Effects of Moisture Content and Additives on the Fermentation Quality and Degradation of Glycoalkaloids in Potato (<i>Solanum tuberosum</i>) Vine Silage in Tibet

Abstract

The objectives of this research were to evaluate the effects of raw material moisture content and additives on the fermentation quality and degradation of glycoalkaloids in potato vine silage and to explore new approaches for feedstuff preservation with the aim of providing a source of sustainable livestock feed. Potato vine was partially wilted to three different target moisture contents [approx. 75% (M1), 65% (M2), and 55% (M3)] and treated with (1) formic acid [1.5% fresh weight (FW), FA]; (2) pre-fermented juices (5.0 mL kg−1 FW, PFJ); (3) corn flour (100 g kg−1 DM, CF); (4) potato pulp (30% FW, PP); and (5) no additives (control). After 45 days of ensiling with polyethylene (100 mL), the fermentation quality, chemical composition, and concentration of glycoalkaloids were determined. The results showed that silage quality and glycoalkaloid concentration were significantly influenced by moisture content and additives (P < 0.05). Lactic acid (LA), pH, acid detergent fiber (ADF), and neutral detergent fiber (NDF) increased slightly with decreasing moisture content; in contrast, the concentration of LA/AA declined. LA content was highest and pH and acetic acid (AA) were lowest at M1 compared with M2 and M3. Little to no butyric acid (BA) was detected in the presence of additives. The FA-treated silage exhibited a significantly reduced pH value and ammonia-N/total-N (NH3-N/TN) content (P < 0.05) and an increased concentration of LA and water-soluble carbohydrates (WSCs). PP-treated silage provided sufficient fermentation substrate, and the DM and WSC contents increased significantly (P < 0.05) compared with the PFJ and CF treatments. Supplementation with PFJ resulted in the pH of the ensiled forage stabilizing at approximately 4.40. With the addition of CF, the LA:AA ratios of the different moisture content treatments were 2.42, 2.15, and 1.75, respectively, which were significantly lower than 3:1 in the other treatments at all moisture contents. The potato glycoalkaloid content of the PV silage increased with decreasing moisture level. Glycoalkaloid concentration was significantly reduced to 0.55, 4.57, and 7.73 100 mg g−1, respectively (P < 0.05), in the different moisture treatments by the addition of FA. In conclusion, the best quality PV silage was produced at 75% moisture content with the addition of FA. Additive ensiling thus constitutes an effective approach for potato vine preservation.