Short communication: The effect of different inclusion levels of polyethylene glycol as a silage additive on ensilage characteristics of pomegranate peel and in vitro rumen fermentation

Abstract

This study was conducted to evaluate the effects of ensiling pomegranate peel (PP) with different levels of polyethylene glycol (PEG) on its chemical composition, tannin content, in vitro gas production and fermentation characteristics. Fresh PP was chopped and ensiled in mini silos made of polyvinyl chloride tubing. Five levels of PEG were studied: 0 (control), 5, 10, 15, and 20% of fresh PP (dry matter basis). Total phenolics, total tannins, crude ash, crude protein, neutral detergent fiber and acid detergent fiber content and pH decreased with increasing PEG levels, whereas dry matter and non-fiber carbohydrates content, non-tannin phenols, lactic acid and ammonia concentrations and buffering capacity increased. The water soluble carbohydrates and ether extract concentrations were not influenced by the addition of PEG. The partitioning factor and efficiency of microbial biomass production were quadratically decreased (p=0.020 and p=0.032, respectively) as PEG inclusion increased, but the in vitro apparent dry matter disappearance did not differ among treatments. Compared to control, the in vitro true disappearance and in vitro fiber digestibility had a tendency to be higher in silages treated with PEG (p=0.081 and p=0.069, respectively). The metabolizable energy content and total volatile fatty acids concentration increased quadratically by PEG inclusion. The asymptotic gas production and rate of gas production were higher in PEG-treated silages. Overall, ensiling PP with PEG can improve the fermentation characteristics of this by-product.