Effect of time of ensiling on the nutritive value of wheat straw treated with urea and molasses

An experiment was conducted with 20 Arabi lambs to study the effect of ensiling time on the nutritive value of wheat straw. Two silages containing 3% urea and 10% molasses, made at early and late summer, were compared in this experiment. Both silages were fed to lambs supplemented with two levels of concentrates. Results showed that ensiling straw at late summer seemed to produce better silage as compared to the quality of early summer silage, according to the chemical composition and organoleptic characteristics, this was probably due to the optimum temperature and short day as compared to the conditions of early summer where high temperature and long day. It was found that storing silage in a high temperature conditions (35.5 C) during July and August reduced intake significantly (P<0.01), which were attributed to the secondary fermentations occurred during ensiling, causing a change in the palatability, but doubling the concentrate level minimized the differences between the two silages, however, it was observed that making straw silage at late summer (during October and November, with a mean temperature of 21.9 C) reduced DM, OM, NFE digestibilities (P<0.05), and EE digestibility (P<0.01) but it improved CF digestibility (P<0.05). CP digestibility did not influenced significantly by ensiling time. Doubling the concentrate level reduced CP and CF digestibility (P<0.05), but it increased the digestibility of EE (P<0.05). Introduction Since large quantities of straws were accumulated as a by product of cereals, it would be efficiently introduced in feeding programs. Many methods were used to improve the low nutritive value of straws, which was attributed to the low content of crude protein and high content of crude fiber. Some methods were physical, others were chemical. Pal and Negi (1977) reported that the correct chemical treatment of straws improved crude protein digestibility. Ensiling is a preservation way, but it could be beneficial, if a good and scientific effort were followed in making silage. The time of ensiling did not investigated, especially in Iraqi conditions. The importance of environmental temperature in making silage was well recognized, it was related to the fermentation processes occurred during ensiling. Good quality silage may be produced if desirable fermentations are obtained. In a high temperature seasons and/or areas, a secondary fermentation was often expected to occur during ensiling. Wilkins, et. al., (1971) indicated that the nutrients losses due to the secondary fermentation of lactic acid to produce butyric acid and the deamination of proteins by the action of Clostridia, these losses were related to the reduction of dry matter intake. Watson and Nash (1960) demonstrated that the proteineous fractions of silage could be affected by the ensiling in a high temperature condition. In such conditions, chemical reactions occurred in a stored roughage, could be accelerated by the high temperature (Dolberg, et. al., 1981), therefore the time of ensiling should be adjusted by the lowering these period.