EFFECT OF ACACIA-CYANOPHYLLA LINDL. FOLIAGE SUPPLY ON INTAKE AND DIGESTION BY SHEEP FED LUCERNE HAY-BASED DIETS

The effect of air-dried Acacia cyanophylla Lindl. foliage supply on ru men fermentation and nutrient digestion was studied in sheep fed on lu cerne hay-based diets at INRA-Tunisia from February to June 1993. Five Queue Fine de l'Ouest sheep fitted with rumen cannulae received 700 g per day lucerne hay alone (0 g acacia) or supplemented with graded am ounts of ah-dried acacia (75, 150, 300 g and ad libitum) according to a 5 X 5 Latin square design. Each experimental period lasted 25 days o f which 15 days were for diet adaptation and the following 10 days for measurements. Apparent digestibility of dietary organic matter (OM), crude protein (CP), neutral detergent fibre (NDF) and acid detergent f ibre (ADF) was measured by total faeces collection. Fermentation param eters (pH, volatile fatty acids (VFA) content acid composition, NH3-N and protozoa in rumen liquor) were measured four times a day (0, 2, 4, and 8 h after the morning feeding). Rumen degradation characteristics of oat hay dry matter and soybean meal nitrogen were measured using t he nylon bag technique. Acacia foliage had a high content of condensed tannins (45 g catechin equivalent per kg DM) and acid detergent ligni n (161 g kg(-1) of DM), as compared to lucerne hay (1 and 63 g kg(-1) of DM, respectively). Crude protein content of acacia and lucerne hay was 136 and 166 g kg(-1) of DM, respectively. About 20% of acacia tota l nitrogen was bound to fibre (ADF-N). Sheep fed acacia supplement ad libitum consumed up to 600 g DM per day of it. Total OM, CP, NDF and A DF digestibility were reduced by the two highest intake levels of acac ia (300 g and ad libitum). Acacia supply caused a linear decrease of p rotozoa number in the rumen fluid. Ammonia nitrogen was significantly reduced with the two highest levels of acacia. There was a clear-cut n egative effect of acacia supply on in-situ DM degradation and a tenden cy towards a decrease of the in-situ nitrogen degradation. The increas e of VFA contents in sheep supplied with acacia may be the consequence of the increase of total intake. It is concluded that acacia supply h ad a negative effect on digestion of lucerne hay based diets when more than 150 g DM of acacia were included in the diet. (C) 1997 Elsevier Science B.V.