A method for obtaining and storing uniform silage for feeding experiments

96 silages selected from farms across Northern Ireland to cover wide ranges of pH values, and dry matter, ammonia and metabolisable energy concentrations, were individually mixed and stored in evacuated polythene bags for 18 +/- 2.1 days before being used in a major voluntary intake study. Composite samples, taken both before and after storage, were analyzed for dry matter content, nitrogenous, volatile and carbohydrate constituents, gross energy concentration, buffering capacity, pH and osmolality. There were no significant changes in the concentrations of dry matter or volatile constituents following storage. When expressed on a fresh basis, total and acid insoluble nitrogen concentrations, water soluble carbohydrate and gross energy concentrations were significantly (P < 0.05) lower after storage, but in all cases the absolute differences in concentration were small. The significance of the change in total and acid insoluble nitrogen, and water soluble carbohydrate concentrations was increased (P < 0.01) when results were expressed on a dry matter basis. Gross energy and neutral detergent fibre concentrations showed a significant decrease (P < 0.05), and acid detergent fibre concentration a significant increase (P < 0.05) after storage, when results were expressed on a dry matter basis. The changes normally associated with aerobic deterioration, such as decreases in lactic and acetic acids, total alcohol, and soluble carbohydrate concentrations, and an increase in ammonia nitrogen level did not occur during the course of the study, neither was there any visual evidence of mould growth. These factors indicate that the methodology adopted for the preservation effectively maintained anaerobic conditions, and offers considerable potential for use in detailed feeding experiments.