Evaluating specific vitamin B concentration and feed manufacturing on growth performance, digestibility, and intestinal integrity in poultry

Abstract

Optimizing nutrient utilization and gastrointestinal health is essential to maximizing growth performance and production efficiency in modern poultry systems. Feed costs account for up to 70% of the modern production costs and therefore nutritional strategies that improve ingredient utilization, and digestive function can enhance nutrient efficiency to maximize growth performance and bird health. Modern poultry production requires increasingly precise nutritional and feed manufacturing strategies to maximize growth performance, nutrient utilization, and gastrointestinal health while maintaining economic efficiency. Improvements in genetic potential of broilers and turkeys have increased metabolic demands, placing greater emphasis on vitamin adequacy, ingredient utilization, and digestive efficiency to support optimal performance. In particular, the role of vitamin nutrition in energy metabolism, the use of alternative feed ingredients, and the interaction between nutrient digestibility and gastrointestinal health remain key areas of investigation. Therefore, the objectives of this dissertation were to evaluate the role of specific vitamin B concentrations in broiler and turkey nutrition (Chapters 1, 2, and 3), and assess sorghum particle size effects on broiler growth performance and digestive physiology (Chapter 4). To achieve these objectives, multiple experiments were conducted in broilers and turkeys. The first study evaluated the effects of niacin (NA) and the emerging NA analog nicotinamide riboside (NR) on growth performance, energy digestibility, and intestinal morphology in broilers (Chapter 1, Exp 1). Supplementation of NA above a basal level of 28 mg/kg or NR addition, did not affect body weight gain (BWG), feed intake (FI), or feed conversion ratio (FCR; P > 0.05), and apparent metabolizable energy (AME) was not improved with additional NA (P > 0.05). In contrast, NR supplementation linearly decreased apparent total tract digestibility of gross energy (P = 0.02) and AME (P = 0.02). While NA increased villus height (quadratically, P = 0.04) and NR increased crypt depth (quadratically, P = 0.01). A second broiler study evaluated increasing NA inclusion from 28 to 268 mg/kg (Chapter 1, Exp 2) and observed a quadratic response in AME (P = 0.08), with no differences in AME up to 208 mg/kg and then reduced at 268 mg/kg (P = 0.02), while growth performance remained unchanged (P > 0.05). These findings suggest that within the limitations of these battery studies, current NA recommendations are adequate for broiler growth and that NR can substitute NA in the diet without negatively impacting growth performance. The third study evaluated NA and NR supplementation in turkey hens from 0 to 42 days of age to determine whether increased NA inclusion improves growth performance and intestinal morphology (Chapter 2). Turkeys fed an additional 70 mg/kg NA demonstrated improved FCR (P = 0.02), while additional 70 mg/kg NR showed a tendency for improved FCR (P = 0.07), with no differences in BWG or FI (P > 0.05). Total dietary NA levels reached 172 mg/kg, exceeding current requirement estimates and suggesting that modern turkey hens may benefit from higher NA inclusion to support feed efficiency. The fourth study investigated riboflavin supplementation in turkey starter diets during summer conditions to evaluate its impact on growth performance and intestinal permeability (Chapter 3). Increasing dietary riboflavin from 11.24 to 28.10 mg/kg resulted in no differences in BWG, FI, or FCR for d 1-21 (P > 0.05). From d 22-43 and overall, there were no linear or quadratic responded in BWG or FI, however, FCR tended to quadratically respond (P = 0.064). There was no response detected in fluorescein isothiocyanate–dextran intestinal permeability with increasing riboflavin inclusion (P > 0.05) even after a period of environmental conditions of >32°C and >50% relative humidity for 5 days. These results suggest that dietary riboflavin inclusion of 11.24 mg/kg is sufficient during the summer months with no negative impact on growth performance or intestinal permeability. The fifth study evaluated sorghum particle size effects on broiler growth performance and digestive physiology from 4 to 49 days of age (Chapter 4). Broilers fed sorghum-based diets had greater BWG and FI compared to those fed corn-based diets (P < 0.05), with no differences in FCR (P > 0.05). Increasing sorghum particle size resulted in a tendency for increased FI (linear, P = 0.059) and BWG (quadratic, P = 0.056), with optimal performance observed between 1,000 and 1,200 [mu]m. Coarser particle size supported improved gizzard development and growth performance, demonstrating that feed manufacturing practices play a critical role in optimizing alternative grain utilization. Overall, the results presented here with in this dissertation demonstrate that optimizing vitamin inclusion and feed processing provides practical and mechanistic framework to improve poultry performance and intestinal health. These findings support evidence-based vitamin recommendations for modern broilers and turkeys, validate sorghum as a viable alternative energy source when properly processed, and emphasize the importance of precision nutrition to enhance metabolic efficiency and intestinal health. Integrating metabolic nutrition with feed manufacturing practices provides poultry nutritionists and feed manufacturers with actionable strategies to improve feed efficiency, reduce production costs, and enhance modern poultry production.