Influence of time after ensiling on distribution of nitrogen in corn silage treated with ammonia

Chopped whole corn plant was treated before ensiling with 1.4% ammonia (of dry matter) to which .36% atom excess of 15N had been added. About 50 kg of material (14 kg dry matter) were placed in .5-mm polyethylene bags (of double thickness) which were evacuated and served as experimental silos. Silage samples were taken on days 0, 3, 7, 14, 21 and 50 and analyzed for N fractions. The 15N content of these fractions was analyzed by a mass spectrophotometer. N fractions of untreated silage were also determined. Between days 0 and 7 of fermentation, ammonia N decreased from 50 to 39% of the total silage N, with a corresponding increase in nonammonia N, from 50 to 60%. Thereafter, little change was noted in these fractions. Approximately 40% of the increase in non-ammonia N was in the soluble portion and 60% was in the insoluble portion. Insoluble N of treated silage was 50% higher than that of control silage. Initially, 89% of the N from added ammonia was recovered as ammonia, but this proportion decreased to 68% by day 7 and changed little thereafter. There was immediate incorporation of 43% of the ammonia into the insoluble N fraction. Most of the initial binding was as intact ammonia, with a subsequent release during fermentation. Because direct ammonia incorporation accounted for a higher percentage of the insoluble N increase on day 0 than on subsequent days, these data support earlier studies which showed that ammonia decreased breakdown of protein of the ensiled corn plant.