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Effects of varying vicine, convicine and tannin contents of faba bean seeds (Vicia faba L.) on nutritional values for broiler chicken
Animal Feed Science and Technology 150 (2009) 114–121
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Effects of varying vicine, convicine and tannin contents of faba bean seeds (Vicia faba L.) on nutritional values for broiler chicken ˜ a, J.P. Métayer a, K. Crépon b, G. Duc c,∗ M. Vilarino a
ARVALIS – Institut du végétal, Station Expérimentale, 41100 Villerable, France UNIP, Union Nationale Interprofessionnelle des Protéagineux, 12 av George V, 75008 Paris, France INRA Institut National de la Recherche Agronomique, UMR 102, Génétique et Ecophysiologie des Légumineuses à Graines, 21110-F Bretenières, France
b c
a r t i c l e
i n f o
Article history: Received 13 March 2006 Received in revised form 5 August 2008 Accepted 12 August 2008 Keywords: Vicia faba Vicine Convicine Tannins Broiler chicken
a b s t r a c t Faba bean tannins are known to decrease apparent protein digestibility. The vicine and convicine contained in the seeds reduce egg size in laying hens, but their effects in broiler chickens have never been reported. Vicia faba genotypes have been identified which result in a major reduction of these compounds in seeds. Tannins are located in seed hulls whereas vicine and convicine (VC) are located in the cotyledons and therefore they can be separated and re-combined in reconstituted faba beans (RFB) by mixing hulls and cotyledons from genotypes with variable tannin and VC contents, in order to evaluate their effects alone or in interaction. Six RFB were built with high, medium or low tannin contents (means of 9.9, 5.8 and 1.3 g/kg, respectively) combined with high or low VC contents (means of 10.1 and 0.7 g/kg, respectively). The six RFB were incorporated in the experimental diets and fed to broiler chickens in a balance experiment to measure apparent protein digestibility and apparent metabolisable energy (AMEn) content. The AMEn was lower for the high- than for the lowtannin RFB (12.08 MJ/kg versus 12.48 MJ/kg DM; P<0.001). Also, the AMEn was lower for the high- than for the low-VC RFB (11.99 MJ/kg versus 12.34 MJ/kg DM; P<0.05). The negative effects of the two anti-nutritional factors on energy were additive and a linear regression on their contents explains 80% of the variability.
Abbreviations: DM, dry matter; AMEn, apparent metabolisable energy, nitrogen corrected; TTAD-N, total tract apparent digestibility of protein; GE, gross energy; VC, vicine and convicine; LVC, low vicine and convicine; HVC, high vicine and convicine; LT, low tannin; MT, medium tannin; HT, high tannin; RFB, reconstituted faba bean. ∗ Corresponding author. Tel.: +33 3 80693148; fax: +33 3 80693263. E-mail address: [email protected] (G. Duc). 0377-8401/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.anifeedsci.2008.08.001
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The total tract apparent protein digestibility was lower for the highthan for the low-tannin RFB (0.75 versus 0.86; P<0.001) with no significant interaction with VC contents, which in contrast have no significant effect on this trait. The results confirm the nutritional advantages of faba bean varieties free of tannins and low in vicine and convicine content in diets for poultry. © 2008 Elsevier B.V. All rights reserved.
1. Introduction Due to its high protein content and broad area of potential cultivation, faba bean (Vicia faba L.) could occupy a larger share of the poultry feed market. Tannins, vicine and convicine are constituents of faba bean seed with anti-nutritive effects in monogastric animals (Olaboro et al., 1981; Grosjean et al., 2000). Over the last 35 years, breeding efforts in Europe have revealed a large genetic variability within the faba bean species, which has been exploited to improve yield potential and seed composition (Bond and Duc, 1994; Duc, 1997). The condensed tannin content of conventional faba bean genotypes varies from 5 to 10 g/kg DM (Duc et al., 1999). Tannins are concentrated in the seed hulls and therefore, they are eliminated by dehulling. Two distinct ZT genes were discovered in faba bean (Picard, 1976) eliminating tannins from the seed and reducing also the proportion of hulls from 143 to 127 g/kg dry matter (DM) (Duc et al., 1999). The vicine and convicine (VC) content ranges from 6 to 14 g/kg of the seed DM (Duc et al., 1999). VC are heat-stable seed constituents located in the cotyledons that cannot be removed easily by technological processes in conventional cultivars. But a mutation at VC-locus reduces 10–20-fold the content of VC in faba bean seeds (Duc et al., 1989). The VC- and ZT genes are independent and can be introgressed in a single genotype to produce double low varieties. Faba bean tannins decreased protein digestibility in poultry due to formation of tannin–protein complexes (Lacassagne et al., 1988; Grosjean et al., 2000). Tannins also reduced energy (Grosjean et al., 2000) and starch digestibilities (Lacassagne et al., 1988) but the effects were not always significant. However, observed a negative effect of tannins on. In the laying hen, Olaboro et al. (1981) demonstrated that VC reduced egg size and Muduuli et al. (1981) related the decrease to erythrocyte haemolysis. However, the effects of VC on digestibility of dietary components or on AMEn content of faba beans have not been reported. The aim of this study was to quantify the effects of removing tannins and VC from faba bean seeds on performance of broilers. Because isogenic lines carrying different allelic combinations at VC- and ZT genes were not available and to reduce the risk of confounding the secondary effect of ZT gene on the proportion of hulls with the effect of the anti-nutritional factors, we reconstituted the faba bean seeds by combining the hulls and the cotyledons originated from a low or high tannin genotype and from a low or high VC genotype in constant proportions. This strategy offers a more accurate evaluation of the individual effects of each of these two anti-nutritional factors and their interactions on nutrient digestibility and AMEn content in broilers. 2. Materials and methods 2.1. Faba bean genotypes and the reconstituted faba bean seeds production Three spring faba bean genotypes were chosen according to their contrasting tannin and VC contents: (1) cv Gloria with high levels of VC (HVC) and low tannin (LT) content determined by ZT1 gene, (2) cv Divine with low levels of VC (LVC) determined by VC- gene and high tannin (HT) content and (3) cv Meli with HVC and HT content. The lines were multiplied in a large field scale in 2002 in order to produce seeds for nutritional experiments. Hulls and cotyledons were separated in a crushing mill (Damman-Croes, Westvlaanderen, Belgium), and then the hulls were aspired on a grain cleaner (Denis D50, Brou, France). On average, hulls and cotyledons represented 125 and 875 g/kg respectively of the faba bean seeds. Then, hulls (1.5 kg) and cotyledons (10.5 kg) of the different cultivars were mixed to
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Table 1 Composition and characteristics of the experimental diets (g/kg unless indicated otherwise) Basal diet
Reconstituted faba bean diets HVC-HTa
HVC-MTb
HVC-LTc
LVC-HTd
LVC-MTe
LVC-LTf
152.3 147.7 142.7 13.3 500.0 7.6 18.2 1.2 1.0 3.0 0.7 0.3 12.0
152.3 147.7 142.7 13.3 500.0 7.6 18.2 1.2 1.0 3.0 0.7 0.3 12.0
152.3 147.7 142.7 13.3 500.0 7.6 18.2 1.2 1.0 3.0 0.7 0.3 12.0
152.3 147.7 142.7 13.3 500.0 7.6 18.2 1.2 1.0 3.0 0.7 0.3 12.0
152.3 147.7 142.7 13.3 500.0 7.6 18.2 1.2 1.0 3.0 0.7 0.3 12.0
152.3 147.7 142.7 13.3 500.0 7.6 18.2 1.2 1.0 3.0 0.7 0.3 12.0
Calculated nutrient content (g/kg dry matter) Crude proteinh 207.0 227.7 Calcium 10.9 11.0 Total phosphorus 6.8 7.4 Available phosphorus 3.9 4.0 Sodium 1.6 1.5 Chlorine 1.8 2.0 Lysine 11.6 14.1 Methionine 6.1 5.5 Methionine + cysteine 9.7 8.8 Threonine 8.4 8.9 Tryptophan 2.8 2.6
228.7 11.0 7.4 4.0 1.5 2.0 14.2 5.5 8.8 8.9 2.6
228.2 11.0 7.4 4.0 1.5 2.0 14.1 5.5 8.8 8.9 2.6
233.2 11.0 7.4 4.0 1.5 2.0 14.5 5.5 8.9 9.0 2.7
232.7 11.0 7.4 4.0 1.5 2.0 14.4 5.5 8.9 9.0 2.6
232.2 11.0 7.4 4.0 1.5 2.0 14.4 5.5 8.9 9.0 2.6
Ingredient Maize Soyabean meal Wheat Soyabean oil Faba beans Calcium carbonate Dicalcium phosphate Sodium bicarbonate l-lysine, HCl dl-methionine l-threonine l-tryptophan Premixg
a b c d e f
319.3 309.7 299.2 27.8 0 7.6 18.2 1.2 1.0 3.0 0.7 0.3 12.0
HVC-HT: high vicine and convicine cotyledons + high tannins hulls (cv. Meli + Meli). HVC-MT: high vicine and convicine cotyledons + medium tannins hulls (cv. Meli + Meli and Gloria). HVC-LT: high vicine and convicine cotyledons + low tannins hulls (cv. Meli + Gloria). LVC-HT: low vicine and convicine cotyledons + high tannins hulls (cv. Divine + Meli). LVC-MT: low vicine and convicine cotyledons + medium tannins hulls (cv. Divine + Meli and Gloria). LVC-LT: low vicine and convicine cotyledons + low tannins hulls (cv. Divine + Gloria).
g The premix provided the following per kg of diet; Fe, 30 mg; Cu, 12 mg; Zn, 60 mg; Mn, 90 mg; I, 1.2 mg; Se, 0.3 mg; Vitamin A, 15000 UI; Vitamin D3, 3000 UI; Vitamin E, 30 UI; Vitamin B1, 1 mg; Vitamin B2, 6 mg; Vitamin B6, 1 mg; Vitamin B12, 0.02 mg; Vitamin K3, 4 mg; Vitamin B3, 40 mg; choline, 400 mg; Diclazuril (Clinacox® , Janssen Pharmaceutica, Beerse, Belgium), 1 mg. h Measured values (n = 2).
reconstitute six faba bean formulas (12 kg per batch). To produce reconstituted faba beans (RFB) with medium tannin contents (MT), hulls from HT genotypes (0.75 kg) and LT genotypes (0.75 kg) were added to cotyledons. Finally the hulls and cotyledon mixtures were ground (2900 rpm, 58 m/s, Ecma, Bourgoin-Jallieu, France) and sieved through a 2-mm screen. The six RFB combined 3 levels of tannins (9.9, 5.8 and 1.3 g/kg) with 2 of VC (10.1 and 0.7 g/kg).
2.2. Experimental diets The composition and the characteristics of the experimental diets are presented in Table 1. Experimental feeds were formulated and manufactured by Arvalis – Institut du végétal (Boigneville, France). Before mixing, wheat, maize and soyabean meal were ground and passed through a 2-mm screen (Titan, 2000, Vitré, France). The basal diet was based on maize, soyabean meal and wheat (Table 1) and the six experimental diets contained 500 g RFB and 500 g basal diet per kg. All diets were pelleted (La Meccanica CLM200, Padova, Italy) with a 2.5-mm diameter and 35-mm length die.
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2.3. Birds management and design A total of 150 Ross PM3 male broiler chicks was used. Birds were placed in a floor pen up to 14 days of age and fed a common standard starter diet. Then, birds were weighed and 63 birds with a body weight in the center of the statistical distribution were used for the experiment. The design was completely randomised with 7 treatments and 9 replicates of one bird each per treatment. 2.4. Balance experiment The balance experiment was carried out from 14 to 24 days of age using the method described by Bourdillon et al. (1990). From day 14 to day 20 (adaptation period) birds were fed ad libitum their respective experimental diets. At day 20, chicks were fasted for 17 h, fed their respective experimental diet for 55 h and fasted again for 17 h. Individual feed intake was measured from day 14 to day 24 and excreta were totally collected from each individual during the last 72 h (21–24 days of age). Daily collection of individual excreta on three days were pooled and stored at −18 ◦ C and then freeze-dried. Prior to analysis, samples were allowed to equilibrate with atmospheric moisture for 24 h and then ground to pass through a 0.5-mm screen. 2.5. Calculation The energy was corrected for N (AMEn) using a value of 34.4 kJ per g of N retained. Total tract apparent digestibility of protein (TTAD-N) was calculated after determining faecal N by the procedure of Terpstra and De Hart (1974). The nutritional value of RFB was calculated by difference between basal and test diet values. 2.6. Analytical methods Crude protein (N ×6.25) was measured according to the method of Dumas (AFNOR, 1997a) with a protein analyser LECO model FP 2000 (St Joseph, MI, USA). Protein content of excreta was determined using the method of Terpstra and De Hart (1974). Water insoluble cell wall content was determined according to the method of Carré and Brillouet (1986). Gross energy (GE) of excreta and feeds was determined with an adiabatic bomb calorimeter (Ika-Werke C7000, Staufen, Germany) standardized with benzoic acid. Starch content was measured in feeds and excreta using the enzymatic method (AFNOR, 1997b). Tannin content (mg gallic acid equivalents/kg) was determined according to BuOHHCl method as described by Duc et al. (1995) and VC content by HPLC as described by Duc et al. (1989). 2.7. Statistical analysis Analyses of variance of AMEn, AMEn/GE and TTAD-N of diets and RFB were performed by two-way ANOVA using Statview 5.0 Software (SAS Institute Inc, 2002). Statistical significance of the variance and means was tested by Fisher and Student–Newman–Keuls test respectively. The relationship between values of nutritional parameters and T and VC contents of RFB was evaluated by linear regression analysis using Statbox 6.23 (Grimmer Soft, Neuilly sur Seine, France). 3. Results 3.1. Chemical composition of faba bean batches The six RFB had similar crude protein, starch and water-insoluble cell wall contents (Table 2). In contrast, the differences in the genotypes for anti-nutritional factors content resulted in RFB varying from 10.1 to 0.7 g VC/kg and from 9.9 to 5.8 and 1.3 g tannins/kg for HT, MT and LT respectively.
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Table 2 Analysed composition of reconstituted faba beans (g/kg of DM unless indicated otherwise)
Dry matter Crude protein Water insoluble cell walls Starch Gross energy, MJ/kg of DM Condensed tannins Vicine Convicine a b c d e f
HVC-HTa
HVC-MTb
HVC-LTc
LVC-HTd
LVC-MTe
LVC-LTf
838 301 189 457 18.8 9.8 6.5 2.8
838 301 182 476 18.8 6.1 7.3 3.1
832 302 167 464 18.8 1.4 7.5 3.2
835 313 183 445 18.9 9.9 0.7 0.1
835 312 184 445 18.8 5.4 0.5 0.1
839 310 201 438 18.8 1.2 0.5 0.1
HVC-HT: high vicine and convicine cotyledons + high tannins hulls (cv. Meli + Meli). HVC-MT: high vicine and convicine cotyledons + medium tannins hulls (cv. Meli + Meli and Gloria). HVC-LT: high vicine and convicine cotyledons + low tannins hulls (cv. Meli + Gloria). LVC-HT: low vicine and convicine cotyledons + high tannins hulls (cv. Divine + Meli). LVC-MT: low vicine and convicine cotyledons + medium tannins hulls (cv. Divine + Meli and Gloria). LVC-LT: low vicine and convicine cotyledons + low tannins hulls (cv. Divine + Gloria).
Table 3 Nutritional values of diets and reconstituted faba beans for poultry (on DM basis) and statistical significance of main factors effects and their interaction Basal diet Diets AMEnj AMEn/GEk TTAD-Nl
Means 13.07 0.690 0.790
Reconstituted faba beans AMEnj AMEn/EBk TTAD-Nl
HVC-HTa
HVC-MTb
HVC-LTc
LVC-HTd
LVC-MTe
LVC-LTf
Tg
12.23 0.661 0.764
12.15 0.658 0.782
12.35 0.671 0.825
12.34 0.667 0.778
12.31 0.665 0.788
12.61 0.683 0.842
RSDh 0.28 0.15 0.28
11.97 0.638 0.741
11.79 0.629 0.774
12.21 0.651 0.850
12.18 0.645 0.768
12.11 0.645 0.784
12.74 0.680 0.879
0.54 0.29 0.50
a
HVC-HT: high vicine and convicine cotyledons + high tannins hulls (cv. Meli + Meli).
b
HVC-MT: high vicine and convicine cotyledons + medium tannins hulls (cv. Meli + Meli and Gloria). HVC-LT: high vicine and convicine cotyledons + low tannins hulls (cv. Meli + Gloria). LVC-HT: low vicine and convicine cotyledons + high tannins hulls (cv. Divine + Meli).
c d e f
VCg
T xVCg
P>Fi ** * ** * *** NS
NS NS NS
** ** ***
NS NS NS
* * NS
LVC-MT: low vicine and convicine cotyledons + medium tannins hulls (cv. Divine + Meli and Gloria). LVC-LT: low vicine and convicine cotyledons + low tannins hulls (cv. Divine + Gloria).
T: tannins; VC: vicine and convicine; T × VC: interaction T x VC. RSD: residual standard deviation. i Probability of Fisher’s test of main factors effects and their interaction, after polyfactorial variance analysis. NS: non significant effect P>0.05; *P<0.05; **P<0.01; ***P<0.001. j AMEn (MJ/kg): apparent metabolisable energy, nitrogen corrected. g
h
k l
AMEn/GE coefficient: apparent metabolisable energy, nitrogen corrected/gross energy. TTAD-N coefficient: total tract apparent digestibility of protein.
3.2. Nutritional value of reconstituted faba beans There was no significant interaction between tannin and VC factors for any studied trait. The effects of tannins were significant for all nutritional traits measured whereas the effects of VC were only significant for AMEn and gross energy digestibility AMEn/GE (Table 3). The average AMEn of the six RFB was 12.17 MJ/kg DM. The average AMEn was lower (P<0.001) for the high- than for low-tannin mixtures, 12.08 and 12.48 MJ/kg DM respectively (Table 3). For the HVC and LVC mixtures, the average AMEn was 11.99 and 12.34 MJ/kg DM respectively (P<0.05). The AMEn of the RFB low in both tannins and VC was the highest (12.74 MJ/kg DM). The standard deviation was higher for the RFB containing high levels of both anti-nutritional factors than for RFB containing low levels (0.8 MJ/kg versus 0.37 MJ/kg DM).
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The coefficient of energy digestibility was higher for LVC-LT RFB than for the HVC-HT and HVCMT RFB (0.68 versus 0.64 and 0.63, respectively) (P<0.01). Starch digestibility was above 0.99 for all treatments. The coefficients of TTAD-N were lower (P<0.001) for HT and MT RFB than for LT RFB. The TTAD-N was 0.75 for HT RFB and 0.86 for LT RFB (P<0.001). In contrast, VC had no significant effect on TTAD-N. 3.3. Prediction of AMEn and apparent total tract digestibility of protein Energy digestibility and TTAD-N were negatively correlated with tannin content (r = −0.76, P<0.05 and r = −0.95, P<0.001, respectively). The linear model, predicting AMEn value from tannin content [AMEn (MJ/kg DM) = −0.0603*tannin (g/kg DM) + 12.53] explained only 50% of the variance observed. The linear model including both tannins and VC [AMEn (MJ/kg DM) = 12.669–0.052*tannin (g/kg DM) – 0.038 VC (g/kg DM)] explained 80% of the variance with an estimated error of 0.19 MJ/kg DM. The linear model predicting TTAD-N from tannin content [TTAD-N = −0.014*tannin (g/kg DM) + 0.878] explained 91% of the variance of the protein digestibility coefficient. 4. Discussion The AMEn value obtained for the HT RFB was 12.1 MJ/kg DM, which agrees with values of 12.3 MJ/kg DM and 11.9 MJ/kg DM measured for high-tannin faba bean cultivars found by Mateos and Puchal (1981a) and Grosjean et al. (2000). The AMEn value of LT RFB was 12.5 MJ/kg DM, in agreement with the value of 12.8 MJ/kg DM found by Grosjean et al. (2000) with tannin-free faba bean cultivars. 4.1. Effect of tannins on faba bean nutritional values It is generally accepted that tannins reduce feed intake in poultry (Iji et al., 2004) interfere with digestive enzyme activity and form complexes with nutrients reducing their digestibility (Jansman and Longstaff, 1993). Feed intake reduction depends probably on the quantity of tannins ingested, since Jansman et al. (1993) showed no decrease in feed intake in broilers fed 300 g/kg high-tannin faba bean, whereas Helsper et al. (1996) observed a significant reduction in feed intake in broilers fed 500 g/kg high-tannin faba bean. Iji et al. (2004) found negative, neutral or positive effects of tannins depending on their concentration in the diet. The predominant effect of tannins in broilers was a reduction in protein and amino acid digestibility (Ortiz et al., 1993; Jansman and Longstaff, 1993; Brufau et al., 1998) although negative effects have also been observed on starch digestibility (Lacassagne et al., 1988; Flores et al., 1994). In the current study, tannins reduced AMEn by 0.5 MJ/kg when HT and low LT RFB were compared. This difference cannot be explained by differences in starch content because it was similar for all RFB. However, Grosjean et al. (2000) found that energy digestibility was significantly affected by tannin content of faba bean in adult cockerels. The present experiment demonstrates that tannins have a negative effect on the digestibility of protein that can partially explain the differences observed in AMEn values. The observed TTAD-N was 13.8% higher for LT- than for HT RFB, which is in agreement with values obtained by Lacassagne et al. (1988) on adult cockerels. 4.2. Effect of vicine and convicine on faba bean nutritional values Very few studies have assessed the impact of VC on the nutritional value of faba bean for poultry and most of them were conducted with laying hens (Muduuli et al., 1981; Mateos and Puchal, 1981b; Grosjean et al., 2000). These studies showed negative effects of VC on egg weight and hypothesized that VC affected the metabolism of the laying hen to explain them. Vicine has been suggested to produce peroxidants that cause lipid peroxidation and erythrocyte hemolysis and interfere with normal lipid metabolism in the hen. In contrast, Hegazy and Marquardt (1984) did not detect any effect on the metabolism of young chickens.
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In the current study, the negative effect of VC on the AMEn of broilers was significant in contrast to the study of Grosjean et al. (2000) who did not detect any effect of feeding 2 HVC to adult cockerels. However in this study only two genotypes of faba beans were used to test the effect of VC on AMEn values and the homogeneity of contents of the accompanying seed compounds was not measured. In the current study the highest AMEn value was obtained with the faba bean low in VC and tannins content, indicating that the effects of these two anti-nutritional factors on AMEn were additive. Accurate mediation of the AMEn content of faba beans should be based on linear models incorporating tannins and VC contents. The present study did not detect any significant effect of VC on TTAD-N, in agreement with data of Grosjean et al. (2000). 5. Conclusion The results confirm that tannins reduced apparent energy and protein digestibility of faba bean in broiler chickens. Also, vicine and convicine contained in faba bean seeds had a negative effect on AMEn but not on TTAD-N. No interactions between tannin and VC contents were observed. These results confirm the interest of faba bean varieties free of tannins and low in vicine and convicine contents in diets for broilers. Acknowledgements This work has been financially supported by the Union Nationale Interprofessionnelle des Plantes riches en protéines (UNIP, France) and by the Office National Interprofessionnel des Oléagineux (ONIOL, France). The authors thank Mr P. Marget and Mr H. Houtin INRA-UMR 102 LEG Dijon and the Experimental Unit of INRA Domaine d’Epoisses 21110 Bretenières, F. for seed multiplication. We thank the technicians who carried out the animal trial at the Experimental Station (Arvalis – Institut du végétal, France). We thank Dr P. Dulieu (RD-Biotech, Besanc¸on, F.) and Mrs F. Cassecuelle (INRA-UMR 102 LEG Dijon, F.) for determination of vicine and convicine contents. We thank Dr R. Thompson and Mr D. Coles for the English language corrections in this paper. References AFNOR, 1997a. Association Franc¸aise de Normalisation. Method NF V 18-120. AFNOR Editions, Paris. AFNOR, 1997b. Association Franc¸aise de Normalisation. Method NF V 18-121. AFNOR Editions, Paris. Bond, D.A., Duc, G., 1994. Plant breeding as a means for reducing anti-nutritional factors in grain legumes. In: Van der Poel, A.F.B., Huisman, J., Saini, H.S. (Eds.), Recent Advances of Research in Antinutritional Factors in Legume Seeds, vol. 70. E.A.A.P, Wageningen pers, pp. 379–396. Bourdillon, A., Carré, B., Conan, L., Duperray, J., Huyghebaert, G., Leclercq, B., Lessire, M., McNab, J., Wiseman, J., 1990. European reference method for the in vivo determination of metabolisable energy with adult cockerels: reproductibility, effect of feed intake and comparison with individual laboratory methods. Br. Poult. Sci. 31, 557–565. Brufau, J., Boros, D., Marquardt, R.R., 1998. Influence of growing season, tannin content and autoclave treatment on the nutritive value of near-isogenic lines of faba beans (Vicia faba L.) when fed to Leghorn chicks. Br. Poult. Sci. 39, 97–105. Carré, B., Brillouet, J.M., 1986. Yield and composition of cell wall residues isolated from various feedstuffs used for non-ruminant farm animals. J. Sci. Food Agric. 37, 345–351. Duc, G., 1997. Faba bean (Vicia faba L.). Field Crops Res. 53, 99–109. Duc, G., Sixdenier, G., Lila, M., Furstoss, V., 1989. Search of genetic variability for vicine and convicine content in Vicia faba L. A first report of a gene which codes for nearly zero-vicine and zero-convicine contents. In: Huisman, A.J.M., Van der Poel, A.F.B., Liener, I.E. (Eds.), Recent Advances of Research in Antinutritionnal Factors in Legumes Seeds. Pudoc, Wageningen, Netherlands, pp. 305–313. Duc, G., Brun, N., Merghem, R., Jay, M., 1995. Genetic variation in tanning related characteristics in faba bean seeds (Vicia faba L.) and their relationship with seed coat colour. Plant Breed. 114, 272–274. Duc, G., Marget, P., Esnault, R., Le Guen, J., Bastianelli, D., 1999. Genetic variability for feeding value of faba bean seeds (Vicia faba L.). Comparative chemical composition of isogenics involving zero-tannin and zero-vicine genes. J. Agric. Sci. 133, 185–196. Flores, M.P., Castanon, J.I.R., McNab, J.M., 1994. Effect of tannins on starch digestibility and TMEn of triticale and semipurified starches from triticale and field beans. Br. Poult. Sci. 35, 281–286. Grosjean, F., Bourdillon, A., Rudeaux, F., Bastianelli, D., Peyronnet, C., Duc, G., Lacassagne, L., 2000. Valeur alimentaire pour la volaille de féveroles isogéniques (Vicia faba L.) avec ou sans tannins et avec ou sans vicine–convicine. Sci. Technol. Avic. 32, 17–23. Hegazy, M.I., Marquardt, R.R., 1984. Metabolism of vicine and convicine in rat tissues: absorption and excretion patterns and sites of hydrolysis. J. Sci. Food Agric. 35, 139–146.
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Helsper, J.P.F.G., Van Loon, Y.P.J., Kwakkel, R.P., Van Norel, A., Van der Poel, A.F.B., 1996. Growth of broiler chicks fed diets containing tannin-free and tannin-containing near-isogenic lines of faba bean (Vicia faba L.). J. Agric. Food Chem. 44, 1070–1075. Iji, P., Khumalo, K., Slippers, S., Gous, R., 2004. Intestinal function and body growth of broiler chickens on maize-based diets supplemented with mimosa tannins and a microbial enzyme. J. Sci. Food Agric. 84, 1451–1458. Jansman, A.J.M., Longstaff, M., 1993. Nutritional effects of tannins and vicine/convicine in legume seeds. In: Van der Poel, A.F.B., Huisman, J., Saini, H.S. (Eds.), Recent Advances of Research in Antinutritional Factors in Legume Seeds, 70. E.A.A.P, Wageningen pers, pp. 301–316. Jansman, A.J.M., Huisman, J., Van der Poel, A.F.B., 1993. Performance of broiler chicks fed diets containing different varieties of faba bean (Vicia faba L.). Arch. Geflügel. 57, 220–227. Lacassagne, L., Francesch, M., Carré, B., Melcion, J.P., 1988. Utilization of tannin-containing and tannin-free faba beans (Vicia faba) by young chicks: effects of pelleting feeds on energy, protein and starch digestibility. Anim. Feed Sci. Technol. 20, 59–68. Mateos, G.G., Puchal, F., 1981a. Raw broad beans (Vicia faba L.) as an energy and protein source for broiler chicks. Poult. Sci. 60, 2486–2493. Mateos, G.G., Puchal, F., 1981b. The nutritional value of broad bean for laying hens. Br. Poult. Sci. 23, 1–6. Muduuli, D., Marquardt, R., Guenter, W., 1981. Effect of dietary vicine on the productive performance of laying chickens. Can. J. Anim. Sci. 61, 757–764. Olaboro, G., Marquardt, R., Campbell, L.D., Fröhlich, A.A., 1981. Purification, identification and quantification of an egg-weightdepressing factor (vicine) in fababeans (Vicia faba L.). J. Sci. Food Agric. 32, 1163–1171. Ortiz, L.T., Centeno, C., Trevino, J., 1993. Tannins in faba beans: effects on the digestion of protein and amino acids in growing chicks. Anim. Feed Sci. Technol. 41, 271–278. Picard, J., 1976. Aperc¸u sur l’hérédité du caractère absence de tanins dans les graines de féverole (Vicia faba L.). Ann. Amél. Plantes 26, 101–106. Institute Inc, S.A.S., 2002. Statview 5.0 Software. Institute Inc., Cary, NC, USA. Terpstra, K., De Hart, N., 1974. The estimation of urinary nitrogen and faecal nitrogen in poultry excreta. J. Anim. Phys. Anim. Nutr. 32, 306–320.
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Effects of varying vicine, convicine and tannin contents of faba bean seeds (Vicia faba L.) on nutritional values for broiler chicken ˜ a, J.P. Métayer a, K. Crépon b, G. Duc c,∗ M. Vilarino a
ARVALIS – Institut du végétal, Station Expérimentale, 41100 Villerable, France UNIP, Union Nationale Interprofessionnelle des Protéagineux, 12 av George V, 75008 Paris, France INRA Institut National de la Recherche Agronomique, UMR 102, Génétique et Ecophysiologie des Légumineuses à Graines, 21110-F Bretenières, France
b c
a r t i c l e
i n f o
Article history: Received 13 March 2006 Received in revised form 5 August 2008 Accepted 12 August 2008 Keywords: Vicia faba Vicine Convicine Tannins Broiler chicken
a b s t r a c t Faba bean tannins are known to decrease apparent protein digestibility. The vicine and convicine contained in the seeds reduce egg size in laying hens, but their effects in broiler chickens have never been reported. Vicia faba genotypes have been identified which result in a major reduction of these compounds in seeds. Tannins are located in seed hulls whereas vicine and convicine (VC) are located in the cotyledons and therefore they can be separated and re-combined in reconstituted faba beans (RFB) by mixing hulls and cotyledons from genotypes with variable tannin and VC contents, in order to evaluate their effects alone or in interaction. Six RFB were built with high, medium or low tannin contents (means of 9.9, 5.8 and 1.3 g/kg, respectively) combined with high or low VC contents (means of 10.1 and 0.7 g/kg, respectively). The six RFB were incorporated in the experimental diets and fed to broiler chickens in a balance experiment to measure apparent protein digestibility and apparent metabolisable energy (AMEn) content. The AMEn was lower for the high- than for the lowtannin RFB (12.08 MJ/kg versus 12.48 MJ/kg DM; P<0.001). Also, the AMEn was lower for the high- than for the low-VC RFB (11.99 MJ/kg versus 12.34 MJ/kg DM; P<0.05). The negative effects of the two anti-nutritional factors on energy were additive and a linear regression on their contents explains 80% of the variability.
Abbreviations: DM, dry matter; AMEn, apparent metabolisable energy, nitrogen corrected; TTAD-N, total tract apparent digestibility of protein; GE, gross energy; VC, vicine and convicine; LVC, low vicine and convicine; HVC, high vicine and convicine; LT, low tannin; MT, medium tannin; HT, high tannin; RFB, reconstituted faba bean. ∗ Corresponding author. Tel.: +33 3 80693148; fax: +33 3 80693263. E-mail address: [email protected] (G. Duc). 0377-8401/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.anifeedsci.2008.08.001
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The total tract apparent protein digestibility was lower for the highthan for the low-tannin RFB (0.75 versus 0.86; P<0.001) with no significant interaction with VC contents, which in contrast have no significant effect on this trait. The results confirm the nutritional advantages of faba bean varieties free of tannins and low in vicine and convicine content in diets for poultry. © 2008 Elsevier B.V. All rights reserved.
1. Introduction Due to its high protein content and broad area of potential cultivation, faba bean (Vicia faba L.) could occupy a larger share of the poultry feed market. Tannins, vicine and convicine are constituents of faba bean seed with anti-nutritive effects in monogastric animals (Olaboro et al., 1981; Grosjean et al., 2000). Over the last 35 years, breeding efforts in Europe have revealed a large genetic variability within the faba bean species, which has been exploited to improve yield potential and seed composition (Bond and Duc, 1994; Duc, 1997). The condensed tannin content of conventional faba bean genotypes varies from 5 to 10 g/kg DM (Duc et al., 1999). Tannins are concentrated in the seed hulls and therefore, they are eliminated by dehulling. Two distinct ZT genes were discovered in faba bean (Picard, 1976) eliminating tannins from the seed and reducing also the proportion of hulls from 143 to 127 g/kg dry matter (DM) (Duc et al., 1999). The vicine and convicine (VC) content ranges from 6 to 14 g/kg of the seed DM (Duc et al., 1999). VC are heat-stable seed constituents located in the cotyledons that cannot be removed easily by technological processes in conventional cultivars. But a mutation at VC-locus reduces 10–20-fold the content of VC in faba bean seeds (Duc et al., 1989). The VC- and ZT genes are independent and can be introgressed in a single genotype to produce double low varieties. Faba bean tannins decreased protein digestibility in poultry due to formation of tannin–protein complexes (Lacassagne et al., 1988; Grosjean et al., 2000). Tannins also reduced energy (Grosjean et al., 2000) and starch digestibilities (Lacassagne et al., 1988) but the effects were not always significant. However, observed a negative effect of tannins on. In the laying hen, Olaboro et al. (1981) demonstrated that VC reduced egg size and Muduuli et al. (1981) related the decrease to erythrocyte haemolysis. However, the effects of VC on digestibility of dietary components or on AMEn content of faba beans have not been reported. The aim of this study was to quantify the effects of removing tannins and VC from faba bean seeds on performance of broilers. Because isogenic lines carrying different allelic combinations at VC- and ZT genes were not available and to reduce the risk of confounding the secondary effect of ZT gene on the proportion of hulls with the effect of the anti-nutritional factors, we reconstituted the faba bean seeds by combining the hulls and the cotyledons originated from a low or high tannin genotype and from a low or high VC genotype in constant proportions. This strategy offers a more accurate evaluation of the individual effects of each of these two anti-nutritional factors and their interactions on nutrient digestibility and AMEn content in broilers. 2. Materials and methods 2.1. Faba bean genotypes and the reconstituted faba bean seeds production Three spring faba bean genotypes were chosen according to their contrasting tannin and VC contents: (1) cv Gloria with high levels of VC (HVC) and low tannin (LT) content determined by ZT1 gene, (2) cv Divine with low levels of VC (LVC) determined by VC- gene and high tannin (HT) content and (3) cv Meli with HVC and HT content. The lines were multiplied in a large field scale in 2002 in order to produce seeds for nutritional experiments. Hulls and cotyledons were separated in a crushing mill (Damman-Croes, Westvlaanderen, Belgium), and then the hulls were aspired on a grain cleaner (Denis D50, Brou, France). On average, hulls and cotyledons represented 125 and 875 g/kg respectively of the faba bean seeds. Then, hulls (1.5 kg) and cotyledons (10.5 kg) of the different cultivars were mixed to
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Table 1 Composition and characteristics of the experimental diets (g/kg unless indicated otherwise) Basal diet
Reconstituted faba bean diets HVC-HTa
HVC-MTb
HVC-LTc
LVC-HTd
LVC-MTe
LVC-LTf
152.3 147.7 142.7 13.3 500.0 7.6 18.2 1.2 1.0 3.0 0.7 0.3 12.0
152.3 147.7 142.7 13.3 500.0 7.6 18.2 1.2 1.0 3.0 0.7 0.3 12.0
152.3 147.7 142.7 13.3 500.0 7.6 18.2 1.2 1.0 3.0 0.7 0.3 12.0
152.3 147.7 142.7 13.3 500.0 7.6 18.2 1.2 1.0 3.0 0.7 0.3 12.0
152.3 147.7 142.7 13.3 500.0 7.6 18.2 1.2 1.0 3.0 0.7 0.3 12.0
152.3 147.7 142.7 13.3 500.0 7.6 18.2 1.2 1.0 3.0 0.7 0.3 12.0
Calculated nutrient content (g/kg dry matter) Crude proteinh 207.0 227.7 Calcium 10.9 11.0 Total phosphorus 6.8 7.4 Available phosphorus 3.9 4.0 Sodium 1.6 1.5 Chlorine 1.8 2.0 Lysine 11.6 14.1 Methionine 6.1 5.5 Methionine + cysteine 9.7 8.8 Threonine 8.4 8.9 Tryptophan 2.8 2.6
228.7 11.0 7.4 4.0 1.5 2.0 14.2 5.5 8.8 8.9 2.6
228.2 11.0 7.4 4.0 1.5 2.0 14.1 5.5 8.8 8.9 2.6
233.2 11.0 7.4 4.0 1.5 2.0 14.5 5.5 8.9 9.0 2.7
232.7 11.0 7.4 4.0 1.5 2.0 14.4 5.5 8.9 9.0 2.6
232.2 11.0 7.4 4.0 1.5 2.0 14.4 5.5 8.9 9.0 2.6
Ingredient Maize Soyabean meal Wheat Soyabean oil Faba beans Calcium carbonate Dicalcium phosphate Sodium bicarbonate l-lysine, HCl dl-methionine l-threonine l-tryptophan Premixg
a b c d e f
319.3 309.7 299.2 27.8 0 7.6 18.2 1.2 1.0 3.0 0.7 0.3 12.0
HVC-HT: high vicine and convicine cotyledons + high tannins hulls (cv. Meli + Meli). HVC-MT: high vicine and convicine cotyledons + medium tannins hulls (cv. Meli + Meli and Gloria). HVC-LT: high vicine and convicine cotyledons + low tannins hulls (cv. Meli + Gloria). LVC-HT: low vicine and convicine cotyledons + high tannins hulls (cv. Divine + Meli). LVC-MT: low vicine and convicine cotyledons + medium tannins hulls (cv. Divine + Meli and Gloria). LVC-LT: low vicine and convicine cotyledons + low tannins hulls (cv. Divine + Gloria).
g The premix provided the following per kg of diet; Fe, 30 mg; Cu, 12 mg; Zn, 60 mg; Mn, 90 mg; I, 1.2 mg; Se, 0.3 mg; Vitamin A, 15000 UI; Vitamin D3, 3000 UI; Vitamin E, 30 UI; Vitamin B1, 1 mg; Vitamin B2, 6 mg; Vitamin B6, 1 mg; Vitamin B12, 0.02 mg; Vitamin K3, 4 mg; Vitamin B3, 40 mg; choline, 400 mg; Diclazuril (Clinacox® , Janssen Pharmaceutica, Beerse, Belgium), 1 mg. h Measured values (n = 2).
reconstitute six faba bean formulas (12 kg per batch). To produce reconstituted faba beans (RFB) with medium tannin contents (MT), hulls from HT genotypes (0.75 kg) and LT genotypes (0.75 kg) were added to cotyledons. Finally the hulls and cotyledon mixtures were ground (2900 rpm, 58 m/s, Ecma, Bourgoin-Jallieu, France) and sieved through a 2-mm screen. The six RFB combined 3 levels of tannins (9.9, 5.8 and 1.3 g/kg) with 2 of VC (10.1 and 0.7 g/kg).
2.2. Experimental diets The composition and the characteristics of the experimental diets are presented in Table 1. Experimental feeds were formulated and manufactured by Arvalis – Institut du végétal (Boigneville, France). Before mixing, wheat, maize and soyabean meal were ground and passed through a 2-mm screen (Titan, 2000, Vitré, France). The basal diet was based on maize, soyabean meal and wheat (Table 1) and the six experimental diets contained 500 g RFB and 500 g basal diet per kg. All diets were pelleted (La Meccanica CLM200, Padova, Italy) with a 2.5-mm diameter and 35-mm length die.
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2.3. Birds management and design A total of 150 Ross PM3 male broiler chicks was used. Birds were placed in a floor pen up to 14 days of age and fed a common standard starter diet. Then, birds were weighed and 63 birds with a body weight in the center of the statistical distribution were used for the experiment. The design was completely randomised with 7 treatments and 9 replicates of one bird each per treatment. 2.4. Balance experiment The balance experiment was carried out from 14 to 24 days of age using the method described by Bourdillon et al. (1990). From day 14 to day 20 (adaptation period) birds were fed ad libitum their respective experimental diets. At day 20, chicks were fasted for 17 h, fed their respective experimental diet for 55 h and fasted again for 17 h. Individual feed intake was measured from day 14 to day 24 and excreta were totally collected from each individual during the last 72 h (21–24 days of age). Daily collection of individual excreta on three days were pooled and stored at −18 ◦ C and then freeze-dried. Prior to analysis, samples were allowed to equilibrate with atmospheric moisture for 24 h and then ground to pass through a 0.5-mm screen. 2.5. Calculation The energy was corrected for N (AMEn) using a value of 34.4 kJ per g of N retained. Total tract apparent digestibility of protein (TTAD-N) was calculated after determining faecal N by the procedure of Terpstra and De Hart (1974). The nutritional value of RFB was calculated by difference between basal and test diet values. 2.6. Analytical methods Crude protein (N ×6.25) was measured according to the method of Dumas (AFNOR, 1997a) with a protein analyser LECO model FP 2000 (St Joseph, MI, USA). Protein content of excreta was determined using the method of Terpstra and De Hart (1974). Water insoluble cell wall content was determined according to the method of Carré and Brillouet (1986). Gross energy (GE) of excreta and feeds was determined with an adiabatic bomb calorimeter (Ika-Werke C7000, Staufen, Germany) standardized with benzoic acid. Starch content was measured in feeds and excreta using the enzymatic method (AFNOR, 1997b). Tannin content (mg gallic acid equivalents/kg) was determined according to BuOHHCl method as described by Duc et al. (1995) and VC content by HPLC as described by Duc et al. (1989). 2.7. Statistical analysis Analyses of variance of AMEn, AMEn/GE and TTAD-N of diets and RFB were performed by two-way ANOVA using Statview 5.0 Software (SAS Institute Inc, 2002). Statistical significance of the variance and means was tested by Fisher and Student–Newman–Keuls test respectively. The relationship between values of nutritional parameters and T and VC contents of RFB was evaluated by linear regression analysis using Statbox 6.23 (Grimmer Soft, Neuilly sur Seine, France). 3. Results 3.1. Chemical composition of faba bean batches The six RFB had similar crude protein, starch and water-insoluble cell wall contents (Table 2). In contrast, the differences in the genotypes for anti-nutritional factors content resulted in RFB varying from 10.1 to 0.7 g VC/kg and from 9.9 to 5.8 and 1.3 g tannins/kg for HT, MT and LT respectively.
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Table 2 Analysed composition of reconstituted faba beans (g/kg of DM unless indicated otherwise)
Dry matter Crude protein Water insoluble cell walls Starch Gross energy, MJ/kg of DM Condensed tannins Vicine Convicine a b c d e f
HVC-HTa
HVC-MTb
HVC-LTc
LVC-HTd
LVC-MTe
LVC-LTf
838 301 189 457 18.8 9.8 6.5 2.8
838 301 182 476 18.8 6.1 7.3 3.1
832 302 167 464 18.8 1.4 7.5 3.2
835 313 183 445 18.9 9.9 0.7 0.1
835 312 184 445 18.8 5.4 0.5 0.1
839 310 201 438 18.8 1.2 0.5 0.1
HVC-HT: high vicine and convicine cotyledons + high tannins hulls (cv. Meli + Meli). HVC-MT: high vicine and convicine cotyledons + medium tannins hulls (cv. Meli + Meli and Gloria). HVC-LT: high vicine and convicine cotyledons + low tannins hulls (cv. Meli + Gloria). LVC-HT: low vicine and convicine cotyledons + high tannins hulls (cv. Divine + Meli). LVC-MT: low vicine and convicine cotyledons + medium tannins hulls (cv. Divine + Meli and Gloria). LVC-LT: low vicine and convicine cotyledons + low tannins hulls (cv. Divine + Gloria).
Table 3 Nutritional values of diets and reconstituted faba beans for poultry (on DM basis) and statistical significance of main factors effects and their interaction Basal diet Diets AMEnj AMEn/GEk TTAD-Nl
Means 13.07 0.690 0.790
Reconstituted faba beans AMEnj AMEn/EBk TTAD-Nl
HVC-HTa
HVC-MTb
HVC-LTc
LVC-HTd
LVC-MTe
LVC-LTf
Tg
12.23 0.661 0.764
12.15 0.658 0.782
12.35 0.671 0.825
12.34 0.667 0.778
12.31 0.665 0.788
12.61 0.683 0.842
RSDh 0.28 0.15 0.28
11.97 0.638 0.741
11.79 0.629 0.774
12.21 0.651 0.850
12.18 0.645 0.768
12.11 0.645 0.784
12.74 0.680 0.879
0.54 0.29 0.50
a
HVC-HT: high vicine and convicine cotyledons + high tannins hulls (cv. Meli + Meli).
b
HVC-MT: high vicine and convicine cotyledons + medium tannins hulls (cv. Meli + Meli and Gloria). HVC-LT: high vicine and convicine cotyledons + low tannins hulls (cv. Meli + Gloria). LVC-HT: low vicine and convicine cotyledons + high tannins hulls (cv. Divine + Meli).
c d e f
VCg
T xVCg
P>Fi ** * ** * *** NS
NS NS NS
** ** ***
NS NS NS
* * NS
LVC-MT: low vicine and convicine cotyledons + medium tannins hulls (cv. Divine + Meli and Gloria). LVC-LT: low vicine and convicine cotyledons + low tannins hulls (cv. Divine + Gloria).
T: tannins; VC: vicine and convicine; T × VC: interaction T x VC. RSD: residual standard deviation. i Probability of Fisher’s test of main factors effects and their interaction, after polyfactorial variance analysis. NS: non significant effect P>0.05; *P<0.05; **P<0.01; ***P<0.001. j AMEn (MJ/kg): apparent metabolisable energy, nitrogen corrected. g
h
k l
AMEn/GE coefficient: apparent metabolisable energy, nitrogen corrected/gross energy. TTAD-N coefficient: total tract apparent digestibility of protein.
3.2. Nutritional value of reconstituted faba beans There was no significant interaction between tannin and VC factors for any studied trait. The effects of tannins were significant for all nutritional traits measured whereas the effects of VC were only significant for AMEn and gross energy digestibility AMEn/GE (Table 3). The average AMEn of the six RFB was 12.17 MJ/kg DM. The average AMEn was lower (P<0.001) for the high- than for low-tannin mixtures, 12.08 and 12.48 MJ/kg DM respectively (Table 3). For the HVC and LVC mixtures, the average AMEn was 11.99 and 12.34 MJ/kg DM respectively (P<0.05). The AMEn of the RFB low in both tannins and VC was the highest (12.74 MJ/kg DM). The standard deviation was higher for the RFB containing high levels of both anti-nutritional factors than for RFB containing low levels (0.8 MJ/kg versus 0.37 MJ/kg DM).
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The coefficient of energy digestibility was higher for LVC-LT RFB than for the HVC-HT and HVCMT RFB (0.68 versus 0.64 and 0.63, respectively) (P<0.01). Starch digestibility was above 0.99 for all treatments. The coefficients of TTAD-N were lower (P<0.001) for HT and MT RFB than for LT RFB. The TTAD-N was 0.75 for HT RFB and 0.86 for LT RFB (P<0.001). In contrast, VC had no significant effect on TTAD-N. 3.3. Prediction of AMEn and apparent total tract digestibility of protein Energy digestibility and TTAD-N were negatively correlated with tannin content (r = −0.76, P<0.05 and r = −0.95, P<0.001, respectively). The linear model, predicting AMEn value from tannin content [AMEn (MJ/kg DM) = −0.0603*tannin (g/kg DM) + 12.53] explained only 50% of the variance observed. The linear model including both tannins and VC [AMEn (MJ/kg DM) = 12.669–0.052*tannin (g/kg DM) – 0.038 VC (g/kg DM)] explained 80% of the variance with an estimated error of 0.19 MJ/kg DM. The linear model predicting TTAD-N from tannin content [TTAD-N = −0.014*tannin (g/kg DM) + 0.878] explained 91% of the variance of the protein digestibility coefficient. 4. Discussion The AMEn value obtained for the HT RFB was 12.1 MJ/kg DM, which agrees with values of 12.3 MJ/kg DM and 11.9 MJ/kg DM measured for high-tannin faba bean cultivars found by Mateos and Puchal (1981a) and Grosjean et al. (2000). The AMEn value of LT RFB was 12.5 MJ/kg DM, in agreement with the value of 12.8 MJ/kg DM found by Grosjean et al. (2000) with tannin-free faba bean cultivars. 4.1. Effect of tannins on faba bean nutritional values It is generally accepted that tannins reduce feed intake in poultry (Iji et al., 2004) interfere with digestive enzyme activity and form complexes with nutrients reducing their digestibility (Jansman and Longstaff, 1993). Feed intake reduction depends probably on the quantity of tannins ingested, since Jansman et al. (1993) showed no decrease in feed intake in broilers fed 300 g/kg high-tannin faba bean, whereas Helsper et al. (1996) observed a significant reduction in feed intake in broilers fed 500 g/kg high-tannin faba bean. Iji et al. (2004) found negative, neutral or positive effects of tannins depending on their concentration in the diet. The predominant effect of tannins in broilers was a reduction in protein and amino acid digestibility (Ortiz et al., 1993; Jansman and Longstaff, 1993; Brufau et al., 1998) although negative effects have also been observed on starch digestibility (Lacassagne et al., 1988; Flores et al., 1994). In the current study, tannins reduced AMEn by 0.5 MJ/kg when HT and low LT RFB were compared. This difference cannot be explained by differences in starch content because it was similar for all RFB. However, Grosjean et al. (2000) found that energy digestibility was significantly affected by tannin content of faba bean in adult cockerels. The present experiment demonstrates that tannins have a negative effect on the digestibility of protein that can partially explain the differences observed in AMEn values. The observed TTAD-N was 13.8% higher for LT- than for HT RFB, which is in agreement with values obtained by Lacassagne et al. (1988) on adult cockerels. 4.2. Effect of vicine and convicine on faba bean nutritional values Very few studies have assessed the impact of VC on the nutritional value of faba bean for poultry and most of them were conducted with laying hens (Muduuli et al., 1981; Mateos and Puchal, 1981b; Grosjean et al., 2000). These studies showed negative effects of VC on egg weight and hypothesized that VC affected the metabolism of the laying hen to explain them. Vicine has been suggested to produce peroxidants that cause lipid peroxidation and erythrocyte hemolysis and interfere with normal lipid metabolism in the hen. In contrast, Hegazy and Marquardt (1984) did not detect any effect on the metabolism of young chickens.
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In the current study, the negative effect of VC on the AMEn of broilers was significant in contrast to the study of Grosjean et al. (2000) who did not detect any effect of feeding 2 HVC to adult cockerels. However in this study only two genotypes of faba beans were used to test the effect of VC on AMEn values and the homogeneity of contents of the accompanying seed compounds was not measured. In the current study the highest AMEn value was obtained with the faba bean low in VC and tannins content, indicating that the effects of these two anti-nutritional factors on AMEn were additive. Accurate mediation of the AMEn content of faba beans should be based on linear models incorporating tannins and VC contents. The present study did not detect any significant effect of VC on TTAD-N, in agreement with data of Grosjean et al. (2000). 5. Conclusion The results confirm that tannins reduced apparent energy and protein digestibility of faba bean in broiler chickens. Also, vicine and convicine contained in faba bean seeds had a negative effect on AMEn but not on TTAD-N. No interactions between tannin and VC contents were observed. These results confirm the interest of faba bean varieties free of tannins and low in vicine and convicine contents in diets for broilers. Acknowledgements This work has been financially supported by the Union Nationale Interprofessionnelle des Plantes riches en protéines (UNIP, France) and by the Office National Interprofessionnel des Oléagineux (ONIOL, France). The authors thank Mr P. Marget and Mr H. Houtin INRA-UMR 102 LEG Dijon and the Experimental Unit of INRA Domaine d’Epoisses 21110 Bretenières, F. for seed multiplication. We thank the technicians who carried out the animal trial at the Experimental Station (Arvalis – Institut du végétal, France). We thank Dr P. Dulieu (RD-Biotech, Besanc¸on, F.) and Mrs F. Cassecuelle (INRA-UMR 102 LEG Dijon, F.) for determination of vicine and convicine contents. We thank Dr R. Thompson and Mr D. Coles for the English language corrections in this paper. References AFNOR, 1997a. Association Franc¸aise de Normalisation. Method NF V 18-120. AFNOR Editions, Paris. AFNOR, 1997b. Association Franc¸aise de Normalisation. Method NF V 18-121. AFNOR Editions, Paris. Bond, D.A., Duc, G., 1994. Plant breeding as a means for reducing anti-nutritional factors in grain legumes. In: Van der Poel, A.F.B., Huisman, J., Saini, H.S. (Eds.), Recent Advances of Research in Antinutritional Factors in Legume Seeds, vol. 70. E.A.A.P, Wageningen pers, pp. 379–396. Bourdillon, A., Carré, B., Conan, L., Duperray, J., Huyghebaert, G., Leclercq, B., Lessire, M., McNab, J., Wiseman, J., 1990. European reference method for the in vivo determination of metabolisable energy with adult cockerels: reproductibility, effect of feed intake and comparison with individual laboratory methods. Br. Poult. Sci. 31, 557–565. Brufau, J., Boros, D., Marquardt, R.R., 1998. Influence of growing season, tannin content and autoclave treatment on the nutritive value of near-isogenic lines of faba beans (Vicia faba L.) when fed to Leghorn chicks. Br. Poult. Sci. 39, 97–105. Carré, B., Brillouet, J.M., 1986. Yield and composition of cell wall residues isolated from various feedstuffs used for non-ruminant farm animals. J. Sci. Food Agric. 37, 345–351. Duc, G., 1997. Faba bean (Vicia faba L.). Field Crops Res. 53, 99–109. Duc, G., Sixdenier, G., Lila, M., Furstoss, V., 1989. Search of genetic variability for vicine and convicine content in Vicia faba L. A first report of a gene which codes for nearly zero-vicine and zero-convicine contents. In: Huisman, A.J.M., Van der Poel, A.F.B., Liener, I.E. (Eds.), Recent Advances of Research in Antinutritionnal Factors in Legumes Seeds. Pudoc, Wageningen, Netherlands, pp. 305–313. Duc, G., Brun, N., Merghem, R., Jay, M., 1995. Genetic variation in tanning related characteristics in faba bean seeds (Vicia faba L.) and their relationship with seed coat colour. Plant Breed. 114, 272–274. Duc, G., Marget, P., Esnault, R., Le Guen, J., Bastianelli, D., 1999. Genetic variability for feeding value of faba bean seeds (Vicia faba L.). Comparative chemical composition of isogenics involving zero-tannin and zero-vicine genes. J. Agric. Sci. 133, 185–196. Flores, M.P., Castanon, J.I.R., McNab, J.M., 1994. Effect of tannins on starch digestibility and TMEn of triticale and semipurified starches from triticale and field beans. Br. Poult. Sci. 35, 281–286. Grosjean, F., Bourdillon, A., Rudeaux, F., Bastianelli, D., Peyronnet, C., Duc, G., Lacassagne, L., 2000. Valeur alimentaire pour la volaille de féveroles isogéniques (Vicia faba L.) avec ou sans tannins et avec ou sans vicine–convicine. Sci. Technol. Avic. 32, 17–23. Hegazy, M.I., Marquardt, R.R., 1984. Metabolism of vicine and convicine in rat tissues: absorption and excretion patterns and sites of hydrolysis. J. Sci. Food Agric. 35, 139–146.
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