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The nutritive value for broiler chickens of pelleting and enzyme supplementation of a diet containing barley, wheat and rye
Animal Feed Science and Technology, 33 ( 1991 ) 1-14
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Elsevier Science Publishers B.V., Amsterdam
The nutritive value for broiler chickens of pelleting and enzyme supplementation of a diet containing barley, wheat and rye D. Pettersson, H. Graham and P. ]~man Swedish University of Agricultural Sciences, Department of Animal Nutrition and Management, S- 750 07 Uppsala (Sweden) (Received 22 May 1990; accepted for publication 5 October 1990)
ABSTRACT Pettersson, D., Graham, H. and/~man, P., 1991. The nutritive value for broiler chickens of pelleting and enzyme supplementation of a diet containing barley, wheat and rye. Anita. Feed Sci. Technol., 33: 1-14. A diet based on barley (40%), wheat (25%), and rye (7%) was given as a mash diet or as dry or steam pelleted diets to a total of 384 broiler chickens. Diets were given with or Without the addition of a fibre-degrading enzyme preparation. Pelleting increased the water solubility (at 38 *C ) of starch and crude protein. There were, however, no notable effects on the solubility of dietary fibre components following pelleting or enzyme supplementation. Buffer extracts from pelleted diets had a high relative viscosity, while mash diets gave the lowest relative viscosity. Enzyme supplementation diminished the high viscosity obtained for pelleted diets and reduced sticky droppings. Pelleting increased weight gain for chickens receiving the unsupplemented diets by ~ 30% and for those fed on the enzyme-supplemented diets by ~ 20%. This improvement, which was similar at both 14 and 20 days of age, was mainly due to a greater feed intake, particularly with the steam pelleting. Enzyme supplementation improved weight gain by 11-24%, and was more effective in the unpelleted diets and at Day 14. This improvement was due to both a higher feed intake and a better feed conversion efficiency. Pelleting tended to increase ileal digestibility of the unsupplemented diet while enzyme supplementation had a similar effect on the unpeUeted diet. The latter treatment also increased whole-tract digestibility.
INTRODUCTION
There are numerous reports regarding the improvements obtained in production from steam pelleting the diets of poultry (Patton et al., 1937; Lindblad et al., 1955; Allred et al., 1957a,b; Sell and Thompson, 1965; Bayley et al., 1968; Summers et al., 1968). The improvements have been attributed to chemical effects such as the destruction of heat-sensitive growth inhibitors. An increased diet density, which improves feed intake and thereby increases 0377-8401/91/$03.50
© 1991 u Elsevier Science Publishers B.V.
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D. PETTERSSON ET AL.
nutrient intake, has also been proposed to improve weight gain and feed conversion efficiency. The primary reasons for steam pelleting poultry diets, however, are to kill bacteria and reduce mould growth (Patterson, 1969; Mossel, 1971; Stott et al., 1975; MacKenzie and Bains, 1976; Tabib ct al., 1984; Cox et al., 1986). The productive value of low-fibre diets based on wheat or maize is generally improved by pelleting (Arscott et al., 1958; Mclntosh et al., 1962). Heat treatment (autoclaving or pelleting) of fibre-rich poultry diets based on barley or rye, on the other hand, may reduce their productive value (Moran and McGinnis, 1968; Moran et al., 1969; Misir and Marquardt, 1978; Ward and Marquardt, 1988). Furthermore, high-temperature treatments (e.g. extrusion) may increase the content of soluble dietary fibres and form resistant starch at high moisture levels (Bj~rck et al., 1984; Siljestr~m et al., 1986). The present experiment was conducted in order to study the effects of pelleting a barley/rye-rich diet, with specific reference to the effects on dietary fibres. Fibre-degrading enzymes were employed to investigate further the influence of the fibre fraction. MATERIAL AND METHODS
Diets
On a fresh weight basis the basal diet (Table 1 ) was designed to have a metabolizable energy (ME) content of ~ 11.8 MJ kg-1 diet (corrected to 33% nitrogen retention) and a crude protein concentration of 17.5% calculated according to the Swedish feed tables (Eriksson et al., 1972). Lysine was provided at a calculated level of 1% and mcthionine at 0.45%. The basal mash diet, milled to pass a 3.5-mm screen, was divided into two large batches, of which one was enzyme supplemented. These two batches were then each subdivided into three parts of which two parts from each of the major batches were pelleted through a 3.5-mm matrix either dry (50°C) or with steam (70°C). The third part of each batch was given as a mash diet. The enzyme was a technical enzyme preparation, Glucanase GP 5000 (GP-5000), from Grindsted Products A/S, Denmark. The preparation was designed to contain both mixed-linked fl-glucanase and arabinoxylanase activity and was added to the basal diet at a level of 0.5 g kg- ~diet. Enzymatic activity was measured by the enzyme manufacturer using a viscosimetric method (fl-glucanase activity) and a reducing end-group method (xylanase activity). The GP-5000 preparation had a fl-glucanase activity (EC 3.2.1.6 ) of 5 units g-~ and a xylanase activity (EC 3.2.1.8 ) of 725 units g - 1.
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TABLE 1 Composition and calculated content of chemical constituents of the basal broiler chicken diet (airdry basis) Ingredient
Composition (%) Wheat Barley Rye Soya-bean meal Fish meal Animal fat Limestone Mono-calcium phosphate Vitamin and trace clement premix ~ Lysine DL-methionine Salt (NaCI)
25.0 40.0 7.1 21.5 1.6 1.0 1.7 1.3 0.2 0.12 0.14 0.34
Calculated analysis 2 Metabolizable energy content (MJ kg- t ) Crude protein (%) Lysine (%) Methionine (%)
17.5 1.0 0.45
I 1.8
tThe vitamin and trace clement premix supplied per kg diet:vitamin A, 17000 IU; vitamin D3, 3000 IU; vitamin E, 60 mg; vitamin K3, 5 mg; vitamin Bt, I mg; vitamin B2, 6 rag; vitamin B6, 3 mg; vitamin B12, 0.02 rag; Ca-pantothcnatc, I0 rag; folicacid, l mg; niacin, 30 mg; biotin, 0.1 mg; Fe, 20 mg; Mn, I00 mg; Zn, I00 rag; Cu, 30 mg; I, 0.5 mg; Sc, 0.1 mg. 2Calculated according to the Swedish Feed Tables (Eriksson et al.,1972 ).
Chemical analysis Prior to chemical analyses, feed samples were ground in a Tecator cyclone sample mill to pass a 0.5-ram screen. Samples of freeze-dried excreta and digesta were ground in a Brabender mill ( 1-mm screen size) and then in a Wiley mill (0.5-mm screen size). Dry matter ( D M ) concentration was determined by oven drying at 105 °C for 16 h and chemical analyses, carried out in duplicate, are reported on a DM basis. Sugars (the sum of free glucose, fructose and sucrose) were analysed by HPLC (Wade and Morris, 1982 ). Starch was determined according to ,~man and Hesselman (1984) and resistant starch according to Westerlund et al. (1989). Mixed-linked fl-glucans were analysed according to/~man and Graham ( 1987 ). Crude protein (N × 6.25 ) analyses and ash determinations were done as outlined in the standard methods of the Association of Official Analytical Chemists (1984). Water-soluble starch, crude protein and mixed-linked fl-glucans were extracted at 38 °C for 2 h and isolated by centrifugation prior to analyses. Crude fat was extracted with diethyl ether in a Tecator Soxtec System HT after acid hydrolysis (Anonymous,
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D. PETI'ERSSON ET AL.
1971 ). Total and insoluble non-starch polysaccharide (NSP) residues and Klason lignin were determined according to Theander and Aman (1979) as modified by Theander and Westeflund (1986 ) and dietary fibre was calculated as the sum of these components. Insoluble NSP residues were determined after extraction of soluble components in H20 at 38 °C for 2 h, while soluble NSP residues were determined by difference. Uric acid was determined according to Marquardt (1983). Chromic oxide was analysed spectrophotometrically, as described by Fenton and Fenton (1979). Relative extract viscosity was calculated as the descent time of extracts divided by the descent time of the extraction medium (0.1 M sodium acetate buffer, pH 5.0) measured on an Ostvald viscometer. Extractions were performed according to Pcttersson et al. ( 1987 ).
Chickens A total of 384 unsexed 1-day-old broiler chickens (Ross) were allocated to 24 groups with 16 birds in each, with an average group weight of 702 g and a maximum difference in weight of 4 g between groups. These groups were then randomly assigned to their treatments in six four-tier battery cages with raised wire floors. There were four replicates of 16 birds in each treatment. The chickens had free access to feed and water throughout the experiment. Light and temperature were regulated according to Pettersson (1988).
Production and digestibility study Group feed intakes (air dry weight, corrected for feed wastage) and individual chicken weights were recorded at 14 and 20 days of age, and group feed conversion ratios were calculated. The occurrence of sticky droppings (i.e. wet excreta sticking to the down of the cloaca) was recorded on Day 7. Between Days 15 and 18 a quantitative digestibility trial was conducted. Excreta were collected twice daily and kept frozen until mixed and freeze-dried. From 18 days of age, diets were given with a marker (Cr203) which was incorporated at a level of 4 g kg- 1 in minor sub-batches of the mash and pellet diets during their manufacture. On Day 2 l, four chickens from each group (16 from each treatment), with weights as close as possible to the average group weight, were killed by dislocation of the neck vertebrae and their gastro-intestinal tract was quickly removed. The small intestine was divided into three parts of which the two first were discarded. The content of the last third of the small intestine (denoted ileum) was collected separately, pooled for each group, frozen ( - 2 5 °C) and freeze-dried. Digestibility in the digesta samples was calculated relative to the chromic oxide marker, while whole-tract digestibility was calculated from total collection of excreta. Whole-tract crude protein and organic matter digestibility was calculated according to Hartfiel
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(1973) and Eriksson ( 1955 ) by assuming that all urinary nitrogen emanated from uric acid, and that urinary organic matter content was four times that of urinary nitrogen content.
Calculations and statistical analyses Chicken weights are reported as group means and feed conversion ratios are calculated as cumulative group feed intakes divided by group weight gains. Statistical evaluations were done by using an analysis of variance procedure, the general linear model (GLM), supported by the statistical analysis system (Statistical Analysis Systems, 1985). In the statistical model the effects of type of diet (mash, dry pelleted or steam pelleted) and enzyme supplementation and also their interaction were taken into account. RESULTS
Diets The dietary content of available carbohydrates (sum of starch and sugars) was as high as 50% (Table 2). Pelleting led to a slight solubilisation of starch which was more pronounced for the enzyme-supplemented diets. Only traces of resistant starch ( < 0.1%) were present in the pelleted diets. The content of crude protein was 20% with a low content of water-soluble crude protein (Table 2 ). Pelleting increased the water solubility of the crude protein fraction, which was also increased by enzyme supplementation. Crude fat and ash contents were 4.2 and 5.8%, respectively, for all diets. Total content of mixedlinked p-glucans was, on average, 2.3% for all diets, with an average content of soluble p-glucans of ~ 1.4% and with only small differences between diets. The total content of NSP residues was, on average, 13%. Soluble arabinose, xylose and glucose residues accounted for 15% of the total NSP content. The total content of dietary fibre was on average 14%. The diets had a low endogenous ~glucanase activity of ~ 0.5 units kg-1 in the unsupplemented mash diet, while only traces ( < 0.1 units kg- ~ diet) of endogenous activity were present in the unsupplemented pelleted diet. Enzyme supplementation of the mash diet gave an activity of 2.5 units kg- l diet which was equivalent to the calculated amount added. Taking the endogenous activity into account, a slight unexplained loss of activity was evident. However, p-glucanase activity was 2 units kg- l diet in both the dry and steam pelleted diets. Thus, the loss of activity (in the added preparation) due to pelleting was 20%, with no differences between pelleting temperatures. Buffer extracts from pelleted diets had a higher relative viscosity than those from mash diets (Table 2 ). The highest relative viscosity was found for extracts from the unsupplemented steam pelleted diet and the next highest value
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D. PETTERSSON ET AL.
TABLE 2 Chemical composition (% of dry matter) and relative extract viscosity of experimental diets Chemical constituent
Mash diet I -
Sugars Starch Total Water-soluble Crude protein Total Water-soluble Crude fat (HCI) Ash Mixed-linked fl-glucans Total Water-soluble Non-starch polysaccharide residues Total Soluble Arabinose Xylose Glucose Insoluble Arabinose Xylose Glucose Klason lignin Dietary fibre Relative extract viscosity Initial After 30 min
Pelleted diet ~ +
Low temperature 2
High temperature 3
-
-
+
+
2.8
2.8
2.8
2.8
2.8
2.8
47.0 0
47.0 0
47.4 1.3
47.7 1.8
47.6 1.1
47.6 1.7
20.0 0.8 4.2 5.8
20.0 1.0 4.2 5.8
20.0 1. I 4.2 5.8
20.0 1.7 4.2 5.8
20.0 2.2 4.2 5.8
20.0 2.6 4.2 5.8
2.4 1.3
2.3 1.4
2.3 1.4
2.3 1.4
2.3 1.5
2.4 1.5
13.3
13.0
12.5
12.3
12.4
13.0
0.2 0.3 1.1
0.3 0.4 1.4
0.2 0.3 1.6
0.2 0.3 1.3
0.3 0.5 1.1
0.3 0.4 !.2
2.1 3.1 3.6 1.0 14.3
1.9 3.2 3.6 1.2 14.2
1.8 3.0 3.3 0.9 13.4
1.8 3.1 3.4 1.2 13.5
1.8 3.1 3.5 0.9 13.3
1.8 3.2 3.6 0.9 13.9
2.4 1.9
2.3 1.9
3.3 2.3
2.7 2.1
3.6 2.4
2.9 2.2
1Diet composition is given in Table 1; without ( - ) and with ( + ) enzyme supplementation. 2Diet was dry pelleted (3.5 m m matrix) giving a pellet temperature of 50 ° C. 3Diet was steam pelleted (3.5 m m matrix) giving a pellet temperature of 70 ° C.
for the unsupplemented dry pelleted diet. Enzyme supplementation reduced the high relative viscosity values of extracts from the pelleted diets.
Production study The overall mortality in the production trial was 0.8% and was not significantly influenced by type of diet, enzyme supplementation or their interaction. At both 14 and 20 days of age, type of diet (mash, dry or steam pelleted) and enzyme supplementation significantly ( P < 0.01 ) affected weight gain, feed intake and feed conversion ratios (Table 3 ).
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TABLE3 Weight gain, cumulative feed intake and feed conversion ratio o f chickens receiving diets in mash form or pelleted at two temperatures (50 or 7 0 ° C ) and given without ( - ) or with ( + ) enzyme supplementation (four replicates per treatment) Production trait
Mash diet ~
Pelleted diets
P-value 4 for main effects
-
Low temperature 2 High temperature 3
Diet
Enzyme
+
Standard error
-
+
-
+
267 b 508 c
312 c 566 a
277 b 517 c
309 c 574 a
0.001 0.001
0.001 0.001
5.0 7.5
422 bc 856 ~
469 d 925 de
451 d~ 898 de
477 d 947 e
0.001 0.001
0.001 0.001
8.1 10.9
1.54 b~ 0.001 1.65 bc 0.001
0.001 0.005
Weight gain (g) Days 1-14 Days 1-20
209 a 400 a
259 b 464 b
Cumulative feed intake (g) Days 1-14 Days 1-20
362 a 716 ~
414 b 807 b
Feed conversion ratio (gfeed/g weight gain) Days 1-14 Days 1-20
1.73 a 1.79"
!.60 b 1.74 ab
1.58 b" 1.69 ~
1.50 ~ 1.63 ~
1.63 b 1.74 ab
0.024 0.020
=Diet composition is given in Table 1, without ( - ) and with ( + ) enzyme supplementation. 2Diet was dry pelleted (3.5 m m matrix) giving a pellet temperature of 50 oC. 3Diet was steam pelleted ( 3.5 m m matrix) giving a pellet temperature of 70 ° C. 4The probability that estimated differences are caused by random effects; no significant interaction effects were found. =b~deMeans within a row not sharing a c o m m o n superscript are significantly different ( P < 0.01 ).
In general, the unsupplemented mash diet gave lower production values than all other diets at both 14 and 20 days of age. Pelleting improved weight gain by almost 30% with the unsupplemented diets and by just over 20% with the enzyme supplemented diets (Table 3). There was little difference between dry or steam pelleted diets with regard to weight gain. With steam pelleting the improvement in weight gain was almost entirely a result of an average 20% increase in feed intake, with feed conversion ratios improved by only about 4%. Dry pelleting improved feed conversion ratios by about 7% and feed intake by about 16%. The improvements in productive value from pelleting were similar at 14 and 20 days. Enzyme supplementation of the mash diet improved weight gain, feed intake and feed conversion ratios by 23, 14 and 7%, respectively, at Day 14 and by 16, 13 and 3%, respectively, at Day 20. Enzyme supplementation of the pelleted diets did not give rise to improvements of the same order. However, at Day 14, enzyme supplementation of the dry and steam pelleted diets improved weight gains by 17 and 12%, respectively, while feed intakes increased by 11 and 6% and feed conversion ratios improved by about 5%. At Day 20 production improvements due to
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D. PETTERSSON ET AL.
enzyme supplementation of the pelleted diets were lower than at Day 14 (Table 3).
Digestibility study The ileal DM content was significantly affected by type of diet (mash, dry or steam pelleted) and there was also a weak tendency ( P = 0.09) for an effect of enzyme supplementation (Table 4). There were also significant ( P < 0.05 ) effects on ileal OM digestibility from enzyme supplementation and a significant interaction between type of diet and enzyme. Starch digestibility was influenced ( P < 0.01 ) by both diet and enzyme supplementation and also by their interaction ( P < 0.05 ). For the whole-tract digestibility of OM, crude protein and crude fat, significant effects were obtained for type of diet ( P < 0.05 ) and also for enzyme supplementation ( P < 0.01 ). There were also TABLE4 Digestibility coefficients o f nutrients in last third o f small intestine ( D a y 21 ) a n d in the whole tract (Days 15-18 ), dry matter (%) o f d i g e s t , a n d excreta a n d the frequency (%) o f sticky droppings at Day 7 (four replicates per t r e a t m e n t ) Production traits
M a s h diet 1
-
+
Pelleted diets ~
P value 4 for m a i n effects
Low temperature 2
High temperature 3
--
--
-I-
+
Diet
Enzyme
Standard error
Last third of small intestine Dry m a t t e r content
17.7"
18.2 "b
20.0 ~d 20.4 d
19.2 ~
20.1 ~
0.001
0.089
0.38
62.2" 66.5 54.4 95.0 ~
68. I b 72.5 65.7 98.8 d
66.6 b 66.8 66.4 95.6 ~
66.7 b 67.3 65.6 96.6"
65.2 b 67.6 60.8 94.4 ab
65.4 b 70.9 59.2 95.0 ~
0.305 0.674 0.311 0.006
0.031 0.199 0.417 0.001
1.05 3.06 4.38 0.46
33.2 a
38.1 ~
35.5 ac
34.0 a
34.0"
33.3 a
0.362
0.434
1.37
75.5 "b 79.8 ~b 67.(P 25.0 a
76.3 a 82.3 ¢ 69.5 ~b 6.3 b
73.8 ~ 78.5" 70.0 ac 23.4"
75.5 ~b 79.3 ab 74.5 d 9.4 b
74.8 b~ 76.3" 78.3" 80.8 b~ 70.0 ab 71.3 ab~ 37.5 ~ 21.9 ~
0.015 0.008 0.011 0.029
0.001 0.001 0.009 0.002
0.39 0.61 1.17 5.35
Ileal digestibility Organic matter Crude protein Crude fat Starch
Excreta Dry matter content
Whole-tract digestibility Organic m a t t e r Crude protein Crude fat
Sticky droppings
1Diet composition is given in Table 1; without ( - ) a n d with ( + ) e n z y m e supplementation. 2Diet was dry pelleted (3.5 m m m a t r i x ) giving a pellet temperature o f 50 ° C. 3Diet was s t e a m pelleted (3.5 m m m a t r i x ) giving a pellet temperature o f 70 ° C. 4The probability that estimated differences are caused by r a n d o m effects. Significant interaction effects were only found for ileal organic m a t t e r ( P = 0.015 ) a n d ileal starch ( P = 0.019) digestibility. ab~°eMeans within a row not sharing a c o m m o n superscript are significantly different ( P < 0.05 ).
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significant effects for diet (P< 0.05) and enzyme supplementation (P< 0.01 ) on the incidence of sticky droppings at Day 7. In general, pelleting reduced ileal DM content, while enzyme supplementation had no effect (Table 4). Pelleting tended to improve the ileal OM digestibility of the unsupplemented diet while enzyme supplementation tended also to increase the ileal OM and starch digestibility, particularly with the mash diet. Pelleting reduced excreta DM content in the supplemented diets while enzyme supplementation of the mash diet gave an increased excreta DM content. Whole-tract digestibility of OM and crude protein tended to be reduced by pelleting while that of crude fat tended to be improved. Enzyme supplementation generally improved whole-tract digestibility. Chickens fed on the unsupplemented mash diet had the lowest ileal digestibility values for OM, CP and crude fat and also had the lowest digesta DM content (Table 4). Enzyme supplementation of the mash diet improved the digestibility ofOM, CP, crude fat and starch at the ileum by 9, 9, 20 and 4%, respectively, but the improvement was statistically significant only for starch digestibility. It is notable that the ileal digestibility of OM, CP and starch was higher for the enzyme-supplementedmash diet than for the enzyme-supplemented pelleted diets and that chickens fed on pelleted diets had a higher digesta DM content than those fed on the equivalent mash diet. With enzyme supplementation, the whole-tract digestibility of OM and crude fat was significantly improved (P< 0.05 ) for chickens fed on the dry pelleted diet, the levels of improvement being 2 and 6%, respectively (Table 4). Similar effects were observed from enzyme supplementation of the steam pelleted diet with significant effects (P<0.05) for the improvements obtained in OM and CP whole-tract digestibility (2 and 3%, respectively). Pelleting the unsupplemented diet gave a lower whole-tract digestibility of OM and CP but a higher crude fat digestibility. The occurrence of sticky droppings on Day 7 was generally higher for chickens fed on the unsupplemented diets than for those fed on the equivalent enzyme-supplemented diets (Table 4). The enzyme-supplemented mash diet gave a significantly (P< 0.05 ) lower occurrence of sticky droppings than the unsupplemented pelleted diets. On average the steam pelleted diets also gave a significantly (P< 0.05 ) higher frequency of sticky droppings than the dry pelleted diets. Enzyme supplementation of the steam pelleted diet reduced the occurrence of sticky droppings only to a level similar to that of chickens fed on unsupplemented mash or dry pelleted diets. DISCUSSION
It is well known that the heating of a starch-rich food or feedstuff with a high moisture content will lead to a gelatinization of starch (Theander and Westerlund, 1984). Even the low moisture and temperature conditions pre-
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D. PETTERSSON ET AL.
vailing during the dry pelleting treatment in the present study increased the water solubility of starch and this probably contributed to the observed increase in buffer extract viscosity. The reduction in endogenous enzymatic activity on pelleting may have led to a delayed degradation of soluble arabinoxylans, and mixed-linked fl-glucans, and consequently to a slower and maybe lesser reduction in viscosity (Hesselman, 1983; Pettersson, 1988). The importance of an unimpaired endogenous enzymatic activity is displayed by the low viscosity of buffer extracts from the unsupplemented mash diet and the decrease in viscosity for buffer extracts from enzyme-supplemented pelleted diets. There were no significant differences in weight gain between chickens fed on the two types of pelleted diets, although those fed on the steam pelleted diets, on average, had a numerically higher weight gain but also a higher feed intake and hence a slightly inferior feed conversion efficiency. As the increased feed intake during the first 14 days was accompanied by an inferior feed conversion efficiency it might be assumed that the nutrient surplus ingested was fermented in the hind gut. The latter effect was probably also associated with the increased occurrence of sticky droppings for chickens fed on the steam pelleted diets. The effects of pelleting were essentially the same at Days 14 and 20, while enzyme supplementation had a much greater effect at Day 14. This suggests that changes in the gastro-intestinal environment, presumably the establishment of a microflora population, occur during this period. The ileal digestibility of CP tended to improve with enzyme supplementation, although not significantly as has been shown for rye/wheat-based broiler chicken mash diets (Pettersson and/~man, 1989). Pelleting causes a greater cell wall breakage (Saunders et al., 1969) and the disruption of the cellular structure is probably similar to the effect obtained by enzyme supplementation (Hesselman, 1983 ). Possible differences in the ileal digestibility of nutrients will consequently be small for pelleted diets given with or without enzyme supplementation, provided that there is no impeded absorption owing to viscous conditions. The enzyme-supplemented mash diet, which had the lowest buffer extract viscosity, had the highest ileal digestibility values for OM, CP and starch. However, there were no significant effects of enzyme supplementation or pelleting on CP digestibility and this could be due to an interference from protein-rich endogenous excretion products, which has been observed in ileal digestibility studies with pigs (Hagemeister, 1985) and poultry (Hurwitz et al., 1979 ). The small differences and high variation obtained between different treatments regarding ileal crude fat digestibility might, in a similar way, have been caused by an endogenous lipid excretion which is known to be of significant importance in the chick (Sklan et al., 1973). For starch, the major dietary component, general improvements in digestibility were obtained following enzyme supplementation, which also has
PELLETINGAND SUPPLEMENTATIONOF CEREALDIETFOR BROILERCHICKENS
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been shown in earlier studies with broiler chickens (Hesselman and/~man, 1986; Pettersson and/~man, 1989) and with pigs (Graham et al., 1989). Improved whole-tract digestibility of CP and crude fat as a result of pelleting has been reported in experiments with pigs (Vanschoubroek et al., 1971; Graham et al., 1989 ) and was thought to be caused mainly by a reduced wholetract bacterial output resulting from a more extensive digestion in the small intestine. However, in the present experiment, pelleting did not improve ileal digestibilityand improved only whole-tract crude fat digestibility, while wholetract OM and CP digestibility values were reduced. Enzyme supplementation, on the other hand, generally improved ileal starch and OM digestibility as well as whole-tract digestibility of OM, CP and crude fat. From the results obtained it can be concluded that during normal pelleting conditions the temperature and moisture levels are not sufficient to solubilise dietary fibres or to form resistant starch. However, even a moderate temperature treatment, such as the dry pelleting process employed in the present study, may solubilise starch and also diminish the important endogenous enzyme activity. This can lead to an increase in digesta viscosity which may impede both the nutrient absorption and the resorption of endogenous excretion products in the small intestine, thereby increasing the amount of substrate available for bacterial growth in the hind gut. A moderate growth of endogenous bacteria may prevent invasion and growth of a pathogenic microflora (Ducluzeau et al., 1981 ). An excessive microbial growth, however, may disturb the gut environment and cause problems such as sticky droppings or necrotic enteritis. The mechanisms involved in these disturbances are not fully understood but are undoubtedly mainly influenced by feeding. However, supplementation with an appropriate enzyme preparation can reduce digesta viscosity and increase nutrient absorption in the small intestine, thus improving production and health in chickens fed on mash or pelleted diets. ACKNOWLEDGEMENTS
The authors wish to thank the Swedish Farmers' Selling and Purchasing Association and Grindsted Products A/S for financial support and co-operation in this investigation. We also would like to thank the staff at the Division of Feed Chemistry for excellent technical assistance.
REFERENCES Allred, J.B., Jensen, L.S. and McGinnis, J., 1957a. Factors affecting the response of chicks and poults to feed pelleting. Poult. Sci., 36:517-523. Allred, J.B., Fry, R.E., Jensen, L.S. and McGinnis, J., 1957b. Studies with chicks on improvement in nutritive value of feed ingredients by pelleting. Poult. Sci., 36: 1284-1289.
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D. PETTERSSON ET AL.
Aman, P. and Graham, H., 1987. Analysis of total and insoluble mixed linked fl-( 1-> 3), (1> 4), -D-glucans in barley and oats. J. Agric. Food Chem., 35: 704-709. Aman, P. and Hesselman, K., 1984. Analysis of starch and other main constituents of cereal grains. Swed. J. Agric. Res., 14: 135-139. Anonymous, 1971. Determination of crude oils and fats. Off. J. Eur. Comm., L297: 995-997. Arscott, G.H., McCluskey, W.H. and Parker, J.E., 1958. The use of barley in high-efficiency broiler rations. 2. Effect of stabilized animal fat and pelleting on efficiency of feed utilization and water consumption. Poult. Sci., 37:117-123. Association of Official Analytical Chemists, 1984. Official Methods of Analysis, 14th edn. Washington DC, 1141 pp. Bayley, H.S., Summers, J.D. and Slinger, S.J., 1968. The influence of steam pelleting conditions on the nutritional value of chick diets. Poult. Sci., 47:931-939. Bj6rck, I., Nyman, M. and Asp, N.-G., 1984. Extrusion cooking and dietary fiber: Effects on dietary fiber content and on degradation in the rat intestinal tract. Cereal Chem., 61:174179. Cox, N.A., Burdick, D., Bailey, J.S. and Thomson, J.E., 1986. Effect of the steam conditioning and pelleting process on the microbiology and quality of commercial-type poultry feeds. PouR. Sci., 65: 704-709. Ducluzeau, R., Dubos, F., Hudault, S., Nicolas, J.-L., Dabard, J. and Raibaud, P., 1981. Microbial barriers against enteropathogenic strains in the digestive tract of gnotoxenic animals. Application to the treatment of Clostridium difficile diarrhoea in the young hare. In: S. Sasaki (Editor), Recent Advances in Germfree Research. Tokai University Press, Tokyo, pp. 135-141. Eriksson, S., 1955. Digestibility and metabolizable energy of poultry rations at different levels of nutrition. Acta Agric. Scand., 5:201-214. Eriksson, S., Sanne, S. and Thomke, S., 1972. Fodermedlen. LT:s f'6rlag, Boris, 299 pp. (in Swedish). Fenton, T.W. and Fenton, M., 1979. An improved procedure for the determination of chromic oxide in feed and feces. Can. J. Anim. Sci., 59: 631-634. Graham, H., Fadel, J.G., Newman, C.W. and Newman, R.K., 1989. Effect of pelleting and flglucanase supplementation on the ileal and whole-tract digestibility of a barley-based diet in the pig. J. Anim. Sci., 67: 1293-1298. H agemeister, H., 1985. Chemical labeling of dietary protein by transformation of lysine to homoarginine; a new technique to follow intestinal digestion and absorption. Proc. Nutr. Soc., 44: 133A (Abstr.). Hartfiel, W., 1973. Richtlinien zur Durchfiihrung von Bilanzversuchen mit Hiihnern. Arch. f. Gefliigelkunde, 2: 49-57. Hesselman, K., 1983. Effects of fl-glucanase supplementation to barley based diets for broiler chickens. Report 112 (Ph.D. Thesis). Swedish University of Agricultural Sciences, Uppsala, 32 pp. Hesselman, K. and Aman, P., 1986. The effect of fl-glucanase on the utilization of starch and nitrogen by broiler chickens fed on barley of low or high viscosity. Anita. Feed Sci. Technol., 15: 83-93. Hurwitz, S., Eisner, U., Dubrov, D., Sklan, D., Risenfeld, G. and Bar, A., 1979. Protein, fatty acids, calcium and phosphate absorption along the gastrointestinal tract of the young turkey. Comp. Biochem. Physiol., 62A: 847-850. Lindblad, G.S., Aitken, J.R. and Hunsaker, W.G., 1955. Studies on the use of barley in broiler rations (abstr.). Poult. Sci., 34: 1208. MacKenzie, M.A. and Bains, B.S., 1976. Dissemination of Salmonella serotypes from raw feed ingredients to chicken carcasses. Poult. Sci., 55: 957-960.
PELLETINGANDSUPPLEMENTATIONOF CEREALDIETFOR BROILERCHICKENS
13
Marquardt, R.R., 1983. A simple spectrophotometric method for the direct determination of uric acid in avian excreta. Poult. Sci., 62: 2106-2108. McIntosh, J.I., Slinger, S.J., Sibbald, I.R. and Ashton, G.C., 1962. Factors affecting the metabolizable energy content of poultry feeds. 7. The effects of grinding, pelleting and grit feeding on the availability of the energy of wheat, corn, oats and barley. 8. A study on the effects of dietary balance. Poult. Sci., 41: 445-456. Misir, R. and Marquardt, R.R., 1978. Factors affecting rye (Secale cereale L.) utilization in growing chicks. IV. The influence of autoclave treatment, pelleting, water extraction and penicillin supplementation. Can. J. Anim. Sci., 58:703-715. Moran, Jr., E.T. and McGinnis, J., 1968. Growth of chicks and turkey poults fed western barley and corn grain-based rations: Effect of autoclaving on supplemental enzyme requirement and asymmetry of antibiotic response between grains. Poult. Sci., 47:152-158. Moran, Jr., E.T., LaU, S.P. and Summers, J.D., 1969. The feeding value of rye for the growing chick: Effect of enzyme supplements, antibiotics, autoclaving and geographical area of production. Poult. Sci., 48: 939-949. Mossel, D.A.A., 197 I. Physiological and metabolic attributes of microbial groups associated with foods. J. Appl. Bacteriol., 34:95-118. Patterson, J.T., 1969. Salmonellae in meat and poultry, poultry plant cooling waters and effluent, and animal feeding stuffs. Appl. Bacteriol., 32: 329-337. Patton, J.W., Buskirk, H.H. and Rauls, L.A., 1937. A study of the relative merits of pellets and mash poultry feeds. Vet. Med., 32: 423-427. Pettersson, D., 1988. Composition and productive value for broiler chickens of wheat, triticale and rye. Rep. 177, Ph.D. Thesis, Swedish University of Agricultural Sciences, Uppsala, 46 PP. Pettersson, D. and Aman, P., 1989. Enzyme supplementation of a poultry diet containing wheat and rye. Br. J. Nutr., 62: 139-149. Pettersson, D., Hesselman, K. and/~anan, P., 1987. Nutritional value for chickens of dried distillers-spent-grain from barley and dehulled barley. Anim. Feed SCi. Technol., 17:145-156. Saunders, R.M., Walker, Jr., H.G. and Kohler, G.O., 1969. Aleurone cells and the digestibility of wheat mill feeds. Poult. SCi., 48: 1497-1503. Sell, J.L. and Thompson, O.J., 1965. The effects of ration pelleting and level of fat on the efficiency of nutrient utilization by the chicken. Br. Poult. SCi., 6: 345-354. Siljest~m, M., Westerlund, E., BjSrek, I., Holm, J., Asp, N.-G. and Theander, O., 1986. The effects of various thermal processes on dietary fibre and starch content of whole grain wheat and white flour. J. Cereal SCi., 4:315-323. Sklan, D., Budowski, P., Ascarelli, I. and Hurwitz, S., 1973. Lipid absorption and secretion in the chick: Effect of raw soybean meal. J. Nutr., 103: 1299-1305. Statistical Analysis Systems, 1985. User's Guide: Statistics. Version 5. Edition SAS Institute Inc., Cary, NC, 956 pp. Stott, J.A., Hodgeson, J.E. and Chaney, J.C., 1975. Incidence of Salmonellae in animal feed and the effect of pelleting on content of Enterobacteriaceae. J. Appl. Bacteriol., 39:41-46. Summers, J.D., Bentley, H.U. and Slinger, S.J., 1968. Influence of method of pelleting on utilization of energy from corn, wheat, shorts and bran. Cereal Chem., 45:612-615. Tabib, Z., Jones, F.T. and Hamilton, P.B., 1984. Effect of pelleting of poultry feed on the activity of molds and mold inhibitors. Poult. SCi., 63:70-75. Theander, O. and/~man, P., 1979. Studies on dietary fibres. 1. Analysis and chemical characterization of water-soluble and water-insoluble dietary fibres. Swed. J. Agric. Res., 9: 97106. Theander, O. and Westerlund, E., 1984. Chemical modification of starch by heat treatment and further reactions of the products formed, In: P. Zeuthen, J.C. Cheftel, C. Eriksson, M. Jul,
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D. PETTERSSONETAL.
H. Leniger, P. Linko, G. Varela and G. Vos (Editors), Thermal Processing and Quality of Foods, Elsevier, London, pp. 202-207. Theander, O. and Westerlund, E., 1986. Studies on dietary fibers. III. Improved procedures for analysis of dietary fibers. J. Agric. Food Chem., 34: 330-336. Vanschoubroek, F., Coucke, L. and van Spaendonck, R., 1971. The quantitative effect of pelleting feed on the performance of piglets and fattening pigs. Nutr. Abstr. Rev., 41: 1-9. Wade, N.L. and Morris, S.C., 1982. Rapid determination of sugars in cantaloupe melon juice by high-performance liquid chromatography. J. Chromatogr., 240:257-261. Ward, A.T. and Marquardt, R.R., 1988. Effect of various treatments on the nutritional value of rye or rye fractions. Br. Poult. Sci., 29: 709-720. Westerlund, E., Theander, O., Andersson, R. and Aman, P., 1989. Effects of baking on polysaccharides in white bread. J. Cereal Sci., 10:149-156.
1
Elsevier Science Publishers B.V., Amsterdam
The nutritive value for broiler chickens of pelleting and enzyme supplementation of a diet containing barley, wheat and rye D. Pettersson, H. Graham and P. ]~man Swedish University of Agricultural Sciences, Department of Animal Nutrition and Management, S- 750 07 Uppsala (Sweden) (Received 22 May 1990; accepted for publication 5 October 1990)
ABSTRACT Pettersson, D., Graham, H. and/~man, P., 1991. The nutritive value for broiler chickens of pelleting and enzyme supplementation of a diet containing barley, wheat and rye. Anita. Feed Sci. Technol., 33: 1-14. A diet based on barley (40%), wheat (25%), and rye (7%) was given as a mash diet or as dry or steam pelleted diets to a total of 384 broiler chickens. Diets were given with or Without the addition of a fibre-degrading enzyme preparation. Pelleting increased the water solubility (at 38 *C ) of starch and crude protein. There were, however, no notable effects on the solubility of dietary fibre components following pelleting or enzyme supplementation. Buffer extracts from pelleted diets had a high relative viscosity, while mash diets gave the lowest relative viscosity. Enzyme supplementation diminished the high viscosity obtained for pelleted diets and reduced sticky droppings. Pelleting increased weight gain for chickens receiving the unsupplemented diets by ~ 30% and for those fed on the enzyme-supplemented diets by ~ 20%. This improvement, which was similar at both 14 and 20 days of age, was mainly due to a greater feed intake, particularly with the steam pelleting. Enzyme supplementation improved weight gain by 11-24%, and was more effective in the unpelleted diets and at Day 14. This improvement was due to both a higher feed intake and a better feed conversion efficiency. Pelleting tended to increase ileal digestibility of the unsupplemented diet while enzyme supplementation had a similar effect on the unpeUeted diet. The latter treatment also increased whole-tract digestibility.
INTRODUCTION
There are numerous reports regarding the improvements obtained in production from steam pelleting the diets of poultry (Patton et al., 1937; Lindblad et al., 1955; Allred et al., 1957a,b; Sell and Thompson, 1965; Bayley et al., 1968; Summers et al., 1968). The improvements have been attributed to chemical effects such as the destruction of heat-sensitive growth inhibitors. An increased diet density, which improves feed intake and thereby increases 0377-8401/91/$03.50
© 1991 u Elsevier Science Publishers B.V.
2
D. PETTERSSON ET AL.
nutrient intake, has also been proposed to improve weight gain and feed conversion efficiency. The primary reasons for steam pelleting poultry diets, however, are to kill bacteria and reduce mould growth (Patterson, 1969; Mossel, 1971; Stott et al., 1975; MacKenzie and Bains, 1976; Tabib ct al., 1984; Cox et al., 1986). The productive value of low-fibre diets based on wheat or maize is generally improved by pelleting (Arscott et al., 1958; Mclntosh et al., 1962). Heat treatment (autoclaving or pelleting) of fibre-rich poultry diets based on barley or rye, on the other hand, may reduce their productive value (Moran and McGinnis, 1968; Moran et al., 1969; Misir and Marquardt, 1978; Ward and Marquardt, 1988). Furthermore, high-temperature treatments (e.g. extrusion) may increase the content of soluble dietary fibres and form resistant starch at high moisture levels (Bj~rck et al., 1984; Siljestr~m et al., 1986). The present experiment was conducted in order to study the effects of pelleting a barley/rye-rich diet, with specific reference to the effects on dietary fibres. Fibre-degrading enzymes were employed to investigate further the influence of the fibre fraction. MATERIAL AND METHODS
Diets
On a fresh weight basis the basal diet (Table 1 ) was designed to have a metabolizable energy (ME) content of ~ 11.8 MJ kg-1 diet (corrected to 33% nitrogen retention) and a crude protein concentration of 17.5% calculated according to the Swedish feed tables (Eriksson et al., 1972). Lysine was provided at a calculated level of 1% and mcthionine at 0.45%. The basal mash diet, milled to pass a 3.5-mm screen, was divided into two large batches, of which one was enzyme supplemented. These two batches were then each subdivided into three parts of which two parts from each of the major batches were pelleted through a 3.5-mm matrix either dry (50°C) or with steam (70°C). The third part of each batch was given as a mash diet. The enzyme was a technical enzyme preparation, Glucanase GP 5000 (GP-5000), from Grindsted Products A/S, Denmark. The preparation was designed to contain both mixed-linked fl-glucanase and arabinoxylanase activity and was added to the basal diet at a level of 0.5 g kg- ~diet. Enzymatic activity was measured by the enzyme manufacturer using a viscosimetric method (fl-glucanase activity) and a reducing end-group method (xylanase activity). The GP-5000 preparation had a fl-glucanase activity (EC 3.2.1.6 ) of 5 units g-~ and a xylanase activity (EC 3.2.1.8 ) of 725 units g - 1.
PELLETINGANDSUPPLEMENTATIONOF CEREALDIETFOR BROILERCHICKENS
3
TABLE 1 Composition and calculated content of chemical constituents of the basal broiler chicken diet (airdry basis) Ingredient
Composition (%) Wheat Barley Rye Soya-bean meal Fish meal Animal fat Limestone Mono-calcium phosphate Vitamin and trace clement premix ~ Lysine DL-methionine Salt (NaCI)
25.0 40.0 7.1 21.5 1.6 1.0 1.7 1.3 0.2 0.12 0.14 0.34
Calculated analysis 2 Metabolizable energy content (MJ kg- t ) Crude protein (%) Lysine (%) Methionine (%)
17.5 1.0 0.45
I 1.8
tThe vitamin and trace clement premix supplied per kg diet:vitamin A, 17000 IU; vitamin D3, 3000 IU; vitamin E, 60 mg; vitamin K3, 5 mg; vitamin Bt, I mg; vitamin B2, 6 rag; vitamin B6, 3 mg; vitamin B12, 0.02 rag; Ca-pantothcnatc, I0 rag; folicacid, l mg; niacin, 30 mg; biotin, 0.1 mg; Fe, 20 mg; Mn, I00 mg; Zn, I00 rag; Cu, 30 mg; I, 0.5 mg; Sc, 0.1 mg. 2Calculated according to the Swedish Feed Tables (Eriksson et al.,1972 ).
Chemical analysis Prior to chemical analyses, feed samples were ground in a Tecator cyclone sample mill to pass a 0.5-ram screen. Samples of freeze-dried excreta and digesta were ground in a Brabender mill ( 1-mm screen size) and then in a Wiley mill (0.5-mm screen size). Dry matter ( D M ) concentration was determined by oven drying at 105 °C for 16 h and chemical analyses, carried out in duplicate, are reported on a DM basis. Sugars (the sum of free glucose, fructose and sucrose) were analysed by HPLC (Wade and Morris, 1982 ). Starch was determined according to ,~man and Hesselman (1984) and resistant starch according to Westerlund et al. (1989). Mixed-linked fl-glucans were analysed according to/~man and Graham ( 1987 ). Crude protein (N × 6.25 ) analyses and ash determinations were done as outlined in the standard methods of the Association of Official Analytical Chemists (1984). Water-soluble starch, crude protein and mixed-linked fl-glucans were extracted at 38 °C for 2 h and isolated by centrifugation prior to analyses. Crude fat was extracted with diethyl ether in a Tecator Soxtec System HT after acid hydrolysis (Anonymous,
4
D. PETI'ERSSON ET AL.
1971 ). Total and insoluble non-starch polysaccharide (NSP) residues and Klason lignin were determined according to Theander and Aman (1979) as modified by Theander and Westeflund (1986 ) and dietary fibre was calculated as the sum of these components. Insoluble NSP residues were determined after extraction of soluble components in H20 at 38 °C for 2 h, while soluble NSP residues were determined by difference. Uric acid was determined according to Marquardt (1983). Chromic oxide was analysed spectrophotometrically, as described by Fenton and Fenton (1979). Relative extract viscosity was calculated as the descent time of extracts divided by the descent time of the extraction medium (0.1 M sodium acetate buffer, pH 5.0) measured on an Ostvald viscometer. Extractions were performed according to Pcttersson et al. ( 1987 ).
Chickens A total of 384 unsexed 1-day-old broiler chickens (Ross) were allocated to 24 groups with 16 birds in each, with an average group weight of 702 g and a maximum difference in weight of 4 g between groups. These groups were then randomly assigned to their treatments in six four-tier battery cages with raised wire floors. There were four replicates of 16 birds in each treatment. The chickens had free access to feed and water throughout the experiment. Light and temperature were regulated according to Pettersson (1988).
Production and digestibility study Group feed intakes (air dry weight, corrected for feed wastage) and individual chicken weights were recorded at 14 and 20 days of age, and group feed conversion ratios were calculated. The occurrence of sticky droppings (i.e. wet excreta sticking to the down of the cloaca) was recorded on Day 7. Between Days 15 and 18 a quantitative digestibility trial was conducted. Excreta were collected twice daily and kept frozen until mixed and freeze-dried. From 18 days of age, diets were given with a marker (Cr203) which was incorporated at a level of 4 g kg- 1 in minor sub-batches of the mash and pellet diets during their manufacture. On Day 2 l, four chickens from each group (16 from each treatment), with weights as close as possible to the average group weight, were killed by dislocation of the neck vertebrae and their gastro-intestinal tract was quickly removed. The small intestine was divided into three parts of which the two first were discarded. The content of the last third of the small intestine (denoted ileum) was collected separately, pooled for each group, frozen ( - 2 5 °C) and freeze-dried. Digestibility in the digesta samples was calculated relative to the chromic oxide marker, while whole-tract digestibility was calculated from total collection of excreta. Whole-tract crude protein and organic matter digestibility was calculated according to Hartfiel
PELLETING AND SUPPLEMENTATION OF CEREAL DIET FOR BROILER CHICKENS
5
(1973) and Eriksson ( 1955 ) by assuming that all urinary nitrogen emanated from uric acid, and that urinary organic matter content was four times that of urinary nitrogen content.
Calculations and statistical analyses Chicken weights are reported as group means and feed conversion ratios are calculated as cumulative group feed intakes divided by group weight gains. Statistical evaluations were done by using an analysis of variance procedure, the general linear model (GLM), supported by the statistical analysis system (Statistical Analysis Systems, 1985). In the statistical model the effects of type of diet (mash, dry pelleted or steam pelleted) and enzyme supplementation and also their interaction were taken into account. RESULTS
Diets The dietary content of available carbohydrates (sum of starch and sugars) was as high as 50% (Table 2). Pelleting led to a slight solubilisation of starch which was more pronounced for the enzyme-supplemented diets. Only traces of resistant starch ( < 0.1%) were present in the pelleted diets. The content of crude protein was 20% with a low content of water-soluble crude protein (Table 2 ). Pelleting increased the water solubility of the crude protein fraction, which was also increased by enzyme supplementation. Crude fat and ash contents were 4.2 and 5.8%, respectively, for all diets. Total content of mixedlinked p-glucans was, on average, 2.3% for all diets, with an average content of soluble p-glucans of ~ 1.4% and with only small differences between diets. The total content of NSP residues was, on average, 13%. Soluble arabinose, xylose and glucose residues accounted for 15% of the total NSP content. The total content of dietary fibre was on average 14%. The diets had a low endogenous ~glucanase activity of ~ 0.5 units kg-1 in the unsupplemented mash diet, while only traces ( < 0.1 units kg- ~ diet) of endogenous activity were present in the unsupplemented pelleted diet. Enzyme supplementation of the mash diet gave an activity of 2.5 units kg- l diet which was equivalent to the calculated amount added. Taking the endogenous activity into account, a slight unexplained loss of activity was evident. However, p-glucanase activity was 2 units kg- l diet in both the dry and steam pelleted diets. Thus, the loss of activity (in the added preparation) due to pelleting was 20%, with no differences between pelleting temperatures. Buffer extracts from pelleted diets had a higher relative viscosity than those from mash diets (Table 2 ). The highest relative viscosity was found for extracts from the unsupplemented steam pelleted diet and the next highest value
6
D. PETTERSSON ET AL.
TABLE 2 Chemical composition (% of dry matter) and relative extract viscosity of experimental diets Chemical constituent
Mash diet I -
Sugars Starch Total Water-soluble Crude protein Total Water-soluble Crude fat (HCI) Ash Mixed-linked fl-glucans Total Water-soluble Non-starch polysaccharide residues Total Soluble Arabinose Xylose Glucose Insoluble Arabinose Xylose Glucose Klason lignin Dietary fibre Relative extract viscosity Initial After 30 min
Pelleted diet ~ +
Low temperature 2
High temperature 3
-
-
+
+
2.8
2.8
2.8
2.8
2.8
2.8
47.0 0
47.0 0
47.4 1.3
47.7 1.8
47.6 1.1
47.6 1.7
20.0 0.8 4.2 5.8
20.0 1.0 4.2 5.8
20.0 1. I 4.2 5.8
20.0 1.7 4.2 5.8
20.0 2.2 4.2 5.8
20.0 2.6 4.2 5.8
2.4 1.3
2.3 1.4
2.3 1.4
2.3 1.4
2.3 1.5
2.4 1.5
13.3
13.0
12.5
12.3
12.4
13.0
0.2 0.3 1.1
0.3 0.4 1.4
0.2 0.3 1.6
0.2 0.3 1.3
0.3 0.5 1.1
0.3 0.4 !.2
2.1 3.1 3.6 1.0 14.3
1.9 3.2 3.6 1.2 14.2
1.8 3.0 3.3 0.9 13.4
1.8 3.1 3.4 1.2 13.5
1.8 3.1 3.5 0.9 13.3
1.8 3.2 3.6 0.9 13.9
2.4 1.9
2.3 1.9
3.3 2.3
2.7 2.1
3.6 2.4
2.9 2.2
1Diet composition is given in Table 1; without ( - ) and with ( + ) enzyme supplementation. 2Diet was dry pelleted (3.5 m m matrix) giving a pellet temperature of 50 ° C. 3Diet was steam pelleted (3.5 m m matrix) giving a pellet temperature of 70 ° C.
for the unsupplemented dry pelleted diet. Enzyme supplementation reduced the high relative viscosity values of extracts from the pelleted diets.
Production study The overall mortality in the production trial was 0.8% and was not significantly influenced by type of diet, enzyme supplementation or their interaction. At both 14 and 20 days of age, type of diet (mash, dry or steam pelleted) and enzyme supplementation significantly ( P < 0.01 ) affected weight gain, feed intake and feed conversion ratios (Table 3 ).
PELLETING AND SUPPLEMENTATIONOF CEREAL DIET FOR BROILER CHICKENS
7
TABLE3 Weight gain, cumulative feed intake and feed conversion ratio o f chickens receiving diets in mash form or pelleted at two temperatures (50 or 7 0 ° C ) and given without ( - ) or with ( + ) enzyme supplementation (four replicates per treatment) Production trait
Mash diet ~
Pelleted diets
P-value 4 for main effects
-
Low temperature 2 High temperature 3
Diet
Enzyme
+
Standard error
-
+
-
+
267 b 508 c
312 c 566 a
277 b 517 c
309 c 574 a
0.001 0.001
0.001 0.001
5.0 7.5
422 bc 856 ~
469 d 925 de
451 d~ 898 de
477 d 947 e
0.001 0.001
0.001 0.001
8.1 10.9
1.54 b~ 0.001 1.65 bc 0.001
0.001 0.005
Weight gain (g) Days 1-14 Days 1-20
209 a 400 a
259 b 464 b
Cumulative feed intake (g) Days 1-14 Days 1-20
362 a 716 ~
414 b 807 b
Feed conversion ratio (gfeed/g weight gain) Days 1-14 Days 1-20
1.73 a 1.79"
!.60 b 1.74 ab
1.58 b" 1.69 ~
1.50 ~ 1.63 ~
1.63 b 1.74 ab
0.024 0.020
=Diet composition is given in Table 1, without ( - ) and with ( + ) enzyme supplementation. 2Diet was dry pelleted (3.5 m m matrix) giving a pellet temperature of 50 oC. 3Diet was steam pelleted ( 3.5 m m matrix) giving a pellet temperature of 70 ° C. 4The probability that estimated differences are caused by random effects; no significant interaction effects were found. =b~deMeans within a row not sharing a c o m m o n superscript are significantly different ( P < 0.01 ).
In general, the unsupplemented mash diet gave lower production values than all other diets at both 14 and 20 days of age. Pelleting improved weight gain by almost 30% with the unsupplemented diets and by just over 20% with the enzyme supplemented diets (Table 3). There was little difference between dry or steam pelleted diets with regard to weight gain. With steam pelleting the improvement in weight gain was almost entirely a result of an average 20% increase in feed intake, with feed conversion ratios improved by only about 4%. Dry pelleting improved feed conversion ratios by about 7% and feed intake by about 16%. The improvements in productive value from pelleting were similar at 14 and 20 days. Enzyme supplementation of the mash diet improved weight gain, feed intake and feed conversion ratios by 23, 14 and 7%, respectively, at Day 14 and by 16, 13 and 3%, respectively, at Day 20. Enzyme supplementation of the pelleted diets did not give rise to improvements of the same order. However, at Day 14, enzyme supplementation of the dry and steam pelleted diets improved weight gains by 17 and 12%, respectively, while feed intakes increased by 11 and 6% and feed conversion ratios improved by about 5%. At Day 20 production improvements due to
8
D. PETTERSSON ET AL.
enzyme supplementation of the pelleted diets were lower than at Day 14 (Table 3).
Digestibility study The ileal DM content was significantly affected by type of diet (mash, dry or steam pelleted) and there was also a weak tendency ( P = 0.09) for an effect of enzyme supplementation (Table 4). There were also significant ( P < 0.05 ) effects on ileal OM digestibility from enzyme supplementation and a significant interaction between type of diet and enzyme. Starch digestibility was influenced ( P < 0.01 ) by both diet and enzyme supplementation and also by their interaction ( P < 0.05 ). For the whole-tract digestibility of OM, crude protein and crude fat, significant effects were obtained for type of diet ( P < 0.05 ) and also for enzyme supplementation ( P < 0.01 ). There were also TABLE4 Digestibility coefficients o f nutrients in last third o f small intestine ( D a y 21 ) a n d in the whole tract (Days 15-18 ), dry matter (%) o f d i g e s t , a n d excreta a n d the frequency (%) o f sticky droppings at Day 7 (four replicates per t r e a t m e n t ) Production traits
M a s h diet 1
-
+
Pelleted diets ~
P value 4 for m a i n effects
Low temperature 2
High temperature 3
--
--
-I-
+
Diet
Enzyme
Standard error
Last third of small intestine Dry m a t t e r content
17.7"
18.2 "b
20.0 ~d 20.4 d
19.2 ~
20.1 ~
0.001
0.089
0.38
62.2" 66.5 54.4 95.0 ~
68. I b 72.5 65.7 98.8 d
66.6 b 66.8 66.4 95.6 ~
66.7 b 67.3 65.6 96.6"
65.2 b 67.6 60.8 94.4 ab
65.4 b 70.9 59.2 95.0 ~
0.305 0.674 0.311 0.006
0.031 0.199 0.417 0.001
1.05 3.06 4.38 0.46
33.2 a
38.1 ~
35.5 ac
34.0 a
34.0"
33.3 a
0.362
0.434
1.37
75.5 "b 79.8 ~b 67.(P 25.0 a
76.3 a 82.3 ¢ 69.5 ~b 6.3 b
73.8 ~ 78.5" 70.0 ac 23.4"
75.5 ~b 79.3 ab 74.5 d 9.4 b
74.8 b~ 76.3" 78.3" 80.8 b~ 70.0 ab 71.3 ab~ 37.5 ~ 21.9 ~
0.015 0.008 0.011 0.029
0.001 0.001 0.009 0.002
0.39 0.61 1.17 5.35
Ileal digestibility Organic matter Crude protein Crude fat Starch
Excreta Dry matter content
Whole-tract digestibility Organic m a t t e r Crude protein Crude fat
Sticky droppings
1Diet composition is given in Table 1; without ( - ) a n d with ( + ) e n z y m e supplementation. 2Diet was dry pelleted (3.5 m m m a t r i x ) giving a pellet temperature o f 50 ° C. 3Diet was s t e a m pelleted (3.5 m m m a t r i x ) giving a pellet temperature o f 70 ° C. 4The probability that estimated differences are caused by r a n d o m effects. Significant interaction effects were only found for ileal organic m a t t e r ( P = 0.015 ) a n d ileal starch ( P = 0.019) digestibility. ab~°eMeans within a row not sharing a c o m m o n superscript are significantly different ( P < 0.05 ).
PELLETING AND SUPPLEMENTATION OF CEREAL DIET FOR BROILER CHICKENS
9
significant effects for diet (P< 0.05) and enzyme supplementation (P< 0.01 ) on the incidence of sticky droppings at Day 7. In general, pelleting reduced ileal DM content, while enzyme supplementation had no effect (Table 4). Pelleting tended to improve the ileal OM digestibility of the unsupplemented diet while enzyme supplementation tended also to increase the ileal OM and starch digestibility, particularly with the mash diet. Pelleting reduced excreta DM content in the supplemented diets while enzyme supplementation of the mash diet gave an increased excreta DM content. Whole-tract digestibility of OM and crude protein tended to be reduced by pelleting while that of crude fat tended to be improved. Enzyme supplementation generally improved whole-tract digestibility. Chickens fed on the unsupplemented mash diet had the lowest ileal digestibility values for OM, CP and crude fat and also had the lowest digesta DM content (Table 4). Enzyme supplementation of the mash diet improved the digestibility ofOM, CP, crude fat and starch at the ileum by 9, 9, 20 and 4%, respectively, but the improvement was statistically significant only for starch digestibility. It is notable that the ileal digestibility of OM, CP and starch was higher for the enzyme-supplementedmash diet than for the enzyme-supplemented pelleted diets and that chickens fed on pelleted diets had a higher digesta DM content than those fed on the equivalent mash diet. With enzyme supplementation, the whole-tract digestibility of OM and crude fat was significantly improved (P< 0.05 ) for chickens fed on the dry pelleted diet, the levels of improvement being 2 and 6%, respectively (Table 4). Similar effects were observed from enzyme supplementation of the steam pelleted diet with significant effects (P<0.05) for the improvements obtained in OM and CP whole-tract digestibility (2 and 3%, respectively). Pelleting the unsupplemented diet gave a lower whole-tract digestibility of OM and CP but a higher crude fat digestibility. The occurrence of sticky droppings on Day 7 was generally higher for chickens fed on the unsupplemented diets than for those fed on the equivalent enzyme-supplemented diets (Table 4). The enzyme-supplemented mash diet gave a significantly (P< 0.05 ) lower occurrence of sticky droppings than the unsupplemented pelleted diets. On average the steam pelleted diets also gave a significantly (P< 0.05 ) higher frequency of sticky droppings than the dry pelleted diets. Enzyme supplementation of the steam pelleted diet reduced the occurrence of sticky droppings only to a level similar to that of chickens fed on unsupplemented mash or dry pelleted diets. DISCUSSION
It is well known that the heating of a starch-rich food or feedstuff with a high moisture content will lead to a gelatinization of starch (Theander and Westerlund, 1984). Even the low moisture and temperature conditions pre-
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D. PETTERSSON ET AL.
vailing during the dry pelleting treatment in the present study increased the water solubility of starch and this probably contributed to the observed increase in buffer extract viscosity. The reduction in endogenous enzymatic activity on pelleting may have led to a delayed degradation of soluble arabinoxylans, and mixed-linked fl-glucans, and consequently to a slower and maybe lesser reduction in viscosity (Hesselman, 1983; Pettersson, 1988). The importance of an unimpaired endogenous enzymatic activity is displayed by the low viscosity of buffer extracts from the unsupplemented mash diet and the decrease in viscosity for buffer extracts from enzyme-supplemented pelleted diets. There were no significant differences in weight gain between chickens fed on the two types of pelleted diets, although those fed on the steam pelleted diets, on average, had a numerically higher weight gain but also a higher feed intake and hence a slightly inferior feed conversion efficiency. As the increased feed intake during the first 14 days was accompanied by an inferior feed conversion efficiency it might be assumed that the nutrient surplus ingested was fermented in the hind gut. The latter effect was probably also associated with the increased occurrence of sticky droppings for chickens fed on the steam pelleted diets. The effects of pelleting were essentially the same at Days 14 and 20, while enzyme supplementation had a much greater effect at Day 14. This suggests that changes in the gastro-intestinal environment, presumably the establishment of a microflora population, occur during this period. The ileal digestibility of CP tended to improve with enzyme supplementation, although not significantly as has been shown for rye/wheat-based broiler chicken mash diets (Pettersson and/~man, 1989). Pelleting causes a greater cell wall breakage (Saunders et al., 1969) and the disruption of the cellular structure is probably similar to the effect obtained by enzyme supplementation (Hesselman, 1983 ). Possible differences in the ileal digestibility of nutrients will consequently be small for pelleted diets given with or without enzyme supplementation, provided that there is no impeded absorption owing to viscous conditions. The enzyme-supplemented mash diet, which had the lowest buffer extract viscosity, had the highest ileal digestibility values for OM, CP and starch. However, there were no significant effects of enzyme supplementation or pelleting on CP digestibility and this could be due to an interference from protein-rich endogenous excretion products, which has been observed in ileal digestibility studies with pigs (Hagemeister, 1985) and poultry (Hurwitz et al., 1979 ). The small differences and high variation obtained between different treatments regarding ileal crude fat digestibility might, in a similar way, have been caused by an endogenous lipid excretion which is known to be of significant importance in the chick (Sklan et al., 1973). For starch, the major dietary component, general improvements in digestibility were obtained following enzyme supplementation, which also has
PELLETINGAND SUPPLEMENTATIONOF CEREALDIETFOR BROILERCHICKENS
1l
been shown in earlier studies with broiler chickens (Hesselman and/~man, 1986; Pettersson and/~man, 1989) and with pigs (Graham et al., 1989). Improved whole-tract digestibility of CP and crude fat as a result of pelleting has been reported in experiments with pigs (Vanschoubroek et al., 1971; Graham et al., 1989 ) and was thought to be caused mainly by a reduced wholetract bacterial output resulting from a more extensive digestion in the small intestine. However, in the present experiment, pelleting did not improve ileal digestibilityand improved only whole-tract crude fat digestibility, while wholetract OM and CP digestibility values were reduced. Enzyme supplementation, on the other hand, generally improved ileal starch and OM digestibility as well as whole-tract digestibility of OM, CP and crude fat. From the results obtained it can be concluded that during normal pelleting conditions the temperature and moisture levels are not sufficient to solubilise dietary fibres or to form resistant starch. However, even a moderate temperature treatment, such as the dry pelleting process employed in the present study, may solubilise starch and also diminish the important endogenous enzyme activity. This can lead to an increase in digesta viscosity which may impede both the nutrient absorption and the resorption of endogenous excretion products in the small intestine, thereby increasing the amount of substrate available for bacterial growth in the hind gut. A moderate growth of endogenous bacteria may prevent invasion and growth of a pathogenic microflora (Ducluzeau et al., 1981 ). An excessive microbial growth, however, may disturb the gut environment and cause problems such as sticky droppings or necrotic enteritis. The mechanisms involved in these disturbances are not fully understood but are undoubtedly mainly influenced by feeding. However, supplementation with an appropriate enzyme preparation can reduce digesta viscosity and increase nutrient absorption in the small intestine, thus improving production and health in chickens fed on mash or pelleted diets. ACKNOWLEDGEMENTS
The authors wish to thank the Swedish Farmers' Selling and Purchasing Association and Grindsted Products A/S for financial support and co-operation in this investigation. We also would like to thank the staff at the Division of Feed Chemistry for excellent technical assistance.
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