysine, % Total sulfur amino acids, % Ether extract, % Calcium, % Available phosphorus, % Chemical analysis4,5 Dry matter, % Ash, % Calcium, % Phosphorus, % Crude protein, % Ether extract, %

Rye1 (%)

50.20 ... 5.00 1.60 30.1 9.00 0.96 1.80 0.45 0.25 0.15 0.50

4.00 50.00 6.00 1.60 32.6 1.90 1.09 1.60 0.45 0.28 0.06 0.50

3,000 22.00 1.29 0.97 7.74 0.93 0.43

2,850 22.00 1.28 0.95 7.87 0.93 0.43

88.9 6.2 1.0 0.7 21.8 7.6

88.7 6.0 0.9 0.7 21.6 7.7

1 Diets were based on one of the three rye varieties (Petkus, Prima, or Saratov V), supplemented or not supplemented with the enzyme complex. The AMEn value corresponds to diets not supplemented with enzymes. 2 Provided the following per kilogram of diet: vitamin A (trans-retinyl acetate), 10,000 IU; cholecalcipherol, 3,000 IU; vitamin E (DL-α-tocopheryl acetate), 30 IU; menadione (sodium bisulfate), 2.0 mg; riboflavin, 6.0 mg; D-calcium pantothenate, 12.0 mg; nicotinic acid, 45.0 mg; pyridoxine hydrochloride, 3.0 mg; folic acid, 1.0 mg; d-biotin, 0.1 mg; thiamin hydrochloride, 1.2 mg; vitamin B12, 16 µg; choline chloride, 300 mg; Mn, 70 mg; Zn, 65 mg; Fe, 40 mg; Cu, 5 mg; I, 0.6 mg; Se, 0.25 mg; and ethoxyquin, 125 mg. 3 Calculated analysis based on values for feed ingredients of Fundacioń Espanõla Desarrollo Nutricioń Animal (1999). 4 As-fed basis. 5 Means of duplicate analyses for control diet. For the rye diets, values correspond to the average value of the three means of duplicate analysis (with and without enzymes) of each variety (mean values for crude protein were 21% for Petkus, 21.6% for Prima, and 22.1% for Saratov V).

Statistical Analyses Statistical analysis of data was performed using the general linear model (GLM) procedure of SAS software (SAS Institute, 1990). Main effects studied were rye vari-

ety (except for data in which only Prima rye was used) and ES, and their interaction. Two non-orthogonal contrasts were also included to compare corn vs. rye diets with or without ES. For studies on intestinal viscosity, time effect was included in the model.

TABLE 2. Chemical analysis and composition of the total nonstarch polysaccharides (NSP) of the rye varieties1 Rye variety Petkus

Prima

Saratov V

Crude protein Ether extract

9.78 3.10

9.82 2.22

11.3 2.30

NSP2 Rhamnose Arabinose Xylose Mannose Galactose Glucose Uronic acids Total NSP

0.040 2.047 2.012 0.356 0.325 4.674 0.200 9.654

0.046 1.895 2.028 0.368 0.316 4.418 0.188 9.259

Percentage dry matter; n = 2. Nonstarch polysaccharides. Fucose < 0.015% dry matter for all rye varieties.

1 2

0.050 1.808 1.788 0.342 0.314 4.198 0.221 8.721

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ENZYMES AND RYE ON DIGESTIVE TRANSIT TIME TABLE 3. Performance of broilers (4 to 25 d) fed corn or rye diets with or without enzyme supplementation (ES) 4 to 11 d ES (ppm)

Cereal Rye Petkus Prima Saratov V Rye Corn SEM1 P Rye variety ES, 0 vs. 500 ppm Rye variety × ES Corn vs. rye without ES Corn vs. rye with ES

0 500 0

11 to 18 d

18 to 25 d

4 to 25 d

Weight gain (g/d)

Feed intake (g/d)

Feed: gain (g/g)

Weight gain (g/d)

Feed intake (g/d)

Feed: gain (g/g)

Weight gain (g/d)

Feed intake (g/d)

Feed: gain (g/g)

Weight gain (g/d)

Feed intake (g/d)

Feed: gain (g/g)

19.3 18.5 19.2

31.4 29.7 31.5

1.62 1.61 1.65

37.7 35.5 35.7

71.5 69.3 68.2

1.91 1.97 1.94

51.3 50.3 47.7

98.4 94.7 92.1

1.95 1.92 1.96

36.1 34.7 34.2

67.1 64.5 63.9

1.83 1.83 1.85

17.8 20.1 20.5 0.37

30.8 30.8 32.9 0.89

1.73 1.53 1.61 0.04

33.2 39.4 40.0 1.13

68.0 71.4 68.7 1.74

2.06 1.82 1.72 0.06

44.2 55.3 59.8 2.21

92.1 98.1 97.9 2.64

2.11 1.78 1.64 0.07

31.7 38.3 40.1 0.99

63.6 66.7 66.5 1.42

1.96 1.71 1.66 0.04

† *** NS *** NS

† NS NS * *

NS2 *** NS * NS

NS *** NS *** NS

NS * NS NS NS

NS *** NS *** NS

NS *** NS *** †

† ** NS † NS

NS *** NS *** †

† *** NS *** †

† ** NS NS NS

NS *** NS *** NS

n = 7. P > 0.10. ***P ≤ 0.001; **P ≤ 0.01; *P ≤ 0.05; †P ≤ 0.10.

1 2

For the digestive transit time study, the cumulative excretion curve of marker of each replicate was modeled using the nonlinear procedure of SAS software (SAS Institute, 1990). The mathematical equation used to study the fitness of data was the following exponential curve (Blaxter et al., 1956; Vergara et al., 1989): y = a + b × (1 − e−ct) where y = chromium excreted, t = time after marker administration, and a = intercept, b = asymptote, and c = slope of the curve. Mean times for 1 and 50% of excretion in feces of the marker supplied were obtained from each curve per replicate, and comparisons between treatments were conducted. Mean retention time (MRT) of marker was calculated using the equation proposed by Coombe and Kay (1965): MRT = Σ (xi ⴢ ti)/Σ xi where xi = amount of marker excreted at time ti after administration.

RESULTS Performance At 25 d of age broilers fed Petkus rye tended to grow faster (36.1 vs. 34.4 g/d; P < 0.10) and to eat more feed (67.1 vs. 64.2 g/d; P < 0.10) than broilers fed the other rye varieties, but no differences were detected for feed to gain ratio (Table 3). Enzyme supplementation improved productive performance of birds fed rye diets at any age, but no interactions between ES and rye variety were detected. At 25 d of age, ES to rye diets improved BW gain by 20.8% (P < 0.001), feed consumption by 4.9% (P < 0.01), and feed

conversion by 12.7% (P < 0.001). Body weight and feed conversion were 20.9 and 18.1% poorer for birds fed the rye diets without ES than for birds fed the corn diet (P < 0.001), but only small differences in weight gains were detected between corn and rye diets with ES (40.1 vs. 38.3 g/d; P < 0.10).

Intestinal Viscosity and Pasting Vents Intestinal viscosity decreased with age (383 vs. 203 cP for 11 and 25 d, respectively; P < 0.05) and was lower for birds fed Petkus than for birds fed Prima or Saratov V rye (122 vs. 414 vs. 341 cP, respectively; P < 0.01). However, percentage of pasting vents was independent of the variety of rye used (Table 4). Enzyme addition reduced intestinal viscosity of digesta in birds fed rye diets (121 vs. 465 cP; P < 0.001) and tended to reduce the incidence of pasting vents (26.1 vs. 18.4%; P < 0.10), but no interaction between rye variety and ES was detected. Birds fed ryebased diets with or without ES had higher viscosity values (P < 0.001 and P < 0.10 for diets without and with ES, respectively) and incidence of pasting vents (P < 0.001) than birds fed the control diet.

Digestive Transit Time The R2 obtained for the cumulative excretion curve of marker was greater than 0.98 in all replicates. Enzyme addition to rye-based diet modified a, b, and c values of the cumulative marker excretion curve (P < 0.10 for a, P < 0.05 for b, and P < 0.01 for c; Table 5). From 4 to 24 h after administration, the excretion of the marker was faster with ES (P < 0.05; Figure 1), but the effects were less evident thereafter (P < 0.10 at 36 h and P > 0.10 at 48 h). At 48 h, marker recovery was 92.3% for the ES diet and 86.4% for the diet not supplemented, but the differences were not significant (P > 0.10). The peak of

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TABLE 4. Intestinal viscosity and incidence of pasting vents of broilers fed corn or rye diets with or without enzyme supplementation (ES)

Cereal

Intestinal viscosity (cP)1

ES (ppm)

Rye Petkus Prima Saratov V Rye Corn SEM2 P

0 500 0

11 d

25 d

Pasting vents (%) 11 d

149 558 442

96 270 240

24.3 23.5 19.0

609 157 6

321 86 5 135

26.1 18.4 2.4 4.2

** *** * NS NS NS NS *** †

NS3 † ... NS ... ... ... *** ***

Rye variety ES, 0 vs. 500 ppm Age, 11 vs. 25 d Rye variety × ES Rye variety × age ES × age Rye variety × ES × age Corn vs. rye without ES Corn vs. rye with ES 1

Centipoises. n = 7. 3 P > 0.10. ***P ≤ 0.001; **P ≤ 0.01; *P ≤ 0.05; †P ≤ 0.10. 2

marker excretion obtained from the non-cumulative curves was observed at 4 h after chromium administration (Figure 2), and the amount of marker excreted at that time tended to be greater with ES (P < 0.10). However, from 4 to 24 h, the quantity of marker excreted was lower with ES, although the differences were only significant at 8 and 12 h (P < 0.05 and P < 0.10, respectively). Enzyme addition also reduced the time required to recover 1% (0.78 vs. 0.98 h; P < 0.05) or 50% (4.2 vs. 6.5 h; P < 0.01) of the chromium supplied, as well as the mean retention time of the marker (17.1 vs. 18.8 h; P < 0.05).

Volatile Fatty Acid Concentration in Cecum Enzyme addition did not modify molar concentration, profile, or total concentration of VFA (16.6 vs. 15.2 µmol/ g for rye diets with or without ES, respectively; P > 0.10) in the ceca of broilers at 25 d (Table 6).

DISCUSSION The inclusion of rye in broiler diets decreases performance, which might be due, at least in part, to an increase in the viscosity of the jejunum content of birds. In our experiment, birds fed Petkus rye had the lowest intestinal viscosity and the highest feed consumption and average daily gain of the three varieties studied, but the results were not related to the content of total NSP (9.65, 9.26, and 8.72% on a dry-matter basis for Petkus, Prima, and Saratov V, respectively). Therefore, a fraction of the NSP rather than total NSP contained in the rye might be responsible for the higher viscosity and the consequent impairment in productivity. Our data are also consistent with data of Scoles et al. (1993) and Ragaee et al. (2001b), which indicate that the high molecular weight fraction of water-soluble NSP rather than total NSP is responsible for the deterioration of growth of broilers. Antoniou and

TABLE 5. Parameters of cumulative excretion curves of marker1 and times for chromium recovery in birds fed rye diets with or without enzyme supplementation (ES) ES

Intercept (a) Asymptote (b) Slope (c) Time (h): 1% Excretion 50% Excretion Mean retention

0 ppm

500 ppm

SEM2

P

−7.8 60.6 9.6

−10.2 67.2 13.2

0.60 1.80 0.60

† * **

0.05 0.49 0.45

* ** *

0.98 6.47 18.77

0.78 4.22 17.06

1 Cumulative chromium excreted: y = a + b × (1 − e−ct); t = time after marker administration, a = intercept, b = asymptote, and c = slope of the curve. 2 n = 7. **P ≤ 0.01; *P ≤ 0.05; †P ≤ 0.10.


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FIGURE 1. Cumulative excretion curve of the marker until 48 h after administration in birds fed Prima rye diets with or without enzyme supplementation (SE). In the equation, y = chromium excreted, t = time after marker administration, a = intercept, b = asymptote, and c = slope of the curve. **P ≤ 0.01; *P ≤ 0.05; †P ≤ 0.10. 1P > 0.10. All values are means ± SEM of seven replicates (two chicks per cage).

FIGURE 2. Non-cumulative excretion curve of the marker until 48 h after administration in birds fed Prima rye diets with and without enzyme supplementation (ES). *P ≤ 0.05; †P ≤ 0.10. 1P > 0.10. All values are means ± SEM of seven replicates (two chicks per cage).

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TABLE 6. Volatile fatty acid (VFA) concentration in cecum of broiler chicks fed Prima rye diets with or without enzyme supplementation (ES)

Cereal Rye 1

SEM P

ES (ppm) 0 500

Acetic acid

Propionic acid

Butyric acid

(µmol/g)

(%)

(µmol/g)

(%)

(µmol/g)

(%)

Total VFA (µmol/g)

11.3 12.5 0.49 NS2

75.3 75.8 2.60 NS

0.6 0.4 0.28 NS

3.6 2.4 1.59 NS

3.3 3.7 0.41 NS

21.1 21.8 1.45 NS

15.2 16.6 0.95 NS

n = 7. P > 0.10.

1 2

Marquardt (1981) indicated that water-soluble pentosans and insoluble pentosans of rye were responsible for the impairment of performance, whereas Fernańdez et al. (1973) recorded that only water-soluble pentosans were responsible for the growth depression. The recovery of the marker obtained in our trial was incomplete and varied between 86.4 and 92.3%, with the highest value corresponding to ES rye diet, although the difference was not significant. Da¨ nicke et al. (1997a) also observed an incomplete recovery of titanium dioxide in the feces of broilers fed rye after 24 h. They observed a tendency for higher recovery when 10% added tallow rather than soy oil was used (85.9 vs. 79.6%). Also, the recovery was greater with ES (90.7 vs. 74.8%). Mateos et al. (1982) found that time for first appearance of chromium in excreta (visually detected) increased as the level of yellow grease increased from 0 to 30% in the diet of laying hens. These observations suggest that the level and the nature of the fat used might influence the entrance of marker into the ceca. In our study, rye diets contained 6% lard, which might have retarded transit time and may explain the incompleteness of marker recovery from feces. In experiments carried out with 60% rye (Da¨ nicke et al., 1997a) or 60% barley (Almirall and Esteve-Garcıá, 1994), an acceleration of digesta transit through the gastrointestinal tract of broilers was observed with ES. In both studies, peaks of marker excretion were higher with ES and occurred proximately at 3 h after marker administration, which was similar to our study. No data are available on the MRT of rye diets. In the experiment carried out by Almirall and Esteve-Garcıá (1994) with 21-d-old broilers and using the same methodology and equation as in the current paper, MRT was reduced from 14.1 to 11.5 h with ES. The existing data indicate that transit time in broilers is less with barley than with rye. In the trial of Almirall and Esteve-Garcıá (1994) using barley, intestinal viscosity was reduced from 29 to 4 cP with ES, whereas in our trial, using broilers of similar age, the reduction was from 405 to 135 cP with Prima rye. Therefore, although ES is very efficient in decreasing intestinal viscosity, the efficacy is inadequate in rye diets and far from the reduction observed by other authors with barley. A reduction of MRT because of ES favors feed consumption and, consequently, improves performance of birds. Volatile fatty acids are the major end products of fermentative processes in the digestive tract of fowl, and

the cecum is the main location for VFA production (Annison et al, 1968). Vukic Vranjes and Wenk (1996) hypothesize that the response to ES in laying hens fed barley was mediated, at least in part by the intestinal flora, and noted a negative interaction between enzyme and antibiotic supplementation of the diet on energy digestibility. Although in our experiment ES reduced the viscosity of the jejunum content and the digestive transit time of broilers, no effects were observed on the fermentation activity of flora in ceca. Viveros et al. (1994) observed that ES reduced concentrations of acetic and butyric acids in ceca of broilers fed barley diets, whereas Choct et al. (1996, 1999) working with wheat recorded an increase of the total concentration of VFA in the ceca and a decrease in the ileum with ES. The discrepancies observed among studies might be due to the age of birds. La´ zaro (1999) working with 46-d-old broilers fed rye observed that ES tended to increase the concentration of VFA (45.9 vs. 38.5 µmol/g) and the length of the ceca (21.6 vs. 20.2 cm). It is possible that a reduction of viscosity and MRT because of ES would decrease bacterial activity in the small intestine with an augmentation of liquid digesta entering the ceca due to a higher rupture of NSP. In our study, acetic acid concentration in ceca of birds fed rye was greater than propionic or butyric acid concentration, which agrees with McNab (1973) and Jamroz et al. (1996), but no effect of ES on ceca fermentation of substrates was observed. Enzyme supplementation might improve broiler performance by at least two mechanisms: increasing feed intake and improving nutrient digestibility. Both mechanisms might be induced, at least partially, by a reduction of the viscosity at the intestinal tract. In this study, ES reduces intestinal viscosity and decreases retention time of digesta in the gut, allowing more consumption and therefore improving growth and indirectly feed conversion. Also, reduced viscosity improves contact between nutrients and endogenous enzymes to improve digestibility (Da¨ nicke et al., 1997b; Langhout et al., 1997). In contrast, in adult birds the first mechanism seems to be less effective, because ES reduces viscosity of jejunum content and improves digestibility of nutrients without affecting feed intake (La´ zaro et al., 2003). Also, no reduction of MRT of barley diets was observed in adult cocks (Almirall and Esteve-Garcıá, 1994). These observations might help to explain the higher response


to ES normally observed with broilers compared to laying hens. We conclude that ES to rye diets reduced intestinal viscosity and transit time but did not modify VFA concentration in the ceca of broilers. A faster digesta transit may enhance feed consumption and, therefore, improve performance of birds. Of the three rye varieties tested, Petkus rye produced the lowest viscosity of jejunum content in broilers and the highest feed consumption and growth of birds up to 25 d.

ACKNOWLEDGMENTS Special thanks are extended to L. Campbell (University of Saskatchewan, Canada) and to Y. Alegre (Universidad Polite´ cinca de Madrid, Spain) for their help in the preparation and typing this manuscript.

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