Inclusion of Lonicerae flos improved anaerobic fermentation and antioxidant activity of mixed silage (agro-residue and alfalfa)

Abstract

Lonicerae flos (SY) is rich in active components including chlorogenic acid, flavonoids, phenols and terpenoids, with antioxidant and antibacterial activities. The present study was designed to evaluate the application potential of SY in silages. Various concentrations of SY (0, 5, 10, 15, 20, and 25 g/kg of fresh weight [FW]) were added to a mixture of alfalfa, distillers dried grains with solubles (DDGS) and soybean meal (80/10/10). All mixtures were ensiled for 30 d in laboratory silos, the experiment followed a completely randomized design, and six treatments were designed according to SY levels, with 5 replicates per treatment. Data were subjected to one-way analysis of variance and polynomial contrasts (SPSS 23.0) to examine effects of varying concentrations of SY. Adding SY enriched relative abundance of Lactobacillus acetotolerans, increased dry matter (DM), water soluble carbohydrate (WSC), chlorogenic acid, total phenolics content, and ferric reducing antioxidant power (FRAP) reducing power, and reduced pH, ammonia nitrogen (AN) and structural carbohydrates (NDF, ADF, and hemicellulose) contents. L. acetotolerans was positively correlated with WSC, DM, chlorogenic acid, total phenolics, FRAP, and 2,2-azinobis-3-ethylbenzothiazoline-6-sulfonic acid diammonium salt radical cation (ABTS) concentrations, while negatively correlated with pH, AN and structural carbohydrates contents. Base on the predicted pathways and phenotype of the bacterial community, the addition of SY promoted the genetic information processing (translation, replication and repair, transcription), and inhibited the abundances of potentially pathogenic, stress tolerant and gram negative. Silages with SY at 20 g/kg FW (SY4) or 25 g/kg FW (SY5) had lower pH, contents of AN and structural carbohydrates than other silages. The chlorogenic acid and total phenolics content in SY3 and SY4 were higher than other silages, while FRAP reducing power and ABTS scavenging activity in SY3 (15 g/kg FW) and SY4 silage was highest, respectively. Overall, the inclusion of SY at 20 g/kg FW decreased pH and AN content, more chlorogenic acid, increased the relative abundance of L. acetotolerans and antioxidant activity, with the potential to serve as a feed additive.