INTAKE AND DIGESTION IN SHEEP GIVEN FRESH OR AIR-DRIED ACACIA-CYANOPHYLLA LINDL FOLIAGE

The effect of air-drying of Acacia cyanophylla Lindl foliage (acacia) on digestion in sheep was studied in November and December 1993 at Inr a-Tunisia. Two groups of animals each including two intact and two rum en-cannulated 'Queue Fine de l'Ouest' adult sheep were offered 600 g d ry matter (DM) lucerne hay and fresh or air-dried acacia foliage ad li bitum. Diets were offered daily in two equal meals (08.00 and 16.00 h) . A digestibility trial involving all animals and a digestion trial in volving only rumen-cannulated animals were conducted according to a 2 x 2 x 4 and a 2 x 2 x 2 crossover design, respectively. Each experimen tal period lasted 25 days, with total faecal collections, rumen fluid samplings (0, 2, 4 and 8 h post feeding) and ruminal cellulolytic acti vity using the nylon bag technique being made over the final IO days. The organic matter, fibre (NDF, ADF and ADL) and crude protein (CP) co ntents were similar in fresh and air-dried acacia (42.9 vs 44.4, 27.0 vs 25.9, 14.1 vs 12.2, 11.9 vs 11.2% of DM, respectively). Acacia foli age, either fresh or air-dried, had a high content of insoluble nitrog en (79.0 and 84.5% of total nitrogen, respectively) and nitrogen bound to ADF (15.4 and 13.8% of total nitrogen, respectively). Air-drying r educed methanol extractable condensed tannins in acacia foliage (from 5.1 to 4.3 g catechin equivalent/100 g DM). DM intake of acacia was si gnificantly increased (P < 0.05) by air-drying (from 52 to 56 g DM kg( -1) LW0.75). Remarkably, acacia intake was changed from day to day. Pe aks were observed every 4 or 5 days in all animals. Sheep seem to regu late acacia consumption in function of tannin accumulation elsewhere i n the body. The diet and acacia nutrient digestibilities were not affe cted by air-drying. CP digestibility of acacia was in the range 23-30% . Patterns of rumen fermentation assessed by pH, ammonia nitrogen and volatile fatty acid concentration and composition were similar in fres h and air-dried acacia treatments. There was no indication of any inhi bition of ruminal fermentation with either diet. Cellulolytic activity was not affected by acacia air-drying. The increased intake of acacia foliage which occurred without any changes of acacia nutrient digesti bilities and pattern of rumen fermentation suggests that the response was mediated probably by a decrease of the astringent taste of fresh a cacia due to air-drying.