Processing of barley and enzyme supplementation in diets for young pigs

Animal Feed Science and Technology 95 (2002) 113–122

Processing of barley and enzyme supplementation in diets for young pigs P. Medela,1, F. Baucellsb, M.I. Graciaa, C. de Blasa, G.G. Mateosa,* a

Departamento de Produccio´n Animal, ETSI Agro´nomos, Universidad Polite´cnica de Madrid, 28040 Madrid, Spain b Pinsos Baucells, 08551 Tona, Barcelona, Spain

Received 5 December 2000; received in revised form 22 October 2001; accepted 3 November 2001

Abstract Two trials were conducted to study the influence of heat processing (HP) of barley and enzyme supplementation (ES) to diets for young pigs. In trial one, six treatments arranged factorially with two types of barley processing (raw or cooked-flaked) and three levels of ES (0, 600 and 1200 mg/kg) were used. Each treatment was replicated four times and five piglets caged together formed the experimental unit. The enzyme complex contained 3100 U a-amylase/g, 400 U xylanase/g and 225 U b-glucanase/g. Growth rate, feed intake and feed conversion were measured at 14 and 28 days. Coefficient of total tract apparent digestibility (CTTAD) of organic matter (OM), energy, crude protein (CP), ether extract (EE), crude fibre and starch were assessed at 14 days. In trial two, 16 piglets were used to measure ileal viscosity (VISC), apparent ileal digestibility of starch, pH at the stomach, caecum and colon and volatile fatty acid (VFA) concentration in the caecum. Only diets containing 0 or 600 mg ES/kg were used. From 0 to 14 days after weaning, piglets fed HP barley grew faster than piglets fed raw barley (0.213 kg per day versus 0.184 kg per day, P ¼ 0:050) but the effect disappeared thereafter. Barley processing increased coefficient of apparent ileal digestibility (CIAD) of starch (0.993 versus 0.984 for HP and raw barley diets; P ¼ 0:017) but VISC, digestive pH or VFA concentration of the caecum were not affected. None of the total tract digestibility coefficients studied was affected by dietary treatment. It is concluded that HP of barley improved piglet growth during the first 14 day post-weaning and increased apparent ileal digestibility of starch, but that ES had no effect on performance of piglets. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Barley; Enzyme supplementation; Heat processing; Young pigs

Abbreviations: ES: enzyme supplementation; HP: heat processing; VFA: volatile fatty acids Corresponding author. Tel.: þ34-915497978; fax: þ34-915499763. E-mail address: [email protected] (G.G. Mateos). 1 Present address: Imasde Agropecuaria, S.L. C/ Isabel Colbrand, 10, Local 90b. 28050 Madrid. *

0377-8401/02/$ – see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 7 - 8 4 0 1 ( 0 1 ) 0 0 3 4 7 - 9

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1. Introduction The digestive system of piglets at weaning is immature, with low levels of production of enzymes such as amylase, saccharase or lipase (Owsley et al., 1986; Aumaitre et al., 1995; Jensen et al., 1997). The lack of enzymatic capacity might be compensated, at least partially, by supplementation of the diet with exogenous enzymes. Inborr et al. (1993) and Li et al. (1996a) have demonstrated that enzyme supplementation (ES) to piglet diets improves the digestibility of some dietary components, such as fibre and starch. On the other hand, heat processing (HP) of cereals gelatinises starch to some extent (Van der Poel et al., 1989; Medel et al., 2000) facilitating its endogenous enzymatic degradation (Osman et al., 1990). In addition, HP solubilizes fibre components (Fadel et al., 1988) an effect that might enhance the activity of exogenous enzymes in pigs as has been demonstrated in broilers (Vukic-Vranjes and Wenk, 1995). Since cereals (mainly maize and wheat but also barley) are the major source of energy in piglet feeds (Partridge and Gill, 1993) both HP and ES might improve their nutritive value in this type of diets. Improvements in piglet performance and nutrient digestibility of barley diets with HP have been reported by Aumaitre (1976), Huang et al. (1998) and Medel et al. (1999, 2000) and with ES by Inborr et al. (1993) and Li et al. (1996a,b). However, no studies have been conducted to test the additiveness of the effects of HP and ES in barley-based diets for piglets. The aim of the current study was to evaluate the influence of HP of barley, ES of diet and its interaction on performance, gut pH, caecum volatile fatty acid (VFA) concentration and digestibility of diets for young pigs.

2. Materials and methods 2.1. Diets and enzyme complex A barley batch was split into two fractions. One of them was ground through a hammer mill (2.5 mm screen) and the other was steam-cooked (KAHL, Hamburg, Germany) for 50 min (99  2 8C), flaked through riffled rolls and then ground as the first batch. A basal diet was formulated to meet or exceed the nutrient requirements recommended by National Research Council (1998) for piglets and to contain 473 g of barley/kg. Its ingredient composition and the estimated nutrient value, according to FEDNA (1999) is shown in Table 1. Six different pelleted (2.5 mm) diets were prepared by combining two barley processing methods (raw or cooked-flaked) and three enzyme doses (0, 600 and 1200 mg/ kg). The enzyme complex contained 3100 U of a-amylase/g (E.C. 3.2.1.1), 275 U/g of bglucanase (E.C. 3.2.1.6) and 400 U/g of xylanase (E.C. 3.2.1.8). Chemical analyses of the barley used are shown in Table 2 and the composition of the experimental diets is shown in Table 3. Chromium oxide was included at 3 g/kg as an indigestible marker for determination of component digestibility. 2.2. Trial one One hundred and twenty male cross-bred (landrace  large white) piglets weaned at 19 days and weighing 5:5  0:9 kg were used in a 28-day trial. Piglets were blocked by litter

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Table 1 Composition and estimated nutrient value of experimental diet (as fed basis)a Ingredient(g/kg) Barley Maize Soya oil Full fat soyabean (extruded) Fish meal LT Blood meal Spray dried animal plasma Spray dried skim milk Dried whey Wheat bran Calcium carbonate Dicalcium phosphate Sodium chloride D, L-Methionine, 99% L-Lysine hydrochloride, 78% Citric acid Chromium oxide Vitamin and mineral premixb

500 47.3 6.8 109 50 25 25 40 160 6 8.3 4.4 0.5 1.2 0.5 10 1 5

a

Estimated nutrient value according to FEDNA (1999): net energy 10.0 MJ/kg; CP: 212.5 g/kg; lysine: 14.2 g/kg; calcium: 7.9 g/kg; available phosphorous: 4.1 g/kg. b Mineral and vitamin composition for 1 kg of complete diet: Vitamin A: 15,000 IU; Vitamin D3: 1900 IU; Vitamin E: 30 IU; Vitamin K: 1.6 mg; thiamine: 1.1 mg; riboflavin: 5 mg; pantothenic acid: 14 mg; niacin: 25 mg; pyridoxin: 2.5 mg; biotin: 150 mg; folic acid: 200 mg; cyanocobalamin: 25 mg; choline: 250 mg; Fe: 75 mg; Cu: 160 mg; Zn: 110 mg; Mn: 50 mg; Co: 100 mg; Se: 300 mg; I: 1 mg; carbadox: 50 ppm.

in a randomised incomplete block design with four animals per block and six treatments. Animals were allotted in groups of five per cage, with four pens per treatment and similar average initial body weight per treatment. The animals were housed in flat-deck pens (1 m  1 m) provided with individual feeders (five spaces) and nipple drinkers, and had ad libitum access to feed throughout the trial. Average daily feed intake, average daily gain Table 2 Determined chemical composition of raw and processeda barley (g/kg, as fed basis) Barley

DM Ash CP CF EE Starch Starch gelatinizationb a b

Cooked (50 min, 99 8C) and flaked. As a proportion of total starch.

Raw

Processed

889 22 105 62 18 520 0.134

891 25 107 59 17 500 0.396

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Table 3 Determined chemical composition of the experimental diets (g/kg, as fed basis) Barley Processeda

Raw ES (mg/kg)

0

600

1200

0

600

1200

DM Ash CP Crude fibre EE

895 80 188 31 64

898 73 189 29 66

899 76 194 25 65

908 73 195 35 73

906 74 201 29 70

903 73 195 29 68

a

Cooked (50 min, 99 8C) and flaked.

and feed conversion ratio were recorded weekly. Diarrhoea incidence and mortality were recorded. At 14 days of the experiment, a pooled sample of faeces from at least four pigs per cage, was taken by rectal massage and frozen at 20 8C until chemical analyses to calculate coefficient of total tract apparent digestibility (CTTAD) of the diets. 2.3. Trial two Sixteen landrace  large white male piglets weaned at 20 days and weighing 5:5  0:9 kg were used in a 14-day trial. The diets used were the same than in trial one but diets containing 1200 mg ES/kg were omitted to reduce the number of pigs to be slaughtered. Piglets were placed in individual digestibility cages (1 m  1 m) at random and had ad libitum access to feed and water. After a 13-day adaptation period, piglets were fasted for 24 h to achieve feed intakes as homogeneous as possible, fed ad libitum for 3 h and then slaughtered. The portion of the digestive system between the cardia and the rectum was removed and the contents of the stomach, caecum and colon were placed in clean plastic test tubes to measure the pH with a temperature-corrected pH-meter (Crison Instruments S.A., Barcelona, Spain). Subsequently, a representative sample of the caecal content was centrifuged at 12; 000  g at 0 8C for 20 min, and the supernatant fluid was used to determine the concentration of VFA. A solution of 5% orthophosphoric acid (v/v) plus 1% mercury chloride (w/v) was added (0.1 ml/ml) to the samples to acidify the medium and stop undesirable fermentations. Samples were frozen at 20 8C until VFA analyses. Ileal viscosity (VISC) was measured in samples taken from the last 30 cm of the ileum. After homogenisation, two Eppendorf tubes containing 1.6 g of sample were centrifuged at 17,500  g at 0 8C for 3 min and the supernatant was used to determine viscosity with a digital rheometer viscometer (Brookfield Engineering Laboratories, Stoughton, MA, USA). The remaining of the ileum contents were immediately frozen for further chemical analyses. 2.4. Chemical analyses Feeds and faeces were heat dried (60 8C, 48 h) and ileal contents were freeze-dried, ground (1 mm screen) and then analysed following the methods of the Association of

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Official Analytical Chemist (2000) to determine dry matter (DM) by the oven-drying method (934.01), organic matter (OM) by muffle furnace incineration (967.05), starch (996.11), crude protein (CP) by the Kjeldahl method (976.05), ether extract (EE) (920.39) and crude fibre by the Weende method. Gross energy was determined by adiabatic bomb calorimetry (IKA-4000, Schott Ibe´ rica, Spain). Chromium content of feed and faeces was analysed by atomic absorption (Smith-Hieftje 22, Thermo Jarrell Ash, MA, USA) using predosed samples of faeces to prepare common-matrix standards. Previously, the samples were ashed (550 8C) and then digested by boiling with a solution of 1.5 M HNO3 and KCl (3.81 g/l). Gelatinised starch, as proportion of total starch, was determined by enzymatic hydrolysis as described by Medel et al. (1999). Caecal VFA concentration was determined in a Hewlett–Packard (5710 A) gas chromatograph, with a flame ionisation detector, a Hewlett–Packard (3390 A) recorder integrator and a steel column. Nitrogen with a flow rate of 30 ml/min was used as carrier gas. The flow of hydrogen and air to the detector was 30 and 200 ml/min, respectively, and the temperature of both injector and detector was 250 8C. The oven temperature was increased during the analysis from 110 to 160 8C at a rate of 8 8C/min. Enzyme analyses were performed prior to the preparation of the diets by the reducing sugar method described by Miller (1959) at 30 8C and pH 4.0. 2.5. Statistical analysis Data were analysed as a completely randomised block design with litter as block effect and HP of barley, ES of the diet and their interactions as main effects by using the GLM Table 4 Effect of HP of barley and ES of the diet on performance of piglets Period (days)

Barley

ES (mg/kg) a

S.E.M. (n ¼ 4)

HP

ES

HP  ES

0.015 0.016 0.07

0.050 NSf NS

NS NS NS

NS NS NS

0.579 0.754 1.30

0.025 0.029 0.04

NS NS NS

NS NS NS

NS NS NS

0.391 0.489 1.25

0.012 0.16 0.03

NS NS NS

NS NS NS

NS NS NS

Raw

Processed

–

600

1200

0–14 ADGb ADFIc FCRd,e

0.185 0.218 1.20

0.214 0.231 1.09

0.193 0.227 1.17

0.202 0.223 1.11

0.203 0.224 1.14

14–28 ADG ADFI FCR

0.573 0.743 1.30

0.570 0.751 1.32

0.556 0.742 1.33

0.578 0.746 1.29

0–28 ADG ADFI FCR

0.379 0.481 1.27

0.392 0.491 1.26

0.374 0.484 1.29

0.391 0.0484 1.23

a

Cooked (50 min, 99 8C) and flaked. Average daily gain (kg). c Average daily feed intake (kg). d Feed conversion ratio (kg feed intake/kg weight gain). e A trend was observed for FCR by HP of barley (P ¼ 0:096). f Non-significant (P > 0:050). b

Significance

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procedure of Statistical Analysis Systems Institute Inc. (1990). ES sums of squares were partitioned into linear and quadratic effects. Initial body weight was used as a linear covariate for all performance traits. Data in tables are presented as least square means.

3. Results The influence of dietary treatments on performance is shown in Table 4. During the first 14 days of the trial, piglets fed HP barley diets grew faster (0.214 kg per day versus 0.184 kg per day; P ¼ 0:050) and tended to be more efficient (1.08 kg food/kg gain versus 1.19 kg food/kg gain; P ¼ 0:096) than piglets fed raw barley diets. However, from 14 to 28 days and for the overall experimental period, the differences were not significant. ES did not affect performance in any period and no interactions between ES and HP were detected for any of the performance traits studied. The effects of dietary treatments on CTTAD are Table 5 Effect of HP of barley and ES of the diet on CTTAD of DM, OM, energy, CP, EE, crude fiber (CF) and starcha Barley

Nutrient DM OM E CP EE CF Starch

ES (mg/kg)

S.E.M. (n ¼ 4)

Raw

Processedb

–

600

1200

0.873 0.888 0.874 0.870 0.762 0.371 0.997

0.877 0.891 0.878 0.874 0.786 0.396 0.998

0.874 0.890 0.876 0.870 0.776 0.372 0.997

0.876 0.890 0.877 0.872 0.779 0.392 0.999

0.876 0.890 0.874 0.874 0.768 0.386 0.998

0.012 0.011 0.013 0.014 0.026 0.070 0.002

a None of the effects (HP, enzyme supplementation or their interaction) was found to be significant (P > 0:050). b Cooked (50 min, 99 8C) and flaked.

Table 6 Effect of HP of barley and ES of the diet on CIAD of starch (IADS), VISC and pH of gut contents Barley

ES (mg/kg)

S.E.M. (n ¼ 4)

Raw

Processeda

–

600

IADS VISC(cP)

0.984 1.34

0.993 1.31

0.986 1.33

0.991 1.31

pH Stomach Caecum Colon

3.52 5.92 6.24

3.61 5.94 6.25

3.37 5.91 6.26

3.51 5.94 6.23

b

a

Cooked (50 min, 99 8C) and flaked. A trend was observed for ES of barley (P ¼ 0:083). c Non-significant (P > 0:050). b

Significance HP

ES

HP  ES

0.003 0.08

0.017 NSc

NS NS

NS NS

0.22 0.16 0.24

NS NS NS

NS NS NS

NS NS NS

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Table 7 Effect of dietary treatment on VFAs (mmol/g of caecal content) at the caecuma Voltatile fatty acid Acetic Propionic Butyric a b

Barley

ES (mg/kg)

Raw

Processedb

–

600

14.11 9.50 2.96

16.29 8.63 2.92

15.29 9.15 3.03

15.11 8.79 2.86

S.E.M. (n ¼ 4) 3.59 2.20 0.97

None of the effects (heat processing, ES or their interaction) was found to be significant (P > 0:050). Cooked (50 min, 99 8C) and flaked.

shown in Table 5, while the effects on the pH of the gut contents, VISC and coefficient of ileal apparent digestibility (CIAD) of starch are shown in Table 6. The effects of treatments on caecal VFA concentration are shown in Table 7. HP of barley improved CIAD of starch (P ¼ 0:017) but the differences were quantitatively small (0.993 versus 0.984). No effects of HP, ES or its interaction were found on CTTAD, VISC, pH of the stomach, caecum or colon contents, or VFA concentrations.

4. Discussion HP of barley improved piglet performance only from 0 to 14 days after weaning but not thereafter. Most of the data reported in the literature indicate that HP improves the nutritional value of barley, but the magnitude of the gains depends on the age of the piglets and the length of the period after weaning considered. In general, the younger the animal, the greater are the effects. Medel et al. (1999, 2000) reported improvements between 8 and 15% in growth rate for the first 14 days after weaning when barley was micronized, extruded or expanded, which is consistent with the 16% improvement found in the current experiment. The improvement in performance from 14 to 28 days after weaning due to HP of barley was significant in the study of Medel et al. (1999) but not in the report of Medel et al. (2000) or in the present study. The interaction of HP and age on piglet performance might be related to the functionality of the gastrointestinal tract, which is not fully developed until at least 2 weeks after weaning (Jensen et al., 1997). It is believed that the improvement in the nutritive value of cereals with HP might be related to the degree of gelatinization of the starch (Lawrence, 1978), but the relationship found by different authors between performance and degree of starch gelatinization is generally poor (Vestergaard et al., 1990; Hongtrakul et al., 1998; Medel et al., 1999, 2000). Vestergaard et al. (1990) compared the influence of roller heating, extruding, steaming, steaming under pressure or micronizing of barley on piglet performance. Although, extruded barley showed the highest degree of starch gelatinization it was found that only roller heating had beneficial effects on piglet growth. A high amount of gelatinization can be detrimental because excessive heating could increase the quantity of retrograded starch and reduce amino acid availability (Siljestro¨ m, 1989), which are not fully available for the animal (Muir and O’Dea, 1992).

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Medel et al. (1999, 2000) have observed significant improvements in CTTAD of OM due to HP of barley, but no benefits were observed in the present study. However, HP improved CIAD of starch, although the difference was quantitatively small (0.993 versus 0.984). Huang et al. (1998) working with hulless barley reported a 22% improvement in CIAD of starch with HP, although the beneficial effect was probably magnified because the CIAD of starch in the basal diet was unusually low and close to 0.790. HP did not affect digestive pH or VISC, which is consistent with previous results (Medel et al., 1999) nor VFA concentration in the caecum, which agrees with the lack of effect observed on CTTAD of fibre with HP barley. In the present study, ES tended to improve ileal digestibility of starch (0.991 versus 0.985, P ¼ 0:083) but had no effect on performance of piglets, CTTAD of components or caecal VFA concentration. These results partially agree with data from Inborr et al. (1993) and Jensen et al. (1998), who found that ES improved CIAD of starch, although the magnitude of the benefit was small. The influence of ES to barley-based diets on performance of piglets is inconclusive. In some studies (Bedford et al., 1992), ES improved piglet performance but not in others (Inborr et al., 1993; Jensen et al., 1998). It has been observed that the activity of b-glucanases and other exogenous enzymes is lower in pigs than in poultry. Dierick and Decuypere (1994) suggested that this observation is due to a greater extent of enzyme denaturation in the pig as a consequence of the higher production of hydrochloric acid in the stomach and the greater concentration of lactobacilli population with b-glucanase activity at the small intestine. The pH of the stomach contents observed in the current study was 3.5, which might have helped to reduce b-glucanase activity. Baas and Thacker (1996), conducted a series of in vitro studies and observed that when the pH was reduced from 5.5 to 3.5, the activity of the enzymes decreased between 26 and 33% depending on the nature of the enzyme and the length of exposure to the acid. The high amount of milk products (20 g/kg) used in the current diets might have enhanced the growth of the lactobacilli population with high b-glucanase activity, even in the enzyme unsupplemented diets. In agreement with Bedford et al. (1992), ES did not modify pH or VISC. The importance of VISC on digestibility is lower in pigs than in poultry (Thacker and Baas, 1995) probably because viscosity in pigs is about 100-fold lower than in broiler chicks. This observation is related to the greater aqueous condition of the digesta of pigs (100 g DM/kg versus 200 g DM/kg) which might dilute the viscosity of the lumen contents reducing its negative effects. It is concluded that HP of barley increased CIAD of starch and improved piglet growth for the first 14 days after weaning. On the other hand, ES tended to improve CIAD of starch, but had no effect on piglet performance. No interactions between ES and barley HP were detected for any of the traits studied.

Acknowledgements This research was supported by EUREKA Project EU-1389. Thanks to ESASA for supplying the ingredients used and to I. Castellanos, A. Sanz, C. Pin˜ eiro and Y. Alegre for their collaboration in the experiment and in the preparation of the manuscript.

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