Quebracho tannins with or without Browse Plus (a commercial preparation of polyethylene glycol) in sheep diets: Effect on digestibility of nutrients in vivo and degradation of grass hay in sacco and in vitro

Quebracho tannins with or without Browse Plus (a commercial preparation of polyethylene glycol) in sheep diets: Effect on digestibility of nutrients in vivo and degradation of grass hay in sacco and in vitro

ANIMALFEED SCIENCEAND TECHNOLOGY b F ELSEVIER Animal Feed Science Technology 69 (1997) 67-78 Quebracho tannins with or without Browse Plus (a comm...

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ANIMALFEED SCIENCEAND TECHNOLOGY

b

F ELSEVIER

Animal Feed Science Technology 69 (1997) 67-78

Quebracho tannins with or without Browse Plus (a commercial preparation of polyethylene glycol) in sheep diets: effect on digestibility of nutrients in vivo and degradation of grass hay in sacco and in vitro M.B. Salawua,bac,T. AcamoviP”,

C.S. StewartC, F.D.DeB. Hovellb

aSAC, 581 King Street, Aberdeen AB24 SUD, Scotland, UK bAberdeen University, 581 King Street, Aberdeen AB24 XJD, UK ‘Rowett Research Institute, Bucksbum, Aberdeen AB21 9SB, Scotland, UK

Abstract

Quebracho tannins (QT, 50 g/kg diet), with or without two levels (0.1 or 1.0 g/kg diet) of a commercial additive containing polyethylene glycol (Browse Plus), were fed to four cannulated sheep receiving a ba?al diet of grass hay, grass cubes and whole barley at maintenance level in a 4 X 4 Latin square over periods of 4 weeks. The control treatment consisted of the basal diet alone. Ruminal in-sacco degradation and in-vitro gas production were measured. Apparent digestibilities of all nutrients were significantly (P < 0.05) depressed by the QTs. Browse Plus was able to remove some, but not all, of the depressions in digestibilities, with the higher level of Browse Plus (1 g/kg diet) tending to produce a significant (P < 0.05) improvement in the digestibilities of all nutrients. The lower level of Browse Plus used (0.1 g/kg) slightly (P > 0.05) improved the digestibilities of all nutrients. There were no differences (P > 0.05) in the degradation and rate of degradation of the hay incubated in sacco in the four rumen environments created by the different tannin content of the experimental diets. However, the rate of degradation of the insoluble but potentially degradable fraction was lowered by the QT diet, indicating the possibility of reduced microbial cellulolysis. Microbial activities measured from gas production were also reduced in vitro. However, unlike the in-vivo and in-sacco experiments, Browse Plus in vitro removed all the depressions in activities of the microbes that could be associated with the tannins. Although Browse Plus was unable to alleviate all of the depression in digestibilities in vivo,

* Corresponding author. E-mail: [email protected] 0377~8401/97/$17.00 0 1997 Elsevier Science B.V. All rights reserved PII SO377-8401(97)000096-5

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it may still be’a useful digestive modifier which partly offsets the inhibitory effects of condensed tannins in ruminant diets, especially in arid environments with poor quality feeds. 0 1997 Elsevier Science B.V. Keywords:

Browse Plus; Condensed tannins; Degradability in sacco; In vitro gas production; In vivo; Quebracho tannins

1. Introduction Condensed tannins are polyphenolics which consists of oligomers of flavan-3-01s and related flavanol residues which typically produce anthocyanidins (and are thus often referred to as proanthocyanidins) on acid degradation (Mangan, 1988). The tannin content of plants varies considerably. For example Reed (19861, in a study of 17 species African browse, found that tannin concentration ranged from 130 to 500 g/kg dry matter (DM) while other workers found levels ranging from 20 to 100 g/kg DM (Terrill et al., 1994) in other feedstuffs. Tannins are widespread in plants and have been demonstrated to be potentially beneficial (e.g. bloat prevention, anthilmentic) as well as having anti-nutritional effects in ruminants (Osborne et al., 1971; Waghorn et al., 1987; Waghorn et al., 1994). The digestibilities of tanniniferous plant forages by ruminants have been shown to be relatively low (Reed et al., 1982) and this may be due in part to their tannin content. Quebracho tannins are condensed tannins extracted from quebracho (Loxoptetygium loetzil). Condensed tannins in plants interact to bring about nutritional effects by binding with proteins and carbohydrates (Makkar et al., 1988). They affect the activities of rumen microbes both directly and indirectly (Haslam, 1981). In vitro, quebracho tannins have been shown to precipitate Fl leaf protein in the pH range of 5.6-7 (Martin and Martin, 1983). They have been reported to inhibit the digestion of cereal grains and cellulose by ruminal micro-organisms (Bae et al., 1994). Polyethylene glycol (PEG) has been shown to reduce the adverse effects of dietary tannins in animal diets. Positive results have been reported for temperate legumes with poultry fed high-tannin faba beans (Ford and Hewitt, 1979) and with sheep fed Lotus (Barry and Duncan, 1984). The utilisation of Browse Plus (a commercial preparation of PEG) has recently been advocated to improve the nutritional values of tannin-containing browses (R. McKenzie, personal communication). Trials on commercial farms in Zimbabwe have demonstrated that Browse Plus improved the performance of cattle fed high tannin diets (Anonymous, 1995a,b). Information on the types of tannins in the diets or the level of Browse Plus used were however not available in these reports. Some in-vitro work tends to support these findings (M. Bliimmel, personal communication; Acamovic et al., 1995). An experiment was designed to investigate the effects of dietary quebracho tannins on the digestibility of a grass-hay based diet in fistulated sheep in vivo, and

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Ii9

on the in-sacco and in-vitro degradation patterns of the hay. The efficacy of Browse Plus as a dietary additive in reducing the effects of tannins in vivo was also examined.

2. Materials and methods 2.1. Experimental design and dietary treatments Four individually penned sheep with a mean live weight of 74 kg, and fitted with ruminal canulae were used in a 4 x 4 Latin square design with feeding periods of 4 weeks. The basal diet, designed to satisfy the nutrient requirements of the sheep, consisted of chopped grass hay [a mixture of perennial rye grass (Lolium perennej, Timothy grass (Phleum pratensej and white clover (Trifolium repensj], grass cubes and whole barley. The composition of the ingredients is presented in Table 1. The quebracho tannins (Hodgson Chemicals Ltd., England) were added at 50 g/kg of the whole diet and the Browse Plus (Agricura (PVT) Ltd., Zimbabwe) was added at 0.1 or 1 g/kg of the whole diet. The sheep were given a mineral supplement at 15 g/day. The grass cubes and the mineral supplement were supplied by North Eastern Farmers Ltd., Aberdeen, UK. The quebracho tannins (50 g/kg) were dissolved in 200 ml of water and thoroughly hand mixed with the grass hay portion Table 1 Compositions of the ingredients of the basal diet Ingredients/composition

Dry matter Crude protein Ether extract NDF ADF Ash Starch Sugar ME (MJ/kg) DCP UDP Calcium Phosphorus Magnesium NaCl

(g/kg)

Grass hay

Grass cubes

Barley

Mineral mix”

903 73 35 509 270 51

957 204 30 472 251 87 40 110 9.5 112 64 5 2.5 1.5 7

913 86 16 143 35 21

-

-

-

-

-

-

-

160 85 100 s9

a The mineral mix also contained 4500 mg/kg Mn, 1500 mg/kg Zn, 150 mg/kg Co, 200 mg/kg I, 16 mg/kg Se, 500 000 iu/kg vitamin A, 50 000 iu/kg vitamin D, and 500 iu/kg cu-tocopherol.

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of the diet on a daily basis just prior to feeding. The Browse Plus was added dry to the concentrate portion of the diet. The treatments were thus: (a) control (0 proportions (b) control plus (c) control plus (d) control plus

- basal diet of grass hay, grass cubes and whole barley (mean of 8:3:1); 50 g/kg QT (CQT); 50 g/kg QT plus 0.1 g/kg Browse Plus (CQT + 0.1); 50 g/kg QT plus 1.0 g/kg Browse Plus (CQT + 1.0).

The sheep were fed twice daily at 08.00 h and 16.00 h. The concentrate portion (grass cubes and barley) with or without the Browse Plus was given first, followed by the grass hay with or without the QT 10 min later. Fresh feed was introduced each feeding time and there were no refusals. The 4-week experimental periods were divided into 3 weeks adjustment followed by observations over 1 week. During the observation week the sheep were harnessed for total faecal collection. During each observation week, feed samples were collected daily to determine the dry matter (DM) of the diet fed and bulked samples were analysed for crude protein (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF) and organic matter (OM) so that intake could be calculated. Faecal collection was for 5 days. Faeces collected daily were thoroughly mixed, weighed and bulked samples taken for analysis of DM, OM, CP, NDF and ADF. Sampled faeces were oven dried at 55°C for 48 h and ground to pass through l-mm aperture before the analyses. 2.3. Degradation studies Hay sampled from the same batch as that fed to the sheep was incubated in sacco in the different rumen environments created by the four diets and DM degradation measured using the nylon bag technique as described by Orskov et al. (1990). The hay was ground to pass through a 3-mm screen and approximately 2.5 g were incubated in bags of nylon filter cloth (Lockertex, Church Street, Warrington, Cheshire, UK), with a mean pore size of approximately 50 pm. Bags were withdrawn after 8, 16, 24, 48, 72 and 96 h. Zero-time washing losses were determined by soaking three bags in warm water (39°C) for 1 h. Both zero-time bags and incubated bags were then washed with cold water for 15 min in a commercial washing machine without spinning. Washed bags were dried for 48 h at 55°C. DM degradation losses were fitted to two models - Orskov and McDonald (1979) and McDonald (1981) - using the ‘Neway’ programme (X.B. Chen, Rowett Research Institute, Aberdeen). These degradation curves are described as: D = u + b(1 - e-C’)

(1)

D =A + B(l - e-c(t-‘l))

(2)

where D = degradation after t hours, a = zero-time intercept (Eq. l), a + b = total potential loss from the bag (degradation plus zero-time losses). In Eq. 2,

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A = the zero-time washing loss, B = the potentially degradable insoluble fraction and is equal to [(a + b) - A] since u + b = A + B of Eq. 1Eq. 2, respectively, c = the fractional rate constant describing and applied to both b (Eq. 1) and B (Eq. 2) and t, = lag time, i.e. the time at which D = A when the curves are extrapolated back in time from the incubation times used. 2.4. In-vitro gas production experiment The degradation characteristics of the hay were also measured from gas production in vitro using the method of Menke and Steingass (19881, in which a 200 mg sample was incubated with 30 ml buffered rumen liquor in 100 ml glass syringes, gas production being measured by the displacement of the plunger. Gas production (ml/200 mg DM) from the hay incubated in rumen liquor from the sheep on the experimental diets was read at 4, 8, 16, 24, 32, 48 and 72 h. Gas production corrected for the gas produced by a rumen liquor blank was also fitted to the same model described as G = a + b(1 - e-C’). Here, by analogy with Eq. 1, G = corrected gas production after t hours, a + b = potential gas production and c = fractional rate of gas production.

3. Laboratory analyses Dry matter and ash were determined (Association of Official Analytical Chemist, 1990) in the dried feed and dried faecal samples, milled to pass through a l-mm screen. The method of Goering and Van Soest (1970) was used to determine the ADF and NDF. All other values were taken from data provided by the supplier of the material (Table 1).

4. Results All sheep remained healthy throughout the experimental periods. The QT diets were eaten by all four sheep in the trial. However, it took all the sheep a longer time to eat the QT treated hay compared with the untreated hay. The mean dry matter intake of the four diets were 1142, 1121,1169 and 1143 (SEM 6.9) g/day for diets C, CQT, CQT + 0.1 and CQT + 1.0, respectively. In period four, the faecal collection was terminated after the second day for the sheep on CQT + 0.1 diet because the sheep became distressed by the harness. Table 2 shows the apparent digestibilities of the diets. QT reduced (P < 0.051 the digestibilities of DM, OM, CP, NDF and ADF. The addition of Browse Plus reduced the effect of QT, with digestibilities tending to be restored, although the difference from CQT was not significant (P > 0.05) at the lower level (0.1 g/kg) of Browse Plus (CQT + 0.1). There was the suggestion that the effect of Browse Plus was progressive, although the difference between the two levels of Browse Plus was significant only for crude protein. With the addition of 1 g/kg Browse Plus

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Table 2 Apparent digestibility of the hay-based basal (control) diet alone, or supplemented with 50 g/kg Quebracho tannin with zero (CQT), 0.1 (CQT + 0.1) or 1.0 (CQT + 1.0) g/kg Browse Plus (BP) (means of 16 observations) Treatment

DM

OM

CP

NDF

ADF

Control CQT CQT + O.l* CQT + 1.0 S.E.M.

0.65” 0.54b 0.55b’ 0.56’ 0.020

0.66a 0.55b 0.57bC 0.58’ 0.019

0.64” 0.54b 0.54b 0.58’ 0.020

0.61a 0.49b 0.52bC o.53c 0.023

0.5ga 0.46b 0.49bC 0.52’ 0.024

aqb,cMeans with different superscripts in columns are significantly different (P < 0.05). Abbreviations: DM = dry matter; OM = organic matter; CP = crude protein; NDF = neutral detergent

fibre; ADF = acid detergent fibre. * means of faecal collections in three periods used.

(CQT + 1) the digestibilities of all components were significantly (P < 0.05) greater than when QT was added alone. However, digestibilities remained less than those of the control diet (P < 0.05). The in sacco degradation characteristics of the hay in sheep given each of the four diets are shown in Table 3 and Fig. 1. The potentially degradable insoluble fraction (B) and asymptote (A + B) of the grass hay in sacco did not differ significantly between the control and the Quebracho tannin diets with or without Browse Plus. The fractional rate of degradation cc> in sheep given QT without Browse Plus (CQT) was lowest, but not significantly different from the control or the Browse Plus-containing diets. The parameters of the fitted curves of the gas productions from the hay incubated in vitro with liquor from the sheep when given each of the four diets are

Table 3 In sacco degradation characteristics of Browse Plus (BP) when degradation D = a + b(l- e-“) or when A is D = A + B(1 -e-c(t-tL)) (McDonald, Treatment

a

b

grass hay in sheep fed Quebracho tannins (QT) with or without D (dry matter loss; g/kg DM) after t hours is given by the zero-time washing loss and t, is the lag time (h), 1981) (means of four observations) A

B

a+b

C

tL

and A + B Control CQT CQT + 0.1 CQT + 1.0 S.E.M.

161 208 135 71 31

577 499 562 612 37

220 220 220 220 0

517 487 478 464 17

737 707 698 684 17

0.0493 0.0340 0.0484 0.0567 0.0052

2.2ab O.ga 3.1ab 4.7b 0.8

a*bMeans in columns with the same superscript are not significantly (P > 0.05) different. control = hay basal diet; CQT = control + 50 g/kg QT, CQT + 0.1 = control + 50 g/kg QT + 0.1 g/kg Browse Plus; CQT + 1.0 = control + 50 g/kg QT + 1.0 g/kg Browse Plus; S.E.M. = standard error of means.

Abbreuiations:

M.B. Salawu et al. /Animal Feed Science Technology 69 (1997) 67-78

73

IS -

60 -

S

E - 45 .-S e -z 2 a 30z

IS -

0

_t_

Control

w-0a___ . &

PlusTannin$O.lgBmwsePlus

+

1 0

I

IS

PlusTannin -

I

PlusTannin& 1.OgBrowse

I

30 4s Incubation time (hours)

Plus

I

I

60

15

Fig. 1. In-sacco degradation of grass hay incubated in the rumens of sheep fed hay with concentrate (control), or control plus 50 g Quebracho tannins, or 50 g Quebracho tannins plus 0.1 or 1.0 g Browse Plus per kg diet (means of four observations), fitted curves drawn.

in Table 4, and Fig. 2. In vitro, the gas production from grass hay showed a slightly different pattern from the DM degradation pattern observed in sacco. In vitro, the rumen liquor from QT-fed sheep reduced the asymptote when compared with that of the control and significantly (P < 0.05) when compared with those of the Browse Plus-containing liquor. The potential gas production (a + b) and the fractional rate of gas production (c) was highest in liquor with 0.1 g Browse Plus. given

5. Discussion The addition of substances which complex with tannins or assist in their metabolic detoxification is gaining importance as a treatment to overcome the anti-nutritional effects of tannins. In Zimbabwe, Browse Plus has been marketed as an effective and safe remedy for problems associated with animals consuming browse plants high in tannins. The main ingredients of Browse Plus are PEG (more than 95% of the dry material), polyvinylpyrrolidone and calcium hydroxide. Tannins are reported to form stronger complexes with PEG than they do with protein (D’Mello, 1992) and PEG can displace proteins in pre-formed tannin-protein complexes (Jones and Mangan, 1977). This property of PEG has been exploited

MB. Salawu et al. /Animal Feed Science Technology 69 (1997) 67-78

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Table 4 Gas production from grass hay incubated in vitro with rumen liquor from sheep fed each of the experimental diets when gas production G (m1/200mg DM) after t hours is given by G = a + b(1 e-C’

I

Treatment

a

b

C

a+b

Control

7.78 -0.8b -4.6b 6.4a

49.7a 54.0a 65.9b 54.7a

0.0528’ 0.0894b 0.0934s 0.0596”

57.4”b 53.2” 61.2b 61.0b

1.4

2.3

CQT CQT + 0.1 CQT + 1.0 S.E.M.

0.0060

1.2

a,b Means with different superscripts in columns are significantly (P < 0.05) different. control = hay basal diet; CQT = control + 50 g/kg QT; CQT + 0.1 = control + 50 g/kg QT + 0.1 g/kg Browse Plus; CQT + 1.0 = control + 50 g/kg QT + 1.0 g/kg Browse Plus; S.E.M. = standard error of means.

Abbreviations:

800-

/.A

700 -

__

/

_s

*T--c

--:.-,-.-;-_.-A

_....

600 -

. .. . .. . . A -T-

.__..

P~~Tmin PlusTannin& 0.18 Browse Plus Plus Tsnnin UCl.Og Browse. Plus

;0

io

Go

Incubationtime (hours) Fig. 2. In-vitro gas production from grass hay incubated in the rumen liquor from sheep fed hay with concentrate (control), or control plus 50 g Quebracho tannins, or 50 g Quebracho tannins plus 0.1 or 1.0 g Browse Plus per kg diet (means of four observations), fitted curves drawn.

with success in nutritional studies involving the use of tannin containing feeds for both monogastrics (Ford and Hewitt, 1979) and ruminants (Barry and Duncan, 1984). Like most other condensed tannins, quebracho tannins depressed the digestibilities of all nutrients at the level used here. The depression in digestibilities

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Science Technology 69 (1997) 67-78

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associated with quebracho tannins might have been due to the formation of complexes between tannins and dietary proteins and carbohydrates (Makkar et al., 19SS>, as well as reducing rumen microbial proteolytic, ureolytic and cellulolytic enzyme activities, general fermentative activities and cell multiplication (Haslam, 1981; Makkar et al., 1988; McAllister et al., 1994; Muhammed et al., 1994). The results of the present study are consistent with the result obtained when Lotus pedunculatus, containing high levels of tannins was fed, with or without PEG, to sheep (Barry and Manley, 1984; Barry and Manley, 1986). Similar results have also been reported from in-vitro experiments (Acamovic et al., 1995; M. Bliimmel, personal communication). The digestibilities of the cell wall components assessed as NDF were most affected by the QT. This observation agrees with the findings made by Robbins et al. (1991), who reported that QT inhibited fibre digestion in sheep. Quebracho tannins have also been demonstrated to inhibit the digestion of cereal grains and cellulose by rumen microbes (Bae et al., 1994; McAllister et al., 1994). In the work reported here, Browse Plus was effective in improving the digestibilities of all nutrients tested, compared to the values obtained with only the QT-supplemented diet. This was presumably because the Browse Plus formed complexes with some of the tannin, thus lessening the effect of the tannin on the activities of rumen microorganisms and their enzymes. In agreement with earlier results with PEG, introduction of Browse Plus was able to reverse some, but not all, of the effects associated with the presence of QT in the diets. This suggests either that the amount of Browse Plus added was not sufficient to fully restore dry matter, organic matter, protein and neutral detergent fibre digestibilities, or that its action could not totally reverse all the factors causing the depression in digestibility due to the QT. The sheep in this trial had not received a tannin-containing diet prior to this experiment and they may not have fully adapted to the tannin containing diets during the adaptation periods of 3 weeks used per period. Browsing marsupials which consume tannin-containing diets constantly have been shown to be less susceptible to the effect of tannins than grazing marsupials which are not constantly exposed to these compounds (McArthur and Sanson, 1993). The lag phase of the grass hay incubated in sacco in sheep fed the CQT diet was shorter (P < 0.05) than those of other sheep fed control or Browse Plus-containing diets. The short lag phase on QT diet might have been introduced as an artefact caused by extrapolation of the curve. Thus a high rate constant (c) would result in a high estimate of the apparent lag time 0,). However, the suggestion of a reduced rate of degradation of the potentially degradable insoluble fraction (Table 2) suggests that cellulolysis was reduced (0rskov and Ryle, 1990). The degradation of hay in vitro measured by gas production followed a slightly different pattern from the results obtained in sacco. In vitro, QT reduced the asymptote of gas production. This suggests a reduction in microbial fermentative activities and it further supported the observation made about the effects of the QT on digestibilities of nutrients in vivo. The improvement in degradation of hay in vitro by Browse Plus was greater than that found in vivo and in sacco. It is possible

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that in in-vivo and in-sacco experiments, the large rumen volume and/or the continuous flow of digesta might result in a reduction of the effect of the Browse Plus. However, the in-vivo and in-sacco experiments most closely model the natural situation and are the best guide to the effects of Browse Plus under practical conditions where nutrient supply is adequate. It should be remembered however that in this work the diets were adequate in all nutrients including trace elements. Thus any adverse effects of tannins, for example chelation of mineral elements and subsequent increased excretion (Mansoori and Acamovic, 1996) and reduced absorption, may have less of an effect than in animals where the nutrient supply, especially trace element, is marginal or limiting. In cases of limited availability of nutrients, such as during drought conditions in Zimbabwe, supplementation of small amounts of Browse Plus may yield greater improvements than in animals fed nutritionally adequate diets. In conclusion, the results of this work demonstrated that QT added to the diets of sheep depressed the apparent digestibilities of nutrients in vivo, reduced the rate of degradation of the slowly degradable fraction in sacco and reduced microbial activities in vitro. Browse Plus was able to alleviate some but not all the reductions in digestibilities associated with the presence of QT in vivo. Further data from experiments with farm animals fed tannin-containing forages are required before the potential benefit of Browse Plus can be fully assessed.

Acknowledgements M.B. Salawu gratefully acknowledges the financial support of the Commonwealth Scholarship Commission. SAC and RR1 are financially supported by SOAEFD. This work was conducted in association with EU project ERBTS3 CT930211. Browse Plus was supplied by Agricura (PVT) Ltd., Zimbabwe.

References Acamovic, T., Garwe, E., Stewart, C.S., Duncan, I.M., 1995. The nutritional and anti-nutritional characteristics of six browse species from Zimbabwe. Anim. Sci. Proc. Br. Sot. Anim. Sci. 60, 112. Anonymous, 1995a. Farming report. Browse Plus expanded food source for livestock. Financial Gazette, 29 June 1995. Anonymous, 1995b. Farming report. Browse Plus trial results available. Financial Gazette, 6 July 1995. Association of Official Analytical Chemist, 1990. Official Method of Analysis, 15th ed. AOAC, Washington DC. Bae, H.D., Yanke, L.J., McAllister, T.A., Forsberg, C.W., Cheng, K.J., 1994. Effects of quebracho (Loxopteygium loetzil) condensed tannins on grain digestion. Proc. Sot. Nutr. Physiol. 3, 200. Barry, T.N., Duncan, S.J., 1984. The role of condensed tannins in the nutritional value of Lotus pedunculatus for sheep. 1. Voluntary intake. Br. J. Nutr. 57, 485-491. Barry, T.N., Manley, T.R., 1984. The role of condensed tannins in the nutritional value of Lotus pedunculatus for sheep. 2. Quantitative digestion of carbohydrates and proteins. Br. J. Nutr. 51, 493-504.

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