Maize for silage II. The effect of urea and acid as preservative treament on rumen fermentations and on feeding values of silages

Abstract

The rumen fermentations and N-balances of rumen fistulated sheep were studied on diets of silages treated with urea and acid preservative. The digestibilities and feeding values of the silages were also calculated. The experiment was performed according to 5 x 5 Latin-square design. The digestibilities were determined by total collection the collection period lasting seven days. The rumen samples were taken on the last two days during the collection periods before and 1.5, 3.0, 4.5 and 6.0 hours after feeding. Besides the silages the animals received mineral mixture and water ad libitum. Urea or acid treatment had no effect (P > 0.05) on the consumption of silage DM. The consumption ranged from 1.7 to 1.9 kg DM/100 kg liveweight. Urea did not have a clear effect on the VFA production in the rumen. It tended, however, to decrease the proportions of C3 and C4—C5 acids in the rumen. Acid preservative decreased the production of VFA and the proportion of C3-acid (P < 0.05) in the rumen. The proportion of C3-acid was higher respectively, (P < 0.05). The rumen ammonia levels were extremely high, 60—80 mg/100 ml, after feeding with urea treated silages. This was possibly partly due to the relatively short (14 days) adaptation time before collection period. The urea or acid preservative treatment gave no clear responses regarding the apparent digestibility values of the silages. The DCP values were highest (P < 0.05) in the urea treated silages, but no differences (P > 0.05) were found between the energy values, which varied between 0,12—0.14 f.u./kg of silage. There were no differences in the N-balances of the animals on different diets. The balances were positive on all diets.