Influence of micronization temperature and pre-conditioning on performance and digestibility in piglets fed barley-based diets

Animal Feed Science and Technology 95 (2002) 73–82

Influence of micronization temperature and pre-conditioning on performance and digestibility in piglets fed barley-based diets L.N. Zarkadas, J. Wiseman* Division of Agriculture and Horticulture, School of Biological Sciences, Sutton Bonington Campus, University of Nottingham, Loughborough, Leics LE12 5RD, UK Received 21 February 2000; received in revised form 21 August 2001; accepted 28 August 2001

Abstract The effect of different micronization temperatures (different heating time as achieved through variable dwell times of 10, 13, 35 s) on the nutritional quality of barley (added at a rate of 700 g/kg diet), as measured by post-weaned piglet performance (using 32 pigs per trial over the live weight range 10–27 kg) and digestibility (determined at 15 kg live weight), was examined (trial 1). The effect of steeping the grain in water for different lengths of time prior to micronization at 2 temperatures was investigated (trial 2). Both trials used the same batch of barley. Different heat treatment considerably increased the proportion of gelatinized starch, as expressed by a more amorphous X-ray diffractogram, which was further increased following an increase of the initial moisture content to 160–170 g/kg. Although the inclusion of differently micronized barley compared with raw form (trial 1) resulted in significantly higher (P ¼ 0:019; 0.009 linear effect) feed intake (FI), there was no significant improvement in average daily live weight gain (DLWG). However increased heating time, which was associated with higher content of gelatinized starch, resulted in significant differences for dry matter (DM, P ¼ 0:026; 0.005 linear effect), and gross energy (GE, P ¼ 0:001; <0.001 linear; 0.010 quadratic effects) coefficient of total tract apparent digestibility (CTTAD). Piglet performance as well as digestibility values were not significantly affected by inclusion of steeped micronized barley (trial 2) regardless of length of steeping period. There was no effect of different steeping time, heating time or their interaction (P > 0:05) on digestibility. Increased proportion of gelatinized starch and viscosity values did not correspond with animal responses. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Micronization; Barely; Starch; Gelatinization; Piglet; Digestibility; Performance

* Corresponding author. Tel.: þ44-115-9516054; fax: þ44-115-9516060. E-mail address: [email protected] (J. Wiseman).

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 2 9 5 - 4

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1. Introduction Barley is one of the main sources of dietary energy in pig diets in those countries where it may be grown. Starch, the major energy-yielding component of the carbohydrate fraction, is found mostly in the endosperm and consists, in normal barley types, of 150–250 g/kg amylose and 750–850 g/kg amylopectin (Ullrich et al., 1986). It is well known that the physical and chemical properties of starch such as the amylose to amylopectin ratio, the crystalline structure of amylose and the starch granule size may influence its digestibility by endogenous a-amylase. Moreover, starch digestibility may be restricted by many factors (e.g. low a-amylase activity or presence of inhibitors) but, on the other hand, can be improved when a physical or heat treatment is applied which results in changes in its crystallinity and/or gelatinization which destroys the granular structure of starch (Holm et al., 1985). Moreover, changes in physical order within the granules occur as a result of a certain degree of degradation (Kulp and Lorenz, 1981). Retrogradation is largely due to crystallization of amylose, which is much more rapid than that of amylopectin. Although regarded as crystalline, retrograded gels are susceptible to amylolysis; however a fraction known as ‘‘resistant starch’’ is resistant to enzyme attack and behaves as dietary fibre (Berry, 1986). Processing of cereals prior to inclusion into diets for pigs is widely practised; however precise descriptions of methodologies together with associated changes in physicochemical properties of cereals following processing are rarely reported. The initial paper (Zarkadas and Wiseman, 2001) considered wheat. The current paper describes a programme with barley. Assessments of performance and digestibility were undertaken to investigate the effect of different micronization temperatures (trial 1) on nutritional value of barley when included in diets for weaned piglets (10–27 kg). Soaking the grains prior to any heat treatment (preconditioning) results in softening, thus penetration of heat subsequently becomes easier and this was examined in a second experiment with post-weaned piglets (trial 2).

2. Experimental 2.1. Diets Four diets were formulated in each trial containing barley (from the same batch) at the same rate of 700 g/kg. Whilst this rate is comparatively high, it was chosen deliberately such that any changes in nutritional values of barley would be apparent in subsequent evaluations. Diet specifications are given in Table 1. For trial 1, a control diet contained raw barley (RB), while the other treatments contained barley micronized at different temperatures by using a Micro Red 20 cereal micronizer with a burner temperature of ca. 200 8C (Dale Country Foods Ltd. Co. Durham, Yorkshire). Barley was micronized at low (dwell time ¼ 10 s, LC), standard (dwell time ¼ 13 s, SC) and high cook conditions (dwell time ¼ 35 s, HC). For trial 2, barley grain (from the same batch) was steeped for two different lengths of time, 2 h short steeped (SS) and twelve hours long steeped (LS). Every batch of the steeped grain was divided into two parts and micronized under two different

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Table 1 Diet specification (experimental diets) Ingredient

Inclusion: trials 1 and 2 (g/kg)

Micronized barley Full fat soya Fish meal Limestone Vitamin–mineral premix (minsal)a Lysine Salt Threonine

700.0 170.0 108.0 3.3 12.5 2.5 2.5 1.2

a Premix (per kg diet): Vitamin A 12,000 IU; Vitamin D3 2000 IU; Vitamin E 50 IU; Vitamin B1 1 mg; Vitamin B2 3 mg; Vitamin B6 1 mg; Vitamin B12 10 mg; Vitamin K 2 mg; Copper (Cupric Sulphate) 175 mg; Nicotinic Acid 12 mg; Pantothenic Acid 10 mg; Iron 200 mg; Cobalt 0.5 mg; Manganese 40 mg; Zinc 90 mg, Iodine 1 mg; Selenium 0.2 mg; Calcium 31.25 g; Salt 25 g; Sodium 10 g. Provided by Trouw Ltd. Wincham, Northwich, Cheshire, UK.

temperatures, low (dwell time ¼ 10 s, LC) and high (dwell time ¼ 35 s, HC) cook conditions. Final exit temperatures on leaving the micronizer ranged between 85 and 110 8C. Micronized flaked barley samples were ground through a 5 mm screen in the University of Nottingham animal feed mill where the diets were produced. Titanium dioxide (TiO2) at a rate of 1 g/kg was used in both experiments as an inert marker to determine the digestibility coefficients. 2.2. Experimental animals The diets were evaluated with 32 post-weaned piglets of ca. 6:84  0:15 kg (trial 1) and 8:94  0:22 kg (trial 2) initial live weight obtained from the University herd (commercial white genotype) over the live weight range 10–27 kg). General procedures have been described elsewhere (Zarkadas and Wiseman, 2001). During the digestibility study (piglets of around 15 kg were used) animals were offered diets containing TiO2, and representative faecal samples were collected (5 day collection period) at regular intervals and were frozen at 20 8C until analyzed. 2.3. Chemical analysis of diets and faecal samples Details of all analyses conducted are described in Zarkadas and Wiseman (2001). 2.4. Procedures Details of all procedures employed to determine average DLWG, average daily feed intake (FI), feed conversion ratio (FCR) and coefficient of total tract apparent digestibilities (CTTAD) are described in Zarkadas and Wiseman (2001). Determination of DLWG was achieved by linear regression of the weekly live weight on days, with the slope (which was used in subsequent analysis of variance) being DLWG. This is a more accurate procedure than reliance only on start and end weights and also allows a precise calculation of the

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number of days that an animal takes to grow over the specific weight range of the trials (10–27 kg). In addition, it allows a precise calculation of the feed intake over this live weight range. 2.5. Statistical analysis Data were subjected to analysis of variance using the Genstat V program (Lawes Agricultural Trust, 1984). trial 1 was analyzed with time of cooking (being 0 for RB, and 10, 13, 35 s corresponding to low, standard and high cook temperatures, respectively) as numerical values to establish linear and non-linear contrasts (i.e. through regression) rather than as four separate treatments; trial 2 was analyzed as a 2 (time of steepingÞ  2 (cooking temperature) factorial design.

3. Results 3.1. Trial 1 The chemical composition of raw and micronized barley is given in Table 2. DM of micronized barley samples was increased with increasing time spent under the micronizer, from 839 g/kg for RB to 872 g/kg for the HC barley as a result of the heat treatment. GE, CP, total fat, EE and ADF values remained almost unchanged for the barley samples. Starch content was lower for the standard cook (SC) and RB, being 592 and 616 g/kg, respectively, while it was increased to a marked extent for the HC barley and the LC form. Results from the X-ray diffractometer studies are shown in Fig. 1. Increasing the time spent under the micronizer resulted in a complete loss of crystallinity for the barley. From the ratio of the crystalline area to the total area of the diffractogram, estimates of the crystallinity of the samples (Fig. 1) revealed that an increase of the micronization temperature resulted in a small decrease in the proportion of gelatinized starch from 0.374 for the LC conditions to 0.348 for the SC barley while it remained almost the same for the HC barley (0.371), Table 3. However, viscosity of the barley samples was markedly increased (Table 3) with increasing processing time. The performance and digestibility results from trial 1 are given in Table 4. There were no significant differences of treatment observed for DLWG (P ¼ 0:385) or FCR (P ¼ 0:925). However FI did increase with cooking time (P ¼ 0:019; 0.009 for linear response; no Table 2 Chemical analysis of micronized barleya (g/kg DM): trial 1 Barley

DM

ASH

GE (MJ/kg DM)

Starch

CP

Total fat

EE

ADF

Raw LC SC HC

839 859 858 872

21 20 21 19

18.35 18.37 18.22 18.25

616 699 592 672

103 101 109 105

32 31 33 28

19 22 29 21

30 23 33 26

a Raw: unprocessed barley; LC: barley low cook; SC: barley standard cook; HC: barley high cook. See text for micronizing conditions.

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Fig. 1. Degree of crystallinity for micronized barley samples A ¼ high cook; B ¼ standard cook; C ¼ low cook and D ¼ raw (unprocessed barley).

significant quadratic response suggesting that the rate of increase in FI was only linear). Values for CTTAD indicated a highly significant effect of treatment for dry matter (P ¼ 0:026; 0.005 for linear; no significant quadratic response) and for gross energy (P ¼ 0:001; <0.001 linear; 0.010 quadratic) both of which increased with cooking time; there was no effect of treatment on CTTAD of crude protein. 3.2. Trial 2 Dry matter of micronized barley (Table 5) was increased with increasing time spent under the micronizer, from 868 and 859 g/kg for the long steeped low cook (LSLC) and the Table 3 Viscosity (cP) measurements (min–max) and proportion of gelatinized starch for micronized barleya Trial 1 Viscosity Raw LC SC High cook

5.8–10.1 b b b

Trial 2 Gelatinized starch

Viscosity

Gelatinized starch

0.000 0.374 0.348 0.371

b

0.590 0.596 0.407 0.588

LSLC LSHC SSLC SSHC

b b b

a Raw: unprocessed barley; LSLC: long steep low cook; LSHC: long steep high cook; SSLC: short steep low cook; SSHC: short steep high cook. See text for processing conditions. b No supernatant was collected because of extreme viscosity.

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Table 4 Performance and coefficient of total tract apparent digestibility for pigs (trial 1) Barleya

Performance b

Raw LC SC HC S.E.D. P

Digestibility coefficients b

b

DLWG

FI

FCR

508 536 515 538 20.5 0.385 0.209 (L) 0.707 (Q) 0.254 (Dev)

787 841 824 852 20.0 0.019 0.009 (L) 0.139 (Q) 0.224 (Dev)

1.568 1.569 1.604 1.587 0.0608 0.925 0.769 (L) 0.748 (Q) 0.608 (Dev)

Dry matter

Gross energy

Crude protein

0.729 0.733 0.749 0.775 0.0128 0.026 0.005 (L) 0.789 (Q) 0.363 (Dev)

0.712 0.748 0.777 0.783 0.0120 0.001 <0.001 (L) 0.010 (Q) 0.149 (Dev)

0.738 0.745 0.736 0.771 0.0251 0.511 0.189 (L) 0.617 (Q) 0.689 (Dev)

a

See text for descriptions of processing. DLWG: daily live weight gain (g per day); FI: feed intake (g DM per day); FCR: feed conversion ratio (g DM/g gain). b

short steeped low cook (SSLC) barley to 884 and 885 g/kg for the long steeped high cook (LSHC) and the short steeped high cook (SSHC) barley, respectively. The same trend was observed for GE which was higher for HC in both steeping treatments compared to LC. Total fat content was not affected to any marked extent, and EE values and ADF were very similar for all treatments. Starch and CP content appeared to be higher for the LSHC barley (644 and 130 g/kg, respectively) compared to the LSLC (593 and 123 g/kg) while the opposite was observed for the SS barley to the same extent. Micronized-steeped barley samples were highly viscous (Table 3); however viscosity was increased for the SSHC diet compared to SSLC, while remaining high but similar for the 2 h steeping. Results from the X-ray diffractometer studies are shown in Fig. 2. HC was associated with reduced crystallinity areas. Higher micronization temperature had no effect in the gelatinized starch (Table 3) for LS barley whereas the difference was marked SS; gelatinized starch was increased from 0.407 for SSLC to 0.588 for SSHC. Main effect means and interactions for DLWG, FI and FCR together with CTTAD means and interactions for DM, GE and CP of the pigs fed diets containing barley treated under different conditions are presented on Table 6. There were no significant differences

Table 5 Chemical analysis of steeped micronized barley (g/kg DM) (trial 2a) Barley

DM

ASH

GE (MJ/kg DM)

Starch

CP

Total fat

EE

ADF

LSLC LSHC SSLC SSHC

868 884 859 885

19 19 19 19

18.33 18.98 18.64 19.07

593 644 596 502

123 130 126 117

35 33 34 35

20 20 21 20

97 92 98 87

a LSLC: long steeped low cook; LSHC: long steeped high cook; SSLC: short steeped low cook, SSHC: short steeped high cook.

LSa

S Long (12 h)

SSa

LCa

HCa

S.E.D.c

Short (2 h)

S (P)

T (P)

ST S.E.D.

P

0.727 0.308 0.739 0.854 0.825 0.313

0.107 0.131 0.683 0.806 0.271 0.002

18.0 19.8 0.0480 0.0086 0.0094 0.0103

0.756 0.845 0.639 0.645 0.724 0.074

T

DLWGb (g per day) Feed intake (g DM per day) FCRb (g DM/g gain) Dry matter digestibility Gross energy digestibility Crude protein digestibility a

Low (LSLC)

High (LSHC)

Low (SSLC)

High (SSHC)

579 792 1.373 0.744 0.759 0.767

605 811 1.343 0.748 0.749 0.753

579 775 1.345 0.745 0.755 0.773

596 799 1.347 0.744 0.750 0.731

LS: long steeped; SS: short steeped; LC: low cook; HC: high cook. DLWG: daily live weight gain; FCR: feed conversion ratio. c Standard error of differences. b

592 802 1.358 0.746 0.754 0.760

587 787 1.346 0.745 0.753 0.752

579 783 1.359 0.744 0.757 0.770

600 806 1.345 0.746 0.750 0.742

12.8 14.0 0.0339 0.0061 0.0066 0.0073

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Table 6 Main effect means and interaction means with main effect and interactions showing the effect of steeping (S) and temperature (T) on performance and coefficient of total tract digestibility with pigs fed steeped-micronized barley diets

79

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Fig. 2. Degree of crystallinity for steeped-micronized barley samples A ¼ LSHC; B ¼ LSLC; C ¼ SSHC and D ¼ SSLC.

observed for any of the factors and interactions with the exception of CTTAD for CP which was significantly reduced with higher cooking (P ¼ 0:002); a trend for a steeping time  temperature interaction was observed (P ¼ 0:074).

4. Discussion For both variables examined (temperature and temperature/steeping time) the degree/ level of crystallinity was always higher for the lower micronization temperatures used. Increasing the dwell time resulted in almost complete gelatinization, where only amorphous scattering areas were detected. Thus, the amount of gelatinized starch available for amylolysis was higher for the HC conditions. Reports in the literature on the effect of micronization of hulled and hulless barley on performance of pigs are variable. Animals used (age, live weight), type of cereal and formulation of the diets may be responsible for these differences. The relatively few studies conducted to date have focused in the growing/finishing period. The lack of effect of treatment on performance in trial 1 is in contrast to data reported by Fernades et al. (1975) with growing pigs (33–80 kg), when ground barley gave better growth rate and FCR than the micronized barley, attributable to the relatively higher crude protein content of the ground form, although digestible energy content was also slightly higher; digestibility values were in good agreement with those obtained in trial 1. Thacker (1999) observed that barley which was preconditioned for 5 min prior to micronization at 110 8C for 50 s resulted in a reduction in growth rate, which was associated with reduced

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feed intake and increased diet viscosity. Although digestibilities of CP and GE of the micronized diets were increased (again, in agreement with current data) it was concluded that micronization appeared to be an ineffective means of improving the nutritional value of barley for growing-finishing pigs. However, later work by Thacker and Cambell (1999) failed to confirm these observations; FCR was significantly improved (P ¼ 0:005) for the micronized barley-based diets. A significantly better growth rate for micronized barley (dwell time ¼ 55 s) compared with ground form had been reported earlier (Lawrence, 1973b) and, although DM conversion efficiency followed the same trend, differences were not significant. Results from a second experiment (Lawrence, 1973b), where the micronized barley diet (micronization at 180 8C for 45 s) were again significantly superior to the ground form for both growth rate and DM conversion efficiency in the periods from 50 kg live weight to slaughter weight, are again in good agreement with the current results (trial 1). Medel et al. (2000) studied the effect of different processing techniques (micronization and extrusion) for cereals (barley and maize) when compared to raw forms in a 25 day performance study using piglets weaned at 23 days. Both micronization and extrusion improved DLWG and FCR; interaction between type of cereal and processing was significant for the first 2 weeks of the experiment and the improvement was greater for barley than for the maize-based diets, but no differences were detected between different processing method or its interaction with type of cereal. Steeping the grain prior to micronization in the current programme resulted in an increase in the moisture content of the barley up to 160 g/kg (2 h) and up to 170 g/kg (12 h). In contrast with observations for micronized steeped wheat (Zarkadas and Wiseman, 2001) neither steeping time nor heating time had a significant effect on piglet performance. Zheng et al. (1998) reported that increasing micronization temperature in barley at high moisture levels would result in severe damage to the proteins as they become more insoluble, which would explain the significant differences observed for CP digestibility during trial 2. Huang et al. (1998) reported that micronized hulless barley, preconditioned with water to raise its moisture content to 180–200 g/kg and cooked for 50 s with infra red radiant energy (90– 95 8C) was associated with higher faecal and ileal digestibilities for DE, GE and CP when compared to a raw sample using piglets of 9.3 kg, weaned at 21 days while starch was in both cases completely digested (0.999 versus 0.996). Thermal processing results in changes in starch granule crystallinity thus making it more susceptible to enzymatic attack; CTTAD from trial 1 are in good agreement with this although content of gelatinized starch for the micronized barley was increased to the same level with all heating conditions. RB digestibility coefficients for DM, GE and CP in the current research programme were lower than any of the micronized barley diets in trial 1. Highest values were observed for HC, in good agreement with the findings of Lawrence (1973a) where pigs of around 24 kg were used to determine CTTAD with differently processed barley. The overall results of the current experiments (trials 1 and 2) examining the effect of different micronization temperatures as well as the effect of steeping the grain prior to the heat treatment, showed that micronization sometimes increases the nutritive value of barley when fed to weaned piglets. Despite the increased gelatinized starch with increased heating time in micronized barley, which was associated with higher CTTAD in trial 1, micro-

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nization did not significantly improve piglet performance in both trials 1 and 2. Thus whilst in vitro analyses of physico-chemical properties of barley are associated with digestibility, correlations with performance are less evident. Vestegraad et al. (1990) as cited by Medel et al. (2000) reported inconsistent improvements due to different processing techniques in barley when fed to 21 day old pigs. Although in vitro starch availability was closely related to the percentage of gelatinized starch, no correlation with animal performance was observed and results from the current experiments are in a good agreement with this observation. Different steeping periods prior to micronization (trial 2) resulted in even higher levels of gelatinized starch. Thus it could be argued that steeping barley under the conditions examined, prior to micronization under the same heating conditions, might have a more positive effect compared with RB and this should be an interesting area for future research. Acknowledgements The financial assistance of Greek State Scholarship Foundation (I.K.Y) and co-operation of I’Anson Brothers (Dale county foods Ltd.) for micronizing the barley is gratefully acknowledged. Thanks also to Dr Wulansari at the Division of Food Science at the University of Nottingham, who carried out the X-ray analysis for the barley samples. References Berry, C.S., 1986. Resistant starch: Formation and measurements of starch that survives exhaustive digestion with amylolytic enzymes during the determination of dietary fibre. Journal of Cereal Science 4, 301–314. Fernades, T.H., Hutton, K., Smith, W.C., 1975. A note on the use of micronized barley for growing pigs. Anim. Prod. 20, 307–310. Holm, J., Bjorck, I., Asp, N.-G., Sjoberg, L.-B., Lundquist, I., 1985. Starch availability in vitro and in vivo after flaking steam-cooking and popping of wheat. Journal of Cereal Science, 3, 193–206. Huang, S.X., Sauer, W.C., Pickard, M., Li, S., Hardin, R.T., 1998. Effect of micronization on energy, starch and amino acid digestibility in hulless barley for young pigs. Can. J. Anim. Sci. 78, 81–87. Kulp, K., Lorenz, K., 1981. Heat moisture treatment of starches. I. Physicochemical properties. Cereal Chemistry 58, 46–48. Lawes Agricultural Trust, 1984. Genstat V: Release 3. Statistics Department, Rothamstead Experimental Station. Lawrence, T.L.J., 1973a. An evaluation of the micronization process for preparing cereals for the growing pig. 1. Effects on digestibility and nitrogen retention. Anim. Prod. 16, 99–107. Lawrence, T.L.J., 1973b. An evaluation of the micronization process for preparing cereals for the growing pig. 2. Effects on growth rate, food conversion efficiency and carcass characteristics. Anim. Prod. 16, 109–116. Medel, P., Garcı´a, M., La´ zaro, R., de Blas, C., Mateos, G.G., 2000. Particle size and heat treatment of barley in diets for early-weaned piglets. Anim. Feed Sci. Technol. 84, 13–21. Thacker, P.A., 1999. Effect of micronization on the performance of growing/finishing pigs fed diets based on hulled and hulless barley. Anim. Feed Sci. Technol. 79, 29–41. Thacker, P.A., Cambell, G.L., 1999. Performance of growing-finishing pigs fed untreated or micronized hulless barley-based diets with or without b-glucanase. J. Anim. Feed Sci. 8, 157–170. Ullrich, S.E., Clancy, J.A., Eslick, R.F., Lance, R.C.M., 1986. Journal of Cereal Science, 4, 279-285. Zarkadas, L.N., Wiseman, J., 2001. Influence of processing variables during micronization on performance and digestibility in weaned piglets fed wheat-based diets. Anim. Feed Sci. Technol., in press. Zheng, G.H., fasina, O., Sosulski, F.W., Tyler, R.T., 1998. Nitrogen solubility of cereals and legumes subjected to micronization. J. Agric. Food Chem. 46, 4150–4157.