The effects of sepiolite in broiler chicken diets of high,
medium and low viscosity. Productive performance
and nutritive value
I. Ouhida, J.F. PeÂrez
*, J. Piedra®ta, J. Gasa
Departament de Patologia i de Produccio Animals. Universitat Autonoma de Barcelona, Bellaterra, 08193 Barcelona, Spain
Received 11 June 1999; received in revised form 12 November 1999; accepted 4 April 2000
Abstract
Productive and digestive parameters (feed:gain conversion rates, whole-tract digestibility, intestinal viscosity and kinetics of digesta ¯ow) were determined in broiler chickens fed on three diets of different viscosities, maize (low viscous), wheat±barley (medium viscous) and maize±10 g/ kg carboxymethyl cellulose (maize±CMC, high viscous) based. The three diets were supplemented with 0, 10 and 20 g/kg of sepiolite (EXAL1UE-562), respectively, to examine how soluble
non-starch polysaccharides per se in¯uence nutrient digestion, and the extent to which sepiolite supplementation (10 or 20 g/kg) could improve dietary OM digestibility and AME content. Broiler chickens fed on maize and barley-wheat showed higher (p<0.001) live weights (664 and 672 g, respectively) at 22 days of age than those fed on maize-CMC (597 g). Signi®cant differences were also observed in the voluntary intake and feed:gain conversion rates. No signi®cant differences were observed in the productive performance of the animals associated with the sepiolite supplementa-tion. Sepiolite increased signi®cantly the organic matter digestibility, in line with decreases in the water-relative viscosity determined in the jejunum, and changes in the kinetics of digesta ¯ow. Sepiolite decreased mean retention time in the whole gastrointestinal tract and small intestine with medium and high viscous diets (barley±wheat, maize±CMC) and prolonged these times with the low viscous diet. No signi®cant relationships were observed between the changes in the retention time of the digesta and the digestibility values estimated after sepiolite supplementation. A likely contribution of other digestive mechanisms, such as changes in the digesta viscosity or microbial activity could be involved.#2000 Elsevier Science B.V. All rights reserved.
Keywords:Sepiolite; Broilers; Viscosity; Retention time 85 (2000) 183±194
*Corresponding author. Tel.:34-93-581-1556; fax:34-93-581-2106.
E-mail address: jfperez@quiro.uab.es (J.F. PeÂrez)
1. Introduction
Traditionally, clays have been incorporated in diets (10±20 g/kg) as a technological additive (lubricant or agglomerant) to improve feed manufacture (Angulo et al., 1995). However, recently a role as enhancer of the nutritive value of diets in ruminants and monogastric animals (Angulo et al., 1996) has been also proposed.
One of these clays, sepiolite, is thought to increase the nutritive value of diets by retaining digesta longer in the gastrointestinal tract. Theoretically, this could increase the ability of the digestive tract to hydrolyse enzymatically dietary polymers (Tortuero et al., 1992), especially in growing broilers which have faster transit times than adults (Almirall and Esteve-Garcia, 1994) and a more immature enzymatic capacity (Noy and Sklan, 1995). In particular, the broiler chicken digestive tract is especially sensitive to the presence of soluble non-starch polysaccharides (NSP, such as b-glucans and arabinoxylans). Soluble NSPs are proven to increase the viscosity and microbial activity of digesta, and reduce its rate of passage through the small intestine (Choct et al., 1995; Bedford, 1996). As a consequence, viscous digesta promote signi®cant decreases in OM digestibility, voluntary intake and productive performance.
In previous results in our laboratory (Ouhida, 1999), sepiolite was proved to be effective in increasing the OM digestibility of barley±wheat diets, but failed to promote additional increases with those diets treated with enzymes (b-glucanase and arabinoxylanase). Thus, sepiolite showed digestive and productive responses that interacted with the presence of NSP in digesta, probably modifying some of their detrimental effects, such as those in intestinal viscosity or kinetic parameters.
The objective of the present experiment was to study the effects of sepiolite (0, 10 and 20 g/kg) on the nutritive value of high- and medium-viscous diets (maize10 g/kg carboxymethyl cellulose and barley±wheat based) as compared with that observed with a non-viscous diet (maize based). Main effects and interactions were evaluated for the productive performance, the apparent whole tract digestibility of OM, fat and protein, and likely mechanisms involved in these changes, digesta viscosity and mean retention time in the gastrointestinal tract.
2. Materials and methods
The experiment was performed in the animal experimental unit of the Universitat AutoÁnoma de Barcelona and received prior approval from the Animal Protocol Review of this institution.
2.1. Animals and diets
(maize10 g/kg carboxy methylcellulose based, SIGMA-C-5013) each supplemented with 0, 10 or 20 g/kg of sepiolite (EXAL1
UE-562, TOLSA, S.A. Madrid). Food and water were given ad libitum with a provision for semicontinuous (23:1) arti®cial light.
2.2. Experimental procedures
Animals were grown from Day 6 to Day 22, according to the following schedule: on Day 12, wet droppings were evaluated (as percentage of animals with no adhered, moderate, and heavily adhered excreta); on Day 20, determination of the non-cumulative excretion of titanium (used as an indirect estimation of digesta kinetics); on days 20±22, a balance trial was performed by recording food consumption (Ti marked diets) and collecting excreta for a 40-h period; on Day 22, birds were slaughtered by cervical dislocation and the gastrointestinal tract and digesta removed for direct measurements of viscosity in the jejunum and ileum, and of digesta kinetics.
2.3. Non-cumulative excretion curves
Indirect measurements of digesta kinetics were obtained as follows: On Day 19, marked diets (5 g TiO2/kg) were administered for a 24-h period, after which it was
Table 1
Ingredient composition (g/kg) and analysis of basal diets (maize, barley wheat)
Ingredient (g/kg) Maize Barley±wheat
Maize grain 54 ±
Barley grain ± 300
Wheat grain ± 308
Soyabean meal (460 g CP/kg) 264 197
Full-fat soyabean meal 120 121
Sun¯ower oil 31 35
DL-methionine 2.0 2.0
L-lysine 1.1 1.8
Sodium chloride 3.5 3.6
Dicalcium phosphate 17.2 18.0
Calcium carbonate 8.8 8.9
Vitamin premixa 4.4 4.5
Calculated analysis(g/kg DM)
Total lysine 14.7 14.8
Calcium 11.8 11.8
Phosphorus 8.9 9.2
Analysis(g/kg DM)
CP 223.1 230.9
EE 102.4 101.0
Ash 73.2 76.3
aPremix contained per kilogram of diet: vitamin A, 9900 IU; cholecalciferol, 5.5 IU; vitamin E (a
-tocopherol), 66 mg E; ribo¯avin, 5.5 mg; pantothenic acid, 14.3 mg; choline chloride, 275 mg; vitamin B12,
13.2mg; vitamin K3, 3.3 mg; folic acid, 1.65 mg; biotin, 55mg. Minerals: Co, 176; Se, 396; Fe, 38.5; Cu, 22;
Mn, 110; Zn, 132; and Ethoxiquin, 70.4 mg.
replaced by a marker-free diet immediately. The non-cumulative excreta excretion curve was obtained from sampling hourly for an 8-h period. Excreta marker excretion curves were ®tted by least-squares mean deviation to the non-cumulative equation derived from that proposed by Van Der Klis and Van Woorst (1993):
TiO2 a 1ÿ 1
1exp ÿb tÿm
from `a' (marker concentration in steady-state conditions), `b' (dilution rate, hÿ1) and `m' (delay time, h). Time required for the excretion of 50% of the marker excreted in the 8-h period was obtained from the following calculated cumulative excretion equation, which assumes a constant rate dry matter faecal excretion (DM/h):
Z 8
0
TiO2dtaln 1exp bm ÿln 1exp b mÿ8 b
The mean retention time (MRT) was estimated using ®tted parameters, `b' and `m':
MTR 1
b
m
2.4. Direct digesta kinetics
Direct measurement of digesta kinetics on Day 22 was obtained as follows: on Day 20, following the 8-h sampling period for obtaining the non-cumulative excretion curve, diets containing (5 g TiO2)/kg were re-administered for a 40-h period until the animals were slaughtered by cervical dislocation. The gastrointestinal tracts were immediately exposed, weighed and segmented into gizzard, duodenum, jejunum, ileum and caecum. Each compartment was then weighed, the total digesta collected, weighed, and pooled two by two animals of similar body weight. Digesta samples were freeze-dried and stored until analysis of Ti. Mean retention time in each compartment `a' (RTa; gizzard, small intestine and caeca) was estimated using the amounts of titanium in each compartment (Qa), and the average hourly intake of titanium per animal on days 20±22 (`Ia' intake/24 h) on each treatment:
RTa Qa
Ia
2.5. Analysis
2.6. Statistical analyses
Values were examined by analyses of variance. Treatment sums of squares were partitioned into fractional factors associated with the basal diets and the sepiolite supplementation. The effect of basal diet, sepiolite level per se (0 vs. treatments containing 10 and 20 g/kg of sepiolite), and interactions (dietsepiolite) were analysed by the contrast method of the SAS version 6.12 (1996). The percentages of birds with no-, moderate- or heavily adhered excreta were compared between treatments using a w2-test (with Yates
correction0.1500, df1).
3. Results
3.1. Productive performance and digestibility
Mean values for feed intake, live weight on Day 22, and feed:gain ratios calculated from days 6±22 are presented in Table 2, together with the digestibility of OM, CP and fat
Table 2
Effect of sepiolite (0, 10 or 20 g/kg) on the voluntary intake, live weight on Day 22 (g/bird), feed: gain conversion and digestibility parameters (digestible component in g/kg for OM, Fat, CP, and in MJ/kg for AMEn,) of diets based on maize (C), barley±wheat (BW) and maize±10 g/kg CMC (CMC)a
Variable Feed
BW 923 672 1.61 736 766 586 13.08
CMC 856 597 1.73 760 768 435 13.21
Sepiolite
0 888 642 1.64 756 769 524 13.46
10 893 655 1.62 769 791 544 13.59
20 875 636 1.64 771 789 553 13.46
S.E. 14.6 12.2 0.024 4.3 3.9 13.1 0.085
aValues are means of nine observations per treatment and their (S.E.). bNot signi®cant.
*p0.05; **p0.01; ***p0.001.
expressed as content of digestible component in g/(kg diet) and AMEn. No interactions were observed among treatments. Then, the average values for each experimental factor are presented and contrasted individually. Chickens fed on maize and barley±wheat weighed more (p<0.001) on Day 22 (664 and 672 g, respectively) than those fed on maize-CMC (597 g). Differences in live weight were associated with differences in the feed:gain conversion ratios (p<0.001), with maize±CMC treatments having higher values (1.73, p<0.001) than barley±wheat (1.61) and maize (1.56). No signi®cant differences were observed in productive performance from the incorporation of sepiolite in the diets. Basal diets also differed signi®cantly in digestibility. Maize±CMC was signi®cantly lower than maize in the apparent whole-tract digestibility of OM (760 vs. 799 g/kg digestible component, p<0.001), CP (768 vs. 815, p<0.001) and fat (435 vs. 600, p<0.001), and in the AMEn content (13.21 vs. 14.21 MJ/g DM, p<0.001). Sepiolite incorporation (10 and 20 g/kg) promoted signi®cant increases (p<0.05) in the OM and CP apparent digestibility. Fat digestibility was also increased with sepiolite in diets of medium (barley±wheat) and high viscosity (maize±CMC), but no signi®cantly interaction was observed. Thus, despite the mineral dilution (10 or 20 g/kg), no signi®cant differences were observed in the AMEn (expressed on a dry-matter basis) among diets including 0, 10 and 20 g/kg of sepiolite.
Basal diets and sepiolite also differed in their effects on the incidence of wet droppings on Day 12 (Fig. 1). Viscous diets increased the incidence of wet droppings (87.5, 33.3 and 29.2% with the high-, medium- and low-viscous treatments) and the percentage of animals with a high degree of adhered faeces, especially with the high-viscous treatment (62.5% with maize±CMC, 29.1% with barley±wheat, and 16.7% with maize,p<0.001). Sepiolite incorporation reduced the number of animals with a high degree of adhered excreta, but only signi®cant for the high viscous treatment (62.5, 29.2 and 25.0% with 0, 10 and 20 g/kg of sepiolite, p<0.05). Simultaneously, an increase was observed (12.5,
54.3 and 58.3%, respectively, p<0.05) on the percentage of animals with no-adhered excreta.
3.2. Viscosity and kinetic parameters
In Fig. 2 are presented the mean values of viscosity measured in jejunal and ileal digesta in 22-day-old broilers. Broilers fed on barley±wheat and maize±CMC diets showed a more viscous ileal digesta than in the jejunum (1.224 vs. 1.185 in maize±CMC, and 1.119 vs. 1.074 in barley±wheat, respectively, p<0.05). Similar increases were not observed in the animals fed on the non-viscous diet (1.071 vs. 1.074 in ileum and jejunum digesta, respectively), which re¯ects a direct effect of soluble NSP on an increasing intestinal viscosity. Incorporation of sepiolite reduced the viscosity of digesta in the jejunum (p<0.05), but not signi®cantly in the ileum (p>0.05).
In Fig. 3, the excretion curves of Ti for the basal diets, maize, barley±wheat or maize± CMC are presented. Their ®tted parameters (a, initial concentration;b, fractional rates, hÿ1; andm, delay time), and the estimated mean retention times are presented in Table 3. Kinetic parameters and digesta retention times were signi®cantly affected by the basal diet and the sepiolite supplementation, showing in some cases an interaction effect. With respect to the basal treatments, medium- and high-viscous diets promoted signi®cant decreases in the initial concentration of Ti in steady-state conditions (parameter `a', 0.402 vs. 0.350 and 0.347 absorbance units, p<0.001) and their fractional rates of decay (parameter `b', 1.695 vs. 1.345 and 1.325 hÿ1, p:0.06) with the non-sepiolite maize, barley±wheat and maize±CMC based diets, respectively. Thus, time required for 50% of marker excretion and MRT differed signi®cantly among treatments, MRT being higher (p<0.001) with the high-viscous diet (maize±CMC, 6.05 h) than with maize (4.83 h) and barley±wheat diets (4.57 h).
Sepiolite incorporation at 10 or 20 g/kg signi®cantly reduced the concentration of Ti at time 0, and modi®ed (p<0.05) fractional rates of Ti decay depending on the basal diet
Fig. 2. Effect of the diet type (maize, barley±wheat and maize±CMC) and sepiolite level supplementation on digesta water relative viscosity (WRV) at Day 22. Different letters re¯ect signi®cant differences between treatments.
considered. From these results, sepiolite increased the mean retention time of digesta with the no-viscous diet (maize) and decreased with the medium- and high-viscous treatment (interaction dietsepiolite,p<0.05).
Direct measurements of digesta kinetics in the gizzard, small intestine, caeca and the whole digestive tract are also presented in Table 3. Average whole-tract retention times were ranked in a manner similar to the indirect measurements. High-viscous treatments promoted longer retention times in the whole digestive tract (3.41 h) than maize (2.93 h) and barley±wheat based diets (2.72 h), showing results similar to the indirect measurements. The small intestine was the compartment in which digesta were retained longer, and showed the largest differences among experimental treatments. With the maize±CMC diet digesta were retained in the small intestine an average of 2.59 h, signi®cantly longer than barley±wheat (1.74 h) and maize (1.63 h). In the small intestine, sepiolite incorporation (10, 20 vs. 0 g/kg) increased the retention times of digesta with non-viscous treatments (maize; 1.97, 2.10 vs. 1.63 h), but decreased (interaction dietsepiolite, p<0.05) with the high-viscous treatment (maize±CMC; 1.89, 2.20 vs. 2.59 h). Sepiolite also promoted signi®cant decreases (p<0.05) in the mean retention time in the gizzard with the three basal diets considered. No signi®cant differences in the digesta kinetics were observed between the treatment incorporating 10 or 20 g/kg of sepiolite.
4. Discussion
Different mechanisms have been proposed to explain the detrimental effects of dietary NSP on poultry digestion. The simplest explanation is thatb-glucans and arabinoxylans
Fig. 3. Faecal excretion curves of Ti (absorbance reading at 410 nm) after substitution of a marked (0.5% TiO2)
The effects of sepiolite incorporation (0, 10 or 20 g/kg) on the kinetic parameters (a,bandm) of the non-cumulative faecal excretion curves of Ti, mean retention times (T50 or MRT) on days 19±20 and mean retention times in gizzard, small intestine and caeca on Day 22 of animals fed on maize (C), barley±wheat (BW) and maize10 g/kg CMC (CMC)a
Variable Kinetic parameters Retention time (h)
a b(hÿ1) m(h) T50 MRT Gizzard Small intestine Caeca Whole tract
C 0 0.402 1.695 4.23 2.13 4.83 0.43 1.63 0.65 2.71
C 10 0.365 1.362 4.59 2.32 5.33 0.32 1.97 0.63 2.93
C 20 0.401 1.322 4.37 2.22 5.13 0.32 2.10 0.69 3.13
BW 0 0.350 1.345 3.81 1.97 4.57 0.35 1.74 0.85 2.96
BW 10 0.333 1.772 3.60 1.83 4.18 0.31 1.63 0.59 2.54
BW 20 0.328 1.711 3.77 1.91 4.36 0.23 1.88 0.55 2.68
CMC 0 0.347 1.325 5.28 2.66 6.05 0.33 2.59 0.78 3.71
CMC 10 0.301 1.553 5.14 2.58 5.81 0.28 1.89 0.77 3.25
CMC 20 0.318 1.348 5.14 2.58 5.90 0.20 2.20 0.86 3.27
S.E. 0.0077 0.1364 0.152 0.074 0.165 0.050 0.180 0.131 0.238
Contrast signi®cance
from the endosperm cell wall could restrict access of digestive enzymes to nutrients found in the cereals endosperm (Edwards et al., 1988; Bedford, 1996). However, similar detrimental effects on growth performance and digestibility have been obtained in broiler chickens after consumption of isolated viscous NSP, as CMC (Smits et al., 1997), pentosans from wheat (Choct et al., 1996) and glucans from barley (White et al., 1981). An alternative explanation, that has been more widely accepted, is that soluble NSP promote increases of digesta viscosity, which could affect intestinal digestion by limiting the diffusion of digestive enzymes and nutrients (Choct et al., 1996), and through primary or secondary increases on the microbial activity in the small intestine (Edwards et al., 1988).
In the present experiment, three diets with an increasing amount of soluble viscous NSP, either from raw ingredients, such as barley or wheat grain, or by increasing the amount of high-viscous polysaccharides arti®cially incorporated in the diet (CMC), were employed. As described above, basal diets effectively promoted a broad range in intestinal viscosity and changes on the productive and digestive results. High-viscous maize±CMC, when compared with maize, depressed productive performance and increased the proportion of wet droppings. Consumption of barley±wheat or maize±CMC depressed also the apparent digestibility of nutrients, probably associated with an increase in the digesta viscosity. Differences were especially important in fat digestibility. A similar pattern was observed in birds fed on diets containing wheat pentosans (Choct and Annison, 1992). Low bile acid concentration in digesta of young birds may limit lipid absorption (InÄarrea et al., 1989) and make lipid digestibility particularly sensitive to the presence of dietary viscous NSP (DaÈnicke et al., 1995; Choct et al., 1996). In particular, viscous digesta have been related with signi®cant longer retention times in the gastrointestinal tract (Van Der Klis and Van Woorst, 1993) and increases in the microbial activity in small intestine (Annison, 1993), which could promote the deconjugation of bile acids and signi®cant decreases in the digestibility of fat.
Sepiolite is a hydrated magnesium silicate clay (Si12Mg8O30 (OH)4(H2O)48H2O) which manifests physical and chemical properties that encourage its technological application as lubricant of ground diets and pelleting agent during feed processing procedures. Recent reports have also suggested a direct effect of sepiolite on the nutrient digestibility and bird performance (Tortuero, 1982). On the present results, sepiolite supplementation (10 or 20 g/kg) increased signi®cantly the digestibility of OM and N with all diets. However, no signi®cant differences were obtained on the live weight and feed:gain conversion rates. Thus, the counteracting effects between the reported increases on digestibility and the simultaneous OM dilution with sepiolite, a mineral non-digestible ingredient, was observed.
treatment, as found by Tortuero et al. (1992), but reduced times of retention in the whole-tract and small intestine with the medium- (barley±wheat) or high-viscous (maize±CMC) treatment. Both the independent procedures ranked treatment similarly. Comparable results were previously observed in our laboratory (Ouhida, 1999). Sepiolite promoted signi®cant increases in the times of retention of digesta in the gastrointestinal tract of birds fed on barley±wheat diets treated with enzymes (40 min longer, of which 20 min represented longer retention in the small intestine). These differences were not observed when this diet was not supplemented with enzymes (Ouhida, 1999). Apparently, sepiolite should be able to slow down more ef®ciently non-viscous digesta (maize or enzyme-treated barley-wheat) than the medium- or high-viscous digesta. It should be pointed out that signi®cant increases in the OM digestibility with sepiolite have not been always associated with longer retention times of digesta in the gastrointestinal tract, which suggests that other digestive parameters could be involved in the nutrient digestibility changes.
In this respect, it could be relevant that sepiolite is a tabular clay (Alvarez, 1984) with a high speci®c surface (Wolter et al., 1990) and a moderate absorption and NH3retention capacity. With these characteristics, it might promote signi®cant modi®cations in the physical and chemical properties of digesta contents. Schutte and Langhout (1998) found that sepiolite supplementation in wheat±soya based diets reduced ileal viscosity of 30-day-old broilers and proposed, through the observation of lower VFA concentrations in caeca (Langhout, 1998), that sepiolite in digesta could bind detrimental microbes promoted by high-soluble NSP diets. The present experiment promoted a broad range of dietary viscosities in digesta, but no measures of microbial activity were obtained. Viscosity of digesta in the jejunum was consistently reduced with the sepiolite supplementation, reaching statistical signi®cance on the viscosity of digesta in the ileum of animals fed on high viscous-promoting treatments. Although these decreases were relatively low, differences were similar to those obtained previously (Ouhida, 1999) after
b-glucanase and arabnoxylanase supplementation of barley±wheat based diets. These changes were associated with signi®cant increases on the OM digestibility and reinforce the reliability of a likely role of viscosity on the mechanisms promoted by sepiolite in poultry diets.
In conclusion, results obtained in the present experiment con®rmed a positive effect of sepiolite on the OM digestibility of broiler chicken diets of different viscosities. No relationships were established between these increases and consistent changes on the times of retention of digesta in the gastrointestinal tract, which suggests that other digestive changes, such as intestinal viscosity or microbial control, could be involved. Further work is proposed to clarify the causal mechanisms likely involved in the use of sepiolite to improve the nutritive value of different diets.
Acknowledgements
The authors wish to express their gratitude to Tolsa S.A. Ctra. Vallecas-Mejorada Del Campo, 28031, Madrid, Spain, for founding this research.
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