FEEDING III. ADDITION OF VARIOUS LEVELS OF ROOTS AND UREA TO SWEET POTATO FORAGE SILAGES1

With the purpose of studying the fermentative conservation of sweet potato foliage, laboratory silos were prepared ' each containing 4 kg of chopped foliage, allocated to 25 treatments resulting from the factorial combination of 5 levels of sweet potato roots (0, 3, 6, 9 and 12 % of the ensiled material, on fresh basis) and 5 levels of urea (0, 0.4, 0.8. 1.2 and 1.6 % of the material, fresh basis). Duplicate silos were used thus resulting in a total of 50 units. The addition of urea caused a linear increment in pH and a quadratic increase in DM losses by putrefaction. However, no definite effects were detected with regard to acetic, butyric and lactic acids. The DM in vitro digestibility remained relatively constant around an overall average of 60.3%. The addition of roots had an acidifying effect which became more marked as the level of urea increased; however the extent of this effect was very modest when compared to the alkaline effect imparted by urea. There were no noticeable effects of root additions upon DM losses by putrefaction and lactic acid concentration. In general, the concentrations of acetic and butyric acids increased with additions of roots. The values for butyric acid changed from 1.07%, to 3.46 % on dry basis, when the level of roots varied from 0 to 121, respectively. The in vitro DM digestibility of the ensiled material improved slightly when roots were added. The silages that contained no additives showed excellent characteristics; their pH values averaged 3.9 and the acid concentrations were 3.49%, 0.68%, and 5.21 % for acetic, butyric and lactic acids, respectively. Losses of DM by putrefaction were low (11.6%) in these silages. In view of the results obtained when no additives were used and when urea or roots were added, it is concluded that silages of excellent quality can be obtained from sweet potato foliage as long as no additives, such as urea or roots, are used