AN EXAMINATION OF THE EFFECTS OF USING GLYCEROL AND WHEAT DRY DISTILLERS’ GRAINS WITH SOLUBLES IN SHEEP DIETS The aims of this research were to assess the effects of feeding glycerol and wheat based dry distillers’ grains with solubles (WDDGS) on rumen metabolism, performance, carcass characteristics and fatty acid composition of adipose tissue of lambs. In study 1, increasing levels of glycerol as replacement of barley grain in in vitro batch cultures did not affect culture pH and total methane (CH4) production, but in vitro dry matter disappearance, total VFA production and propionate proportions were linearly increased. In study 2, increasing levels of glycerol in a forage diet increased total VFA, propionate and butyrate production and DM and neutral detergent fibre (NDF) disappearance in semi continuous fermenters. Methane production was linearly increased despite increases in propionate concentrations as a result of the more reduced state of glycerol as compared to carbohydrates which implies there is no net incorporation of electrons into glycerol when it is metabolised to propionate. In study 3, increasing concentrations of glycerol did not alter in vivo diet digestibility or CH4 production. However, dry matter intake (DMI) was reduced at high glycerol concentrations (210 g/kg DM) and average daily gain (ADG) tended to decrease. Fatty acid profiles were improved by reducing concentrations of palmitic, trans-10 octadecenoic and linoleic acids and the n-6/n-3 ratio and increasing stearic and oleic acids. In study 4, increasing concentrations of WDDGS as direct replacement of barley grain resulted in increased eating rates, DMI and ADG. Linolenic acid in backfat tissue was also increased without altering the n-6/n-3 ratio. However, when WDDGS were included in iso nitrogenous diets as replacement of soybean meal and alfalfa, DM, NDF and CP in sacco effective degradability and in vitro CH4 production were increased. Animal DMI, ADG and hot carcass weight were linearly reduced but feed efficiency was unaffected and trans-10 octadecenoic and linoleic acids were increased
