Livestock Research for Rural Development 21 (4) 2009 Guide for preparation of papers LRRD News

Citation of this paper

Seasonal changes in chemical composition and in vitro gas production of six plants from Eastern Algerian arid regions

M-L Haddi, H Arab*, F Yacoub*, J-L Hornick**, F Rollin** and S Mehennaoui*

Faculté des Sciences de la Nature, Université de Constantine, Route Ain El Bey, 25000 Constantine, Algeria
*Laboratoire LRESPA, Département des Sciences Vétérinaires, Université de Batna, Algeria
**Faculty of Veterinary Medicine, University of Liège, Belgium
haddil@yahoo.com

Abstract

Seasonal variations of nutritive value of six important plants from Algerian arid regions were investigated. Edible aerial parts were monthly sampled, when available, from October 2002 to July 2003 and their chemical composition and their in vitro gas production (GP) parameters evaluated using a logistic model. Metabolisable energy (ME) and organic matter digestibility (OMD) were also estimated. Arid plants were three halophytes shrubs (Atriplex halimus, Salsola vermiculata and Sueada mollis), one tree fodder (Tamarix africana) and two herbaceous plants (Cynodon dactylon and Cyperus conglomeratus). Three semi-arid forages (green wheat Triticum aestivum, green leguminous Hedysarum coronarium) and commercial mixed hay were used for comparison.

 

Organic matter (OM), crude protein (CP), neutral detergent fibre (NDF), calcium, GP kinetic parameters, ME and OMD were significantly lower (P<0.05) for arid plants and their NDF, ADF and ADL contents (480 ± 215, 281 ± 150 and 76.3 ± 45.0 g/kg DM, respectively) were not significantly affected by the season. CP content was significantly lower (P<0.05) in summer (108± 4.1 g/kg DM). Within arid plants, seasonal changes were significant for DM (P<0.001), CP (P<0.001), copper (P<0.05), phosphorus (P<0.0001), ME (P<0.001) and OMD (P<0.001). Maximum rate of GP (rm) for arid feeds occurred in winter (0.049 h-1, January) with the lower value in autumn (0.025 h-1, October), while the highest asymptotic GP “b” was reached in winter (February: 277 ml/g OM). Seasonal changes were highly significant for b, t1 (half time of b), tm (time needed for rm), rm, GP at 24 h (b24), GP at 48 h (b48) and GP at 96 h (b96). Depending on the season, some arid plants were better fermented in winter: Atriplex halimus in January (rm=0.069 h-1), Sueada mollis in February (0.052 h-1), Tamarix africana in January (0.062 h-1); others in spring: Cynodon dactylon in March (0.037 h-1) and Cyperus conglomeratus in May (0.055 h-1), while Salsola vermiculata reached its rm in summer (0.056 h-1, in July),). ADL content was negatively correlated to GP (-0.27≤r≤-0.34), ME (r=-0.50) and OMD (r=-0.35) only for arid plants. Cu content (10.0 mg/Kg DM; CV: 24.6 %) was positively correlated to the constant of fitting curve “c” (r=0.38) and GP (r=0.19). P content was essentially correlated to the GP (0.18≤r≤0.34). Arid plants, except Salsola vermiculata, have better nutritional characteristics in winter and spring, the wet and cold seasons.

Keywords: arid shrubs, Atriplex, Cynodon, Cyperus, Salsola, Sueada, Tamarix


Introduction

 The contribution of the native pastures to the nutritional requirements of domestic animals is essential in the Eastern Algerian arid zones. Chenopodiaceous shrubs like Atriplex, Salsola and Sueada, and herbaceous plants like Cynodon dactylon are the main forage plants. Atriplex spp. is a world spread halophyte shrub especially in salty soils. Their various agronomic and nutritional aspects are well characterized (Haddi et al 2002; El Waziry 2007). In the cold season (from October to March), part of the 19 millions of sheep move to the arid pastures where dromedaries and other domestics animals live all the year. So the stoking rate arises and subsequently becomes detrimental for forage plants and the local environment where the ranging is essentially extensive due to the scarcity of water and feeds. Scare and irregular precipitations, excessive temperatures, drought, salinity and evapotranspiration in the arid regions influence the life cycle and annual regrowth of xerophytes plants. Incidence of these factors on nutritional value of arid browses is not yet established. The potential feeding value and the nutritive characteristics of available browses in the natural pastures of salty arid regions remains poorly investigated. Understanding if the domestic animals meet their needs in terms of energy, nitrogen and mineral nutrients in these regions, can help to manage better the animal production and can ovoid possible nutritional deficits and their consequences on animal health. Our objective was to evaluate the seasonal changes of the nutritive value, by the determination of chemical composition and the in vitro gas production kinetics of six important plants browsed in the salty arid region in South-East Algeria. In order to rank these arid plants, partial comparison was made with three semi arid forages. Arid plants nutritionally evaluated here were only part of numerous plants daily browsed by domestic ruminants in the concerned region.

 

Material and methods 

Plant material and sampling areas

 

Six arid plants were collected monthly (when available) from the South-East Biskra from October 2002 to July 2003. Only edible green aerial parts, from 15 to 25 cm of length, were manually clipped from three halophytes shrubs (Atriplex halimus, Salsola vermiculata and Sueada mollis), one tree fodder (Tamarix africana) and two herbaceous plants: Cynodon dactylon and Cyperus conglomeratus. For several reasons, particularly the overgrazing, edible green aerial parts of arid plants were not quantitatively available all the time in the pasture and consequently it was not easy to find enough plant material at each sampling. Semi arid forages, used for comparison, were collected once in spring 2003 at Constantine (280 Km at North Biskra) and included green wheat plant, green leguminous Sulla (Hedysarum coronarium) and one commercial mixed hay. As reported by Lemnaouar (2001), mixed hay was the cheapest forage composed by several herbaceous dried plants and sold around the year in the market. The sampling site of arid plants was 5 m below sea level and is characterized by high salinity of soil. Average annual precipitation is 140 mm (Hirche et al 2007) concentrated during 30-40 days in the cold season, from the ending of autumn to the beginning of spring. The area is considered arid on the UNESCO classification scale (Pagot 1992).

 

Analytical methods

 

Chemical analysis of feeds

 

Whole plants were dried in air forced oven at 55° C for 72 h. Then, leaves and stems were manually separated for Atriplex halimus, Salsola vermiculata, Sueada mollis and Tamarix africana. For the others arid browses separation was not applicable. Semi arid forages were evaluated as whole plants. Samples were milled to pass 1 mm screen and stored in polypropylene bottles at room temperature for subsequent analysis. Dry matter (DM), ash, crude protein (CP), ether extract (fat) were determined using the AOAC procedures (AOAC 1990). Calcium, copper and manganese were determined using an atomic absorption spectrophotometer after wet digestion in nitric and perchloric acid and ashing. Phosphorus was determined by the phospho-molybdate reaction method using a photo flame spectrophotometer. Contents of neutral detergent fibre (NDF), acid detergent fibre (ADF) were analyzed according to Van Soest et al (1991), without α-amylase and sodium sulphite and expressed free of ash. Acid detergent lignin (72% H2SO4 , ADL) and acid insoluble ash (ASHINS) were determined following Robertson and Van Soest (1981). All samples were analyzed in duplicate.

 

Rumen fluid collection and in vitro gas production trials

 

Rumen content of slaughtered dromedaries was chosen for its appropriate in vitro gas production characteristics (Haddi et al 1999).The donor animals were adult males browsing in the same arid region of plant sampling, weekly transported from Biskra to municipal slaughterhouse at Constantine. The whole rumen content was collected in pre-warmed thermos, tightly closed and immediately transported to the laboratory. For in vitro trials, 200 ± 10 mg of dried samples were placed in 100 ml calibrated glass syringes witch were greased with Vaseline and pre-warmed. In a Wolfe flask, 1 volume of strained rumen fluid was mixed with 2 volumes of artificial saliva (Menke and Steingass 1988) at 39°C in water bath under free oxygen CO2 flux. Syringes were filled with 30 ml of the mixture, degassed and incubated at 39°C. Evolved gas was read every two hours in the first 24 h and every 6 h thereafter. The content of syringes was gently homogenised at each reading. Each batch for all samples was repeated twice in a different weeks and three syringes of blank (containing no feeds) were included. Cumulative gas was corrected for the blank and expressed in millilitres of gas produced (GP) per gram of organic matter (OM).

 

Data analysis

 

Corrected gas data were fitted to the monophasic logisitic model according to Groot et al (1996), g(t) = b/(1+(t1/t)c), where “t” is the time of in vitro incubation in hour, g(t) the cumulative gas produced expressed in ml/g OM, “b” the asymptotic gas production, t1 the time required to reach 50% of b, “c” an unitless constant reflecting the shape of the fitting curve. The fractional rate r(t) of GP was computed as follow r(t)=c.tc-1/(t1c+tc) (hour-1) and its maximum (rm) was reached when d(r(t))/dt=0 at trm, the time of maximum rate of GP. Gas production was also estimated at 24 h of incubation (b24), 48 h (b48) and 96 h (b96). Using cumulative gas (ml) produced by 200 mg DM of feed at 24 h and the content of CP (g/kg DM), metabolisable energy (ME) and organic matter digestibility (OMD) were estimated using the following regression equations of Menke and Steingass (1988) for roughage feeds:

ME (Mega Joules/Kg DM) =2.2+0.1357*GP (ml/200 mg DM) +0.0057*CP (g/kg DM) +0.0002859*CP2;


OMD (g/Kg DM) = 24.91+0.7222*GP (ml/200 mg DM) +0.0815* CP (g/kg DM).


In order to evaluate the effect of various factors, data were subjected to analysis of variance using the following general linear model:

Yi = µ + Fi + ei,

Where:

Yi = observation,
µ = population mean,
Fi = factor (plant species, location, morphological fraction or season) effect and
ei the residual error.

 

Means were separated using the Student Newman Keuls multiple range test in the GLM procedure of the SAS statistics software (SAS 2003). The correlation analysis and the non linear fitting were performed using the corresponding procedures of the same software.

 

Results 

Seasonal variation of chemical constituents

 

Arid plants seemed to maintain constant the major part of their nutritional constituents around the year (table 1).


Table 1. Chemical composition of arid plants (g/Kg DM) and effect of plant species, morphology and seasons on its variation

 

n#

DM, g

OM, g

ASHINS, g

EE, g

CP,g

NDF, g

ADF, g

ADL, g

Arid plants species

Atriplex halimus

53

244b

777bc

15,3c

18,6

131ab

440b

287

81,1ab

Cynodon dactylon

62

506a

843ab

77,0a

13,2

103b

676a

332

55,1bc

Cyperus conglomeratus

23

240b

867a

53,0b

16,0

139a

620a

309

40,0c

Salsola vermiculata

57

240b

741c

18,2c

15,5

128ab

420b

259

91,8a

Sueada mollis

53

214b

778bc

15,0c

15,7

147a

435b

260

76,0ab

Tamarix africana

47

509a

824abc

10,4c

14,4

139a

440b

269

87,1a

CV(§)

 

22,8

14,5

54,6

45,9

32,9

41,3

53,4

56,1

Morphological fractions

Leaves

110

284b

687b

21,1b

20,9a

172a

238b

138

64,0b

Stems

100

280ab

874a

8,6c

11,2c

96,5c

647a

414

106a

Whole plant

85

388a

854a

66,6a

14,4b

119b

651a

322

48,4c

CV

 

43,5

10,2

54,8

37,7

22,0

14,9

29,7

50,7

Seasons

 

 

 

 

 

 

 

 

 

Winter

87

282b

797

23,2

15,1

145a

461

262

71,0

Spring

102

243b

789

26,7

17,1

138a

473

290

78,0

Summer

65

380a

780

27,9

15,8

108b

499

280

76,3

Autumn

41

361a

8127

26,8

15,2

133a

498

298

82,8

CV

 

38,8

10,2

53,2

38,1

18,5

14,3

29,2

49,2

Overall means

 

304

793

25,9

15,9

132

480

281

76,3

Main effects

 

 

 

 

 

 

 

 

 

species

 

***

***

***

ns

*

***

ns

***

morphology

 

***

***

***

***

***

***

***

***

season

 

***

ns

ns

ns

***

ns

ns

ns

*: P<0,05; **: P<0,01; ***: P<0,001; ns: not significant (P>0,05); CV(§): coefficient of variation. Means with different letters, in each group, are significantly different (P<0,05). (#): sample size.


Seasonal variations were not significant (P>0.05) for organic matter, acid insoluble ash, ether extract, cell wall content (NDF), lignocellulosic content of cell wall (ADF) and for acid lignin (ADL), but significant (P<0.001) for only few chemical constituents: DM, CP, P and Cu (Table 2). The highest contents of DM were reached in the driest seasons, summer and autumn (380 and 361 g/kg of fresh matter, respectively). Summer was also a season with lowest CP (108 g /kg DM) and Cu (8.3 mg/kg DM) contents. Winter, a cold and humid season, seemed to be better for CP and P (145 g and 2.8 g/Kg DM, respectively). Cu content was significantly low in summer but relatively constant elsewhere.


Table 2.  Mineral composition of arid plants (g or mg/Kg DM) and effect of plant species, morphology and seasons on its variation

 

n#

Ca, g

P, g

Cu, mg

Mn, mg

Arid plants species

 

Atriplex halimus

53

10,5c

2,8a

14,1a

22,6c

 

Cynodon dactylon

62

13,0b

2,6ab

8,6c

59,2b

 

Cyperus conglomeratus

23

10,1c

2,7ab

10,4b

187a

 

Salsola vermiculata

57

9,7c

2,5ab

7,7c

27,5c

 

Sueada mollis

53

7,3d

1,8c

9,5bc

31,0c

 

Tamarix africana

47

22,0a

2,1bc

8,5c

28,0c

 

CV(§)

 

30,8

36,9

24,6

55,1

Morphological fractions

 

Leaves

110

13,6a

2,7a

10,7

37,4b

 

Stems

100

9,4b

2,0b

9,8

15,6c

 

Whole plant

85

11,7a

2,6a

9,4

116a

 

CV

 

47,0

37,4

33,5

81,8

Seasons

 

 

 

 

 

 

 

Winter

87

10,9

2,8a

10,2a

42,9

 

Spring

102

11,7

2,6ab

10,5a

47,8

 

Summer

65

12,5

1,8b

8,3b

50,8

 

Autumn

41

11,3

2,4a

11,4a

40,0

 

CV

 

47,2

32,5

32,0

80,4

Overall means

 

 

11,6

2,4

10,0

46,1

Main effects

 

 

 

 

 

 

species

 

***

***

***

***

 

morphology

 

***

***

ns

***

 

season

 

ns

***

***

ns

See Table 1


Chemical constituents of the morphological fractions

 

Morphological composition of arid plants  significantly (P<0.001) affected the contents of all nutrients, excepted Cu. Leaves have a highest content of EE, CP, Ca, P and a lowest content of ADF (138 g/kg DM). ADF and ADL were significantly higher for stems which have also significantly less ASHINS, EE, CP and Mn than leaves. OM content of stems was significantly higher than leaves but similar to whole plants (table 1).

 

Whole plant refers here only to herbaceous species (Cyperus conglomeratus and Cynodon dactylon) for which stems and leaves are difficult to separate in our context. DM, ASHINS, NDF and Mn were high in these plants, but their ADL content was significantly lower than leaves and stems of the arid plants.

 

Chemical constituents of arid species

 

Arid plants belong to different categories: shrubs, tree fodders and herbaceous plants, and showed different nutritional contents. Nutritional differences between plant species were large, in terms of CV,0 for ADL, Mn, ASHINS and ADF, but limited for OM. Herbaceous plants were less lignified than shrubs: Cyperus conglomeratus was the less lignified and Tamarix africana, was the more lignified.

 

Compared to semi arid forages, arid plants showed significantly less OM (P<0.001), CP (P<0.05) and Ca (P<0.001). Nevertheless, arid and semi-arid forages have comparable contents of DM, ASHINS, EE, NDF, ADF, ADL, P, Cu and Mn (P>0.05) (Tables 3 and 4).


Table 3.  Chemical composition (g/Kg DM) of semi arid forages compared with arid plants

 

n(#)

DM, g

OM, g

ASHINS, g

EE, g

CP, g

NDF, g

ADF, g

ADL, g

Semi-arid forages

Commercial mixed hay

7

879

927

20,8

15,5

93,8

644

426

94,5

Green wheat

7

299

925

38,2

20,4

126

498

250

19,6

 

Green Sulla

8

124

880

5,8

21,1

201

322

271

110

 

CV(§)

 

3,0

0,8

85,0

24,9

6,8

12,3

19,1

32,5

 

means

 

365

900

14,7

19,4

159

439

312

92,9

Overall means

 

Arid

295

305

793b

25,9

15,9

132b

480

281

76,3

 

Semi-arid

22

365

900a

14,7

19,4

159a

439

312

92,9

Location effect

 

ns

***

ns

ns

*

ns

ns

ns

 

RMSE

 

162

116

25,4

7,2

45,3

211

146

44,8

See Table 1



Table 4.  Mineral composition of semi arid forages compared with arid plants, mg or g/Kg DM

 

n#

Ca, g

P, g

Cu, mg

Mn, mg

Semi-arid forages

Commercial mixed  hay

7

18,2

1,7

9,6

28,1

 

Green wheat

7

8,4

2,3

9,7

42,9

 

Green Sulla

8

23,1

2,9

11,9

32,3

 

CV

 

34,7

18,2

24,3

33,2

 

means

 

19,6

2,5

10,9

32,7

Overall means

 

Arid

295

11,6b

2,4

10,0

46,1

 

Semi-arid

22

19,6a

2,5

10,9

32,7

Location effect

 

***

ns

ns

ns

 

RMSE

 

5,9

0,9

3,3

51,2

See Table 1


Average CP of arid plants content was 132 (g/kg DM) and ranged from 103 for Cynodon dactylon to 148 for Sueada mollis, and its seasonal variation was significant (P<0.001) (table 1).

 

However this content referred only to edible green aerial parts of arid plants. Figures 1a to 1e show the CP content variation during the period of study. For Cyperus conglomeratus, CP content increased irregularly from autumn (November) to spring (May), culminating in March (174 ± 1.0) (figure 1a to 1e) and then decreased. The highest CP content for Cynodon dactylon was also observed in spring (May: 132.1 ± 2.3) (figure 1a).



Figure 1a.
 Crude protein change of Cyperus conglomeratus
and Cynodon dactylon from October to July, g/kg DM


Figure 1b.
Crude protein change of leaves and stems of
Sueada mollis from October to July, g/kg DM


For this graminaceous herb, CP content increased first from October to December and then from February to May. From June to October CP content was the lowest and nearly constant.

 

Stems of Sueada mollis were less rich in CP than leaves and their content ranged from 65.9 in May to 118 in November (figure 1b). For leaves, CP decreased constantly from December (236 ± 6.3 g/kg DM), to May (177 ± 4.8) and then increased from May to July. For Tamarix africana CP content also decreased from autumn to summer for leaves and stems (figure 1c).



Figure 1c. Crude protein change of leaves
and stems of Tamarix africana from October to July, g/kg DM


Figure 1d.  Crude protein change of leaves and stems of
Salsola vermiculata from October to July, g/kg DM


In this tree fodder the lowest CP content was observed during July with 104 ± 7.6 for leaves and 90.4 ± 14.1 for stems. Salsola vermiculata and Atriplex halimus showed a nearly similar seasonal change of CP content, for both leaves and stems (figures 1d and 1e).



 


Figure 1e. Crude protein change of leaves and stems of
Atriplex halimus from October to July, g/kg DM


Apart from Sueada mollis, CP contents of arid plants decreased in the warm and dry seasons and increased in the cold and humid seasons. However, lignin and all the structural constituents remained unchanged between the seasons.

 

In vitro gas production parameters

 

Seasonal variation of kinetic parameters of GP

 

Characteristics of in vitro gas production are shown in tables 5 and 6.


Table 5.  In vitro kinetic parameters of arid plants and the main effects of plant species, morphology and seasons

 

c

B, ml/ g OM

t1, h

trm, h

rm, h-1

b24, ml/ g OM

b48, ml/ g OM

b96, ml/ g OM

rsd

Arid plants species

Atriplex halimus

2,1a

207c

21,8ab

20,7a

0,056a

126b

175c

196c

3,9

Cynodon dactylon

1,5cd

286b

27,0a

16,4b

0,033c

135b

202b

248b

14,1

Cyperus conglomeratus

1,6bc

320a

19,0b

13,8b

0,046b

193a

262a

298

6,5

Salsola vermiculata

1,7b

195c

27,7a

20,7a

0,038bc

90,7c

140e

172d

3,6

 

Sueada mollis

1,5cd

178d

28,1a

12,8b

0,040bc

92,4c

131e

154e

6,2

Tamarix africana

1,4d

205c

19,6b

8,9c

0,047b

121b

159d

183cd

3,5

 

CV(§)

17,9

17,8

50,8

46,7

36,7

28,6

21,6

18,2

 

Morphological fractions

 

Leaves

1,8a

200b

26,4

18,1a

0,046a

107b

153b

180b

5,2

 

Stems

1,6bc

191b

22,4

13,8b

0,044a

106b

148b

172b

3,4

 

Whole plant

1,5b

295a

24,8

15,7b

0,037b

151a

219a

261a

12,1

 

CV

21,7

18,6

52,2

52,6

39,7

32,8

24,6

20,1

 

Seasons

 

 

 

 

 

 

 

 

 

 

 

Winter

1,7a

238a

23,2

16,8a

0,044

129a

184a

215a

8,1

 

Spring

1,7a

229a

23,9

16,3a

0,043

124ab

177ab

207a

6,4

 

Summer

1,5b

198b

25,0

12,3b

0,042

106b

148c

174b

3,8

 

Autumn

1,7a

226a

28,2

19,2a

0,039

108b

161bc

196a

7,8

 

CV

22,1

26,7

52,4

52,2

40,7

36,0

29,5

26,9

 

 

Arid means

1,6

225

24,6

16,0

0,043

119

170

200

6,5

Main effects

 

species

***

***

***

***

***

***

***

***

 

 

morphology

***

***

ns

**

***

***

***

***

 

 

seasons

**

***

ns

***

ns

**

***

***

 

See Table 1



Table 6 .  In vitro kinetic parameters of  semi arid forages compared with arid plants

 

c

B, ml/ g OM

t1, h

trm , h

rm, h-1

b24, ml/ g OM

b48, ml/
 g OM

b96, ml/
g OM

rsd

Semi arid forages

Commercial hay

1,5

284b

14,3

8,7

0,059

193b

242b

267c

3,2

Green wheat

1,5

391a

12,2

7,5

0,063

286a

346a

373a

7,9

Green Sulla

1,5

333b

10,1

6,1

0,088

265a

304a

321b

4,5

CV(§)

12,0

9,9

27,7

23,7

27,8

14,3

11,3

10,2

 

Overall means

Arid means

1,6

225b

24,6a

16a

0,043b

119b

170b

200b

6,5

Semi arid means

1,5

330a

11,4b

6,9b

0,078a

252a

296a

316a

4,7

Location effect

ns

***

**

***

***

***

***

***

 

RMSE

0,4

60,5

12,5

8,3

0,02

44,1

51,5

55,2

 

See Table 1


Arid plants species were differently degraded by ruminal microflora and their kinetic parameters were significantly different (P<0.001). Effect of the season was significant for all in vitro kinetic parameters, excepted t1, the time needed for half GP and rm, the maximum rate of gas production. The lowest values of c, b, tm and b96 were reached in summer. In this season arid feeds gave less gas (b: 198 ml/g OM, P<0.05) and the maximum rate was reached faster after only 12.3 h of incubation. Comparable t1 were needed for the half gas production, and ranged from 23.2 h in winter to 28.2 h in autumn. Asymptotic gas production b ranged from 198.4 in summer to 238 ml/g OM in winter but remained lower than semi arid feeds: 330 ml/g OM, (table 6). Arid plants produced gas with comparable rm, witch ranged from 0.044 in winter to 0.039 h-1 in autumn but remained lower than semi arid forages (0.078 h-1). Kinetic parameter c varied significantly (P<0.05) from 1.5 in summer to 1.7 in the other seasons.

 

All kinetic parameters were also significantly affected by morphology (excepted t1) and species (table 5). Gas productions b, b24, b48 and b96 were higher for herbaceous whole plants Cyperus conglomeratus and Cynodon dactylon, but leaves and stems of shrubs were fermented at higher rm (0.044–0.046 h-1). For leaves, c and tm were significantly higher (1.8 and 18.1 h, respectively). Leaves and stems of shrubs and herbaceous whole plants reached t1 between 22.4 and 26.4 h and were not significantly different (P<0.05). Within the six arid species, Atriplex halimus had high c, t1, tm and rm but its GP were lower than Cyperus conglomeratus and Cynodon dactylon. Cyperus conglomeratus had the highest gas production b, b24, b48 and b96 but a lower t1 and tm, all positive features for its nutritive value. In contrast, Salsola vermiculata was characterised by a high t1 and tm and by a low GP and rm, a negative aspects for animal nutrition. Sueada mollis showed the significantly lower GP (b, b24, b48 and b96) than others shrubs. Its rm was reached 12.8 h after the beginning of incubation, but its t1 was reached later at 28.1 h. Tamarix africana showed the lowest tm (8.9 h) and a comparable amount of gas at 24 h (b24) than Atriplex halimus.

 

Semi arid forages differed significantly only by their GP. Green wheat had the highest GP followed by green Sulla and commercial mixed hay. Differences between arid and semi arid feeds were significant for all the kinetic parameters, excepted the parameter c. Mixed hay was the nearest to arid plants in terms of GP (table 6).

 

Figures 2a to 2e show the seasonal changes of rm of in vitro gas production for arid plants between October 2002 and July 2003.



Figure 2a.  Rm of GP for whole plant of Cyperus conglomeratus and Cynodon dactylon from October to July, h-1

 


Figure 2b.  Rm of GP for leaves and stems of
Sueada mollis
from October to July, h-1

 


Figure 2c.  Rm of GP for leaves and stems of
Tamarix africana from October to July, h-1



Figure 2d.  Rm of GP for leaves and stems of
Salsola vermiculata from October to July, h-1



Figure 2e.
 Rm of GP for leaves and stems of Atriplex halimus from October to July, h-1


Different trends of rm were observed within species and their morphological fractions. Arid plants reached their maximum rate of in vitro GP between January and May, excepted Salsola vermiculata with an exactly opposite trend.

 

Table 7 shows the significant relationships between chemical constituents and kinetic parameters of gas production, for arid plants.


Table 7.  Pearson coefficients of significant correlations between chemical constituents and estimated in vitro GP
 kinetic parameters for arid plants

 

c

b

t1

tm

rm

b24

b48

b96

DM

-0,32***

 

 

-0,30***

 

 

 

 

OM

-0,35***

0,20**

 

-0,30***

 

 

 

 

ASHINS

 

0,43***

 

 

 

0,29***

0,34***

0,29***

EE

0,22*

 

 

0,17*

 

 

 

 

CP

0,22**

 

0,17*

0,16*

 

 

 

 

NDF

-0,32***

0,22**

-0,17*

-0,27***

 

0,18*

0,32***

0,32***

ADF

-0,27***

-0,27***

-0,16*

-0,26***

 

 

 

 

ADL

 

-0,33***

 

 

 

-0,31***

-0,34***

-0,27***

Ca

 

 

-0,28***

 

0,24**

0,19*

0,19*

 

P

0,37***

0,32***

 

0,24**

 

0,32***

0,34***

0,18*

Cu

0,37***

 

 

0,18*

0,26**

0,19**

0,18*

 

Mn

 

0,61***

 

 

 

0,48***

0,51***

0,45***

*: P<0,05; **: P<0,01; ***: P<0,001. Not significant for P>0,05


Correlation coefficients of Pearson, ranged from -0.16 for t1 and ADF to 0.61 for b and Mn. The cell wall content (NDF) was correlated to all kinetic parameters of gas production, excepted rm: negatively to c, t1, tm b48 and b96 and positively to b and b24. A part from the negative correlation between t1 and Ca, all significant relationships between mineral contents and kinetic parameters were positive. Acid insoluble ash was positively correlated with GP (0.29 ≤ r ≤0.43) but ADL was acid lignin content was negatively correlated to GP at any incubation time.

 

According to regression equations for roughages (Menke and Steingass 1988), metabolisable energy (MJ/Kg DM) and organic matter digestibility (g/Kg DM) were estimated (table 8).  


Table 8.  Estimated metabolisable energy and organic matter digestibility for arid plants compared with semi arid forages.

 

ME, MJ/kg DM

OMD, g/kg DM

Arid plants species

 

Atriplex halimus

5,50b

495,1b

 

Cynodon dactylon

5,36b

506,9b

 

Cyperus conglomeratus

6,71a

608,7a

 

Salsola vermiculata

4,92b

451,0c

 

Sueada mollis

5,09b

475,7bc

 

Tamarix africana

5,43b

512,2b

 

CV(§)

17,10

11,0

Morphological fractions

 

Leaves

5,83a

498,5b

 

Stems

4,57b

462,7c

 

Whole plant

5,96a

552,1a

 

CV

15,0

12,1

Seasons

 

Winter

5,57

514,8a

 

Spring

5,58

508,2a

 

Summer

5,01

462,9b

 

Autumn

5,16

487,7ab

 

CV

18,6

13,2

Main effects

 

species

***

***

 

morphology

***

***

 

season

ns

**

Semi-arid forages

 

Mixed hay

6,41b

594,9b

 

Green wheat

8,56a

739,8a

 

Green Sulla

8,50a

738,3a

 

CV

8,0

6,1

Overall means

 

Arid

5,38b

496,3b

 

Semi-arid

7,91a

697,6a

Location effect

 

***

***

 

RMSE

1,0

68,9

*: P<0,05; **: P<0,01; ***: P<0,001; ns: not significant (P>0,05);  CV(§): coefficient of

variation. Means with different letters, in each group, are significantly different (P<0,05)


ME energy of arid plant ranged from 5.01 (in summer) to 5.58 MJ (winter-spring). Compared to semi arid forages and as for all others nutritional aspects, aridplants showed a significantly (P<0.05) lower ME and OMD. Winter and spring have a higher but not different from autumn (P>0.05). While leaves and stems showed a similar ME and OMD, whole plants of Cyperus conglomeratus and Cynodon dactylon have a highest value of ME and OMD (5.96 and 552, respectively). Studying mature Cynodon dactylon in Brazil, Nogueira Filho et al (2000), reported a similar value for ME (5.76 MJ/kg DM), but a lower value for OMD (409 g/kg DM). Atriplex halimus, a completely sampled shrubs from October to July, had its highest ME a nd OMD values in February (6.4 and 574.0 respectively), with an increasing trend from December to March and a decreasing one from  March to June both for leaves and stems (figures 3a and 3b).



Figure 3a.  Estimated organic matter digestibility for leaves and
stems of Atriplex halimus from October to July, g/Kg DM


Figure 3b.  Estimated metabolisable energy for leaves and
stems of Atriplex halimus from October to July , g/Kg DM


But leaves of Atriplex halimus reached the highest ME value in March. Valderrábano et al (1996), reported similar ME value (7.5 MJ/Kg DM) in Northern regions of the Mediterranean sea. Salsola vermiculata showed the highest ME and OMD values in December, with a decreasing trend from December to May, both for leaves and stems (data not showen). Similarly, Sueada mollis had its highest ME and OMD values in December, with continuous decreasing trend from December to May. Tamarix africana had its highest ME and OMD values in November (6.24; 584), Cyperus conglomeratus in May (8.19; 695) and Cynodon dactylon also in May (6.81; 611).

 

Discussion 

Nutritional of arid plants were wholly lower than semi arid forages. Among the later, mixed hay was the nearest feed to arid plants. These characteristics were discrete during autumn, an intermediate season, then increased during the cold and wet seasons (winter and spring) and finally decreased from June to October during warm and dry seasons. Salsola vermiculata, an abundant halophyte shrub presented a reverse trend and gave a better nutritional and kinetic characteristics in the warm and dry season maybe for its bitter taste during the regrowth in the cold and humid seasons. In arid regions, plant forages grow at low density and became difficult to harvest for sampling, especially green edible aerial parts. In attempt to evaluate the density of some halophyte shrubs in the same area in April 1999 (unpublished data), we find, in the very dense zone, 0.7 tons/hectare for Atriplex halimus, 0.5 t/ha for Salsola vermiculata, 0.2 t/ha for Tamarix africana and 0.06 t/ha for Sueada mollis. However, only few percents for this biomass are edible.

 

Leaves of arid shrubs were less fibrous than stems. Lignocellulosic content (express as ADF) was more abundant in stems witch also were more lignified than leaves and herbaceous whole plants. In fact, Cyperus conglomeratus and Cynodon dactylon, have the lowest ADL contents, and are generally intensively browsed and rapidly exhausted from pasture like many others herbaceous plants. Surprisingly, edible aerial parts of arid shrubs have a lower ADL content than a whole semi arid leguminous Sulla (76.3 vs. 110 g/kg DM) and have less NDF fibres than many cereal straws, as reported by Wanapat et al (1989). In any case, arid browses were less ligneous than some Mediterranean shrubs (Ammar et al 2005). Arid plants evaluated in this study can supply adequate mineral level for Ca, P, Cu and Mn for maintenance needs for ruminants (Ca: 4.0, P: 3.0 g/kg DM, Mn: 50.0 and Cu 10.0 mg /Kg DM) according to Andrieu and Demarquilly (1987). However, positive correlations between P content and GP indicate a stimulatory effect of increasing P concentration on cell content degradation and consequently on the amount of gas produced. Probably a higher mineral content is needed for used ruminal microflora. For phosphorus, Komisarczuk-Bony and Durand (1991) suggested that 5 g/kg ODM were required for ruminants fed on roughages; consequently, less than 50% of P is supply by our arid plants. CP contents of studied arid plants were valuable and comparable with some woody plant foliages from African semi-arid regions as reported by Breman and Kessler (1995). ME and OMD were low for arid plants and if we assume that 10 g microbial protein are produced per 1 MJ of ME intake (AFRC 1993); only 50-60 g of microbial protein can be synthesized per Kg of DM, in the rumen. Current results are concordant with those from previous study conducted in the same area from March to June 1996 (Haddi et al 2003). In this study whole plant of Salsola vermiculata, Atriplex halimus, Sueada mollis and two others shrubs showed their best nutritive characteristics in spring, even with significant differences between species. Chemical aspects seemed less affected than kinetic parameters by the season, suggesting that the rumen microflora encountered additional constraints linked to physical structure of plant tissues or toxic substances witch change during the life cycle of plants.

 

Conclusion 

Arid plants and semi arid forages differed mainly by their in vitro degradation parameters witch reflect not only the chemical aspects but also others characterics related to the tissues structure elaborated as an adaptive response to the arid context. The fact that maximum rate (rm) of in vitro degradation of the arid browses was similar around the year can be assigned to the constant fibrous but not highly lignified structure of arid cell wall.

 

Arid plants are for essential importance in supporting basic nutritional requirements of domestic ruminants in the arid regions. They are fibrous but not ligneous and their nutritive constituents were low compared to those of semi arid zones. However, arid plants can reveal their nutritive potential (minerals, energy and nitrogen) through their leaves during the wet and cold season, when several thousand ovine are browsing in these regions. Plant species and morphological composition were the discriminatory factors for the nutritive value essentially for chenopodium shrubs and tree fodder. Many different factors like precipitation regimen, specific growth cycle of each arid plant, animal browsing pressure, anti-nutritional substances, etc.., can influence their nutritive value and deserve further investigations.

 

Acknowledgments 

This study was supported by University of Constantine (Algeria) and University of Liege (Belgium) through the CUD-PIP collaborative project “Health and production of ruminants in East Algeria”, funded by General Directory of Cooperation and Development (GDCD, Brussels). The first author would thank Dr. D Pizzighello (University of Padua, Italy) for assistance during statistical analysis and Dr. A Boukerrou (Veterinary Regional Laboratory, Constantine) for laboratory facilities.

 

References  

AFRC 1993 Energy and protein requirements of ruminants. An advisory manual prepared by the AFRC Technical Committee on Response to Nutrients. CAB International, Wallingford, UK.

 

Ammar H, López, S and González J S 2005 Assessment of the digestibility of some Mediterranean shrubs by in vitro techniques. Animal Feed Science and Technology 119: 323-331

 

Andrieu J and Demarquilly C 1987 Valeur alimentaire des foins et des pailles. In « Les fourrages secs : récolte, traitement, utilisation ». INRA Editor, Paris, pp.163-182.

 

AOAC 1990 Official Methods of Analysis, 15th ed. Association of Official Analytical Chemists, Washington, DC.

 

Breman H and Kessler J J 1995 Woody plants in agro-ecosystems of semi-arid regions. Springer-Verlag Berlin, Germany, 341 p.

 

El- Waziry A M 2007 Nutritive value assessment of ensiling or mixing acacia and Atriplex using in vitro gas production technique. Ressources Journal of Agriculture and Biological Science 3(6): 60-614

 

Groot J C J, Cone J W, Williams B A, Debersaques F M A and Lantinga E A 1996 Multiphasic analysis of gas production kinetics for in vitro fermentation of ruminants feeds. Animal Feed Science and Technology 64: 77-89

 

Haddi M L, Filacorda S, Meniai K, Rollin F and Susmel P 2003 In vitro fermentation kinetics of some halophyte shrubs sampled at three stages of maturity. Animal Feed Science and Technology 104: 215-225

 

Haddi M L, Filacorda S and Susmel P 1999 Comparison of different inocula to describe some halophyte shrubs using the gas-test. In “Recent progress in animal production Science. 1”. Proceedings of the ASPA XIII Congress, Piacenza (Italy), June 21-24, pp: 360-362

 

Haddi M L, Meniai K, Filacorda S and Susmel P 2002 Comparison between exponential and logistic models for estimation of kinetic parameters of in vitro fermentation of Atriplex halimus. Annals of Agricultural Sciences (Cairo, Egypt). Sp. Issue 2, 575-593

 

Hirche A, Boughani A and Salamani M 2007 Evolution de la pluviosité annuelle dans quelques stations arides algériennes. Sècheresse 18(4): 314-20 http://www.john-libbey-eurotext.fr/e-docs/00/04/39/F4/vers_alt/VersionPDF.pdf

 

Komisarczuk-Bony S and Durand M 1991 Nutrient requirement of rumen microbes. In “Recent advances on the nutrition of herbivores”, MSAP, pp. 133-141

 

Lemnaouar N F Z 2001 Etude comparative de deux pâturages (jachère et médicago). Thèse de Magistère en sciences vétérinaires. Université de Constantine. Algeria, 156 p.

 

Menke K H and Steingass H 1988 Estimation of the energetic feed value obtained from chemical analysis and in vitro gas production using rumen fluid. Animal Research and Development 28: 7-55

 

Nogueira Filho J C M, Fondevila M, Urdaneta A B and Gonzalez Ronquillo M 2000 In vitro microbial fermentation of tropical grasses at advanced maturity stage. Animal Feed Science and Technology 83: 145-157

 

Pagot J 1992 Animal production in the tropics. ACTT. Macmillan Publisher, pp.32-66

 

Robertson J B and Van Soest P J 1981 The detergent system of analysis. In: James W P T and Theander O (Editors), The analysis of dietary fiber in food, Volume 123. Marcel Dekker, NY, p. 158.

 

SAS (Statistical Analysis System) 2003 User’s Guide, SAS Institute, Cary, NY, USA.

 

Valderrábano J, Munoz F and Delgado I 1996 Browsing ability and utilization by sheep and goats of Atriplex halimus L. shrubs. Small Ruminant Research 19: 131-136

 

Van Soest P J, Robertson J B and Lewis B A 1991 Methods for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition. Journal of Dairy Science 74: 3583-3597 http://jds.fass.org/cgi/reprint/74/10/3583.pdf

 

Wanapat W, Varvikko T and Vanhatalo A 1989 Degradability of cereal straw using in sacco and mobile bag techniques. Australian Journal of Animal Science 2 (3): 421-423



Received 2 May 2008; Accepted 12 March 2009; Published 18 April 2009

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