Karakteristik Fermentasi Silase Daun Singkong (Manihot esculenta Crantz) dengan Aditif Gliserol dan Ekstrak Tanin Chesnut

Abstract

Cassava leaves (Manihot esculenta Crantz) productivity has a big potential to be valuable protein supplement for ruminant. However, due to the abundant availability when crop, cassava leaves requires a storage technology to maintain its nutritious composition. The one of better way is by ensilage. The ensiling process of cassava leaves required additives because its low content of WSC. Additives used in this present study were glycerol and chesnut tannin extract. Meta-analysis of glycerol supplementation in vitro did to support the hypothesis regarding of glycerol usage to substitute energy source as silage additives. This study aimed to evaluate the glycerol supplementation on rumen fermentation characteristics in vitro by quantitatively meta-analysis, to evaluate the fermentation characteristics of cassava leaves silage with glycerol and chestnut tannin extract additives during ensilage and in vitro gas production. Meta-analysis quantitatively was applied to 13 experiments and 42 treatments dealing with glycerol supplementation in ruminant. Data were estimated by linear regression of each parameter and analyzed by general linier model procedure with glycerol levels as fixed effect. Data for both fermentation characteristics of cassava leaves silage and its in vitro gas production were analyzed using analysis of variance then significant means were separated using Duncan multiple range F-test. Cassava leaves was ensiled using four different types of additive on the laboratory-scale silo. They were control (without additive, S0), glycerol 3% DM (SG), chesnut tannin 3% DM (ST), and mix of glycerol 3% DM and chesnut tannin 3% DM (SGT). Parameters on meta-analysis and in vitro gas production study were in vitro digestibility, rumen fermentation characteristics and total gas production. Parameters on silage study were nutrient composition, organic acids and N-NH3 concentration. Glycerol supplementation on meta-analysis quantitatively did not affect the in vitro digestibility and total VFA. Total VFA insignificantly showed propiogenic characteristics. It significantly decreased molar proportion of acetate and iso-valerate. In contrast, molar proportion of propionate, butyrate and valerate significantly increased, and thus the ratio of acetate to propionate became declined linearly. Methane production decreased linearly although the total gas production significantly increased as an increasing levels of glycerol supplementation but showed low enteric methane and no effect for microbial protein production. Every single cassava leaves silages in present study showed well-preserved quality depended on high concentration of lactic acid, not detected butyric acid, low concentration of N-NH3 although the pH value slightly higher. In addition, the well-preserved quality also supported by a low reduction of OM content (about 0.2%) and not changed CP content in silage between week 0 and 4. Rumen fermentation characteristics of cassava leaves silage by in vitro gas production showed an increasing IVOMD and total VFA production between week 0 and 4, but the silage treatment was not significant on each week. Glycerol as silage additive at week 0 showed propiogenic properties but not appeared on SG and SGT week 4. Contrary, the main properties of chesnut tannin was shown on in vitro gas production of ST and SGT week 4 that reduced proportion of N-NH3 and iso-acid production related to amino acid degradation. Based on results, it can be concluded that meta-analysis on the fate of glycerol as an energy substitution in ruminant feed showed propiogenic characteristics and identified to have no detrimental effects in the rumen and environmentally friendly. Cassava leaves silage with or without glycerol and/or chestnut tannin extract additives can improve silage quality and showed well-preserved on week 4. However, ruminal fermentation in vitro study showed that the usage of glycerol additives for silage should be accompanied by chestnut tannin extract to improve the protein utility in the post-rumen digestion.