Exploring the combination of wilting and different types of additives to improve silage quality of highland alfalfa: Fermentation quality, nutritional values, molecular structural features, and ruminal degradability

Abstract

The study aimed to explore the interaction between wilting pretreatment and different types of ensiling additives on silage quality, nutritional value, molecular structural features, and ruminal degradability of highland alfalfa. A total of 48 bags of alfalfa forage were randomly assigned into one of eight treatments in a 2 × 4 factorial arrangement (6 replication bags/treatment). One kg of either unwilted (72 % moisture) or wilted (60 %) alfalfa forage was inoculated with acidic salt, lactic acid bacteria, organic acids, or left without additive (control). Our results indicated that the wilting process increased lactic acid and crude protein levels, decreased the NH₃-N level in silage, and increased its in vitro DM digestibility (all P < 0.05). The wilting treatment increased the amide I/II ratio by 31.7 % and the total carbohydrate II regions by 19.6 % (both P < 0.05). Inoculating pre-wilted alfalfa with lactic acid bacteria further reduced the pH and NH₃-N levels and increased the lactic acid level and DM digestibility in silage (all P < 0.05). The addition of organic acids decreased silage pH and increased lactic acid, crude protein, and starch contents, and DM digestibility (all P < 0.05). Correlation analysis indicated that silage with a higher amide I/II peak height ratio and TC2 areas had more digestible nutrients and higher DM digestibility. In conclusion, wilting pretreatment combined with lactic acid bacteria inoculant is an effective approach to improve quality and nutrient availability of highland alfalfa silage. The non-invasion spectrometer has the potential to reveal the molecular spectral characteristics of alfalfa silage and predict nutrient availability.