Pretreatment and fermentation of lignocellulose from oil palm fronds as a potential source of fibre for ruminant feed: a review

Oil palm fronds are plantation waste widely available in large quantities and have great potential as a source of ruminant feed due to their high fibre content. However, the lignocellulose content can inhibit feed digestion. This review examines methods that can reduce the lignocellulose content and improve the nutritional quality of palm fronds. The lignin content of palm fronds ranges from 17% to 20%, while the maximum lignin content in ruminant feed is 7%. Processing processes such as pretreatment are needed to reduce the lignocellulose content. Pretreatment can be done physically, chemically, biologically or in combination with other methods. Physical pretreatment aims to reduce the size of lignocellulose, chemical pretreatment seeks to break the crystallinity structure of lignocellulose with chemical solutions such as acids or alkalis, and biological pretreatment degrades the structure of lignocellulose with the help of enzymes produced by microbes. The protein content of palm fronds also does not meet the feed standard, which is only 5%, while according to Indonesian national standards, ruminant feed, especially cattle, must have a minimum protein content of 14%. Therefore, it is necessary to improve the nutritional quality of palm fronds through fermentation methods. The selection of the right microbes is the main factor in the success of increasing nutrition. The SSF fermentation method is frequently used in feed manufacturing. By synthesizing the current knowledge, this review also highlights the challenges of the pretreatment process as well as solutions that include prospects in the research of palm fronds as ruminant feed, which in turn can contribute to the increased utilization of lignocellulosic waste as animal feed.