Some properties of apple pomace ensiled with and without additives

Abstract

The apple pomace used in this study is a by-product of the fruit juice industry. The samples examined had a mean pH of 3.84 and a dry matter content between 172 and 284 g kg −1 fresh material. Apple pomace with dry matter > 220 g kg −1 was suitable for handling and was ensiled with urea alone or in combination with activated sodium montmorillonite (Benal) in the laboratory in three separate experiments. The organoleptic properties of pomace ensiled with urea (10 g kg −1 fresh material) for 28 days were more favourable than pomace ensiled without urea, but acid production during ensilage lowered the pH to 3.35. The presence of Benal (10 g kg −1) ameliorated the changes in acidity occurring during ensilage. Moreover, Benural-70, a product containing urea and Benal (7:3), increased the crude protein content of ensiled pomace when added at 30 g kg −1. Hydrolysis of urea during ensilage was low and ammonia accumulation slight. Using 15N-urea, it was confirmed that nitrogen was not lost during ensilage of apple pomace for a period of several months. Samples of pomace which had been ensiled with 15N-urea and Benal for 1, 7, 28 and 85 days were incubated in sacco in the ovine rumen for periods of up to 48 h. Diffusion of 15N into the whole rumen content was rapid. No evidence was obtained that the length of ensilage affected the kinetics of retention of total N or 15N in the bags. As a whole, the results indicate that the major part of the urea added to apple pomace should function as a supplementary nitrogen source in the rumen, because only a small part is utilized in the silo regardless of the length of storage.