Preservation Efficiency and Dairy Heifer Response from Unwilted Formic and Wilted Untreated Silages

Four experiments were planned directly to compare unwilted formic acid treated forage with untreated forage wilted to about 35~ dry matter and stored in conventional tower silos. In two experiments forage was wilted from about 19 to 35~ dry matter. A third attained similar wilting starting from 32% dry matter forage, but in the fourth weather prevented any wilting. In each experiment digestibility was determined with ad libitum and maintenance feeding in 4 x 4 Latin square trials while ad libitum feed intake and growth were measured concurrently in continuous growth trials of dairy heifers. In the three experiments where wilting occurred, daily gains were slightly more on two of three formic silages while energy digestibilities and intakes were slightly better on all three untreated silages. Energy recoveries were larger on the two untreated silages which were enstied at about 35% dry matter than on formic silage, but writing to 47% dry matter depressed energy recovery considerably below formic silage. Gain per metric ton of dry matter ensiled was slightly more for untreated silages enstied at about 35~ dry matter than for formic silages, but when ensiled at 47?o dry matter it dropped to two-thirds that of formie silage. When untreated forage could not be wilted, the silage contained 1.9~ butyric acid in dry matter and 29~ of nitrogen as ammonia. Animals consumed this forage at essentially maintenance, and energy digestibility was depressed to 89~ of formic silage. Gain per metric ton of forage dry matter was depressed to about 10~ of values usual with good forages. Well made wilted silage without treatment was equivalent or slightly better than unwilted formic silage. Practical