The Lactic Acid and Volatile Fatty Acid Content and In Vitro Organic Matter Digestibility of Silages Made from Potato Processing Residues and Barley Straw

In vitro organic matter digestibility (IVOMD) of silages made from potato processing residues (PPR) and barley straw was studied in two replicated experiments using a split-block design. Lactic acid content as well as acetic, propionic and butyric acid (VFA) levels of silages were determined. Silages were made from either filter cake (FC), dry peel (DP) or a mixture of equal parts of FC and DP and chopped barley straw in Exp. 1. Mixture diets for Exp. 2 were 50:50, 75:25 or 80:20% DP to FC, with barley straw added to make up one-half the dry matter (DM) of the silages. Silages made with FC and barley straw had lower (P<.05) IVOMD, averaging 57.4% in Exp. 1 and 56.1% in Exp. 2, than silages composed of either DP and barley straw or mixtures of FC and DP added to barley straw. Lactic acid levels of silages made from DP and barley straw were 4.7 and 4.5%, respectively, for Exp. 1 and 2, while lactic acid in silages made from FC or mixtures of PPR and barley straw ranged from 6.5 to 7.1%. Total VFA were higher (P<.05) in silages made from PPR mixtures than either product tested singly in each experiment. Butyric acid represented most of the VFA content (over 70%) in silages made from only DP and straw as compared with about 35% of total VFA in the other silages. Based on these studies, IVOMD of low quality roughage can be improved by ensiling with PPR if 20% FC is included in the PPR to insure adequate lactic acid production during ensiling.