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In vitro digestibility kinetics of diets containing different cereal sources
Livestock Science 134 (2010) 47–49
Contents lists available at ScienceDirect
Livestock Science j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / l i v s c i
In vitro digestibility kinetics of diets containing different cereal sources☆ A.M. Pérez-Vendrell, D. Torrallardona ⁎ IRTA-Centre Mas de Bover, Ctra. Reus-El Morell, km. 3.8, E-43120 Constantí, Spain
a r t i c l e
i n f o
a b s t r a c t
Keywords: In vitro digestibility Cereals Dry matter Organic matter
Two experiments were conducted to study the effect of cereal source on the in vitro digestibility of pig feeds. Dry matter and organic matter digestibilities were evaluated using the multi-enzymatic method described by Boisen and Fernández (1997). The rate at which the different diets were digested, was estimated at 3 different time points: (1) after incubation with pepsin for 75 min; (2) after incubation with pepsin for 75 min and pancreatin for 3.5 h and; (3) after incubation with pepsin for 75 min, pancreatin for 3.5 h and carbohydrases for 18 h. In the first experiment, digestibility was evaluated in six diets containing 60% of rice (R), rice supplemented with wheat bran (RW), barley (B), maize (M), oats (O), or naked oats (NO). Diets containing NO and O had the highest digestibility after pepsin incubation, M, R and RW had the lowest and that of B was intermediate. After incubation with pepsin and pancreatin, digestibility was highest for R, RW and NO diets and lowest for M and O diets, B being intermediate. With the complete in vitro digestion procedure (pepsin, pancreatin and carbohydrases), R presented the highest digestibility followed by NO, M, B and O. In the second experiment, the effect of cereal extrusion was also evaluated in diets containing 60% of R, NO or B, either in raw or in extruded form (total of six diets). Following pepsin incubation, R presented a lower digestibility than B and NO; with pepsin and pancreatin incubations, NO presented the highest digestibility followed by R and B; and after incubation with pepsin, pancreatin and carbohydrases, R presented the highest digestibility followed by NO and B. It is concluded that cereals present differences in their in vitro digestion kinetics. This may be a useful tool to estimate possible differences in digestibility kinetics between cereals in the proximal gastrointestinal tract of the pig. © 2010 Elsevier B.V. All rights reserved.
1. Introduction
estimate in vivo nutrient digestibility. The in vitro techniques intend to simulate the digestion process, using either an inoculum prepared from pig digestive contents (Löwgren et al., 1989) or enzymatic preparations (Boisen and Fernández, 1997). The three-step multi-enzyme system developed by Boisen and Fernández (1997) simulates the digestion in the stomach, the small intestine and the large intestine, and appears to be an effective system to predict organic matter digestibility in pigs (Pujol and Torrallardona, 2007), although it doesn't take into account some aspects of in vivo digestion such as endogenous secretions, absorption and transit (Noblet and Jaguelin-Peyraud, 2007; Wilfart et al., 2008). Usually, with this in vitro method an end-point digestibility value is obtained after the complete enzymatic hydrolysis of the feeds. The objective of the present study was to evaluate
To estimate the nutritive value of a feed for pigs its chemical composition and the corresponding digestibility coefficients (at the ileal or the faecal level) are used. These digestibility coefficients have been traditionally estimated with in vivo trials involving surgically modified animals. In recent years, several in vitro methods have been developed to
☆ This paper is part of the special issue entitled “11th International Symposium on Digestive Physiology of Pigs”. ⁎ Corresponding author. IRTA-Centre Mas de Bover, Ctra. Reus-El Morell, km. 3.8, E-43120 Constantí, Spain. Tel.: + 34 977 32 84 24; fax: + 34 977 34 40 55. E-mail address: [email protected] (D. Torrallardona). 1871-1413/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.livsci.2010.06.093
48
A.M. Pérez-Vendrell, D. Torrallardona / Livestock Science 134 (2010) 47–49
the potential of the three-step multi-enzyme method of Boisen and Fernández (1997) to study the dry matter (DM) and organic matter (OM) hydrolysis kinetics of different cereal-based feeds and to estimate their digestibility in the proximal sections of the pig's gastrointestinal tract. 2. Materials and methods 2.1. Feeds Two trials were conducted to analyse the in vitro digestibility of dry matter and organic matter at different time points. In the first experiment, six complete pig diets differing in their cereal composition were tested. They contained 60% of either: rice (R), rice supplemented with wheat bran (RW), barley (B), maize (M), oats (O), or naked oats (NO). In the second experiment, the effect of cereal extrusion was also evaluated in complete diets containing 60% of R, NO or B, either in raw or in extruded form (total of six diets). For both trials the remaining 40% of the diet was composed by 14% sweet milk whey, 11% of a soybean meal product containing 56% crude protein (HP-300®, Hamlet Protein, Horsens, Denmark), 10% poatato protein (Protastar®, Avebe group Veendam, The Netherlands), 2% lard and amino acids, vitamins and minerals to meet or exceed the animals' requirements (NRC, 1998). The analysed nutrient composition of these diets is presented in Table 1. 2.2. In vitro technique The three-step multi-enzyme system developed by Boisen and Fernández (1997) was carried out in three successive steps. The first step simulating the digestion in the stomach was an enzymatic hydrolysis with a pepsin solution at pH 2.0 and 40 °C for 75 min, in the presence of chloramphenicol. This step was followed by hydrolysis with the multi-enzyme Pancreatin (mixture of protease, amylase and lipase, from porcine pancreas, Sigma ref. P1750) at pH 6.8 and 40 °C for 3.5 h. This step could be associated with the digestion obtained in the small intestine. The third digestion step (digestion in the large intestine) was performed using Viscozyme® enzyme solution (mixture of microbial carbohydrases, including b-glucanase, xylanase, arabinase, cellulase Table 1 Analysed composition of the experimental diets (%, as fed basis).
and pectinase, from Novo-Nordisk, Denmark) at pH 4.8 and 40 °C for 18 h. The undigested residues were quantitatively recovered in a fritted glass filter crucible (Foss, porosity 2), containing around 400 mg of exactly-weighed Celite ® (diatomaceous earth). The residues were rinsed with ethanol, acetone and pure water. The crucibles were oven-dried at 103 °C for 4 h, cooled and weighed, and subsequently placed in a furnace at 525 °C for 8 h, and again cooled and weighed. A blank was included in each procedure batch and each measurement was performed in duplicate. DM and OM were determined according to AOAC (1990) methods. The rate, at which the different diets were digested, was estimated at 3 different time points: after incubation with pepsin for 75 min, after incubation with pepsin for 75 min and pancreatin for 3.5 h and after incubation with pepsin for 75 min, pancreatin for 3.5 h and carbohydrases for 18 h. 3. Results and discussion In the first experiment, diets containing NO and O had the highest DM and OM digestibilites at 75 min of incubation, M, R and RW had the lowest and that of B was intermediate (Table 2). This may be explained by differences in composition of the non starch polysaccharide fraction of the cereals that may differently affect the access of pepsine to the protein fraction. The small intestine is the main site of starch digestion, and for cereals, starch is almost completely digested at the end of the small intestine (Wilfart et al., 2008). After the 3 h 30 min of incubation with pancreatin, the in vitro digestibility of DM and OM was highest for the starch rich cereals R, RW and NO diets and lowest for O and M diets, being intermediate for B. The third digestion step (viscozyme incubation) promoted a moderate increase in the digestion of DM and OM, ranging from approximately a 3% increase in O, NO, M, RW diets to a 7 and 10% increase in B and R diet, respectively. The R diets presented the highest DM and OM digestibilities followed by NO, M, B and O. In the second experiment, the effect of cereal extrusion was also evaluated in diets containing 60% of R, NO or B,
Table 2 In vitro digestibility of dry matter (DM) and organic matter (OM) of different cereal-based feeds after incubation with pepsin for 75 min, after incubation with pepsin for 75 min and pancreatin for 3.5 h and after incubation with pepsin for 75 min, pancreatin for 3.5 h and carbohydrases for 18 h. Digestibility (%)
Experimental diets
Dry matter
Organic matter
Pepsin
Crude protein
First experiment (feeds with 60% different cereals) Rice 90.66 85.69 Barley 91.64 85.83 Rice + wheat bran 90.20 85.72 Maize 90.21 85.31 Oats 91.42 85.94 Naked oats 91.53 86.04
20.99 23.14 21.11 20.40 21.54 23.19
Second experiment (feeds with 60% different cereals raw or Raw rice 90.49 86.21 Extruded rice 91.43 86.53 Raw naked oats 91.42 85.88 Extruded naked oats 91.71 85.92 Raw barley 91.48 85.95 Extruded barley 91.70 86.16
extruded) 21.26 22.09 24.24 23.72 22.82 24.33
DM Rice Barley Rice + wheat bran Maize Oats Naked oats Root MSE Statistics (Pr N F) Cereal a–f
OM
39.0 c 35.1 c 41.6 bc 37.6 b 39.1 c 34.9 c
Pepsin + pancreatin
Pepsin + pancreatin + carbohydrase
DM
OM
DM
OM
86.8 ab 81.6 bc 91.6 a
87.4 a 80.4 b 88.3 a
96.9 a 88.8 d 95.7 ab
96.8 a 87.5 e 95.1 b
77.1 c 75.7 c 88.5 a 0.71
92.6 c 83.1 e 94.2 b 0.64
91.6 d 81.2 f 92.9 c 0.33
b 0.001 b 0.001
b0.001
39.2 c 35.8 bc 78.9 c 44.0 ab 39.7 a 79.3 c 45.1 a 41.2 a 91.0 a 1.05 0.81 2.80 0.004
0.001
0.009
Values in the same column with different letters are significantly different at Pb0.05.
A.M. Pérez-Vendrell, D. Torrallardona / Livestock Science 134 (2010) 47–49
49
Table 3 Effect of extrusion of different cereal-based feeds on their in vitro digestibility of dry matter (DM) and organic matter (OM) after incubation with pepsin for 75 min, incubation with pepsin for 75 min and pancreatin for 3.5 h and incubation with pepsin for 75 min, pancreatin for 3.5 h and carbohydrases for 18 h. Digestibility (%)
Raw cereals Rice Naked oats Barley Extruded cereals Rice Naked oats Barley Root MSE Factorial analysis (Pr N F) Cereal Extrusion Cereal × extrusion a–e
Pepsin
Pepsin + pancreatin
Pepsin + pancreatin + carbohydrase
DM
OM
DM
OM
DM
OM
37.3 e 50.5 a 46.9 b
33.8 c 45.1 a 40.4 b
77.7 e 85.5 c 80.9 d
75.5 b 87.2 a 79.3 b
98.0 a 95.8 b 90.1 c
97.1 a 94.5 c 87.8 d
40.0 d 41.6 d 44.5 c 0.81
33.7 c 39.4 b 41.8 b 1.04
89.6 a 87.9 b 81.6 d 0.63
88.5 a 87.4 a 79.8 b 1.81
97.0 a 95.3 b 88.7 d 0.51
95.9 b 94.4 c 87.5 e 0.09
b 0.001 0.001 b 0.001
b0.001 0.050 0.007
b 0.001 b 0.001 b 0.001
0.001 0.002 0.002
b 0.001 0.040 0.650
b 0.001 b 0.001 b 0.001
Values in the same column with different letters are significantly different at Pb0.05.
either in raw or in extruded form (total of six diets). The in vitro DM and OM digestibilities measured for the different diets are presented in Table 3. After incubation with pepsine, R presented lower DM and MO digestibilities than B and NO, and whereas extrusion improved DM digestibility of rice, it reduced that of NO and B. Extrusion also reduced OM digestibility of NO after pepsine incubation. After digestion with pepsine and pancreatin, NO presented the highest DM and OM digestibilities followed by R and B. The extrusion of the cereals improved in all cases the in vitro digestibility of DM and OM relative to raw cereals. The highest improvement was observed in rice, for which DM digestibility increased from 77.7% to 89.6% and OM digestibility from 75.5% to 88.5%. The lowest values were obtained in barley diets, probably due to their lower starch and higher fiber contents relative to rice or naked oats. The starch that is not digested in the small intestine, reaches the large intestine where it becomes a substrate for microbial fermentation (Englyst, 1989). After the third incubation step with viscozyme for 18 h, which simulates the large intestine digestion process, R presented the highest DM and OM digestibilities followed by NO and B. In this phase, the extrusion of cereals had a slight negative effect on digestibilities of DM and OM. The differences in the effects of extrusion on the DM and OM digestibilities of the different cereals studied could be explained by the differences on the impact of this treatment on their starch availability. 4. Conclusion It is concluded that cereals present differences in their in vitro digestion kinetics. This may be a useful tool to estimate
possible differences in digestibility kinetics between cereals in the proximal gastrointestinal tract of the pig.
Conflict of interest There are no conflicts of interest.
Acknowledgments The authors wish to thank IRTA's laboratory staff for their assistance during the trials. This study was supported by CICYT project AGL2005-07438-C02-02.
References Boisen, S., Fernández, J.A., 1997. Prediction of the total tract digestibility of energy in feedstuffs and pig diets by in vitro analyses. Anim. Feed Sci. Technol. 68, 277–286. Englyst, H., 1989. Classification and measurement of plant polysaccharides. Anim. Feed Sci. Technol. 23, 27–42. Löwgren, W., Graham, H., Aman, P., 1989. An in vitro method for studying digestion in the pig. Simulating digestion in the different compartments of the intestine. Br. J. Nutr. 61, 673–687. Noblet, J., Jaguelin-Peyraud, Y., 2007. Prediction of digestibility of organic matter and energy in the growing pig from an in vitro model. Anim. Feed Sci. Technol. 134, 211–222. NRC, 1998. Nutrient requirements of swine. National Research Council, 10th Revised Edition. National Academy Press, Washington, DC. USA. Pujol, S., Torrallardona, D., 2007. Evaluation of in vitro methods to estimate the in vivo nutrient digestibility of barley in pigs. Livest. Sci. 109, 186–188. Wilfart, A., Jaguelin-Peyraud, Y., Simmins, H., Noblet, J., van Milgen, J., Montagne, L., 2008. Kinetics of enzymatic digestion of feeds as estimated by a stepwise in vitro method. Anim. Feed Sci. Technol. 141, 171–183.
Contents lists available at ScienceDirect
Livestock Science j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / l i v s c i
In vitro digestibility kinetics of diets containing different cereal sources☆ A.M. Pérez-Vendrell, D. Torrallardona ⁎ IRTA-Centre Mas de Bover, Ctra. Reus-El Morell, km. 3.8, E-43120 Constantí, Spain
a r t i c l e
i n f o
a b s t r a c t
Keywords: In vitro digestibility Cereals Dry matter Organic matter
Two experiments were conducted to study the effect of cereal source on the in vitro digestibility of pig feeds. Dry matter and organic matter digestibilities were evaluated using the multi-enzymatic method described by Boisen and Fernández (1997). The rate at which the different diets were digested, was estimated at 3 different time points: (1) after incubation with pepsin for 75 min; (2) after incubation with pepsin for 75 min and pancreatin for 3.5 h and; (3) after incubation with pepsin for 75 min, pancreatin for 3.5 h and carbohydrases for 18 h. In the first experiment, digestibility was evaluated in six diets containing 60% of rice (R), rice supplemented with wheat bran (RW), barley (B), maize (M), oats (O), or naked oats (NO). Diets containing NO and O had the highest digestibility after pepsin incubation, M, R and RW had the lowest and that of B was intermediate. After incubation with pepsin and pancreatin, digestibility was highest for R, RW and NO diets and lowest for M and O diets, B being intermediate. With the complete in vitro digestion procedure (pepsin, pancreatin and carbohydrases), R presented the highest digestibility followed by NO, M, B and O. In the second experiment, the effect of cereal extrusion was also evaluated in diets containing 60% of R, NO or B, either in raw or in extruded form (total of six diets). Following pepsin incubation, R presented a lower digestibility than B and NO; with pepsin and pancreatin incubations, NO presented the highest digestibility followed by R and B; and after incubation with pepsin, pancreatin and carbohydrases, R presented the highest digestibility followed by NO and B. It is concluded that cereals present differences in their in vitro digestion kinetics. This may be a useful tool to estimate possible differences in digestibility kinetics between cereals in the proximal gastrointestinal tract of the pig. © 2010 Elsevier B.V. All rights reserved.
1. Introduction
estimate in vivo nutrient digestibility. The in vitro techniques intend to simulate the digestion process, using either an inoculum prepared from pig digestive contents (Löwgren et al., 1989) or enzymatic preparations (Boisen and Fernández, 1997). The three-step multi-enzyme system developed by Boisen and Fernández (1997) simulates the digestion in the stomach, the small intestine and the large intestine, and appears to be an effective system to predict organic matter digestibility in pigs (Pujol and Torrallardona, 2007), although it doesn't take into account some aspects of in vivo digestion such as endogenous secretions, absorption and transit (Noblet and Jaguelin-Peyraud, 2007; Wilfart et al., 2008). Usually, with this in vitro method an end-point digestibility value is obtained after the complete enzymatic hydrolysis of the feeds. The objective of the present study was to evaluate
To estimate the nutritive value of a feed for pigs its chemical composition and the corresponding digestibility coefficients (at the ileal or the faecal level) are used. These digestibility coefficients have been traditionally estimated with in vivo trials involving surgically modified animals. In recent years, several in vitro methods have been developed to
☆ This paper is part of the special issue entitled “11th International Symposium on Digestive Physiology of Pigs”. ⁎ Corresponding author. IRTA-Centre Mas de Bover, Ctra. Reus-El Morell, km. 3.8, E-43120 Constantí, Spain. Tel.: + 34 977 32 84 24; fax: + 34 977 34 40 55. E-mail address: [email protected] (D. Torrallardona). 1871-1413/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.livsci.2010.06.093
48
A.M. Pérez-Vendrell, D. Torrallardona / Livestock Science 134 (2010) 47–49
the potential of the three-step multi-enzyme method of Boisen and Fernández (1997) to study the dry matter (DM) and organic matter (OM) hydrolysis kinetics of different cereal-based feeds and to estimate their digestibility in the proximal sections of the pig's gastrointestinal tract. 2. Materials and methods 2.1. Feeds Two trials were conducted to analyse the in vitro digestibility of dry matter and organic matter at different time points. In the first experiment, six complete pig diets differing in their cereal composition were tested. They contained 60% of either: rice (R), rice supplemented with wheat bran (RW), barley (B), maize (M), oats (O), or naked oats (NO). In the second experiment, the effect of cereal extrusion was also evaluated in complete diets containing 60% of R, NO or B, either in raw or in extruded form (total of six diets). For both trials the remaining 40% of the diet was composed by 14% sweet milk whey, 11% of a soybean meal product containing 56% crude protein (HP-300®, Hamlet Protein, Horsens, Denmark), 10% poatato protein (Protastar®, Avebe group Veendam, The Netherlands), 2% lard and amino acids, vitamins and minerals to meet or exceed the animals' requirements (NRC, 1998). The analysed nutrient composition of these diets is presented in Table 1. 2.2. In vitro technique The three-step multi-enzyme system developed by Boisen and Fernández (1997) was carried out in three successive steps. The first step simulating the digestion in the stomach was an enzymatic hydrolysis with a pepsin solution at pH 2.0 and 40 °C for 75 min, in the presence of chloramphenicol. This step was followed by hydrolysis with the multi-enzyme Pancreatin (mixture of protease, amylase and lipase, from porcine pancreas, Sigma ref. P1750) at pH 6.8 and 40 °C for 3.5 h. This step could be associated with the digestion obtained in the small intestine. The third digestion step (digestion in the large intestine) was performed using Viscozyme® enzyme solution (mixture of microbial carbohydrases, including b-glucanase, xylanase, arabinase, cellulase Table 1 Analysed composition of the experimental diets (%, as fed basis).
and pectinase, from Novo-Nordisk, Denmark) at pH 4.8 and 40 °C for 18 h. The undigested residues were quantitatively recovered in a fritted glass filter crucible (Foss, porosity 2), containing around 400 mg of exactly-weighed Celite ® (diatomaceous earth). The residues were rinsed with ethanol, acetone and pure water. The crucibles were oven-dried at 103 °C for 4 h, cooled and weighed, and subsequently placed in a furnace at 525 °C for 8 h, and again cooled and weighed. A blank was included in each procedure batch and each measurement was performed in duplicate. DM and OM were determined according to AOAC (1990) methods. The rate, at which the different diets were digested, was estimated at 3 different time points: after incubation with pepsin for 75 min, after incubation with pepsin for 75 min and pancreatin for 3.5 h and after incubation with pepsin for 75 min, pancreatin for 3.5 h and carbohydrases for 18 h. 3. Results and discussion In the first experiment, diets containing NO and O had the highest DM and OM digestibilites at 75 min of incubation, M, R and RW had the lowest and that of B was intermediate (Table 2). This may be explained by differences in composition of the non starch polysaccharide fraction of the cereals that may differently affect the access of pepsine to the protein fraction. The small intestine is the main site of starch digestion, and for cereals, starch is almost completely digested at the end of the small intestine (Wilfart et al., 2008). After the 3 h 30 min of incubation with pancreatin, the in vitro digestibility of DM and OM was highest for the starch rich cereals R, RW and NO diets and lowest for O and M diets, being intermediate for B. The third digestion step (viscozyme incubation) promoted a moderate increase in the digestion of DM and OM, ranging from approximately a 3% increase in O, NO, M, RW diets to a 7 and 10% increase in B and R diet, respectively. The R diets presented the highest DM and OM digestibilities followed by NO, M, B and O. In the second experiment, the effect of cereal extrusion was also evaluated in diets containing 60% of R, NO or B,
Table 2 In vitro digestibility of dry matter (DM) and organic matter (OM) of different cereal-based feeds after incubation with pepsin for 75 min, after incubation with pepsin for 75 min and pancreatin for 3.5 h and after incubation with pepsin for 75 min, pancreatin for 3.5 h and carbohydrases for 18 h. Digestibility (%)
Experimental diets
Dry matter
Organic matter
Pepsin
Crude protein
First experiment (feeds with 60% different cereals) Rice 90.66 85.69 Barley 91.64 85.83 Rice + wheat bran 90.20 85.72 Maize 90.21 85.31 Oats 91.42 85.94 Naked oats 91.53 86.04
20.99 23.14 21.11 20.40 21.54 23.19
Second experiment (feeds with 60% different cereals raw or Raw rice 90.49 86.21 Extruded rice 91.43 86.53 Raw naked oats 91.42 85.88 Extruded naked oats 91.71 85.92 Raw barley 91.48 85.95 Extruded barley 91.70 86.16
extruded) 21.26 22.09 24.24 23.72 22.82 24.33
DM Rice Barley Rice + wheat bran Maize Oats Naked oats Root MSE Statistics (Pr N F) Cereal a–f
OM
39.0 c 35.1 c 41.6 bc 37.6 b 39.1 c 34.9 c
Pepsin + pancreatin
Pepsin + pancreatin + carbohydrase
DM
OM
DM
OM
86.8 ab 81.6 bc 91.6 a
87.4 a 80.4 b 88.3 a
96.9 a 88.8 d 95.7 ab
96.8 a 87.5 e 95.1 b
77.1 c 75.7 c 88.5 a 0.71
92.6 c 83.1 e 94.2 b 0.64
91.6 d 81.2 f 92.9 c 0.33
b 0.001 b 0.001
b0.001
39.2 c 35.8 bc 78.9 c 44.0 ab 39.7 a 79.3 c 45.1 a 41.2 a 91.0 a 1.05 0.81 2.80 0.004
0.001
0.009
Values in the same column with different letters are significantly different at Pb0.05.
A.M. Pérez-Vendrell, D. Torrallardona / Livestock Science 134 (2010) 47–49
49
Table 3 Effect of extrusion of different cereal-based feeds on their in vitro digestibility of dry matter (DM) and organic matter (OM) after incubation with pepsin for 75 min, incubation with pepsin for 75 min and pancreatin for 3.5 h and incubation with pepsin for 75 min, pancreatin for 3.5 h and carbohydrases for 18 h. Digestibility (%)
Raw cereals Rice Naked oats Barley Extruded cereals Rice Naked oats Barley Root MSE Factorial analysis (Pr N F) Cereal Extrusion Cereal × extrusion a–e
Pepsin
Pepsin + pancreatin
Pepsin + pancreatin + carbohydrase
DM
OM
DM
OM
DM
OM
37.3 e 50.5 a 46.9 b
33.8 c 45.1 a 40.4 b
77.7 e 85.5 c 80.9 d
75.5 b 87.2 a 79.3 b
98.0 a 95.8 b 90.1 c
97.1 a 94.5 c 87.8 d
40.0 d 41.6 d 44.5 c 0.81
33.7 c 39.4 b 41.8 b 1.04
89.6 a 87.9 b 81.6 d 0.63
88.5 a 87.4 a 79.8 b 1.81
97.0 a 95.3 b 88.7 d 0.51
95.9 b 94.4 c 87.5 e 0.09
b 0.001 0.001 b 0.001
b0.001 0.050 0.007
b 0.001 b 0.001 b 0.001
0.001 0.002 0.002
b 0.001 0.040 0.650
b 0.001 b 0.001 b 0.001
Values in the same column with different letters are significantly different at Pb0.05.
either in raw or in extruded form (total of six diets). The in vitro DM and OM digestibilities measured for the different diets are presented in Table 3. After incubation with pepsine, R presented lower DM and MO digestibilities than B and NO, and whereas extrusion improved DM digestibility of rice, it reduced that of NO and B. Extrusion also reduced OM digestibility of NO after pepsine incubation. After digestion with pepsine and pancreatin, NO presented the highest DM and OM digestibilities followed by R and B. The extrusion of the cereals improved in all cases the in vitro digestibility of DM and OM relative to raw cereals. The highest improvement was observed in rice, for which DM digestibility increased from 77.7% to 89.6% and OM digestibility from 75.5% to 88.5%. The lowest values were obtained in barley diets, probably due to their lower starch and higher fiber contents relative to rice or naked oats. The starch that is not digested in the small intestine, reaches the large intestine where it becomes a substrate for microbial fermentation (Englyst, 1989). After the third incubation step with viscozyme for 18 h, which simulates the large intestine digestion process, R presented the highest DM and OM digestibilities followed by NO and B. In this phase, the extrusion of cereals had a slight negative effect on digestibilities of DM and OM. The differences in the effects of extrusion on the DM and OM digestibilities of the different cereals studied could be explained by the differences on the impact of this treatment on their starch availability. 4. Conclusion It is concluded that cereals present differences in their in vitro digestion kinetics. This may be a useful tool to estimate
possible differences in digestibility kinetics between cereals in the proximal gastrointestinal tract of the pig.
Conflict of interest There are no conflicts of interest.
Acknowledgments The authors wish to thank IRTA's laboratory staff for their assistance during the trials. This study was supported by CICYT project AGL2005-07438-C02-02.
References Boisen, S., Fernández, J.A., 1997. Prediction of the total tract digestibility of energy in feedstuffs and pig diets by in vitro analyses. Anim. Feed Sci. Technol. 68, 277–286. Englyst, H., 1989. Classification and measurement of plant polysaccharides. Anim. Feed Sci. Technol. 23, 27–42. Löwgren, W., Graham, H., Aman, P., 1989. An in vitro method for studying digestion in the pig. Simulating digestion in the different compartments of the intestine. Br. J. Nutr. 61, 673–687. Noblet, J., Jaguelin-Peyraud, Y., 2007. Prediction of digestibility of organic matter and energy in the growing pig from an in vitro model. Anim. Feed Sci. Technol. 134, 211–222. NRC, 1998. Nutrient requirements of swine. National Research Council, 10th Revised Edition. National Academy Press, Washington, DC. USA. Pujol, S., Torrallardona, D., 2007. Evaluation of in vitro methods to estimate the in vivo nutrient digestibility of barley in pigs. Livest. Sci. 109, 186–188. Wilfart, A., Jaguelin-Peyraud, Y., Simmins, H., Noblet, J., van Milgen, J., Montagne, L., 2008. Kinetics of enzymatic digestion of feeds as estimated by a stepwise in vitro method. Anim. Feed Sci. Technol. 141, 171–183.