Fermentation Characteristics, In Situ Rumen ‎Degradation and Aerobic Stability of Whole Crop ‎Barley Ensiled with Urea or Aqueous Ammonia

Abstract

Various chemical compounds might be added to forage to maintain or ‎improve the quality value of a crop ensiled. The aim of the present experiment was to evaluate the fermentation characteristics, in situ ‎rumen degradation and Aerobic Stability ‎of whole crop barley ensiled with Urea or aqueous Ammonia.‎‎ In the first experiment, Whole crop barley was harvested (35% DM), chopped, and then ensiled using laboratory silos (n= 4) as untreated (UT) or treated with urea (10, 20, 30 and 40 g kg-1 DM; U1, U2, U3 and U4, respectively) or aqueousammonia (10 and 20 g kg-1 DM; A1 and A2, respectively) for 30 days. Standard procedures were used to determine the chemical composition of the samples. The pH of the aqueous silage extract was determined using a pH meter. Ammonia-N concentration was determined in acidified silage extract (5 ml of the extract + 5 ml of 0.2 M HCl) using a distillation method. Four sheep (live weight: 44±3 kg) fitted with rumen fistulae were used. Approximately 5 g DM of each sample was placed in a polyester nylon cloth bag (10 × 12 cm, pore size of 52 µm, n=4), then incubated in the rumen for 0.0, 2, 4, 8, 16, 24, 48, 72 and 96 h. Rumen removal bags were washed in cold running water and dried in oven (60 °C, 48 h), then weighted to determine DM disappearance. The equation of P= a+b (1-e-ct) was applied to determine the coefficients (a= quickly degradable fraction, b= slowly degradable fraction, c= fractional degradation rate constant). Both urea and anhydrous ammonia caused a significant (P <0.05) increase in silage pH and NH3-N, and CP concentrations. The slowly degradable fraction (b) of the silage treated with urea was significantly (p <0.05) higher than those of the untreated sample. Potential degradability of U4 was higher than other treatments. In a second experiment, whole crop barley was harvested (32.5% DM), chopped, ‎and then ‎ensiled (n= 4) for 35 days as untreated (UT) ‎or treated with urea (23.4 g Kg-1DM) or ‎aqueous ammonium (13.1 g Kg-1DM), to obtain a final application rate of about 0.35% N ‎of fresh forage weight. The population of yeasts and molds (colony-forming unit= CFU) was determined by spread plating of filtered extract silages on malt extract agar. Aerobic stability was defined as the time it took for the temperature in the silage masses to rise 2 °C above ambient temperature. Whileboth of urea and ammonia had no effect on the initial number of mold in the silages, these treatments significantly lowered CFU of yeast in fresh silages. In this experiment both Ammonia and urea had a significant effect on inhibition of rising temperature and yeast in aerated silages. Urea and ammonia treatments significantly enhanced ‎aerobic stability of silages.