Chemical composition, in vitro gas production, methane production and fatty acid profile of canola silage (Brassica napus) with four levels of molasses

摘要

The objective of this study was to investigate the effect of four levels of molasses on chemical composition, in vitro digestibility, methane production and fatty acid profile of canola silages. A canola (Brassica napus var. Monty) crop was established in a small-scale agricultural farm and harvested 148days after sowing. Four levels of molasses were tested with respect to the fresh weight (1.5kg); these were 1% (CS-1), 2% (CS-2), 3% (CS-3) and 4% (CS-4) molasses, and 0% molasses (CS-0) was included as a control. A total of 45 microsilages were prepared using PVC pipes (4in. of diameter x 20cm of length), and the forage was compressed using a manual press. The effects of control and treatments were tested using the general linear model Y=+T-i+E-ij. The linolenic acid (C18:3n3), palmitic acid (C16:0) and linoleic acid methyl ester (C18:2n6c) accounted for 30%, 21% and 10.5% of total fatty acids, respectively; the fermentation parameters and in vitro methane production were not affected (P>0.05) by treatments; in vitro digestibility decreased significantly (P0.05) as the level of molasses increased. It was concluded that CS-4 improved the DM content by 9% and showed high content of linolenic acid methyl ester. The gross energy of canola silages could favour the oleic acid methyl ester.