Effects of Pro-nutrient Feed Additives on Live Performance and Gastrointestinal Health of Broilers and Turkeys

Nutrient digestibility directly influences intestinal health and growth performance of broilers and turkeys. Coccidiosis is among the most economically important enteric diseases in turkeys as it has adverse effects on performance and resistance to other enteric pathogens. Increasing public perception against the use of anticoccidials requires the industry to consider additional alternatives. Moreover, the potential economic value of supplemental enzymes that improve energy availability increases as dietary energy costs increase, especially when used in low energy diets that may contain grain by-products such as distiller's dried grains with solubles (DDGS). Increasing dietary inclusion of DDGS may contribute to variable performance of poultry because of its high nutritional variability and low energy value, but this may be remediated by dietary enzyme supplementation. Similarly, dietary phytase inclusion increases phosphorus availability, decreasing feed cost of inorganic phosphorus, and reducing fecal phosphorus emission. This dissertation evaluated two alternatives to antibiotics under a coccidia-challenge model in poults. Additionally, energy-releasing enzyme products were evaluated with and without DDGS inclusion in two experiments: one experiment evaluated pelleted diets fed to toms, and the other was mash fed to mixed-sex broilers. Finally, the efficacy a novel phytase was evaluated in a tritration study with poults.;The first experiment evaluated ReganoRTM on poult performance, relative intestinal weight (rIW) and histomorphology during a coccidia-challenge until 15 d of age. Eimeria challenge significantly reduced 14 d BW and increased 15 d rIW. ReganoRTM supplementation significantly reduced 7 d BW but had no significant effect on 14 d BW. Growth performance coincided with scanning electron microscopy observations and histomorphometrical analysis. ReganoRTM supplementation did not improve poult response to Eimeria challenge perhaps due to excessive dose level.;Experiment 2 was similar to Experiment 1, but an all-natural proprietary composition product Natusta(TM) (Alltech, Inc., Nicholasville, KY) was assessed. Natustat(TM) supplementation did not improve poult performance during this cocci-challenge, but it may improve compensatory absorption of nutrients in the jejunum after challenge.;In Experiment 3, a phytase product with and without an enzyme product containing xylanase, amylase, and protease (XAP) activities was supplemented in corn-soy diets fed to toms with and without DDGS inclusion until 20 weeks. Increasing DDGS to 15 % had no negative effect on BW gain but negatively affected FCR and pellet quality. The addition of phytase -/+ XAP enzymes resulted in an apparent uplift of over 150 kcal ME/kg, reducing the need for dietary fat and inorganic phosphate inclusion, regardless of the dietary DDGS level.;Similarly, Experiment 4 contained an enzyme product supplemented in corn-soy diets with and without DDGS inclusion. However, the enzymes in Experiment 4 were a xylanase and an enzyme with xylanase and beta-glucanase activities fed in mash form to mixed-sex broilers until 49 d. Dietary supplementation of xylanase improved performance of broilers fed mash corn-soy diets with 10 % DDGS and in low-energy diets containing DDGS restored broiler performance to the level of the high-energy control at 49 d.;Experiment 5 was a dose titration study of a novel phytase in poults until 28 d. Phytase supplementation significantly improved turkey growth response, which was associated with improved feed intake and nutrient bioavailability. The optimum dose of this dietary phytase was identified to be approximately 1000 FTU/kg of feed.;In conclusion, the alternatives to antibiotics examined did not prevent performance reduction associated with the cocci-challenge. Furthermore, energy releasing enzymes improve nutrient utilization and growth performance in corn-soy diets but did not provide additional benefit with dietary DDGS inclusion.