Qualitative characteristics, microbial populations and nutritive values of orange pulp ensiled with nitrogen supplementation

Abstract

The aim of this study was to evaluate the qualitative characteristics, microbial profile and nutritive value of high-moisture orange pulp co-ensiled with poultry by-product meal (PBM) or urea as additional nitrogen (N) source. The optimum dry matter (DM) content of each experimental silage was achieved by adding the appropriate proportion of wheat straw. A control silage was also prepared with orange pulp and wheat straw, but without any supplemental nitrogen. Each experimental silage was ensiled in three replicates of 12 kg mini-silos and left intact for 90 days. The evaluated traits were: silage pH, microbial population, lactate, acetate, butyrate, crude protein (CP), true protein and NH3 -N contents. In addition to these, in situ dry matter and CP degradability as well as ruminal and post-ruminal CP disappearance rates were also measured. Both N-supplemented silages showed higher pH values and CP contents compared to the control silage (P<0.05). With regard to NH3 -N, the lowest values were detected in silage supplemented with PBM (P<0.05). The highest acetate production and total bacteria (TB) count (P<0.05) and the lowest lactic acid bacteria count (P<0.05) were observed in silage supplemented with urea. Control silage and urea supplemented silage had the highest and lowest lactate contents, respectively. Addition of PBM and urea did not alter degradation rates (c) of DM and CP, however, the latter caused a significantly increased (P<0.05) potentially degradable CP fraction (b). The highest (P<0.05) post-ruminal CP disappearance rate, gas production rate and ME value were observed in silage supplemented with PBM (P<0.05). In conclusion, both nitrogen sources used in this study enhanced nutritive value of orange pulp silage. Ensiling may be applied as a practical approach for long-term preservation of fresh orange pulp.