potential of cytisus and allied genera (genisteae: fabaceae) as forage...

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Potential of Cytisus and allied genera(Genisteae: Fabaceae) as forage shrubsFernando González‐Andrés a & Jesús María Ortiz a

a Departamento de Biología Vegetal, Escuela Técnica Superior deIngenieros Agrónomos , Universidad Politécnica de Madrid , Madrid,28040, SpainPublished online: 17 Mar 2010.

To cite this article: Fernando González‐Andrés & Jesús María Ortiz (1996) Potential of Cytisus andallied genera (Genisteae: Fabaceae) as forage shrubs, New Zealand Journal of Agricultural Research,39:2, 205-213, DOI: 10.1080/00288233.1996.9513179

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New Zealand Journal of Agricultural Research, 1996, Vol. 39: 205-2130028-8233/96/3902-0205 $2.50/0 © The Royal Society of New Zealand 1996

205

Potential of Cytisus and allied genera (Genisteae: Fabaceae) asforage shrubs2. Chemical composition of the forage and conclusions

FERNANDO GONZALEZ-ANDRESJESÚS MARÍA ORTIZ

Departamento de Biología VegetalEscuela Técnica Superior de Ingenieros

AgrónomosUniversidad Politécnica de Madrid28040 Madrid, Spain

Abstract The chemical composition of theherbage produced by shrubs belonging to the genusCytisus and allied genera (Cytisophyllum,Chamaecytisus, and Genista sect. Teline) wasdetermined to appraise its potential value for forage.In their third year, eight accessions were assessedin a semi-arid environment (400 mm annual rainfall)for seasonal variation of leaf/stem ratio, andcontents of ashes, neutral detergent fibre (NDF),acid detergent fibre (ADF), acid detergent lignin(ADL), and crude protein (CP). Fibre and crudeprotein concentration were similar to those of best-quality shrubby legumes like Medicago sp. pi.Colutea sp. pi., or Chamaecytisus palmensis (ADF,18-35%; CP, 14-24%). Genista monspessulanahad low fibre and high protein contents, whichwere the most constant during the year. From theresults obtained in this and the previous agro-nomic study, Part 1 of this series (Gonzalez-Andrés& Ortiz 1996), Genista monspessulana,Chamaecytisus podolicus, and C. supinus arerecommended as potentially useful forage shrubsbecause of their high dry matter productionpotential, high survival rate, and favourablechemical composition. This needs to be validatedin studies involving animals.

A95064Received 10 October 1995; accepted 12 February 1996

Keywords Cytisophyllum; Cytisus; Genista;Chamaecytisus; Teline; crude protein; neutraldetergent fibre; acid detergent fibre; acid detergentlignin; forage quality

INTRODUCTION

The nutritive value of trees and shrubs for browsinganimals depends not only on the forage digestibility,but also on the amount voluntarily eaten by animals.This depends on its palatability (Wilson 1977)which can vary seasonally (Dann & Low 1988),and its accessibility (availability). Digestibilityindicates the food portion that is actually used bythe animal (Holochek et al. 1982). It may be directlyestimated in vivo or by using indirect procedures.These procedures are cheaper and more convenientthan in vivo estimation, and they are based onseveral different techniques (incubation in rumen,in vitro incubation in the ruminal liquid, NIRspectroscopy, etc). One of these indirect proceduresinvolves linear regression equations estimated fromthe chemical composition of forages, specificallythe different proportions of the cell wall components(Susmel et al. 1991). However, the prediction ofshrubby forage digestibility using the regressionequations obtained for grasses is not usuallyaccurate (Nefzaoui & Chermiti 1991), and it isnecessary to define specific equations for differentshrub types (Susmel et al. 1991). In addition, proteinavailability of shrubs is sometimes limited becauseof effects of anti-quality factors such as lignin andtannins, on breakdown in the animal (Dann & Low1988). Therefore, the study of the chemicalcomposition of shrubby species intended to beused for browse is important for two reasons. First,it is necessary to know the proportion of thedifferent nutrients in order to predict a priori itspotential feeding value. Conversely, determiningforage chemical composition, followed by theestimation of in vivo digestibility, is necessary forthe calculation of regression equations, used toestimate the digestibility.

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206 New Zealand Journal of Agricultural Research, 1996, Vol. 39

The forage composition varies from season toseason because of the physiological changes whichoccur in plants during their growing season.However, species vary in their response to climaticand physiological changes (Dann & Low 1988),and these differences determine their practical valueas forage shrubs.

The main objective of this work was todetermine the seasonal variation in chemicalcomposition of eight accessions selected from thetaxa analysed in Part 1 (Gonzalez-Andres & Ortiz1996). A secondary objective was to use thisinformation to identify accessions for furtherevaluation as potential forage shrubs for smallruminants, mainly sheep. The closely relatedspecies tagasaste (Chamaecytisus palmensis) hasthe following fibre and protein contents: NDF,41%; ADF, 25%; ADL, 7%; CP 15,6%. In vivodigestibility was 54% (3 h) and 79% (48 h). Invitro digestibility was 71% (data from Lambert etal. 1989).

MATERIALS AND METHODS

Plant material and sampling procedurePlant material (Table 1) was obtained from theexperimental plot described by Gonzalez-Andres& Ortiz (1996), during the third growing season(1994). Eight accessions were selected for thechemical composition study, each representativeof the main groups of accessions described in a

previous botanical characterisation study(Gonzalez-Andres 1995). Up to five samplings wereconducted during the year: early spring ("Spring1"); late spring ("Spring 2"); middle summer; earlyautumn; and middle winter. For each season, thoseaccessions with unhealthy or low vigour foliage asa result of the environmental stress were notsampled in that season. Leaves and stems up to 4mm in diameter were classified as the browsingfraction for sheep, and the rest of the herbageabove the ground level as the non-browsing fraction.For the chemical analyses, three randomly selectedplots were sampled per accession. One hundred gof fresh browsing fraction was collected from thethree plants of every selected plot. Fresh materialwas dried for 48 h at 60-65°C and used for theanalysis. The determination of the ratio browsingversus non-browsing fraction was conducted at theend of the experiment (autumn 1994). Three plotsper accession were randomly selected and onerandomly selected plant from each plot washarvested to ground level, and both fractionsseparatedly dried at 105°C.

Chemical analysisChemical analysis of the browsing fraction wascarried out following A.O.A.C. (1984) proceduresfor determination of dry matter (DM) and ash.Nitrogen (N) concentration was determinedcolorimetrically after Kjeldahl digestion (Williams& Twine 1967). Crude protein was estimated as

Table 1 Plant material and physiological state of eigth accessions al five sampling times.

Species

Cytisophyllumsessilifolium

Cytisus villosus

Chamaecytisuspodolicus

Chamaecytisusruthenicus

Genista tenera

Genistamonpessulana

Genistamonspessulana

Genista tenera

Ace. #

01

14

18

20

23

24

25

28

Spring 1

Flowering

Flowering

Vegetative

Flowering

Flowering

Flowering

Flowering

Vegetative

Spring 2

Fruiting

Fruiting

Flowering

Fruiting

Fruiting

Fruiting

Fruiting

Flowering

Summer

Dormant

Dormant

Fruiting

Dormant

Dormant

Dormant

Dormant

Fruiting

Autumn

NSNo leaves

Dormant

Dormant

NSNo leaves

Dormant beforeautumn regrowth



Summer rest

Winter

NSDormantNSDormantNo leaves

Dormant

Dormant

Dormant

NSWinter rest

NS = not sampled.

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Gonzalez-Andres & Ortiz—Chemical composition of forage shrubs 207

N x 6.25. Acid detergent fibre (ADF) and aciddetergent lignin (ADL) were determined by theprocedure of Van Soest (1963), and neutraldetergent fibre (NDF) following Roberston & VanSoest (1977).

Statistical analysisStatistical analysis of data involved analysis ofvariance (two-way ANOVA). Two different aspectswere studied for each dependent variable. First,the variation among the different samplings for agiven accession was studied. In this instance thesources of variation were the date of sampling andthe block. The second aspect was the variationamong the different accessions on a given samplingdate. The sources of variation were accessions andblocks. The Duncan's test was used to comparemeans (P < 0.05). The software package SAS (SASInstitute 1985) was used for all the statisticalanalyses.

RESULTS

Leaf/stem ratiosLeaf/stem ratios for the browsable fraction werehighest in spring and subsequently decreased insummer and autumn (Table 2). Genista linifolia

(#23) and G. monspessulana (#24, 25) showedhigher ratios in winter than in autumn.

G. tenera (#28) had a significantly lowest ratiothan the rest of the accessions throughout the year.

Dry matterDry matter percentages were significantly lowestin spring (Table 3). The highest values correspondedto summer, autumn, and/or winter according to thedifferent species.

Genista linifolia (# 23) had the highest DMpercentage throughout the year, together withCytisophyllum sessilifolium (#1) in Spring 2, andC. sessilifolium and Chamaecytisus ruthenicus(#20) in summer.

AshAsh content progressively decreased in Genistalinifolia (#23) and G. monspessulana (#24, 25)throughout the growing season. However, for therest of the accessions, ash decreased in Spring 2with respect to Spring 1, increased in summer, anddecreased again in winter.

Cytisus villosus (#14) had the highest ashcontent throughout the year (6.5-7.7%), togetherwith Genista monspessulana (#24) in Spring 1, 2,and autumn, Chamaecytisus podolicus (#18) in

Table 2 Seasonal variation of leaf/stem ratio for the browsable fraction. Values are accession means.

Accession

1 Cp. sessilifolium

14 Cy. villosus

18 Ch. podolicus

20 Ch. ruthenicus

23 G. linifolia

24 G. monspessulana

25 G. monspessulana

28 G. tenera

Degree freedom errorPooled standard error

Spring 1

1.95

2.7

2.46

2.34

3.82

2.85

2.78

0.84

380.154

eAbAdBdBaAbAbeAfB

Spring 2

2.01

2.77

3.14

3.02

2.42

2.37

2.25

1.02

380.116

dAbAaAaAcBcBcBeA

Summer

1.31

1.90

2.07

1.75

1.87

1.91

1.60

0.76

380.106

dBabBaCbeCabCabCcDeB

Autumn

-

1.50

1.91

-

1.36

1.59

1.04

0.77

280.07f

beCaC

cDbDdEeB

Winter

-

-

-

1.81 b

c1.93 ab

c1.99 a

c

130.070

DFE

13

18

18

13

23

23

23

18

Pooled SE

0.103

0.080

0.094

0.117

0.079

0.119

0.070

0.054

Capital letters indicate significant differences among sampling dates for a given accession (rows) and small lettersindicate differences among accessions for the same sampling date (columns) (Duncan's test, P < 0.05).

Cp: Cytisophyllum; Cy: Cytisus; Ch: Chamaecytisus; G: Genista.DFE: Degrees of freedom for the error. Pooled SE: Pooled standard error.

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autumn, and G. linifolia (#23) in Spring 2.Cytisophyllum sessilifolium (#1) consistently hadthe lowest ash content, although other accessionshad similar (P > 0.05) estimates at some samplings.

NDFNDF contents for all accessions were significantlylower in Spring 1 than at the later sampling times(Table 4).

Table 3 Seasonal variation of dry matter content (%). Values are accession means.

Accession

1 Cp. sessilifolium

14 Cy. villosus

18 Ch. podolicus

20 Ch. ntthenicus

23 G. linifolia

24 G. monspessulana

25 G. monspessulana

28 G. tenera


Spring 1

29.6

26.6

25.4

22.5

34.5

25.1

24.0

28.5

380.421

bBdDeC

gCaBeCfDcC

[

Spring 2

32.0

29.1

25.2

29.0

32.4

26.0

26.6

28.0

380.865

aBbCdCbBaBdCcdCbeC

Summer

40.4 a

A

35.6 c

B

37.8 b

A

38.9 ab

A

40.6 a

A

31.2 d

A

34.4 c

A

37.7 b

A

380.832

Autumn

-

38.0

34.4

-

40.1

27.7

34.6

31.2

bAcB

aAeBcAdB

280.821

Winter

-

-

-

-

40.1 a

A

31.4 b

A

32.9 b

B-

131.520

DFE

13

18

18

13

23

23

23

18

Pooled SE

0.980

0.615

0.432

0.484

1.300

0.696

0.458

0.714

Capital letters indicate significant differences among sampling dates for a given accession (rows) and small lettersindicate differences among accessions for the same sampling date (columns) (Duncan's test P < 0.05).


Table 4 Seasonal variation of neutral detergent fibre (NDF) content (%/DM). Values are accession means.

Accession

1 Cp. sessilifolium

14 Cy. villosus

18 Ch. podolicus

20 Ch. ntthenicus

23 G. linifolia

24 G. monspessulana

25 G. monspessulana

28 G. tenera


Spring

30.7

53.3

46.7

47.2

43.7

33.5

40.1

43.2

1fcaCbBbBcCeCdCcD

381.001

Spring

39.7

56.8

48.9

49.7

49.6

40.8

46.8

46.3

381.199

2

eBaAbeAbAbBeBcdAdC

Summer

44.7

54.1

49.9

47.1

50.9

40.9

45.4

56.3

eAbBCcAdBcABfBdeABaA

380.948

Autumn

-

55.0

49.7

-

50.2

42.1

45.2

49.6

aBbA

bABdAcBbB

281.070

Winter

-

-

-

-

51.3

40.4

44.7

-

aAcBbB

130.716

DFE

13

18

18

13

23

23

23

18

Pooled SE

1.831

0.591

0.677

0.636

0.583

0.449

0.700

0.611



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Cytisus villosus (#14) had significantly highervalues throughout the year except for summer,when Genista tenera (#28) had the highest NDF.C. villosus was not sampled in winter, and G.linifolia (#23) had the maximum value. Signi-ficantly lowest values occurred for Cytisophyllumsessilifolium (#1) in Spring 1, for C. sessilifoliumand G. monspessulana (#24) in Spring 2, and forG. monspessulana (#24) in the rest of the samplings.

ADFADF contents (Table 5) were significantly lowestin Spring 1, except for Chamaecytisus ruthenicus(#20) which had its maximum value for thatsampling.

Significantly highest values were shown byCytisus villosus (#14) in Spring 1, C. villosus,Genista linifolia (#23), and G. tenera (#28) insummer, and C. villosus and G. linifolia for the restof the samplings. Lowest values corresponded toG. monspessulana (#24) throughout the year,together with Cytisophyllum sessilifolium (#1) inSpring 1 and 2, and Chamaecytisuspodolicus (#18)in autumn.

ADLADL contents (Table 6) were lowest in Spring 1for all the accessions except for Chamaecytisus

ruthenicus (#20). The highest contents occurred insummer or winter according to the different species.

Cytisus villosus (#14) had the highest ADLcontents and Genista monspessulana ( #24) hadthe lowest contents.

Crude proteinCrude protein contents (Table 7) were maximumin spring, and decreased through the growingseason. Genista monspessulana (#24, 25) hadhigher contents in winter than in autumn.

Crude protein contents were significantlyhighest for Genista monspessulana (#24, 25)throughout the year, except for Spring 1 in whichthe maximum value was for Chamaecytisusruthenicus (#20). Furthermore, C. ruthenicus insummer, and Chamaecytisus podolicus (#18) andG. tenera (#28) in autumn, did not significantlydiffer from G. monspessulana. G. linifolia (#23)had the lowest values throughout the year, togetherwith Cytisophyllum sessilifolium (#1) and G. tenera(#28) in summer and Cytisus villosus (#14) inautumn.

Browsable versus non-browsable fraction ratioBrowsable versus non-browsable fraction ratio washighest for Cytisus villosus (#14), Chamaecytisussp. pi. (#18,20), and Genista tenera (#28) (Table 8).

Table 5 Seasonal variation of acid detergent fibre (ADF) content (%/DM). Values are accession means.

Accession

1 Cp. sessilifolium

14 Cy. villosus

18 Ch. podolicus

20 Ch. ruthenicus

23 G. linifolia

24 G. monspessulana

25 G. monspessulana

28 G. tenera


Spring 1

19.3

30.5

24.6

28.5

27.4

18.0

23.7

24.9

dCaCcCbAb

cdDcBcD

380.802

Spring 2

21.4

33.1

28.6

24.1

33.5

21.4

24.6

26.6

eBaBbAdBaABeCdBcC

380.674

Summer

25.0

34.5

29.2

24.8

35.0

23.3

27.0

36.0

dAaAbAdeBaAeBcAaA

380.771

Autumn

-

32.8

25.7

-

32.9

26.3

28.1

29.0

aBdB

aBdAbAbB

280.920

Winter

-

-

—

-

33.1 a

B

21.4 c

c27.0 b

A-

130.880

DFE

13

18

18

13

23

23

23

18

Pooled SE

0.754

0.596

0.401

0.591

0.765

0.670

0.688

0.295



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Table 6 Seasonal variation of acid detergent lignin (ADL) content (%/DM). Values are accession means.

Accession

1 Cp. sessilifoliutn

14 Cy. villosus

1 8 Ch. podolicus

20 Ch. ruthenicus

23 G. linifolia

24 G. monspessulana

25 G. monspessulana

28 G. tenera


Spring 1

7.4

13.5

10.1

12.1

8.7

6.1

7.3

8.1

eBaDcBbAdCfCeCdeC

380.460

Spring 2

8.4

15.4

11.3

9.8

10.3

7.3

8.2

8.6

dAaBbAcBcB

eBdBdBC

380.414

Summer

8.5

16.2

11.2

9.8

12.7

7.6

8.8

11.3

eAaAcAdBbAf

Be

B

c

A

380.377

Autumn

-

14.5

10.7

-

10.8

7.9

8.8

8.9

aCbAB

bBdBcdBcB

280.446

Winter

—

-

-

-

12.1 a

A

8.9 c

A

10.8 b

A

130.337

DFE

13

18

18

13

23

23

23

18

Pooled SE

0.207

0.296

0.463

0.406

0.418

0.344

0.369

0.250



Table 7 Seasonal variation of crude protein content (%/DM). Values are accession means.

Accession

1 Cp. sessilifolium

14 Cy. villosus

18 Ch. podolicus

20 Ch. ruthenicus

23 G. linifolia

24 G. monspessulana

25 G. monspessulana

28 G. tenera


Spring 1

22.1

22.0

21.3

23.9

16.5

21.7

22.2

21.9

bAbAbAaAcAbAbBbA

380.678

Spring 2

18.6

20.8

18.5

20.1

17.4

22.1

24.3

19.4

eB

cBeBcdBfAbAaA

deB

380.497

Summer

14.4

16.2

16.0

18.9

15.0

19.3

19.6

15.3

cCbCbCaCbeBaBaDbeD

380.584

Autumn

-

14.6

16.1

-

13.4

17.2

17.3

16.8

bDaC

bCa

C

a

E

a

C

280.613

Winter

-

-

-

-

14.3 b

C

19.9 a

B

20.4 a

c

130.578

DFE

13

18

18

13

23

23

23

18

Pooled SE

0.246

0.269

0.334

0.499

0.455

0.734

0.224

0.218


Cp: Cytisophyllum; Cy: Cytisus; Ch: Chamaecytisus; G: Genista.DFE: Degrees of freedom for the error. Pooled S.E. Pooled Standard Error.

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Conversely, the lowest values occurred forCytisophyllum sessilifolium (#1) and G. mon-spessulana (# 24, 25).

DISCUSSION

The potential feeding value of a forage can beestimated from its chemical composition. A lowcontent of non-digestible cell wall components(estimated as ADF and ADL) and a high proteincontent (estimated as crude protein) suggest goodforage quality (Van Soest 1983). Leaves have lowerfibre and higher protein contents than stems, andthe difference increases with age. Therefore, leaveshave higher nutritive value than stems. At thebeginning of the growing season, the leaf/stemratio generally reaches a maximum and decreasesthereafter. This is because of internode lengtheningand leaf drop during the summer, this latter inresponse to moisture stress. This evolution wasshown in the studied species. Genista linifolia andG. monspessulana had higher leaf/stem ratios inwinter than in autumn, because of the typicalautumn regrowth which occurred after the autumnsampling. This is very important for forage shrubsystems, where the main interest of shrubs assources of fodder is to cover forage gaps duringsummer and/or winter (Correal 1995). Autumnregrowth also occurred in Medicago species (Marborea andM strasseri) (Alegre et al. 1993).

Table 8 Browsable/non-browsable fraction ratio forherbage above ground level. Values are accession means.

Accession

Whole plantdry matter(g/plant) Ratio

114182023242528

Cp. sessilifoliumCy. villosusCh. podolicusCh. ruthenicusG. linifoliaG. monspessulanG.monspessulanaG. tenera

DFEPooled SE

750953578682

120019091156363

0.39c

0.68a

0.76a

0.65ab

0.57b

0.41c

0.4 lc

0.67ab

4485.2

Values followed by the same letter do not significantlydiffer (Duncan's test, P < 0.05)

DFE: Degrees of freedom for the error. Pooled SE:Pooled standard error.

As a consequence of the higher fibre content ofstem compared with leaf, estimated fibre content isinversely related to leaf/stem ratio. For this reason,fibre estimation parameters had lower values at thebeginning of spring. However, Chamaecytisusruthenicus (#20) was an exception: ADF and ADLwere significantly higher at the beginning of thespring. This was because that species is deciduousand is slow to commence growth in spring. In oursampling, a high proportion of the previous season'sshoots—more lignified—were collected. On theother hand, Genista tenera had an abnormally highfibre content in summer because of the high amountof fruit produced by that species at that time.

In contrast to fibre content, crude protein contentis maximum at the beginning of the spring, anddecreases during the growing season. This is aresponse to tissue aging on the one hand, and aconsequence of the decrease in the leaf/stem ratioon the other. The decrease in crude protein duringthe growing season was comparatively slower forGenista linifolia and G. monspessulana than forthe rest of the species. G. monspessulana had higherprotein content in winter than in autumn, becauseits autumn regrowth maintained good quality duringwinter.

Non-digestible cell wall components werehighest for Cytisus villosus and Genista linifoliathroughout the year (ADF contents ranging from27.4 to 35%). Moreover, C. villosus had the highestlignin content (13.5-16.2%), suggesting that itsforage is potentially the least digestible. Conversely,G. monspessulana (#24) had the lowest non-digestible cell wall contents (ADF of 18-26% andADL of 6.1—8.9%). Average contents obtained weresimilar to those of the high-quality shrubby foragelegumes such as Medicago sp. pi., (Lambert et al.1989; Alegre et al. 1993; Sancha et al. 1993),Colutea sp. pi. (Sancha et al. 1993; Zulueta 1983;EZN 1993), and tagasaste (Chamaecytisuspalmensis) (Lambert et al. 1989). Our values areclose to those of the herbaceous legumes such aslucerne (Medicago sativa) or sainfoin (Onobrychissativa) (Andrieu et al. 1988).

Crude protein content was highest for the twoaccessions of Genista monspessulana (17.2—24.3%), and they had the most constant contentsthroughout the year. G. linifolia had a fairly constantcontent, but with the lowest values (13.4—17.4%).Moreover, the crude protein content of Cytiso-phyllum sessilifolium declined dramatically fromspring (22.1%) to summer (the lowest with 14.4%).The protein contents were medium—high when

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compared with the shrubby legume species cited inthe previous paragraph. They were similar to thoseof lucerne (16.8-25.9%) and higher than those ofsainfoin (13.1%—18.4%) [data taken from Andrieuetal. (1988)].

Ash content is usually higher in leaves than instems (Lambert et al. 1989), but in our study wefound a positive correlation between leaf/stem ratioand ash content only for Genista linifolia andG. monspessulana (Pearson coefficient >0.70,P < 0.05). The remaining species had a maximumin summer, as did Colutea and Medicago sp. pi.when evaluated under the same ecogeographicalconditions (Alegre et al. 1993).

We have conducted a preliminary study onphenolic compounds as potentially anti-nutritionalfactors (unpubl. data). This involved flow-backextraction for 30 m with 50% ethanol-water, anddetermination of the whole phenolic compoundscontent following the protocol of Horwitz (I960).Tagasaste {Chamaecytisus palmensis) was used asthe control. Cytisus villosus had twice the contentof tagasaste, Chamaecytisus podolicus andChamaecytisus ruthenicus about the same contentthat the control, and Cytisophyllum sessilifolium,Genista monspessulana, and G. tenera half thecontent of tagasaste.

Because of its excellent chemical composition,further studies involving animals should beconducted to determine if Genista monspessulanacould be useful as the sole diet at certain times ofthe year.

CONCLUSIONS

Results from this study and Part 1 (Gonzalez-Andres & Ortiz 1996) indicate that the followingshrub species are potentially useful for forage inarid regions.

Genista monspessulana

The advantages include its perennial nature andgood forage quality during winter; its high seedgermination and plant survival in the field; its highDM production potential; and its favourable andconsistent chemical composition during the year,with low fibre and high crude protein content.Conversely, the main disadvantages are thecomparatively lower ratio of browsable/non-browsable material, and the excessive.growth aboveanimal browsing.

Genista monspessulana (#24) was botanically(Gonzalez-Andres 1995) and agronomicallydifferent from other accessions of the species withrespect to lower germination percentage, lowerfield survival rates, and more dense foliage. It alsohad lower fibre content than other accessions.Further studies are necessary to determine if thisaccession is a polyploid variation.

Genista canariensis was very similar to G.monspessulana in its performance although it wasnot as tall as G. monspessulana. This might be anadvantage for sheep browsing.

Chamaecytisus podolicus and C. supinus (aclosely related species) were also potentiallyinteresting. Although these are deciduous shrubs,the leaves remain on the plant until late autumn,and autumn forage has good quality. The specieshas a low height/diameter ratio which is good fromthe point of view of browse for sheep, and alsoshowed it could provide good wildlife shelter. Fieldsurvival of this species was excellent.

Further studies are being conducted with allabove-mentioned species in order to determine (i)their performance in different environments; (ii) invivo nutritive value; and (iii) voluntary intake.

The remaining species were of less interest asforage shrubs.

Cytisophyllum sessilifolium, Cytisus hetero-chrous,Chamaecytisus glaber, C. hirsutus, and C.ruthenicus are deciduous shrubs and forage qualitydecreases very quickly from mid summer onwards.Cytisus villosus and Genista linifolia are particularlyhairy, reflected in the high fibre content, and theyprobably would have low palatability. However,the good field survival shown by all the mentionedspecies could make them adequate for N fixation, abenefit for the ecosystem (Gadgil 1971)

Cytisus arboreus, C. baeticus, C. grandiflorus,C. purgans, C. reverchonii, C. scoparius, and C.striatus shed leaves very early in spring, and theremaining fibrous stems would probably be toohard for animal browsing. Most of these speciesplus Genista tenera also had low survival rates.Hence these species cannot be recommended, atleast for the ecological conditions in which theywere tested.

ACKNOWLEDGMENTS

We thank the Departamento de Alimentacion Animal,Universidad Politecnica de Madrid, Spain, and especiallyDrs C. Rodriguez, J. Gonzalez-Cano, and R. Alvir, fortheir advice and assistance with the chemical analyses.

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Williams, G. W.; Twine, J. R. 1967: Determination ofnitrogen, sulphur, phosphorous, potassium,sodium, calcium and magnesium in plant materialby atutomatic analysis. Division of Plant Industrytechnical paper no. 24, CSIRO, Australia.

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potential of cytisus and allied genera (genisteae: fabaceae) as forage...

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