Abstract
In an attempt to clarify the effect of aerobic deterioration on the nutritive value of silage, a digestion and nitrogen balance study was conducted, using four wether sheep in a Latin-square design. They were fed grass silages which were at different stages of aerobic deterioration, having been stacked in the open air after being removed from the silo for 4 (4D-silage), 7 (7D-silage) and 10 days (10D-silage). For a control, undeteriorated silage was given immediately after being removed from silo, with no temperature rise. The results obtained are summarized as follows. 1) The aerobic deterioration resulted in higher pH, decreased lactic acid and total VFA contents and increased the VBN content of the silages. Except for the VBN content, these changes were not to any extent proportional to the number of days the silage had undergone an increase in temperature. There was no marked difference in the general chemical composition among the silages. 2) The digestibility of crude protein, NFE and energy tended to be lower with aerobic deterioration, and the differences in the digestibility of crude protein between the control silage and 7D and 10D-silages were significant at the 5% level. However, the digestibility of ADF was somewhat higher (P<0.05) for the deteriorated silages than for the control silage. 3) The nutrient content of the silages decreased with aerobic deterioration, and the DCP contents of 4D, 7D and 10D-silages were lower by 4, 7 and 9% than those of the control silage, respectively. The TDN and DE contents decreased less than the DCP content did and, in 10D-silage, were lower by 2 and 4% than those of the control silage, respectively. 4) The sheep fed on 10D-silage excreted more nitrogen (P<0.01) in their feces, but somewhat less nitrogen in their urine and had, though non-significant, lower nitrogen retention values when compared with those fed on the control silage. 5) Ammonia and total VFA concentrations in the rumen of the sheep were affected somewhat by feeding on the deteriorated silages.
