In vitro fermentation measurements to evaluate interactions between date palm leaves and two arid forages ( Aristida pungens and Astragalus gombiformis ) Arhab R 1,2., Macheboeuf D 3., Lassalas B 3., Bergeault R 3. & Bousseboua H Département de biologie, Institut des Sciences de la Nature, Université Cheikh Larbi Tébessi, Tébessa. 2- Laboratoire de Génie Microbilogique et Applications, Université Mentouri, Constantine. 3- Unité de Recherche sur les Herbivores, INRA, Saint Genés-Champanelle.

Introduction: 2- Animal is fed a mixture of ingredients. 1- Feeds are commonly evaluated as single entities. Associative effects between forages are generally negliged by this approach. Aims: Study of associative effects between date palm leaves (rich in tannins content) and two browse shrubs : A. pungens (rich in fibre content) and A. gombiformis (rich in crude protein content)

Material and Methods: 1- Single Substrates: Date palm leaves: DM, g/kg ; MAT, 59.5 g/kg ; NDF, g/kg, TT, 49.1 g/kg ; TCT, 36.2 g/kg. A. pungens: DM, g/kg ; MAT, 53.6 g/kg ; NDF, g/kg, TT, 1.60 g/kg ; TCT, 3 g/kg. A. gombiformis: DM, g/kg ; MAT, 125 g/kg ; NDF, g/kg, TT, 21.3 g/kg ; TCT, 4 g/kg. 2- Substrate mixtures: a)Date palm leaves + A. pungens: 0, 10, 20, 30, 40, 50%. b)Date palm leaves + A. gombiformis: 0, 10, 20, 30, 40, 50%. c)A. pungens + A. gombiformis: 0, 10, 20, 30, 40, 50%.

Incubation at 39°C and 130 rpm/mn Rumen liquor Artificial saliva 400 mg of mixtures Inoculum (40 ml) Pressure recorded at different incubation times. 3- In vitro gas production technique (Theodoreau et al. 1994) -Volatile fatty acids (AGV) were determined by gas chromatography (CHROPACK CP 9002). - Ammoniacal nitrogen was evaluated on the basis of Berthelot reaction.

Results: Table 1. Mean values (n = 4) of cumulative gas produced at different times of forage incubation mixtures and gas production estimate with exponential function.

Table 2. In vitro fermentation end-products (individual and total fatty acids, and ammonia productions) and in vitro digestibility of dry and organic matter (DMD, DMO) of the forages mixtures.

Table 3. Differences (%) between the observed gas production of the mixtures and that predicted from feedstuffs fermented separately.

Conclusions Utilisation des techniques in vitro constituent un outil appréciable pour l’évaluation en amont des effets associatives (interactions entre aliments). Utilisation des techniques in vitro constituent un outil appréciable pour l’évaluation en amont des effets associatives (interactions entre aliments). L’approche mathématique utilisée met en évidence aussi bien les effets antagonistes et synergiques. L’approche mathématique utilisée met en évidence aussi bien les effets antagonistes et synergiques. L’interaction négatif de l’association palmes et Astragalus est principalement due aux tanins. L’interaction négatif de l’association palmes et Astragalus est principalement due aux tanins. L’interaction positive entre Astragalus et A. pungens est expliquée par le rapport carbone et azote. L’interaction positive entre Astragalus et A. pungens est expliquée par le rapport carbone et azote.