The evaluation of novel bio-ethanol derived co-products as potential feed ingredients for carp Cyprinus carpio and tilapia Oreochromis niloticus

The nutritional value of novel yeast products were evaluated for warmwater fish species. A yeast co-product (yeast protein concentrate unrefined (YPCU)) obtained from a bio-ethanol process using wheat was tested using iso-nitrogenous (38% crude protein) and iso-lipidic (8%) diets for juvenile mirror carp (Cyprinus carpio). The fishmeal (FM) protein component of a basal diet was replaced by (YPCU) at 7.5, 15, 20, and 50% of total dietary protein. After an 8 week feeding trial, all fish fed YPCU yielded better growth performance than the control fed fish, with diets containing 15% and 20% YPCU being optimal. Whole body composition was unaffected by dietary treatment, however, ash levels were elevated in fish fed >15% YPCU. Hepatic alanine amino transferase (ALAT) and aspartate amino transferase (ASAT) were measured as bio-indicators of liver function in carp. Only ASAT activity was significantly lower for carp fed 20% and 50% YPCU. Additionally, histological assessment of liver and intestinal tissues gave no indication of impairment, but high YPCU inclusion (>15%) elevated the number of goblet cells present in the posterior intestine. Molecular microbiological analysis using DGGE revealed no definitive changes in intestinal microbial communities. In a second study, bio-ethanol yeast (refined YPCR and unrefined YPCU) and dried distillers grain with solubles (DDGS) a co-product of the bio-fuel process and distillery yeast from potable alcohol (whisky) production (YPCPA) were evaluated as before for carp. FM was replaced with 30% of YPCU, YPCR and YPCPA and 15, or 30 % DDGS with a combination of 10% YPCR. Weight gain, and Apparent Net Protein Utilization (ANPU%) were higher in fish fed YPCU 30%, equivalent for fish fed FM, YPCR 30%,DDGS 15% and DDGS 30%, and lower in fish fed YPCPA 30% diets. Feed conversion ratio was significantly increased in carp fed YPCU 30% and decreased for carp fed DDGS 30% and YPC PA 30% compared with the control group. A significant improvement of net mineral retention was seen for carp feed the yeast supplementation diets compared to the fishmeal control group. The YPCU 30% diet produced the highest mineral retention in fish fed yeasts and the YPCPA 30% gave lowest retention. The microvilli density of the intestinal tract decreased for carp fed YPCR 30%, but microvilli length significantly increased in fish fed YPCU 30% compared with other groups, thus indicating changes in gut integrity. In the third study, four diets were formulated to replace 0, 10, 20 and 30% of the fishmeal with refined yeast protein concentrate (YPCR) for Nile tilapia (O. niloticus) of mean weight 12.39g. Growth performance and feed efficiency were not affected with up to 20% replacement with YPCR. There were no obvious changes in the liver structure, but high yeast inclusion showed higher numbers of intestinal goblet cells with increasing YPCR dietary inclusion suggesting enhanced intestinal integrity. Microvilli density and length was significantly (P = 0.025) improved with up to 10% and 30% YPCR inclusion in comparison to other dietary treatments. It was generally concluded that YPC co-products were effectively viable for both juvenile carp and tilapia offering an option for partial fish meal replacement.EThOS - Electronic Theses Online ServiceMinistry of Higher Education and Scientific Research, Kurdistan Region, IraqGBUnited Kingdo