A comparison of nutritional value of raisin wastes obtained from two Iranian grape varieties by in vitro rumen fermentation

Abstract

In vitro cumulative gas production and some laboratory methods were used to evaluate raisin wastes obtained from two Iranian grape varieties (Paykami and Askari) for their nutritive value and chemical composition. Results showed that Paykami raisin wastes (PRW) had numerically more (P>0.05) dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), ether extract (EE) and ash than Askari raisin wastes (ARW). In another experiment, an in vitro gas production (GP) technique was applied to evaluate the nutritive value of  raisin wastes. Total gas volume (GP24, GP48 and GP96h after incubation), total volume of gas produced from the insoluble and fermentable section (B_gas), constant rate for total gas production (C_gas), short chain volatile fatty acids (SCFA), microbial protein yield (MPY), organic matter digestibility (OMD), metabolisable energy (ME) and degradability of dry matter (DMD) were not differ significantly between two treatments. Both treatments had high levels of tannin and phenolic compounds (especially for Askari raisin wastes). Despite having moderate nutritive values for both raisin wastes with high concentration of tannins, the feed consumption of them should be with caution in livestock.