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Apparent digestibility (ileal and overall) of nutrients and
endogenous nitrogen losses in growing pigs fed wheat (var.
Soissons) or its by-products without or with xylanase
supplementation
a,f c d e e
Y.-L. Yin , J.D.G. McEvoy , H. Schulze , U. Hennig , W.-B. Souffrant ,
a,b ,
*
K.J. McCracken
a
Department of Agricultural and Environmental Science, The Queen’s University of Belfast, Newforge Lane, Belfast BT9 5PX,
Northern Ireland, UK
b
Department of Agriculture for Northern Ireland, Newforge Lane, Belfast BT9 5PX, Northern Ireland, UK
c
Veterinary Sciences, Department of Agriculture for N. Ireland, Stoney Road, Belfast BT4 3SD, Northern Ireland, UK
d
Finnfeeds International Ltd., Marlborough, Wiltshire SN8 1AA, UK
e
¨ ¨
Forschungsbereich Ernahrungsphysiologie‘‘Oskar Kellner’’, Forschungsinstitut f ur die Biologie Landwirtschaftlicher Nutztiere,
Rostock, Germany
f
Present address: Department of Animal Science, University of Manitoba, Winnipeg, Canada R3T 2N2 Received 28 July 1998; received in revised form 3 February 1999; accepted 15 June 1999
Abstract
The main aims of this experiment were: 1) to study the sites and extent of digestion of the nutrients in wheat (var. Soissons) and its by-products (bran, middlings) and in recombined wheat (flour1bran1middlings); 2) the contribution of microbial action (VFA apparent production) and endogenous secretion of N in the small intestine; and 3) interactions with an exogenous non-starch polysaccharide (NSP) degrading enzyme (xylanase). The post valve ‘‘T’’ caecal cannulae (PVTC, 12 pigs) and end-to-end ileo-rectal anastomosis (IRA, 30 pigs) ileal digesta collection methods with TiO and Cr O as the2 2 3
15
indigestible markers, and the N-isotope dilution technique were used in this study. Four diets, based on wheat (W), recombined wheat (WR), wheat plus bran (WB) or wheat plus middlings (WM) were used without or with xylanase addition. NSP content was highest in the diet based on wheat bran and lowest in the W and WR diets. Recombination of the milled fractions had no effect on digestibility values relative to the ground wheat. Negative correlations (P,0.001) occurred for apparent overall and ileal digestibility of dry matter (DM), energy, crude protein (CP) and amino acids with NSP content. As shown in some previous studies, NSP contributed to a higher ileal flow of endogenous nitrogen (P,0.001) and volatile fatty acids (VFA) (P50.021) and the proportion of DM fermented in the large intestine was increased (P,0.001). Although statistically significant (P,0.05), the improvements associated with enzyme addition in overall apparent digestibility of DM, CP and gross energy were only of the order of 1% and those at the ileal level were less than 2%
*Corresponding author. Tel.:144-1232-255-368; fax:144-1232-662-007.
E-mail address: [email protected] (K.J. McCracken)
(P.0.05). However, with the WB diet the improvements for all three parameters were approximately 2% for overall apparent digestibility and 4% for ileal apparent digestibility. 2000 Elsevier Science B.V. All rights reserved.
15
Keywords: Wheat; Wheat by-products; Overall and ileal apparent digestibility; N-isotope technique; Endogenous N flow; VFA production; Xylanase
1. Introduction NSP degrading enzyme (xylanase). One source of
wheat (var. Soissons) and its by-products was used to There is considerable interest in the use of fibrous eliminate differences due to the nature and com-feeds for pigs. However, pigs do not produce the position of dietary fibre. Ground wheat was com-endogenous enzymes required to break down cell pared with its recombined fractions (flour1bran1
wall non-starch polysaccharides (NSP). The negative middlings; designated recombined wheat) to deter-relationship between dietary fibre and digestibility of mine the extent to which physical separation of the nutrients is well established (Low, 1985; McClean, components might affect digestion. This experiment 1993; Yin, 1994; Jørgensen et al., 1996). The was conducted in collaboration with the Research reduced apparent digestibility of energy from high- Institute for the Biology of Farm Animals, Depart-fibre feeds can be attributed to differences in the ment of Nutritional Physiology ‘‘Oskar Kellner’’, physical or chemical structure of feeds and the Rostock, Germany. The same diets were used at both shorter transit time of digesta (Graham et al., 1986). institutions, except that the WR diet was only used in The decreased apparent digestibility of crude protein Belfast. Whereas PVTC cannulae were used in and amino acids, however, might be due to increased Belfast, the end-to-end ileo-rectal anastomosis (IRA) endogenous nitrogen (N) secretion (de Lange et al., method was used in Rostock.
1990) or reduced digestibility of feed N due to the physical and chemical structure of the feed affecting
accessibility of protein-degrading enzymes or a 2. Materials and methods
combination of both.
Addition of exogenous enzymes to diets based on 2.1. Experiment 1 barley and wheat improves both nutrient digestibility
and performance of pigs (Taverner and Campbell, 2.1.1. Animals and experimental design ¨
1988; Bohm, 1990; Li et al., 1994; Dierick and Twelve male Large White3Landrace pigs,
ap-Decuypere, 1995; Baidoo et al., 1997). Therefore, proximately 26 kg, were fitted with post valve ‘‘T’’ the enzymes are capable of reducing some of the caecal cannulae (PVTC), according to the procedures anti-nutritive properties of cell wall NSP. In broiler of van Leeuwen et al. (1991). The pigs were chickens, reduced digesta viscosity, following en- randomly allocated, in a four period crossover de-zyme supplementation of barley- and wheat-based sign, to eight diets based on wheat (W), wheat1
diets, is correlated with improved performance, middlings (WM), wheat1bran (WB) or recombined particularly in relation to feed efficiency (Bedford wheat (WR), given without or with xylanase addition and Classen, 1992; Choct et al., 1994; Preston, (Finnfeeds International Ltd) (Table 1). Each of the 1997). Similar relationships have not been estab- four main diets was mixed as a single batch and then
lished in pigs (Bedford et al., 1992). divided for addition of the enzyme. The bran, flour
Table 1 followed by two 12 h collections of ileal digesta
a
Composition of experimental diets (g / kg) (08.00 to 20.00 h on consecutive days).
Diet W WR WM WB
2.2. Experiment 2
Wheat 760 380 380
Wheat flour 570
Wheat bran 60 380 2.2.1. Animals and experimental design
Wheat middlings 130 380 Thirty German Landrace barrows were obtained
Soybean meal 170 170 170 170
from the farm of the Research Institute for the
Fish meal 30 30 30 30
Biology of Farm Animals (Dummerstorf, Rostock,
Soybean oil 10 10 10 10
Dicalcium phosphate 5 5 5 5 Germany). When the pigs weighed approximately 15
Limestone 10.1 10.1 10.1 10.1 kg an ileo-rectal anastomosis was performed accord-Lysine 0.4 0.4 0.4 0.4 ing to the procedure described by Hennig et al.
b
Binder 9 9 9 9
c (1986). In each series, six of the diets used in Belfast
Mineral / vitamins 2.5 2.5 2.5 2.5
d (W, WM and WB, each without or with xylanase
Markers 3 3 3 3
addition) were allocated at random to five pigs per
a
Enzyme (xylanase, Trichoderma longibrachiatum, 0.321 g / kg
diet.
diet, guaranteed minimum enzyme activity 5000 units / kg diet,
On day 10 after surgery, the pigs were
individual-added to one half of each diet. Enzyme activity was determined by
the manufacturer, Finnfeeds International Ltd.). ly housed in metabolism cages and given the
appro-b
Lignobond 2X (Lignotech, Norway). priate experimental diet. On day 15 following the
c
Pigmv No. 2 (Devenish Feed Supplements, Belfast),
sup-IRA surgery two indwelling silicone (Silastic, Dow
plying (per kg diet): vitamin A 8000 i.u.; vitamin D 2000 i.u.;3
Corning, Michigan) catheters (internal diameter 1.5
vitamin E 40 mg; vitamin K 1 mg; vitamin B 2 mg; vitamin B2 12
mm) were surgically implanted into the pig, one into
0.012 mg; iodine 0.85 mg; selenium 0.2 mg; cobalt 0.54 mg; iron
15
58 mg; zinc 72 mg; manganese 42 mg; copper 15 mg; calcium the external jugular vein (for the infusion of
N-500 mg; anti-oxidant 10 mg. leucine) and the other into the carotid artery (for
d
TiO (1 g / kg) and Cr O (2 g / kg) were added to each diet.2 2 3 blood sampling), according to the procedures
de-scribed by Weirich et al. (1970). The animals were allowed 48 h to recover from the second surgical ible markers, were cold-pelleted (3 mm die) and fed manipulation before starting a ten-day experimental
dry. period.
In order to minimise between-pig variation the
experiment was based on a cross-over design with 2.2.2. Feeding regimen and sampling of ileal each pig undergoing four collection periods. This digesta and blood
meant that each of the eight dietary treatments was Feed intake was 500 g / d for each diet and the pigs replicated six times. Pigs were randomly allocated to were fed in two equal portions at 07:30 and 18:30 h individual pens according to the initial randomisation during the entire experimental period. In order to
of the treatments. compensate for by-passing the caecum and colon, the
diets (Table 1) were additionally supplemented with 2.1.2. Feeding regimen and sampling of faeces sodium chloride (4 g / kg diet), sodium bicarbonate
and ileal digesta (4 g / kg diet) and a vitamin mix (1 g / kg diet). Two
Pigs were fed daily at 08:00 and 17:00 h (20:00 h days after insertion of the catheters, a 10 day
15 15
during the faeces and ileal digesta collection continuous infusion of N-leucine (95% N-enrich-periods). They were given a fixed allowance which ment) via the jugular catheter was initiated. On the was kept constant during each experimental period. day prior to the start of the 10 day infusion period, The amount given was the intake of the pig with the ileal digesta and blood samples (10 ml) were taken
15
15
NaCl solution containing 1.5 mg N-leucine (95% trated phosphoric acid, using a Pye Unicam 304 gas
15
N labelled). An infusion pump (Harvard 22, Har- chromatograph with a 10 m Hewlett Packard
(HP-vard instruments, Cambridge, USA) was used to 20M) Carbowax column.
infuse the solution.
15
From the first day of infusion of the N-leucine to
2.4. Calculation and statistical analysis the last day, blood samples (10 ml) were taken twice
a day (8:00 and 19:00) from the carotid catheter.
The results obtained from the PVTC method Immediately after sampling, the blood was
cen-(Belfast) were analysed using the ANOVA procedure trifuged (10 min 30003g, temperature 48C) and the
of the statistical package Genstat 5 (1993) corre-plasma was removed. The corre-plasma protein was
pre-sponding to the 12 pigs34 periods partially bal-cipitated by mixing 5 ml plasma with 5 ml 10% TCA
anced change over design (six replicates per treat-and centrifuging at a speed of 4000 g at a
tempera-ment). This removed the effects of pigs and periods ture of 48C. The supernatant fluid (TCA-soluble
and tested for the main effect of diets and xylanase fraction) from the samples taken from each animal
and their interaction. per day were stored at 2208C for further analyses.
The amount of endogenous N (five replicates per
Ileal digesta were collected for 5 days from the 6th 15
treatment) was calculated from the ratio of N-day after infusion to the last N-day of the experiment.
enrichment in ileal digesta (Ed) to that in the TCA-At the end of each experiment a last blood sample
15 soluble blood plasma of the corresponding day using
was taken from each animal for N-enrichment
the following formula according to Souffrant et al. analysis and the animals were killed by euthanasia
(1981) and de Lange et al. (1990): with Hexobarbital-Na (Hexobarbital Natrium AWD,
VEB Arzneimittelwerke, Dresden).
Ne5Nd3[(Ed–Enf) /(Epl–Enpl)] 2.3. Chemical analysis
where Ne is the endogenous N loss (g / d or g / kg Samples of faeces and ileal digesta were freeze- DM intake); Nd is the total amount of N in the ileal
15
dried and pooled within period and pig for each digesta (g / d or g / kg DMI); Ed is the
N-enrich-15
dietary treatment. The proximate analysis was car- ment in ileal digesta; Enf is the background
N-15
ried out according to AOAC (1984). Amino acid enrichment in the digesta; Epl is the N-enrichment (AA) analyses of diets and ileal digesta were carried in the TCA-soluble blood plasma; and Enpl is the
15
out on an LKB 4400 Amino Acid Analyser using background N-enrichment in the TCA-soluble
norleucine as the internal standard, after hydrolysis blood plasma. The factor [(Ed–Enf) /(Epl–Enpl)], for 22 h in 6N HCl. Gross energy of diets, ileal referred to as the dilution factor, was calculated for digesta and faeces was determined using an adiabatic each animal for each individual day of ileal digesta
bomb calorimeter (Gallenkamp, Model CBA-305). collection.
15
TiO2 was measured according to Leone (1973). Daily values for the N-enrichment excess were
Cr O2 3 was measured according to the method of subjected to non-linear regression (Proc. NLIN,
Saha and Gilbreath (1991) by atomic absorption modified Gauss–Newton method, SAS, 1990)
ac-spectrophotometry. Soluble and insoluble NSP cording to the formula given by Souffrant et al.
15
sugars and uronic acids and total NSP in diets were (1993), to calculate the steady state N-enrichment determined by gas chromatography (Pye Unicam of total N in the chosen precursor pool.
304) according to Englyst and Cummings (1984). The results obtained from the IRA method
(Ros-15
3. Results Conversely, the total NSP content was highest for diet WB (193.5 g / kg), followed by diet WM (151.6 The analyses of a number of chemical constituents g / kg), diet W and diet WR (82.8, 83.2 g / kg). Of this of the diets, including amino acids are shown in 9.89, 9.88, 8.36, 8.41 g / kg were soluble. The Table 2. The CP was highest for diet WM (232 arabinoxylans comprised 76.3, 72.0, 69.3, 69.1% of g / kg) and lowest for diets W and WR (219 and 218 the total insoluble NSP for diets WB, WM, W and g / kg), whereas the crude ash and oil were highest WR respectively.
for WB (67, 30 g / kg) and lowest for diets W (51, 22 There were no significant diet*enzyme interactions g / kg) and WR (53, 23 g / kg). The gross energy for any of the parameters reported throughout the content was higher for the WM and WB diets than paper. The inclusion of both high fibre products for the wheat diets (W and WR) in keeping with the (wheat middlings and bran) in the diets significantly
higher levels of protein and oil. decreased (P,0.001) the dry matter content of the
The total AA contents were slightly higher for diet faeces, relative to diets W and WR, the values being WM and diet WB (192 g / kg) than for diets W and lowest for diet WB. The total faecal output was WR (183 g / kg). The lysine concentration was also highest (P,0.001) for diet WB, but the ileal digesta higher in diets WM and WB (9.9 g / kg) than in diet output measured with the PVTC method
(Experi-W (8.7 g / kg) or (Experi-WR (8.6 g / kg). ment 1) for diet WB was significantly lower than for
Table 2
Proximate analysis, amino acid and NSP analysis of diets (DM basis)
Diet W WR WM WB
Crude protein (g / kg) 219 218 232 227
Crude ash (g / kg) 51 53 62 67
Oil (acid hydrolysis) (g / kg) 22 23 28 30
Crude fibre (g / kg) 28.9 29 50.2 63.8
Gross energy (MJ / kg) 18.1 18.1 18.8 18.5
Essential AA(g /kg)
Threonine 6.7 6.6 7.2 7.2
Valine 8.3 8.7 9.4 9.1
Cystine 8.4 8.7 8.9 9.6
Methionine 4.0 4.0 3.9 4.1
Isoleucine 7.5 7.7 8 7.6
Leucine 1.34 1.37 1.39 13.9
Phenylalanine 8.9 9.2 9.0 9.0
Lysine 8.7 8.6 9.9 9.9
Histidine 4.3 4.4 4.8 4.9
Non-essential AA(g /kg)
Arginine 11.1 11.0 12.9 13
Tyrosine 5.9 5.7 6.1 6.1
Aspartic acid 14.9 14.8 16.3 16.5
Serine 9.2 9.2 9.2 9.4
Glutamic acid 42.7 41.4 41.1 41.1
Proline 12.9 13.0 13.2 12.2
Glycine 8.9 8.8 9.8 9.9
Alanine 7.7 7.9 8.7 8.7
Total AA 182.8 183.4 192.5 191.9
Insoluble NSP 74.5 74.8 141.7 183.6
WM. The ileal digesta values (g / kg DM intake) for and several AA (P,0.05) calculated with the PVTC diet WR tended to be lower than for diet W and the TiO2 method (Tables 4,5). Enzyme addition also effect was significant (P,0.05) for fresh digesta significantly improved the IAD of DM and gross weight. Enzyme inclusion only significantly reduced energy measured with the IRA method. The im-the fresh and dried ileal digesta output measured provements in ileal digestibility were mainly due to with the IRA method (Table 3), though there also increased digestibility coefficients for diet WB, was a trend towards reduced faecal output in Experi- increases being 4.7% (0.607 vs. 0.580), 5.8% (0.619
ment 1. vs. 0.585), 3.3% (0.732 vs. 0.708) and 4.6% (0.799
There were significant differences between diets in vs. 0.764) for DM, energy, CP and total amino acids, the digestibility of all measured nutrients (P,0.001) respectively. Enzyme inclusion did not significantly including amino acids (Tables 4–7) with values improve the IAD of CP and AA measured with the being highest for diets W and WR and lowest for IRA method (Tables 4,7) or any IAD parameters WB, except for the ileal results from the PVTC total measured with PVTC Cr O (Tables 4,6), except for2 3
collection method (Table 4). In general, there were threonine, aspartic acid, serine and glycine.
no significant differences in ileal or overall diges- In Experiment 2, wheat middlings or wheat bran tibility of nutrients between diets W and WR. inclusion significantly (P,0.001) increased the ileal Although the pattern of the results was similar for total N, endogenous N (g / d) and endogenous N the PVTC TiO2 and PVTC Cr O2 3 methods, the (g / kg dry matter intake, DMI) compared with diet absolute values for IAD of DM, gross energy, CP W, but no differences were observed between diets and AA in all diets measured with PVTC Cr O2 3 WB and WM (Table 8). There were no statistically were lower than those measured with PVTC TiO2 significant effects of enzyme addition on ileal total N (Tables 4–6). The IAD of DM, CP, energy and AA or endogenous N flow but in each case the values in all diets measured by the IRA method were in were numerically lower with enzyme addition, par-good agreement with those measured by the PVTC ticularly with diet WB, where the endogenous N
TiO method.2 flow was reduced by 19% (2.35 vs. 2.80 g / d).
Enzyme inclusion improved overall apparent di- The ileal total apparent VFA production (ex-gestibility (OAD) of DM, energy and CP (P,0.05) pressed g / d per kg DM intake) for WM and WB measured by the PVTC method and IAD of DM, CP were significantly (P,0.05) greater than for W and
Table 3
Outputs (g / kg DM intake) of faeces and ileal digesta and their DM concentrations (g / kg) measured with PVTC and IRA methods
Diet Enzyme
W WR WM WB s.e.d. P 2 1 s.e.d. P
Faeces weight(g /kg DM intake)
c c b a
Fresh 371 395 672 1030 19.3 ,0.001 630 605 13.3 NS
c c b a
Dry 110 114 184 243 4.1 ,0.001 167 159 8.1 NS
a a,b b c
DM (g / kg) 298 289 275 236 8.8 ,0.001 279 270 6.3 NS
Ileal digesta(g /kg DM intake)
c d a b
Fresh (PVTC) 2288 2203 2902 2583 20.4 ,0.001 252 247 14.0 NS
b b,c a a,b
Dry (PVTC) 232 215 312 277 23.5 ,0.001 261 258 16.1 NS
DM (g / kg) 102 98 107 107 3.2 NS 104 104 2.3 NS
c b a
Fresh (IRA) 2135 ND 3327 3789 15.9 ,0.001 3178 2955 10.8 0.01
c b a
Dry (IRA) 237 ND 376 413 10.4 ,0.001 356 328 8.38 0.01
DM (g / kg) 111 ND 113 109 2.3 NS 112 111 1.8 NS
a,b,c,d
Table 4
Ileal and overall apparent digestibility of DM, CP and gross energy (E)
Diet Enzyme
W WR WM WB s.e.d. P 2 1 s.e.d. P
a d d e f
Ileal DM 0.773 0.766 0.673 0.594 0.0098 ,0.001 0.694 0.709 0.0066 ,0.05
d d e f
CP 0.807 0.802 0.757 0.720 0.0050 ,0.001 0.765 0.778 0.0034 ,0.05
d d e f
E 0.787 0.771 0.683 0.595 0.0091 ,0.001 0.704 0.714 0.0062 NS
b d d e f
Ileal DM 0.741 0.752 0.632 0.558 0.0107 ,0.001 0.668 0.674 0.0072 NS
d d e f
CP 0.779 0.790 0.727 0.695 0.0082 ,0.001 0.744 0.752 0.0056 NS
d d e f
E 0.757 0.758 0.644 0.560 0.0097 ,0.001 0.679 0.680 0.0066 NS
c d g e f
Ileal DM 0.763 ND 0.624 0.587 0.0104 ,0.001 0.644 0.672 0.0084 ,0.01
d e e
CP 0.811 ND 0.747 0.745 0.0123 ,0.001 0.760 0.776 0.0099 NS
d e f
E 0.784 ND 0.656 0.603 0.0111 ,0.001 0.670 0.692 0.0091 ,0.05
a d d e f
Overall DM 0.890 0.885 0.816 0.758 0.0038 ,0.001 0.833 0.841 0.0027 ,0.05
d d e f
CP 0.903 0.903 0.864 0.831 0.0043 ,0.001 0.872 0.878 0.0030 ,0.05
d d e f
E 0.897 0.886 0.819 0.759 0.0039 ,0.001 0.837 0.843 0.0031 ,0.05
a
Measured with the PVTC TiO method.2 b
Measured with PVTC Cr O method.2 3 c
Measured with IRA method.
d,e,f
Values within the same row without a common superscript are significantly different (P,0.05).
g
ND, not determined.
Table 5
Ileal apparent digestibility of amino acids measured with the PVTC TiO method2
Diet Enzyme
W WR WM WB s.e.d. P 2 1 s.e.d. P
Essential amino acids
a a b c
Threonine 0.770 0.767 0.743 0.708 0.0064 ,0.001 0.738 0.756 0.0084 ,0.05
a a b c
Valine 0.766 0.777 0.749 0.701 0.0073 ,0.001 0.741 0.756 0.0069 ,0.05
a a b b
Methionine 0.898 0.894 0.861 0.851 0.0108 ,0.001 0.871 0.881 0.0051 ,0.05
a a b c
Isoleucine 0.831 0.836 0.803 0.767 0.0044 ,0.001 0.805 0.814 0.0057 ,0.05
a a b c
Leucine 0.848 0.841 0.807 0.779 0.0102 ,0.001 0.812 0.826 0.0075 NS
a a b c
Phenylalanine 0.935 0.934 0.918 0.904 0.0028 ,0.001 0.920 0.926 0.0083 NS
a a b c
Lysine 0.843 0.832 0.820 0.786 0.0051 ,0.001 0.815 0.821 0.0043 NS
a a b c
Histidine 0.865 0.862 0.847 0.824 0.0052 ,0.001 0.844 0.855 0.0043 ,0.05
Non-essential amino acids
a a b b
Cystine 0.814 0.817 0.780 0.784 0.0100 ,0.01 0.789 0.808 0.0079 ,0.05
Arginine 0.887 0.882 0.885 0.876 0.0054 NS 0.878 0.887 0.0042 ,0.05
a a b c
Tyrosine 0.849 0.852 0.833 0.789 0.0044 ,0.001 0.828 0.834 0.0093 NS
a a b c
Aspartic acid 0.777 0.779 0.751 0.716 0.0066 ,0.001 0.749 0.763 0.0051 ,0.05
a a b c
Serine 0.834 0.836 0.800 0.778 0.0052 ,0.001 0.805 0.819 0.0085 ,0.05
a a b b
Glutamic acid 0.909 0.907 0.879 0.873 0.0055 ,0.001 0.889 0.895 0.0054 NS
b a b c
Proline 0.768 0.881 0.763 0.709 0.0268 ,0.001 0.773 0.787 0.0184 NS
a a b c
Glycine 0.749 0.739 0.719 0.674 0.0138 ,0.001 0.706 0.734 0.0099 ,0.05
a a b c
Alanine 0.737 0.749 0.719 0.665 0.0087 ,0.001 0.714 0.722 0.0057 NS
b a c d
Total 0.834 0.854 0.810 0.783 0.0053 ,0.001 0.815 0.826 0.0050 ,0.05
a,b,c,d
Table 6
Ileal apparent digestibility of amino acids measured with the PVTC Cr O method2 3
Diet Enzyme
W WR WM WB s.e.d. P 2 1 s.e.d. P
Essential amino acids
a a b c
Threonine 0.737 0.753 0.710 0.683 0.0091 ,0.001 0.714 0.728 0.0057 ,0.05
b a b c
Valine 0.733 0.763 0.718 0.674 0.0089 ,0.001 0.717 0.727 0.0093 NS
a,b a c b,c
Cystine 0.786 0.805 0.750 0.765 0.0142 0.006 0.769 0.784 0.0110 NS
a a b b
Methionine 0.884 0.888 0.843 0.838 0.0060 ,0.001 0.859 0.867 0.0098 NS
b a c d
Isoleucine 0.808 0.827 0.778 0.747 0.0074 ,0.001 0.788 0.792 0.0085 NS
a a b c
Leucine 0.827 0.831 0.783 0.760 0.0111 ,0.001 0.796 0.805 0.0080 NS
b a c d
Phenylalanine 0.830 0.846 0.797 0.777 0.0061 ,0.001 0.811 0.815 0.0083 NS
a a a b
Lysine 0.811 0.821 0.797 0.768 0.0076 ,0.001 0.799 0.800 0.0075 NS
a a b c
Histidine 0.845 0.854 0.827 0.809 0.0059 ,0.001 0.830 0.838 0.0042 NS
Non-essential amino acids
Arginine 0.871 0.875 0.871 0.865 0.0050 NS 0.867 0.874 0.0093 NS
b a c d
Tyrosine 0.828 0.844 0.813 0.771 0.0054 ,0.001 0.813 0.815 0.0074 NS
a b b c
Aspartic acid 0.760 0.723 0.720 0.688 0.0039 ,0.001 0.875 0.881 0.0028 ,0.05
a a b c
Serine 0.810 0.826 0.775 0.759 0.0068 ,0.001 0.787 0.798 0.0047 ,0.05
a a b b
Glutamic acid 0.897 0.902 0.863 0.862 0.0066 ,0.001 0.879 0.883 0.0093 NS
b a c d
Proline 0.731 0.874 0.733 0.683 0.0276 ,0.001 0.748 0.762 0.0190 NS
a a b c
Glycine 0.712 0.726 0.679 0.645 0.0132 ,0.001 0.680 0.701 0.0093 ,0.05
b a b c
Alanine 0.700 0.735 0.683 0.636 0.0110 ,0.001 0.688 0.689 0.0080 NS
b a c d
Total 0.810 0.846 0.785 0.764 0.0060 ,0.001 0.798 0.805 0.0084 NS
a,b,c,d
Values within the same row without a common superscript are significantly different (P,0.05).
Table 7
Ileal apparent digestibility of amino acids measured with IRA method
WR, respectively, but there were no significant
Diet differences between diet WB and WM (Table 9).
The increase in total VFA on diets WB and WM was
W WM WB s.e.d. P
a b b reflected in the individual VFAs. Xylanase
supple-Threonine 0.764 0.732 0.702 0.0177 ,0.01
a b b mentation had no significant effect on ileal VFA
Valine 0.805 0.769 0.756 0.0115 ,0.001
a b b
Isoleucine 0.843 0.815 0.800 0.0112 ,0.01 apparent production, although there were numerical
a a b
Leucine 0.851 0.82 0.807 0.0096 ,0.001 increases with supplementation of 16, 14, 17, 21%
a b b
Phenylalanine 0.876 0.851 0.834 0.0096 ,0.001 on average for total, acetic, propionic and butyric
a a b
The extent of fermentation (Ferm) occurring in the
Tyrosine 0.851 0.858 0.834 0.0111 NS
large intestine assessed in various ways is shown in
Arginine 0.908 0.901 0.895 0.0061 NS
a b b Table 9. The difference between overall and ileal
Aspartic acid 0.799 0.769 0.750 0.0149 ,0.01
a b c
Serine 0.836 0.801 0.786 0.0112 ,0.001 digestibility coefficients (i.e. extent of hindgut
fer-a b b
Glutamic acid 0.912 0.873 0.879 0.0078 ,0.001 mentation) was expressed as Ferm 1. Ferm 2 was the
a b b
Proline 0.891 0.858 0.854 0.0083 ,0.001
proportion of hindgut fermentation (Ferm 1)
ex-a a b
Alanine 0.770 0.741 0.714 0.0151 ,0.01
a b b pressed as a fraction of the overall digestibility. Ferm
Glycine 0.784 0.740 0.732 0.0179 ,0.05
a b b 3 was Ferm 1 expressed as a proportion of the
Total 0.856 0.825 0.814 0.0097 ,0.001
a,b,c undigested residue flowing through the terminal
Values within the same row without a common superscript
ileum. The results showed that when the
fermen-are significantly different (P,0.05). No significant effects (P.
Table 8
Nitrogen (N) flows at the terminal ileum measured with IRA method
Diet Enzyme
Endogenous N (g / d) 1.71 2.79 2.57 0.231 ,0.001 2.46 2.25 0.185 NS
b a a
Endogenous N (g / kg of DMI) 4.14 6.42 5.98 0.527 ,0.001 5.75 5.28 0.424 NS
a,b
Values within the same row without a common superscript are significantly different (P,0.05).
Table 9
Ileal VFA apparent production (g / per kg DM intake) and estimates of hindgut fermentation (Ferm) measured with PVTC method
Diet
W WR WM WB s.e.d. P
e e d d
Total VFA 3.64 3.57 5.32 5.56 0.6138 0.021
e e d d
Acetic 2.78 2.81 3.83 3.82 0.4177 0.01
e e d d
Propionic 0.51 0.46 1.02 1.28 0.1589 ,0.001
e e d d
Butyric 0.35 0.3 0.47 0.46 0.0789 0.07
a f f e d
Ferm 1 DM 0.117 0.120 0.143 0.173 0.0101 ,0.001
CP 0.096 0.102 0.107 0.108 0.0047 0.074
f f e d
GE 0.110 0.116 0.136 0.162 0.0088 ,0.001
b f f e d
Ferm 2 DM 0.131 0.135 0.175 0.229 0.0124 ,0.001
e,f e d,e d
CP 0.106 0.113 0.123 0.131 0.0052 ,0.001
f f e d
GE 0.123 0.131 0.165 0.214 0.0104 ,0.001
c d d e e
Ferm 3 DM 0.514 0.510 0.435 0.426 0.0223 ,0.001
d d e f
CP 0.495 0.512 0.436 0.386 0.0179 ,0.001
d d e e
GE 0.515 0.506 0.426 0.401 0.0217 ,0.001
a
Fermentation expressed as the difference between overall and ileal digestibility coefficients (5overall digestibility–ileal digestibility).
b
As a proportion of overall digestibility (5Ferm 1 / overall digestibility).
c
Fermentation as a proportion of undigested material reaching the hindgut (5Ferm 1 / 1–ileal digestibility).
d,e,f
Values within the same row without a common superscript are significantly different (P,0.05). No significant effects (P.0.05) of enzyme occurred.
of DM and energy fermentation were highest for diet 4. Discussion
WB (P,0.001), followed by diet WM, except for
CP (Ferm 1). However, when fermentation was 4.1. Effects of dietary NSP on ileal apparent considered as the proportion of undigested residue digestibility of nutrients, ileal endogenous N flow flowing through the terminal ileum which disap- and microbial fermentation
peared in the hindgut (Ferm 3), the extent of
Fig. 1. Relationship between ileal apparent digestibility of energy and dietary total NSP.
products does not affect digestion and absorption. (g / kg DM intake) increased by 1.7-fold when the The well-established negative influence of dietary dietary total NSP increased from 83 g / kg (diet, W) fibre on digestibility is demonstrated in Fig. 1, using to 193 g / kg (diet, WB). This result is similar to those the results for ileal apparent digestibility of gross of Schulze (1994) and Jørgensen et al. (1996) who energy, measured by the TiO method, as an exam-2 also observed a significant influence of dietary NSP ple. Similar relationships were seen for DM, crude on ileal DM output. For example, Schulze (1994) protein and amino acids and the slopes for the reported that the ileal DM output (g / kg DM intake) regression equations differed from zero (P,0.05). increased 2-fold when the dietary NDF increased For example the negative relationship with crude from 83 g / kg to 195 g / kg.
protein digestibility was described by the equation: Dietary fibre has an influence on microbial fer-IAD (CP)50.87320.00078 X (r50.999), where mentation not only in the large intestine, but also in
enterotox-ins, all of which, in high concentrations, have a terminal ileum of pigs fed diets containing protein damaging effect on the mucosa of the small intestine (de Lange et al., 1990; Souffrant, 1991; Souffrant et and, therefore, may reduce the host digestion and al., 1993).
absorption rate for nutrients, and increase metabolic The present results clearly show that the depressed demand (Just et al., 1979, 1981; McKinnon, 1985; ileal apparent digestibility of protein with increased
Chesson, 1994). dietary NSP is mainly due to increased ileal
endog-Dietary fibre also affects the endogenous N flow enous N. When dietary total NSP was increased from and apparent digestibility of protein. An increase in 83 g / kg (diet W) to 193 g / kg (diet WB), the endogenous ileal N and AA with higher levels of calculated total N excreted in ileal digesta was fibre in diets has been demonstrated (Sauer et al., increased by 1.3 g / d, while the increased ileal 1977; Taverner et al., 1981; Schulze, 1994). The endogenous N flow was 0.9 g / d. The calculated true additional ileal endogenous N was 1.84 g / kg DM CP digestibility was 2% higher for diet W than diet intake as the dietary total NSP increased from 83 WB (93 vs. 91%).
g / kg (diet W) to 193 g / kg (diet WB). This result is
somewhat higher than that of Schulze (1994) who 4.2. Effects of enzyme addition on ileal
reported that the additional ileal endogenous N flow digestibility of nutrients, and growth performance was 1.13 g / kg DM intake when the dietary NDF
content was increased from 60 to 177 g / kg by As discussed above, there is a strong negative
inclusion of wheat bran. relationship between dietary NSP and ileal
diges-Sauer (1976) suggested that the increase in endog- tibility and absorption of nutrients. It has been enous output caused by increased fibre intake was suggested that xylanase addition could cause im-due to increased cellular losses of epithelial cells or provements through disruption or solubilization of increased mucus secretion or both. He suggested also cell wall polysaccharides, resulting in reduction or that increasing dietary fibre levels resulted in in- elimination of the encapsulating effects of the cell creased water-holding capacity of the digesta, caus- wall and a consequent shift of digestion of energy ing an increase in physical abrasion of epithelial cells and protein towards the proximal region of the small by the digesta. In the present experiment, however, intestine (Dierick and Decuypere, 1994). The present whereas there was a significant increase in ileal DM study and others (Dierick and Decuypere, 1994; flow from diet WM (152 g NSP/ kg) to diet WB (196 Schulze et al., 1996) have shown that the main g NSP/ kg), this had no effect on the ileal N flow, source of dietary NSP in wheat is arabinoxylans and suggesting that this relationship may not be linear. in barley, arabinoxylans plus glucans. These groups This agrees with the results of Taverner et al. (1981) comprise over 50% of the total NSP in the whole who reported that endogenous N ileal output in- grain. Although the observed improvements in over-creased with dietary fibre up to approximately 100 g all and ileal apparent digestibility of DM, CP and
NDF / kg, but not thereafter. energy were statistically significant (P,0.05), the
The total quantity of nitrogenous material passing effects of xylanase supplementation with wheat-the terminal ileum is dependent on both wheat-the undi- based diets were small when compared with the
˚
gested dietary N and the endogenous N that is not results for poultry (Pettersson and Aman, 1989; re-absorbed. The present experiment shows that the Preston, 1997). The improvements of overall di-ileal endogenous N flow is very high, being over half gestibility of DM, energy and CP were only of the of the total N. It is important that both quantities are order of 1% and those at the ileum less than 2%. known (Huisman et al., 1993). However, in order to However, the effects were greater for the high fibre distinguish between the endogenous and exogenous diet WB where the mean ileal apparent digestibilities
N fractions, specific experimental and analytical of CP and energy were improved by 3 and 5%
methods are required. Although not entirely above respectively with enzyme addition. This, taken with criticism (Fuller, 1991; de Lange et al., 1992), the the results of Choct et al. (1994) and Knudsen and
15
depen-dent on the substrate available to the exogenous protected in the pre-gastric and gastric region. En-enzyme. For diets of high fibre content, the di- zyme stability is therefore an important factor in gestibility is relatively low and, therefore, there is determining efficacy (Baas and Thacker, 1996). The more scope for enzyme action (Collier and Hardy, pH in the stomach of pigs fed ad libitum rarely rises
1986; Knudsen and Hansen,1991). above pH 3.0 (Kidder and Manners, 1978). Although
The present study shows that there was a numeri- low pH levels may also be reached in the gizzard of cal trend of increased apparent ileal VFA production poultry (Hill, 1971), the duration of exposure to the with xylanase addition, especially for diet WB where low pH is much shorter than with pigs. Therefore, a ileal apparent VFA production was increased by greater proportion of enzyme activity would be 38%. This suggests that enzyme addition increased expected to survive in the small intestine of chickens the availability of nutrients to the microorganisms compared with pigs. However, Baas and Thacker and that part of the energy digestibility at the distal (1996) found that, although the low gastric pH ileum for diet WB was due to fermentation. How- observed in the stomach of the pig has a detrimental ever, as discussed earlier, this effect would account effect on b-glucanase activity, enzyme activity was for less than 1% of DM intake and, therefore, the still present in the small intestine of the pig and increased ileal digestibility of gross energy by en- enzyme addition significantly improved the ileal zyme addition would appear to be mainly due to digestibility of nutrients in barley-based diet com-increased host enzyme digestion. Inborr et al. (1994), pared with the control group. The feed enzyme Li et al. (1994) and Baidoo et al. (1997) suggested xylanase used in this study has been selected to be that the increased apparent ileal digestibility of CP active under the conditions encountered in the and AA with enzyme supplemented barley-based stomach and in the small intestine and to effectively diets for pigs was due to reduction in the physical degrade targeted polysaccharides (optimum pH range barrier created by the gel-forming property of b- 3.5–6.5, according to Finnfeeds International Ltd.). glucans, therefore providing an ideal environment for In addition, the amount of xylanase activity included
the interaction between endogenous digestive en- was about 30% above the guaranteed minimum.
zymes and respective substrates. However, the nu- Therefore, it seems unlikely that the modest re-merical increase in apparent ileal digestibility of CP, sponses in digestibility of nutrients are due to poor
measured with the IRA method, can be mainly survival of enzyme. It may be that the exogenous
attributed to the reduced ileal endogenous N secre- xylanase is not fully effective in solubilizing NSP tion. The calculated mean values of the total ileal N under the conditions prevailing in the small intestine flow of the diets W, WM and WB were reduced by or that there is already significant hydrolysis by 0.26 g / d by enzyme addition, while the ileal endog- microbial enzymes. Quantitatively the contribution enous N flow was reduced by 0.21 g / d and the true of microbial fermentation in the small intestine is ileal digestibility of CP with or without enzyme was small but microbial xylanase activity and its effects
the same (92%). on NSP degradation may be biologically significant.
Contrary to the results with poultry (Pettersson The relatively long small intestine in the pig (18 m
˚
and Aman, 1988, 1989; Choct et al., 1994), the vs. 120 cm for poultry) increases transit time and present results clearly indicate that the effects of provides increased opportunity for microbial coloni-enzyme preparations containing xylanase on nutrient sation of the small intestine. In retrospect it would utilization of wheat or its by-products in diets for have been interesting to examine the microflora in growing pigs are small. The main reason for the various regions of the small intestine in the absence difference in results may be the anatomical differ- or presence of enzyme.
ences between pigs and poultry. In pigs, the stomach acts as the primary reservoir for food (Kidder and
Manners, 1978) and, unlike the crop of poultry, 5. Conclusions
gastric pH may decline to low levels that are
15
pigs as determined with the N-isotope dilution technique. J.
digestibility resulting in increased DM output,
en-Anim. Sci. 68, 409–418.
dogenous N secretion and microbial fermentation
de Lange, C.F.M., Sauer, W.C., Souffrant, W.B., Lien, K.A., 1992.
15 15
(apparent VFA production and overall–ileal differ- N-leucine and N-isoleucine isotope dilution techniques
15
ences in digestibility) in pigs. There were small, but versus N dilution technique for determining the recovery of endogenous protein and amino acids in digesta collected from
significant improvements in overall digestibility of
the distal ileum in pigs. J. Anim. Sci. 70, 1848–1856.
DM, CP and energy and ileal digestibility of DM,
Dierick, N.A., Decuypere, J.A., 1994. Enzymes and growth in
CP, energy and some AA associated with xylanase pigs. In: Cole, D., Wiseman, J., Varley, M. (Eds.), Principles of inclusion. The increased apparent ileal digestibility Pig Science, Nottingham University Press, p. 168.
Dierick, N.A., Decuypere, J.A., 1995. Advances in the use of
of gross energy by xylanase addition observed in this
supplementary enzymes in pig nutrition. In: van Hartingsveldt,
study may be mainly due to the increased host
W., Hessing, M., van der Lugt, J.P., Somers, W.A.C. (Eds.),
endogenous enzyme digestion and partly due to the Proceedings of the Second European Symposium on Feed increased fermentation in the small intestine. The Enzymes, Noordwijkerhout, Drukkerij Elinkwijk B.V, Zurich, increased ileal apparent crude protein digestibility pp. 23–29.
Englyst, H.N., Cummings, J.A., 1984. Simplified method for the
appears to be mainly due to the reduced endogenous
measurement of total NSP by gas liquid chromatography of
nitrogen reaching the ileum rather than to improved
constituent sugars as alditol acetates. Analyst 109, 937–942.
true digestibility of protein. Fuller, M.F., 1991. Methodologies for the measurement of
diges-tion. In: Verstegen, M.W.A., Huisman, J., den Hartog, L.A. (Eds.), Proceedings of the Fifth International Symposium on Digestive Physiology in Pigs, Pudoc Scientific Publishers,
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