Ammonia-treated alfalfa silage for lactating dairy cows

Alfalfa was treated (3.3% of forage wet weight) with an aqua-NH3 (14% N) mix prior to ensiling in 2 consecutive yr. In the 1st yr, NH3-treated silage containing 30.5% DM was higher in pH, N, NH3N, acetic acid and butyric acid contents, and lower in amino acids, soluble carbohydrates, and lactic acid than two untreated silages having 32.8 and 47.5% DM. Milk composition and DM intake did not differ among treatments when these silages constituted 50% of the dietary DM and were fed to lactating cows. In situ and in vitro, but not in vivo, digestion of NDF was greater for NH3 silage. Dry matter content of NH3-treated silage in the 2nd yr was 36.1% and that of the two untreated silages was 37.8 and 54.9%. Silage N, NH3N, and acetic acid content were greater in treated silage. However, pH and butyric acid content were similar among treatments and lactic acid was greater for treated silage. Similar to findings in the 1st yr, milk production and DM intake were not different among treatments. Adding NH3 to alfalfa decreased proteolysis; however, when DM was low (30.5%), the buffering effect of NH3 apparently resulted in increased clostridial fermentation. This did not occur when silage DM was increased to 36.1%, presumably due to higher osmotic pressure. Ammonia addition enhanced fiber digestibility but had no effect on milk production.