Valeur alimentaire des foins traités par l'ammoniac

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Abstract
Using hays of very different values, the effect of ammonia treatment was measured on 6 hays treated with 30-40 kg of anhydrous ammonia/ton. Their chemical composition and feeding value, as well as the characteristics of their rumen digestion in sheep were compared to those of hays before treatment. Ammonia treatment strongly increased the crude protein level of hays from 86 to 152 g/kg dry matter (DM), 37% of NH3 being fixed during the treatment. At the same time, the level of undigestible crude protein increased from 44 to 67 g/kg DM, only 64% of the fixed ammonia being useful for the animals. Intake and digestibility of hays increased very markedly for those with a low feeding value, but not for those with a good value. The feeding behavior of sheep receiving rye-grass hay was modified but only with hay of high value before treatment. The effect of treatment on ruminal pH was small, but the level of ammonia in rumen juice increased from 40-70 mg/l. A decrease in the cellulolytic activity of the rumen was observed when the rate of digestion was enhanced by the treatment. A better understanding of the utilization of fixed ammonia is required so as to determine more accurately the meaning of the cellulolytic activity decrease in the rumen after treatment.