Effects of Preheated Additives on the Fermentation Quality of Napiergrass Silage

Hydrolysis of plant protein to non-protein nitrogen (N) or ammonia can reduce quality of silage crops. Heating or non-enzymatic browning is a treatment to inhibit this hydrolysis. This experiment was conducted to examine the effects of pre-heated soybean meal and molasses on the fermentation quality of napiergrass silage. The initial growth of napiergrass was harvested at 85 days of age and immediately chopped into about 1 cm length. About 700 g of the grass was ensiled into a laboratory silo (1.0 liter polyethylene container) and incubated for 30 days at room temperature ($28^{\circ}C$). No additives (control), molasses, soybean meal and molasses + soybean meal treatments were prepared. All additives were non-heated or heated in an oven at $150^{\circ}C$ for 30 minutes before ensiling. Molasses was added at 3% on the fresh weight basis and soybean meal was added at 0.5% N, respectively. After opening the silo, pH, total nitrogen (TN), volatile basic nitrogen (VBN), lactic acid (LA), acetic acid (AA), butyric acid (BA) and dry matter (DM) contents were determined. The data were analyzed statistically by analysis of variance. Compared with control, molasses addition significantly decreased pH value, VBN/TN, AA and BA and increased LA production. Soybean meal addition significantly increased TN and VBN/TN of silage. Both molasses and soybean meal addition significantly reduced pH value, AA, and BA and increased DM and LA contents of silage. The heating of additives was only effective to reduce VBN/TN production compared with non-heated additives in soybean meal and soybean meal with molasses addition.