Effect of silage juice feeding on pig production performance, meat quality and gut microbiome

Traditionally grass has been considered a suitable feed only for ruminants. Due to global challenges related to growing human population, sustainable feed materials for pigs are actively searched and grasses as a high yielding biomass have been seen as an interesting addition to pig feeds. The digestible nutrients in grasses are embedded in a fibre matrix not digestible to pigs, but suitable processing could alleviate this. The aim of the present study was to evaluate whether silage juice could provide a new sustainable diet ingredient for fattening pigs. Grass silage was fractionated with a twin-screw press to liquid and solid fractions. The silage juice was included into liquid feed of 112 fattening pigs from 62 kg live weight until slaughter (124 kg live weight) and compared to 96 pigs on a conventional control diet. Feed allowance was ad libitum until it reached 33.6 MJ net energy day⁻¹ per pig which was kept as the maximum feed allowance until slaughter. The average daily gain of all the pigs was over 1000 g day⁻¹ in the experimental period but no difference between silage juice fed and control group was found. The feed conversion ratio was, as expected, higher in barrows than gilts, but no difference was found between the two treatment groups. Variation in silage juice dry matter content during the experimental period may have led to a lower dry matter intake of silage juice fed pigs. Gilts had statistically significantly higher meat percentage than barrows in both treatments, but no difference was found between the treatment groups. Meat quality (pH, colour, drip loss and sensory analyses) results were similar in both treatment groups. For gut microbiota, no statistically significant differences were found in any of the bacterial families studied (Actinobacteriota, Bacteroidota, Firmicutes, Deferrivacterota, Spirochaetota, Minor Phyla). In conclusion, silage juice is a potential feed ingredient in liquid feed for pigs. Microbiological data indicates that silage juice does not cause gastrointestinal microbiota imbalance in pigs.