Abstract/Summary

Feed is the greatest cost to the commercial poultry producer and any steps that act to reduce these costs while maintaining production efficiency are welcomed. The by-product of bioethanol production from corn, corn distillers dried grains with solubles (cDDGS), have been considered as a potential feed ingredient. However, as poultry are traditionally fed low fibre diets, the high fibre content of cDDGS could result in reduced digestibility and therefore performance. This project aimed to investigate the impact of the use of cDDGS on the performance, caecal community and metabolic profile of broilers. In order to investigate this two broiler trials were run, one 3S-day trial testing the impact of increasing inclusions of cDDGS (Trial 1) and a 38-day intervention trial utilising 28% cDDGS and a novel in-feed enzyme combination containing a commercial xylanase ß-glucanase with an experimental protease in comparison to acorn-soy control diet (Trial 2). There was a trend toward reduced performance with increasing cDDGS in Trial 1. Whilst there were no large shifts in the caecal community some OTUs were found that were highly related to known fibre degraders such as Ethanoligenens harbinense and Ruminococcus champanellensis. Trial 2 showed that cDDGS inclusion (28%) had a negative impact on feed conversion (p<O.OOl), and acted to reduce the breast muscle yield (p<O.OS) and increase abdominal fat pad as a percentage of total carcass weight in comparison to 'Control' (p<O.Ol). The addition of enzyme to the diet acted to reverse this towards that of the 'Control' potentially acting to increase amino acid digestibility, compensating for a lack of arginine present in the cDDGS diets. Enzyme had minimal impact on the caecal community, with cDDGS inclusion having a greater impact either due to increased fibre (e.g Faecalibacterium prausnitzii and B/autia producta) or due to the increased soy oil (e.g Rikenellaceae). Caecal content of birds fed cDDGS had relatively lower proportions of each measured metabolite in comparison to the 'Control' indicating a reduced level of fermentation either from endogenous processes or the microbiota. Correlation analysis found that taxonomic groups previously associated with cDDGS inclusion were correlated with the short chain fatty acids propionate and butyrate. Although the use of cDDGS may have resulted in extra dietary variables other than increased fibre, this work still illustrated the consequences of utilising this feedstuff in a commercial diet. This thesis is the first attempt to correlate performance with diet, the gut microbiota and its metabolic profile. Importantly the enhanced presence of bacteria that could be capable of degrading fibre and thus extract more energy out of the diet was illustrated.