Influence de la complémentation des foins traités à l'ammoniac sur leur valeur nutritive

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Abstract
Three trials were conducted in sheep. In trial I a wet hay was used untreated or treated by 8 and 16 kg ammonia per ton. In trial II an untreated hay, a treated hay and two combinations of these two hays were fed to sheep. In trial III the same treated hay supplemented with soybean meal, isoacids and minerals was fed. Supplementation improved cellulolytic activity in the rumen. Chemical composition of hays is given in table 1 and the characteristics of the studied diets in table 2. In trial I, the treatment increased intake and digestibility (table 3). It was the same in trial II where forage offered was limited to 50 g DM/kg W0.75. In trial III supplementation had a positive effect. Nitrogen retention was measured for all diets (table 4). N-retention increased slightly, but not significantly, after treatment in trial I, and also in trial II. In trial III supplementation had a positive effect. It was concluded that nitrogen value was increased by the treatment. Accordingly, the decrease in nitrogen value observed by other authors does not seem to be systematic, especially when hay has a poor value. Mean characteristics of rumen juice were measured in the three trials and are given in table 5. Variation in pH in trial III is given in figure 1, N-NH3 in the three trials in figure 2 and figure 3. The maximum levels observed was 450 mg/l, 1 hour after the beginning of the first meal. Cellulytic activity, estimated by the degradation of straw or hay in nylon bags suspended in the rumen is also given in table 5. A more precise description is given in figure 4 for trial I, in figure 5 for trial III and in figure 6 for trial III. All these figures confirm the negative effect of treatment on cellulolytic activity in the rumen. Dilution of treated hay into the diet (trial II) or addition of adequate complements (trial III) increased cellulolytic activity in the rumen. Nevertheless in sacco digestibility of treated hay never reached potential in sacco digestibility measured in sheep fed lucerne hay (table 6). VFA content of rumen juice was measured in trial III.